| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/regex-1.8.3/src/dfa.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>dfa.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../regex/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../regex/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| <span id="1910">1910</span> |
| <span id="1911">1911</span> |
| <span id="1912">1912</span> |
| <span id="1913">1913</span> |
| <span id="1914">1914</span> |
| <span id="1915">1915</span> |
| <span id="1916">1916</span> |
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| <span id="1918">1918</span> |
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| <span id="1929">1929</span> |
| <span id="1930">1930</span> |
| <span id="1931">1931</span> |
| <span id="1932">1932</span> |
| <span id="1933">1933</span> |
| <span id="1934">1934</span> |
| <span id="1935">1935</span> |
| <span id="1936">1936</span> |
| <span id="1937">1937</span> |
| <span id="1938">1938</span> |
| <span id="1939">1939</span> |
| <span id="1940">1940</span> |
| <span id="1941">1941</span> |
| <span id="1942">1942</span> |
| <span id="1943">1943</span> |
| <span id="1944">1944</span> |
| <span id="1945">1945</span> |
| </pre><pre class="rust"><code><span class="doccomment">/*! |
| The DFA matching engine. |
| |
| A DFA provides faster matching because the engine is in exactly one state at |
| any point in time. In the NFA, there may be multiple active states, and |
| considerable CPU cycles are spent shuffling them around. In finite automata |
| speak, the DFA follows epsilon transitions in the regex far less than the NFA. |
| |
| A DFA is a classic trade off between time and space. The NFA is slower, but |
| its memory requirements are typically small and predictable. The DFA is faster, |
| but given the right regex and the right input, the number of states in the |
| DFA can grow exponentially. To mitigate this space problem, we do two things: |
| |
| 1. We implement an *online* DFA. That is, the DFA is constructed from the NFA |
| during a search. When a new state is computed, it is stored in a cache so |
| that it may be reused. An important consequence of this implementation |
| is that states that are never reached for a particular input are never |
| computed. (This is impossible in an "offline" DFA which needs to compute |
| all possible states up front.) |
| 2. If the cache gets too big, we wipe it and continue matching. |
| |
| In pathological cases, a new state can be created for every byte of input. |
| (e.g., The regex `(a|b)*a(a|b){20}` on a long sequence of a's and b's.) |
| In this case, performance regresses to slightly slower than the full NFA |
| simulation, in large part because the cache becomes useless. If the cache |
| is wiped too frequently, the DFA quits and control falls back to one of the |
| NFA simulations. |
| |
| Because of the "lazy" nature of this DFA, the inner matching loop is |
| considerably more complex than one might expect out of a DFA. A number of |
| tricks are employed to make it fast. Tread carefully. |
| |
| N.B. While this implementation is heavily commented, Russ Cox's series of |
| articles on regexes is strongly recommended: <https://swtch.com/~rsc/regexp/> |
| (As is the DFA implementation in RE2, which heavily influenced this |
| implementation.) |
| */ |
| |
| </span><span class="kw">use </span>std::collections::HashMap; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::iter::repeat; |
| <span class="kw">use </span>std::mem; |
| <span class="kw">use </span>std::sync::Arc; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::exec::ProgramCache; |
| <span class="kw">use </span><span class="kw">crate</span>::prog::{Inst, Program}; |
| <span class="kw">use </span><span class="kw">crate</span>::sparse::SparseSet; |
| |
| <span class="doccomment">/// Return true if and only if the given program can be executed by a DFA. |
| /// |
| /// Generally, a DFA is always possible. A pathological case where it is not |
| /// possible is if the number of NFA states exceeds `u32::MAX`, in which case, |
| /// this function will return false. |
| /// |
| /// This function will also return false if the given program has any Unicode |
| /// instructions (Char or Ranges) since the DFA operates on bytes only. |
| </span><span class="kw">pub fn </span>can_exec(insts: <span class="kw-2">&</span>Program) -> bool { |
| <span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| <span class="comment">// If for some reason we manage to allocate a regex program with more |
| // than i32::MAX instructions, then we can't execute the DFA because we |
| // use 32 bit instruction pointer deltas for memory savings. |
| // If i32::MAX is the largest positive delta, |
| // then -i32::MAX == i32::MIN + 1 is the largest negative delta, |
| // and we are OK to use 32 bits. |
| </span><span class="kw">if </span>insts.dfa_size_limit == <span class="number">0 </span>|| insts.len() > ::std::i32::MAX <span class="kw">as </span>usize { |
| <span class="kw">return </span><span class="bool-val">false</span>; |
| } |
| <span class="kw">for </span>inst <span class="kw">in </span>insts { |
| <span class="kw">match </span><span class="kw-2">*</span>inst { |
| Char(<span class="kw">_</span>) | Ranges(<span class="kw">_</span>) => <span class="kw">return </span><span class="bool-val">false</span>, |
| EmptyLook(<span class="kw">_</span>) | Match(<span class="kw">_</span>) | Save(<span class="kw">_</span>) | Split(<span class="kw">_</span>) | Bytes(<span class="kw">_</span>) => {} |
| } |
| } |
| <span class="bool-val">true |
| </span>} |
| |
| <span class="doccomment">/// A reusable cache of DFA states. |
| /// |
| /// This cache is reused between multiple invocations of the same regex |
| /// program. (It is not shared simultaneously between threads. If there is |
| /// contention, then new caches are created.) |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>Cache { |
| <span class="doccomment">/// Group persistent DFA related cache state together. The sparse sets |
| /// listed below are used as scratch space while computing uncached states. |
| </span>inner: CacheInner, |
| <span class="doccomment">/// qcur and qnext are ordered sets with constant time |
| /// addition/membership/clearing-whole-set and linear time iteration. They |
| /// are used to manage the sets of NFA states in DFA states when computing |
| /// cached DFA states. In particular, the order of the NFA states matters |
| /// for leftmost-first style matching. Namely, when computing a cached |
| /// state, the set of NFA states stops growing as soon as the first Match |
| /// instruction is observed. |
| </span>qcur: SparseSet, |
| qnext: SparseSet, |
| } |
| |
| <span class="doccomment">/// `CacheInner` is logically just a part of Cache, but groups together fields |
| /// that aren't passed as function parameters throughout search. (This split |
| /// is mostly an artifact of the borrow checker. It is happily paid.) |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>CacheInner { |
| <span class="doccomment">/// A cache of pre-compiled DFA states, keyed by the set of NFA states |
| /// and the set of empty-width flags set at the byte in the input when the |
| /// state was observed. |
| /// |
| /// A StatePtr is effectively a `*State`, but to avoid various inconvenient |
| /// things, we just pass indexes around manually. The performance impact of |
| /// this is probably an instruction or two in the inner loop. However, on |
| /// 64 bit, each StatePtr is half the size of a *State. |
| </span>compiled: StateMap, |
| <span class="doccomment">/// The transition table. |
| /// |
| /// The transition table is laid out in row-major order, where states are |
| /// rows and the transitions for each state are columns. At a high level, |
| /// given state `s` and byte `b`, the next state can be found at index |
| /// `s * 256 + b`. |
| /// |
| /// This is, of course, a lie. A StatePtr is actually a pointer to the |
| /// *start* of a row in this table. When indexing in the DFA's inner loop, |
| /// this removes the need to multiply the StatePtr by the stride. Yes, it |
| /// matters. This reduces the number of states we can store, but: the |
| /// stride is rarely 256 since we define transitions in terms of |
| /// *equivalence classes* of bytes. Each class corresponds to a set of |
| /// bytes that never discriminate a distinct path through the DFA from each |
| /// other. |
| </span>trans: Transitions, |
| <span class="doccomment">/// A set of cached start states, which are limited to the number of |
| /// permutations of flags set just before the initial byte of input. (The |
| /// index into this vec is a `EmptyFlags`.) |
| /// |
| /// N.B. A start state can be "dead" (i.e., no possible match), so we |
| /// represent it with a StatePtr. |
| </span>start_states: Vec<StatePtr>, |
| <span class="doccomment">/// Stack scratch space used to follow epsilon transitions in the NFA. |
| /// (This permits us to avoid recursion.) |
| /// |
| /// The maximum stack size is the number of NFA states. |
| </span>stack: Vec<InstPtr>, |
| <span class="doccomment">/// The total number of times this cache has been flushed by the DFA |
| /// because of space constraints. |
| </span>flush_count: u64, |
| <span class="doccomment">/// The total heap size of the DFA's cache. We use this to determine when |
| /// we should flush the cache. |
| </span>size: usize, |
| <span class="doccomment">/// Scratch space used when building instruction pointer lists for new |
| /// states. This helps amortize allocation. |
| </span>insts_scratch_space: Vec<u8>, |
| } |
| |
| <span class="doccomment">/// The transition table. |
| /// |
| /// It is laid out in row-major order, with states as rows and byte class |
| /// transitions as columns. |
| /// |
| /// The transition table is responsible for producing valid `StatePtrs`. A |
| /// `StatePtr` points to the start of a particular row in this table. When |
| /// indexing to find the next state this allows us to avoid a multiplication |
| /// when computing an index into the table. |
| </span><span class="attribute">#[derive(Clone)] |
| </span><span class="kw">struct </span>Transitions { |
| <span class="doccomment">/// The table. |
| </span>table: Vec<StatePtr>, |
| <span class="doccomment">/// The stride. |
| </span>num_byte_classes: usize, |
| } |
| |
| <span class="doccomment">/// Fsm encapsulates the actual execution of the DFA. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>Fsm<<span class="lifetime">'a</span>> { |
| <span class="doccomment">/// prog contains the NFA instruction opcodes. DFA execution uses either |
| /// the `dfa` instructions or the `dfa_reverse` instructions from |
| /// `exec::ExecReadOnly`. (It never uses `ExecReadOnly.nfa`, which may have |
| /// Unicode opcodes that cannot be executed by the DFA.) |
| </span>prog: <span class="kw-2">&</span><span class="lifetime">'a </span>Program, |
| <span class="doccomment">/// The start state. We record it here because the pointer may change |
| /// when the cache is wiped. |
| </span>start: StatePtr, |
| <span class="doccomment">/// The current position in the input. |
| </span>at: usize, |
| <span class="doccomment">/// Should we quit after seeing the first match? e.g., When the caller |
| /// uses `is_match` or `shortest_match`. |
| </span>quit_after_match: bool, |
| <span class="doccomment">/// The last state that matched. |
| /// |
| /// When no match has occurred, this is set to STATE_UNKNOWN. |
| /// |
| /// This is only useful when matching regex sets. The last match state |
| /// is useful because it contains all of the match instructions seen, |
| /// thereby allowing us to enumerate which regexes in the set matched. |
| </span>last_match_si: StatePtr, |
| <span class="doccomment">/// The input position of the last cache flush. We use this to determine |
| /// if we're thrashing in the cache too often. If so, the DFA quits so |
| /// that we can fall back to the NFA algorithm. |
| </span>last_cache_flush: usize, |
| <span class="doccomment">/// All cached DFA information that is persisted between searches. |
| </span>cache: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>CacheInner, |
| } |
| |
| <span class="doccomment">/// The result of running the DFA. |
| /// |
| /// Generally, the result is either a match or not a match, but sometimes the |
| /// DFA runs too slowly because the cache size is too small. In that case, it |
| /// gives up with the intent of falling back to the NFA algorithm. |
| /// |
| /// The DFA can also give up if it runs out of room to create new states, or if |
| /// it sees non-ASCII bytes in the presence of a Unicode word boundary. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub enum </span><span class="prelude-ty">Result</span><T> { |
| Match(T), |
| NoMatch(usize), |
| Quit, |
| } |
| |
| <span class="kw">impl</span><T> <span class="prelude-ty">Result</span><T> { |
| <span class="doccomment">/// Returns true if this result corresponds to a match. |
| </span><span class="kw">pub fn </span>is_match(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">match </span><span class="kw-2">*</span><span class="self">self </span>{ |
| Result::Match(<span class="kw">_</span>) => <span class="bool-val">true</span>, |
| Result::NoMatch(<span class="kw">_</span>) | Result::Quit => <span class="bool-val">false</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Maps the given function onto T and returns the result. |
| /// |
| /// If this isn't a match, then this is a no-op. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"perf-literal"</span>)] |
| </span><span class="kw">pub fn </span>map<U, F: FnMut(T) -> U>(<span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> <span class="prelude-ty">Result</span><U> { |
| <span class="kw">match </span><span class="self">self </span>{ |
| Result::Match(t) => Result::Match(f(t)), |
| Result::NoMatch(x) => Result::NoMatch(x), |
| Result::Quit => Result::Quit, |
| } |
| } |
| |
| <span class="doccomment">/// Sets the non-match position. |
| /// |
| /// If this isn't a non-match, then this is a no-op. |
| </span><span class="kw">fn </span>set_non_match(<span class="self">self</span>, at: usize) -> <span class="prelude-ty">Result</span><T> { |
| <span class="kw">match </span><span class="self">self </span>{ |
| Result::NoMatch(<span class="kw">_</span>) => Result::NoMatch(at), |
| r => r, |
| } |
| } |
| } |
| |
| <span class="doccomment">/// `State` is a DFA state. It contains an ordered set of NFA states (not |
| /// necessarily complete) and a smattering of flags. |
| /// |
| /// The flags are packed into the first byte of data. |
| /// |
| /// States don't carry their transitions. Instead, transitions are stored in |
| /// a single row-major table. |
| /// |
| /// Delta encoding is used to store the instruction pointers. |
| /// The first instruction pointer is stored directly starting |
| /// at data[1], and each following pointer is stored as an offset |
| /// to the previous one. If a delta is in the range -127..127, |
| /// it is packed into a single byte; Otherwise the byte 128 (-128 as an i8) |
| /// is coded as a flag, followed by 4 bytes encoding the delta. |
| </span><span class="attribute">#[derive(Clone, Eq, Hash, PartialEq)] |
| </span><span class="kw">struct </span>State { |
| data: Arc<[u8]>, |
| } |
| |
| <span class="doccomment">/// `InstPtr` is a 32 bit pointer into a sequence of opcodes (i.e., it indexes |
| /// an NFA state). |
| /// |
| /// Throughout this library, this is usually set to `usize`, but we force a |
| /// `u32` here for the DFA to save on space. |
| </span><span class="kw">type </span>InstPtr = u32; |
| |
| <span class="doccomment">/// Adds ip to data using delta encoding with respect to prev. |
| /// |
| /// After completion, `data` will contain `ip` and `prev` will be set to `ip`. |
| </span><span class="kw">fn </span>push_inst_ptr(data: <span class="kw-2">&mut </span>Vec<u8>, prev: <span class="kw-2">&mut </span>InstPtr, ip: InstPtr) { |
| <span class="kw">let </span>delta = (ip <span class="kw">as </span>i32) - (<span class="kw-2">*</span>prev <span class="kw">as </span>i32); |
| write_vari32(data, delta); |
| <span class="kw-2">*</span>prev = ip; |
| } |
| |
| <span class="kw">struct </span>InstPtrs<<span class="lifetime">'a</span>> { |
| base: usize, |
| data: <span class="kw-2">&</span><span class="lifetime">'a </span>[u8], |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Iterator <span class="kw">for </span>InstPtrs<<span class="lifetime">'a</span>> { |
| <span class="kw">type </span>Item = usize; |
| |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="kw">if </span><span class="self">self</span>.data.is_empty() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="kw">let </span>(delta, nread) = read_vari32(<span class="self">self</span>.data); |
| <span class="kw">let </span>base = <span class="self">self</span>.base <span class="kw">as </span>i32 + delta; |
| <span class="macro">debug_assert!</span>(base >= <span class="number">0</span>); |
| <span class="macro">debug_assert!</span>(nread > <span class="number">0</span>); |
| <span class="self">self</span>.data = <span class="kw-2">&</span><span class="self">self</span>.data[nread..]; |
| <span class="self">self</span>.base = base <span class="kw">as </span>usize; |
| <span class="prelude-val">Some</span>(<span class="self">self</span>.base) |
| } |
| } |
| |
| <span class="kw">impl </span>State { |
| <span class="kw">fn </span>flags(<span class="kw-2">&</span><span class="self">self</span>) -> StateFlags { |
| StateFlags(<span class="self">self</span>.data[<span class="number">0</span>]) |
| } |
| |
| <span class="kw">fn </span>inst_ptrs(<span class="kw-2">&</span><span class="self">self</span>) -> InstPtrs<<span class="lifetime">'_</span>> { |
| InstPtrs { base: <span class="number">0</span>, data: <span class="kw-2">&</span><span class="self">self</span>.data[<span class="number">1</span>..] } |
| } |
| } |
| |
| <span class="doccomment">/// `StatePtr` is a 32 bit pointer to the start of a row in the transition |
| /// table. |
| /// |
| /// It has many special values. There are two types of special values: |
| /// sentinels and flags. |
| /// |
| /// Sentinels corresponds to special states that carry some kind of |
| /// significance. There are three such states: unknown, dead and quit states. |
| /// |
| /// Unknown states are states that haven't been computed yet. They indicate |
| /// that a transition should be filled in that points to either an existing |
| /// cached state or a new state altogether. In general, an unknown state means |
| /// "follow the NFA's epsilon transitions." |
| /// |
| /// Dead states are states that can never lead to a match, no matter what |
| /// subsequent input is observed. This means that the DFA should quit |
| /// immediately and return the longest match it has found thus far. |
| /// |
| /// Quit states are states that imply the DFA is not capable of matching the |
| /// regex correctly. Currently, this is only used when a Unicode word boundary |
| /// exists in the regex *and* a non-ASCII byte is observed. |
| /// |
| /// The other type of state pointer is a state pointer with special flag bits. |
| /// There are two flags: a start flag and a match flag. The lower bits of both |
| /// kinds always contain a "valid" `StatePtr` (indicated by the `STATE_MAX` |
| /// mask). |
| /// |
| /// The start flag means that the state is a start state, and therefore may be |
| /// subject to special prefix scanning optimizations. |
| /// |
| /// The match flag means that the state is a match state, and therefore the |
| /// current position in the input (while searching) should be recorded. |
| /// |
| /// The above exists mostly in the service of making the inner loop fast. |
| /// In particular, the inner *inner* loop looks something like this: |
| /// |
| /// ```ignore |
| /// while state <= STATE_MAX and i < len(text): |
| /// state = state.next[i] |
| /// ``` |
| /// |
| /// This is nice because it lets us execute a lazy DFA as if it were an |
| /// entirely offline DFA (i.e., with very few instructions). The loop will |
| /// quit only when we need to examine a case that needs special attention. |
| </span><span class="kw">type </span>StatePtr = u32; |
| |
| <span class="doccomment">/// An unknown state means that the state has not been computed yet, and that |
| /// the only way to progress is to compute it. |
| </span><span class="kw">const </span>STATE_UNKNOWN: StatePtr = <span class="number">1 </span><< <span class="number">31</span>; |
| |
| <span class="doccomment">/// A dead state means that the state has been computed and it is known that |
| /// once it is entered, no future match can ever occur. |
| </span><span class="kw">const </span>STATE_DEAD: StatePtr = STATE_UNKNOWN + <span class="number">1</span>; |
| |
| <span class="doccomment">/// A quit state means that the DFA came across some input that it doesn't |
| /// know how to process correctly. The DFA should quit and another matching |
| /// engine should be run in its place. |
| </span><span class="kw">const </span>STATE_QUIT: StatePtr = STATE_DEAD + <span class="number">1</span>; |
| |
| <span class="doccomment">/// A start state is a state that the DFA can start in. |
| /// |
| /// Note that start states have their lower bits set to a state pointer. |
| </span><span class="kw">const </span>STATE_START: StatePtr = <span class="number">1 </span><< <span class="number">30</span>; |
| |
| <span class="doccomment">/// A match state means that the regex has successfully matched. |
| /// |
| /// Note that match states have their lower bits set to a state pointer. |
| </span><span class="kw">const </span>STATE_MATCH: StatePtr = <span class="number">1 </span><< <span class="number">29</span>; |
| |
| <span class="doccomment">/// The maximum state pointer. This is useful to mask out the "valid" state |
| /// pointer from a state with the "start" or "match" bits set. |
| /// |
| /// It doesn't make sense to use this with unknown, dead or quit state |
| /// pointers, since those pointers are sentinels and never have their lower |
| /// bits set to anything meaningful. |
| </span><span class="kw">const </span>STATE_MAX: StatePtr = STATE_MATCH - <span class="number">1</span>; |
| |
| <span class="doccomment">/// Byte is a u8 in spirit, but a u16 in practice so that we can represent the |
| /// special EOF sentinel value. |
| </span><span class="attribute">#[derive(Copy, Clone, Debug)] |
| </span><span class="kw">struct </span>Byte(u16); |
| |
| <span class="doccomment">/// A set of flags for zero-width assertions. |
| </span><span class="attribute">#[derive(Clone, Copy, Eq, Debug, Default, Hash, PartialEq)] |
| </span><span class="kw">struct </span>EmptyFlags { |
| start: bool, |
| end: bool, |
| start_line: bool, |
| end_line: bool, |
| word_boundary: bool, |
| not_word_boundary: bool, |
| } |
| |
| <span class="doccomment">/// A set of flags describing various configurations of a DFA state. This is |
| /// represented by a `u8` so that it is compact. |
| </span><span class="attribute">#[derive(Clone, Copy, Eq, Default, Hash, PartialEq)] |
| </span><span class="kw">struct </span>StateFlags(u8); |
| |
| <span class="kw">impl </span>Cache { |
| <span class="doccomment">/// Create new empty cache for the DFA engine. |
| </span><span class="kw">pub fn </span>new(prog: <span class="kw-2">&</span>Program) -> <span class="self">Self </span>{ |
| <span class="comment">// We add 1 to account for the special EOF byte. |
| </span><span class="kw">let </span>num_byte_classes = (prog.byte_classes[<span class="number">255</span>] <span class="kw">as </span>usize + <span class="number">1</span>) + <span class="number">1</span>; |
| <span class="kw">let </span>starts = <span class="macro">vec!</span>[STATE_UNKNOWN; <span class="number">256</span>]; |
| <span class="kw">let </span><span class="kw-2">mut </span>cache = Cache { |
| inner: CacheInner { |
| compiled: StateMap::new(num_byte_classes), |
| trans: Transitions::new(num_byte_classes), |
| start_states: starts, |
| stack: <span class="macro">vec!</span>[], |
| flush_count: <span class="number">0</span>, |
| size: <span class="number">0</span>, |
| insts_scratch_space: <span class="macro">vec!</span>[], |
| }, |
| qcur: SparseSet::new(prog.insts.len()), |
| qnext: SparseSet::new(prog.insts.len()), |
| }; |
| cache.inner.reset_size(); |
| cache |
| } |
| } |
| |
| <span class="kw">impl </span>CacheInner { |
| <span class="doccomment">/// Resets the cache size to account for fixed costs, such as the program |
| /// and stack sizes. |
| </span><span class="kw">fn </span>reset_size(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.size = (<span class="self">self</span>.start_states.len() * mem::size_of::<StatePtr>()) |
| + (<span class="self">self</span>.stack.len() * mem::size_of::<InstPtr>()); |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Fsm<<span class="lifetime">'a</span>> { |
| <span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">pub fn </span>forward( |
| prog: <span class="kw-2">&</span><span class="lifetime">'a </span>Program, |
| cache: <span class="kw-2">&</span>ProgramCache, |
| quit_after_match: bool, |
| text: <span class="kw-2">&</span>[u8], |
| at: usize, |
| ) -> <span class="prelude-ty">Result</span><usize> { |
| <span class="kw">let </span><span class="kw-2">mut </span>cache = cache.borrow_mut(); |
| <span class="kw">let </span>cache = <span class="kw-2">&mut </span>cache.dfa; |
| <span class="kw">let </span><span class="kw-2">mut </span>dfa = Fsm { |
| prog, |
| start: <span class="number">0</span>, <span class="comment">// filled in below |
| </span>at, |
| quit_after_match, |
| last_match_si: STATE_UNKNOWN, |
| last_cache_flush: at, |
| cache: <span class="kw-2">&mut </span>cache.inner, |
| }; |
| <span class="kw">let </span>(empty_flags, state_flags) = dfa.start_flags(text, at); |
| dfa.start = |
| <span class="kw">match </span>dfa.start_state(<span class="kw-2">&mut </span>cache.qcur, empty_flags, state_flags) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>Result::NoMatch(at), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(dfa.start != STATE_UNKNOWN); |
| dfa.exec_at(<span class="kw-2">&mut </span>cache.qcur, <span class="kw-2">&mut </span>cache.qnext, text) |
| } |
| |
| <span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">pub fn </span>reverse( |
| prog: <span class="kw-2">&</span><span class="lifetime">'a </span>Program, |
| cache: <span class="kw-2">&</span>ProgramCache, |
| quit_after_match: bool, |
| text: <span class="kw-2">&</span>[u8], |
| at: usize, |
| ) -> <span class="prelude-ty">Result</span><usize> { |
| <span class="kw">let </span><span class="kw-2">mut </span>cache = cache.borrow_mut(); |
| <span class="kw">let </span>cache = <span class="kw-2">&mut </span>cache.dfa_reverse; |
| <span class="kw">let </span><span class="kw-2">mut </span>dfa = Fsm { |
| prog, |
| start: <span class="number">0</span>, <span class="comment">// filled in below |
| </span>at, |
| quit_after_match, |
| last_match_si: STATE_UNKNOWN, |
| last_cache_flush: at, |
| cache: <span class="kw-2">&mut </span>cache.inner, |
| }; |
| <span class="kw">let </span>(empty_flags, state_flags) = dfa.start_flags_reverse(text, at); |
| dfa.start = |
| <span class="kw">match </span>dfa.start_state(<span class="kw-2">&mut </span>cache.qcur, empty_flags, state_flags) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>Result::NoMatch(at), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(dfa.start != STATE_UNKNOWN); |
| dfa.exec_at_reverse(<span class="kw-2">&mut </span>cache.qcur, <span class="kw-2">&mut </span>cache.qnext, text) |
| } |
| |
| <span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">pub fn </span>forward_many( |
| prog: <span class="kw-2">&</span><span class="lifetime">'a </span>Program, |
| cache: <span class="kw-2">&</span>ProgramCache, |
| matches: <span class="kw-2">&mut </span>[bool], |
| text: <span class="kw-2">&</span>[u8], |
| at: usize, |
| ) -> <span class="prelude-ty">Result</span><usize> { |
| <span class="macro">debug_assert!</span>(matches.len() == prog.matches.len()); |
| <span class="kw">let </span><span class="kw-2">mut </span>cache = cache.borrow_mut(); |
| <span class="kw">let </span>cache = <span class="kw-2">&mut </span>cache.dfa; |
| <span class="kw">let </span><span class="kw-2">mut </span>dfa = Fsm { |
| prog, |
| start: <span class="number">0</span>, <span class="comment">// filled in below |
| </span>at, |
| quit_after_match: <span class="bool-val">false</span>, |
| last_match_si: STATE_UNKNOWN, |
| last_cache_flush: at, |
| cache: <span class="kw-2">&mut </span>cache.inner, |
| }; |
| <span class="kw">let </span>(empty_flags, state_flags) = dfa.start_flags(text, at); |
| dfa.start = |
| <span class="kw">match </span>dfa.start_state(<span class="kw-2">&mut </span>cache.qcur, empty_flags, state_flags) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>Result::NoMatch(at), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(dfa.start != STATE_UNKNOWN); |
| <span class="kw">let </span>result = dfa.exec_at(<span class="kw-2">&mut </span>cache.qcur, <span class="kw-2">&mut </span>cache.qnext, text); |
| <span class="kw">if </span>result.is_match() { |
| <span class="kw">if </span>matches.len() == <span class="number">1 </span>{ |
| matches[<span class="number">0</span>] = <span class="bool-val">true</span>; |
| } <span class="kw">else </span>{ |
| <span class="macro">debug_assert!</span>(dfa.last_match_si != STATE_UNKNOWN); |
| <span class="macro">debug_assert!</span>(dfa.last_match_si != STATE_DEAD); |
| <span class="kw">for </span>ip <span class="kw">in </span>dfa.state(dfa.last_match_si).inst_ptrs() { |
| <span class="kw">if let </span>Inst::Match(slot) = dfa.prog[ip] { |
| matches[slot] = <span class="bool-val">true</span>; |
| } |
| } |
| } |
| } |
| result |
| } |
| |
| <span class="doccomment">/// Executes the DFA on a forward NFA. |
| /// |
| /// {qcur,qnext} are scratch ordered sets which may be non-empty. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">fn </span>exec_at( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| qcur: <span class="kw-2">&mut </span>SparseSet, |
| qnext: <span class="kw-2">&mut </span>SparseSet, |
| text: <span class="kw-2">&</span>[u8], |
| ) -> <span class="prelude-ty">Result</span><usize> { |
| <span class="comment">// For the most part, the DFA is basically: |
| // |
| // last_match = null |
| // while current_byte != EOF: |
| // si = current_state.next[current_byte] |
| // if si is match |
| // last_match = si |
| // return last_match |
| // |
| // However, we need to deal with a few things: |
| // |
| // 1. This is an *online* DFA, so the current state's next list |
| // may not point to anywhere yet, so we must go out and compute |
| // them. (They are then cached into the current state's next list |
| // to avoid re-computation.) |
| // 2. If we come across a state that is known to be dead (i.e., never |
| // leads to a match), then we can quit early. |
| // 3. If the caller just wants to know if a match occurs, then we |
| // can quit as soon as we know we have a match. (Full leftmost |
| // first semantics require continuing on.) |
| // 4. If we're in the start state, then we can use a pre-computed set |
| // of prefix literals to skip quickly along the input. |
| // 5. After the input is exhausted, we run the DFA on one symbol |
| // that stands for EOF. This is useful for handling empty width |
| // assertions. |
| // 6. We can't actually do state.next[byte]. Instead, we have to do |
| // state.next[byte_classes[byte]], which permits us to keep the |
| // 'next' list very small. |
| // |
| // Since there's a bunch of extra stuff we need to consider, we do some |
| // pretty hairy tricks to get the inner loop to run as fast as |
| // possible. |
| </span><span class="macro">debug_assert!</span>(!<span class="self">self</span>.prog.is_reverse); |
| |
| <span class="comment">// The last match is the currently known ending match position. It is |
| // reported as an index to the most recent byte that resulted in a |
| // transition to a match state and is always stored in capture slot `1` |
| // when searching forwards. Its maximum value is `text.len()`. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>result = Result::NoMatch(<span class="self">self</span>.at); |
| <span class="kw">let </span>(<span class="kw-2">mut </span>prev_si, <span class="kw-2">mut </span>next_si) = (<span class="self">self</span>.start, <span class="self">self</span>.start); |
| <span class="kw">let </span><span class="kw-2">mut </span>at = <span class="self">self</span>.at; |
| <span class="kw">while </span>at < text.len() { |
| <span class="comment">// This is the real inner loop. We take advantage of special bits |
| // set in the state pointer to determine whether a state is in the |
| // "common" case or not. Specifically, the common case is a |
| // non-match non-start non-dead state that has already been |
| // computed. So long as we remain in the common case, this inner |
| // loop will chew through the input. |
| // |
| // We also unroll the loop 4 times to amortize the cost of checking |
| // whether we've consumed the entire input. We are also careful |
| // to make sure that `prev_si` always represents the previous state |
| // and `next_si` always represents the next state after the loop |
| // exits, even if it isn't always true inside the loop. |
| </span><span class="kw">while </span>next_si <= STATE_MAX && at < text.len() { |
| <span class="comment">// Argument for safety is in the definition of next_si. |
| </span>prev_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(next_si, text, at) }; |
| at += <span class="number">1</span>; |
| <span class="kw">if </span>prev_si > STATE_MAX || at + <span class="number">2 </span>>= text.len() { |
| mem::swap(<span class="kw-2">&mut </span>prev_si, <span class="kw-2">&mut </span>next_si); |
| <span class="kw">break</span>; |
| } |
| next_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(prev_si, text, at) }; |
| at += <span class="number">1</span>; |
| <span class="kw">if </span>next_si > STATE_MAX { |
| <span class="kw">break</span>; |
| } |
| prev_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(next_si, text, at) }; |
| at += <span class="number">1</span>; |
| <span class="kw">if </span>prev_si > STATE_MAX { |
| mem::swap(<span class="kw-2">&mut </span>prev_si, <span class="kw-2">&mut </span>next_si); |
| <span class="kw">break</span>; |
| } |
| next_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(prev_si, text, at) }; |
| at += <span class="number">1</span>; |
| } |
| <span class="kw">if </span>next_si & STATE_MATCH > <span class="number">0 </span>{ |
| <span class="comment">// A match state is outside of the common case because it needs |
| // special case analysis. In particular, we need to record the |
| // last position as having matched and possibly quit the DFA if |
| // we don't need to keep matching. |
| </span>next_si &= !STATE_MATCH; |
| result = Result::Match(at - <span class="number">1</span>); |
| <span class="kw">if </span><span class="self">self</span>.quit_after_match { |
| <span class="kw">return </span>result; |
| } |
| <span class="self">self</span>.last_match_si = next_si; |
| prev_si = next_si; |
| |
| <span class="comment">// This permits short-circuiting when matching a regex set. |
| // In particular, if this DFA state contains only match states, |
| // then it's impossible to extend the set of matches since |
| // match states are final. Therefore, we can quit. |
| </span><span class="kw">if </span><span class="self">self</span>.prog.matches.len() > <span class="number">1 </span>{ |
| <span class="kw">let </span>state = <span class="self">self</span>.state(next_si); |
| <span class="kw">let </span>just_matches = |
| state.inst_ptrs().all(|ip| <span class="self">self</span>.prog[ip].is_match()); |
| <span class="kw">if </span>just_matches { |
| <span class="kw">return </span>result; |
| } |
| } |
| |
| <span class="comment">// Another inner loop! If the DFA stays in this particular |
| // match state, then we can rip through all of the input |
| // very quickly, and only recording the match location once |
| // we've left this particular state. |
| </span><span class="kw">let </span>cur = at; |
| <span class="kw">while </span>(next_si & !STATE_MATCH) == prev_si |
| && at + <span class="number">2 </span>< text.len() |
| { |
| <span class="comment">// Argument for safety is in the definition of next_si. |
| </span>next_si = <span class="kw">unsafe </span>{ |
| <span class="self">self</span>.next_si(next_si & !STATE_MATCH, text, at) |
| }; |
| at += <span class="number">1</span>; |
| } |
| <span class="kw">if </span>at > cur { |
| result = Result::Match(at - <span class="number">2</span>); |
| } |
| } <span class="kw">else if </span>next_si & STATE_START > <span class="number">0 </span>{ |
| <span class="comment">// A start state isn't in the common case because we may |
| // want to do quick prefix scanning. If the program doesn't |
| // have a detected prefix, then start states are actually |
| // considered common and this case is never reached. |
| </span><span class="macro">debug_assert!</span>(<span class="self">self</span>.has_prefix()); |
| next_si &= !STATE_START; |
| prev_si = next_si; |
| at = <span class="kw">match </span><span class="self">self</span>.prefix_at(text, at) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::NoMatch(text.len()), |
| <span class="prelude-val">Some</span>(i) => i, |
| }; |
| } <span class="kw">else if </span>next_si >= STATE_UNKNOWN { |
| <span class="kw">if </span>next_si == STATE_QUIT { |
| <span class="kw">return </span>Result::Quit; |
| } |
| <span class="comment">// Finally, this corresponds to the case where the transition |
| // entered a state that can never lead to a match or a state |
| // that hasn't been computed yet. The latter being the "slow" |
| // path. |
| </span><span class="kw">let </span>byte = Byte::byte(text[at - <span class="number">1</span>]); |
| <span class="comment">// We no longer care about the special bits in the state |
| // pointer. |
| </span>prev_si &= STATE_MAX; |
| <span class="comment">// Record where we are. This is used to track progress for |
| // determining whether we should quit if we've flushed the |
| // cache too much. |
| </span><span class="self">self</span>.at = at; |
| next_si = <span class="kw">match </span><span class="self">self</span>.next_state(qcur, qnext, prev_si, byte) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>result.set_non_match(at), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(next_si != STATE_UNKNOWN); |
| <span class="kw">if </span>next_si & STATE_MATCH > <span class="number">0 </span>{ |
| next_si &= !STATE_MATCH; |
| result = Result::Match(at - <span class="number">1</span>); |
| <span class="kw">if </span><span class="self">self</span>.quit_after_match { |
| <span class="kw">return </span>result; |
| } |
| <span class="self">self</span>.last_match_si = next_si; |
| } |
| prev_si = next_si; |
| } <span class="kw">else </span>{ |
| prev_si = next_si; |
| } |
| } |
| |
| <span class="comment">// Run the DFA once more on the special EOF sentinel value. |
| // We don't care about the special bits in the state pointer any more, |
| // so get rid of them. |
| </span>prev_si &= STATE_MAX; |
| prev_si = <span class="kw">match </span><span class="self">self</span>.next_state(qcur, qnext, prev_si, Byte::eof()) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>result.set_non_match(text.len()), |
| <span class="prelude-val">Some</span>(si) => si & !STATE_START, |
| }; |
| <span class="macro">debug_assert!</span>(prev_si != STATE_UNKNOWN); |
| <span class="kw">if </span>prev_si & STATE_MATCH > <span class="number">0 </span>{ |
| prev_si &= !STATE_MATCH; |
| <span class="self">self</span>.last_match_si = prev_si; |
| result = Result::Match(text.len()); |
| } |
| result |
| } |
| |
| <span class="doccomment">/// Executes the DFA on a reverse NFA. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">fn </span>exec_at_reverse( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| qcur: <span class="kw-2">&mut </span>SparseSet, |
| qnext: <span class="kw-2">&mut </span>SparseSet, |
| text: <span class="kw-2">&</span>[u8], |
| ) -> <span class="prelude-ty">Result</span><usize> { |
| <span class="comment">// The comments in `exec_at` above mostly apply here too. The main |
| // difference is that we move backwards over the input and we look for |
| // the longest possible match instead of the leftmost-first match. |
| // |
| // N.B. The code duplication here is regrettable. Efforts to improve |
| // it without sacrificing performance are welcome. ---AG |
| </span><span class="macro">debug_assert!</span>(<span class="self">self</span>.prog.is_reverse); |
| <span class="kw">let </span><span class="kw-2">mut </span>result = Result::NoMatch(<span class="self">self</span>.at); |
| <span class="kw">let </span>(<span class="kw-2">mut </span>prev_si, <span class="kw-2">mut </span>next_si) = (<span class="self">self</span>.start, <span class="self">self</span>.start); |
| <span class="kw">let </span><span class="kw-2">mut </span>at = <span class="self">self</span>.at; |
| <span class="kw">while </span>at > <span class="number">0 </span>{ |
| <span class="kw">while </span>next_si <= STATE_MAX && at > <span class="number">0 </span>{ |
| <span class="comment">// Argument for safety is in the definition of next_si. |
| </span>at -= <span class="number">1</span>; |
| prev_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(next_si, text, at) }; |
| <span class="kw">if </span>prev_si > STATE_MAX || at <= <span class="number">4 </span>{ |
| mem::swap(<span class="kw-2">&mut </span>prev_si, <span class="kw-2">&mut </span>next_si); |
| <span class="kw">break</span>; |
| } |
| at -= <span class="number">1</span>; |
| next_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(prev_si, text, at) }; |
| <span class="kw">if </span>next_si > STATE_MAX { |
| <span class="kw">break</span>; |
| } |
| at -= <span class="number">1</span>; |
| prev_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(next_si, text, at) }; |
| <span class="kw">if </span>prev_si > STATE_MAX { |
| mem::swap(<span class="kw-2">&mut </span>prev_si, <span class="kw-2">&mut </span>next_si); |
| <span class="kw">break</span>; |
| } |
| at -= <span class="number">1</span>; |
| next_si = <span class="kw">unsafe </span>{ <span class="self">self</span>.next_si(prev_si, text, at) }; |
| } |
| <span class="kw">if </span>next_si & STATE_MATCH > <span class="number">0 </span>{ |
| next_si &= !STATE_MATCH; |
| result = Result::Match(at + <span class="number">1</span>); |
| <span class="kw">if </span><span class="self">self</span>.quit_after_match { |
| <span class="kw">return </span>result; |
| } |
| <span class="self">self</span>.last_match_si = next_si; |
| prev_si = next_si; |
| <span class="kw">let </span>cur = at; |
| <span class="kw">while </span>(next_si & !STATE_MATCH) == prev_si && at >= <span class="number">2 </span>{ |
| <span class="comment">// Argument for safety is in the definition of next_si. |
| </span>at -= <span class="number">1</span>; |
| next_si = <span class="kw">unsafe </span>{ |
| <span class="self">self</span>.next_si(next_si & !STATE_MATCH, text, at) |
| }; |
| } |
| <span class="kw">if </span>at < cur { |
| result = Result::Match(at + <span class="number">2</span>); |
| } |
| } <span class="kw">else if </span>next_si >= STATE_UNKNOWN { |
| <span class="kw">if </span>next_si == STATE_QUIT { |
| <span class="kw">return </span>Result::Quit; |
| } |
| <span class="kw">let </span>byte = Byte::byte(text[at]); |
| prev_si &= STATE_MAX; |
| <span class="self">self</span>.at = at; |
| next_si = <span class="kw">match </span><span class="self">self</span>.next_state(qcur, qnext, prev_si, byte) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>result.set_non_match(at), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(next_si != STATE_UNKNOWN); |
| <span class="kw">if </span>next_si & STATE_MATCH > <span class="number">0 </span>{ |
| next_si &= !STATE_MATCH; |
| result = Result::Match(at + <span class="number">1</span>); |
| <span class="kw">if </span><span class="self">self</span>.quit_after_match { |
| <span class="kw">return </span>result; |
| } |
| <span class="self">self</span>.last_match_si = next_si; |
| } |
| prev_si = next_si; |
| } <span class="kw">else </span>{ |
| prev_si = next_si; |
| } |
| } |
| |
| <span class="comment">// Run the DFA once more on the special EOF sentinel value. |
| </span>prev_si = <span class="kw">match </span><span class="self">self</span>.next_state(qcur, qnext, prev_si, Byte::eof()) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>Result::Quit, |
| <span class="prelude-val">Some</span>(STATE_DEAD) => <span class="kw">return </span>result.set_non_match(<span class="number">0</span>), |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="macro">debug_assert!</span>(prev_si != STATE_UNKNOWN); |
| <span class="kw">if </span>prev_si & STATE_MATCH > <span class="number">0 </span>{ |
| prev_si &= !STATE_MATCH; |
| <span class="self">self</span>.last_match_si = prev_si; |
| result = Result::Match(<span class="number">0</span>); |
| } |
| result |
| } |
| |
| <span class="doccomment">/// next_si transitions to the next state, where the transition input |
| /// corresponds to text[i]. |
| /// |
| /// This elides bounds checks, and is therefore not safe. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">unsafe fn </span>next_si(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr, text: <span class="kw-2">&</span>[u8], i: usize) -> StatePtr { |
| <span class="comment">// What is the argument for safety here? |
| // We have three unchecked accesses that could possibly violate safety: |
| // |
| // 1. The given byte of input (`text[i]`). |
| // 2. The class of the byte of input (`classes[text[i]]`). |
| // 3. The transition for the class (`trans[si + cls]`). |
| // |
| // (1) is only safe when calling next_si is guarded by |
| // `i < text.len()`. |
| // |
| // (2) is the easiest case to guarantee since `text[i]` is always a |
| // `u8` and `self.prog.byte_classes` always has length `u8::MAX`. |
| // (See `ByteClassSet.byte_classes` in `compile.rs`.) |
| // |
| // (3) is only safe if (1)+(2) are safe. Namely, the transitions |
| // of every state are defined to have length equal to the number of |
| // byte classes in the program. Therefore, a valid class leads to a |
| // valid transition. (All possible transitions are valid lookups, even |
| // if it points to a state that hasn't been computed yet.) (3) also |
| // relies on `si` being correct, but StatePtrs should only ever be |
| // retrieved from the transition table, which ensures they are correct. |
| </span><span class="macro">debug_assert!</span>(i < text.len()); |
| <span class="kw">let </span>b = <span class="kw-2">*</span>text.get_unchecked(i); |
| <span class="macro">debug_assert!</span>((b <span class="kw">as </span>usize) < <span class="self">self</span>.prog.byte_classes.len()); |
| <span class="kw">let </span>cls = <span class="kw-2">*</span><span class="self">self</span>.prog.byte_classes.get_unchecked(b <span class="kw">as </span>usize); |
| <span class="self">self</span>.cache.trans.next_unchecked(si, cls <span class="kw">as </span>usize) |
| } |
| |
| <span class="doccomment">/// Computes the next state given the current state and the current input |
| /// byte (which may be EOF). |
| /// |
| /// If STATE_DEAD is returned, then there is no valid state transition. |
| /// This implies that no permutation of future input can lead to a match |
| /// state. |
| /// |
| /// STATE_UNKNOWN can never be returned. |
| </span><span class="kw">fn </span>exec_byte( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| qcur: <span class="kw-2">&mut </span>SparseSet, |
| qnext: <span class="kw-2">&mut </span>SparseSet, |
| <span class="kw-2">mut </span>si: StatePtr, |
| b: Byte, |
| ) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| |
| <span class="comment">// Initialize a queue with the current DFA state's NFA states. |
| </span>qcur.clear(); |
| <span class="kw">for </span>ip <span class="kw">in </span><span class="self">self</span>.state(si).inst_ptrs() { |
| qcur.insert(ip); |
| } |
| |
| <span class="comment">// Before inspecting the current byte, we may need to also inspect |
| // whether the position immediately preceding the current byte |
| // satisfies the empty assertions found in the current state. |
| // |
| // We only need to do this step if there are any empty assertions in |
| // the current state. |
| </span><span class="kw">let </span>is_word_last = <span class="self">self</span>.state(si).flags().is_word(); |
| <span class="kw">let </span>is_word = b.is_ascii_word(); |
| <span class="kw">if </span><span class="self">self</span>.state(si).flags().has_empty() { |
| <span class="comment">// Compute the flags immediately preceding the current byte. |
| // This means we only care about the "end" or "end line" flags. |
| // (The "start" flags are computed immediately following the |
| // current byte and are handled below.) |
| </span><span class="kw">let </span><span class="kw-2">mut </span>flags = EmptyFlags::default(); |
| <span class="kw">if </span>b.is_eof() { |
| flags.end = <span class="bool-val">true</span>; |
| flags.end_line = <span class="bool-val">true</span>; |
| } <span class="kw">else if </span>b.as_byte().map_or(<span class="bool-val">false</span>, |b| b == <span class="string">b'\n'</span>) { |
| flags.end_line = <span class="bool-val">true</span>; |
| } |
| <span class="kw">if </span>is_word_last == is_word { |
| flags.not_word_boundary = <span class="bool-val">true</span>; |
| } <span class="kw">else </span>{ |
| flags.word_boundary = <span class="bool-val">true</span>; |
| } |
| <span class="comment">// Now follow epsilon transitions from every NFA state, but make |
| // sure we only follow transitions that satisfy our flags. |
| </span>qnext.clear(); |
| <span class="kw">for </span><span class="kw-2">&</span>ip <span class="kw">in </span><span class="kw-2">&*</span>qcur { |
| <span class="self">self</span>.follow_epsilons(usize_to_u32(ip), qnext, flags); |
| } |
| mem::swap(qcur, qnext); |
| } |
| |
| <span class="comment">// Now we set flags for immediately after the current byte. Since start |
| // states are processed separately, and are the only states that can |
| // have the StartText flag set, we therefore only need to worry about |
| // the StartLine flag here. |
| // |
| // We do also keep track of whether this DFA state contains a NFA state |
| // that is a matching state. This is precisely how we delay the DFA |
| // matching by one byte in order to process the special EOF sentinel |
| // byte. Namely, if this DFA state containing a matching NFA state, |
| // then it is the *next* DFA state that is marked as a match. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>empty_flags = EmptyFlags::default(); |
| <span class="kw">let </span><span class="kw-2">mut </span>state_flags = StateFlags::default(); |
| empty_flags.start_line = b.as_byte().map_or(<span class="bool-val">false</span>, |b| b == <span class="string">b'\n'</span>); |
| <span class="kw">if </span>b.is_ascii_word() { |
| state_flags.set_word(); |
| } |
| <span class="comment">// Now follow all epsilon transitions again, but only after consuming |
| // the current byte. |
| </span>qnext.clear(); |
| <span class="kw">for </span><span class="kw-2">&</span>ip <span class="kw">in </span><span class="kw-2">&*</span>qcur { |
| <span class="kw">match </span><span class="self">self</span>.prog[ip <span class="kw">as </span>usize] { |
| <span class="comment">// These states never happen in a byte-based program. |
| </span>Char(<span class="kw">_</span>) | Ranges(<span class="kw">_</span>) => <span class="macro">unreachable!</span>(), |
| <span class="comment">// These states are handled when following epsilon transitions. |
| </span>Save(<span class="kw">_</span>) | Split(<span class="kw">_</span>) | EmptyLook(<span class="kw">_</span>) => {} |
| Match(<span class="kw">_</span>) => { |
| state_flags.set_match(); |
| <span class="kw">if </span>!<span class="self">self</span>.continue_past_first_match() { |
| <span class="kw">break</span>; |
| } <span class="kw">else if </span><span class="self">self</span>.prog.matches.len() > <span class="number">1 |
| </span>&& !qnext.contains(ip <span class="kw">as </span>usize) |
| { |
| <span class="comment">// If we are continuing on to find other matches, |
| // then keep a record of the match states we've seen. |
| </span>qnext.insert(ip); |
| } |
| } |
| Bytes(<span class="kw-2">ref </span>inst) => { |
| <span class="kw">if </span>b.as_byte().map_or(<span class="bool-val">false</span>, |b| inst.matches(b)) { |
| <span class="self">self</span>.follow_epsilons( |
| inst.goto <span class="kw">as </span>InstPtr, |
| qnext, |
| empty_flags, |
| ); |
| } |
| } |
| } |
| } |
| |
| <span class="kw">let </span>cache = <span class="kw">if </span>b.is_eof() && <span class="self">self</span>.prog.matches.len() > <span class="number">1 </span>{ |
| <span class="comment">// If we're processing the last byte of the input and we're |
| // matching a regex set, then make the next state contain the |
| // previous states transitions. We do this so that the main |
| // matching loop can extract all of the match instructions. |
| </span>mem::swap(qcur, qnext); |
| <span class="comment">// And don't cache this state because it's totally bunk. |
| </span><span class="bool-val">false |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">true |
| </span>}; |
| |
| <span class="comment">// We've now built up the set of NFA states that ought to comprise the |
| // next DFA state, so try to find it in the cache, and if it doesn't |
| // exist, cache it. |
| // |
| // N.B. We pass `&mut si` here because the cache may clear itself if |
| // it has gotten too full. When that happens, the location of the |
| // current state may change. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>next = |
| <span class="kw">match </span><span class="self">self</span>.cached_state(qnext, state_flags, <span class="prelude-val">Some</span>(<span class="kw-2">&mut </span>si)) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>(next) => next, |
| }; |
| <span class="kw">if </span>(<span class="self">self</span>.start & !STATE_START) == next { |
| <span class="comment">// Start states can never be match states since all matches are |
| // delayed by one byte. |
| </span><span class="macro">debug_assert!</span>(!<span class="self">self</span>.state(next).flags().is_match()); |
| next = <span class="self">self</span>.start_ptr(next); |
| } |
| <span class="kw">if </span>next <= STATE_MAX && <span class="self">self</span>.state(next).flags().is_match() { |
| next |= STATE_MATCH; |
| } |
| <span class="macro">debug_assert!</span>(next != STATE_UNKNOWN); |
| <span class="comment">// And now store our state in the current state's next list. |
| </span><span class="kw">if </span>cache { |
| <span class="kw">let </span>cls = <span class="self">self</span>.byte_class(b); |
| <span class="self">self</span>.cache.trans.set_next(si, cls, next); |
| } |
| <span class="prelude-val">Some</span>(next) |
| } |
| |
| <span class="doccomment">/// Follows the epsilon transitions starting at (and including) `ip`. The |
| /// resulting states are inserted into the ordered set `q`. |
| /// |
| /// Conditional epsilon transitions (i.e., empty width assertions) are only |
| /// followed if they are satisfied by the given flags, which should |
| /// represent the flags set at the current location in the input. |
| /// |
| /// If the current location corresponds to the empty string, then only the |
| /// end line and/or end text flags may be set. If the current location |
| /// corresponds to a real byte in the input, then only the start line |
| /// and/or start text flags may be set. |
| /// |
| /// As an exception to the above, when finding the initial state, any of |
| /// the above flags may be set: |
| /// |
| /// If matching starts at the beginning of the input, then start text and |
| /// start line should be set. If the input is empty, then end text and end |
| /// line should also be set. |
| /// |
| /// If matching starts after the beginning of the input, then only start |
| /// line should be set if the preceding byte is `\n`. End line should never |
| /// be set in this case. (Even if the following byte is a `\n`, it will |
| /// be handled in a subsequent DFA state.) |
| </span><span class="kw">fn </span>follow_epsilons( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| ip: InstPtr, |
| q: <span class="kw-2">&mut </span>SparseSet, |
| flags: EmptyFlags, |
| ) { |
| <span class="kw">use </span><span class="kw">crate</span>::prog::EmptyLook::<span class="kw-2">*</span>; |
| <span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| |
| <span class="comment">// We need to traverse the NFA to follow epsilon transitions, so avoid |
| // recursion with an explicit stack. |
| </span><span class="self">self</span>.cache.stack.push(ip); |
| <span class="kw">while let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>ip) = <span class="self">self</span>.cache.stack.pop() { |
| <span class="comment">// Try to munch through as many states as possible without |
| // pushes/pops to the stack. |
| </span><span class="kw">loop </span>{ |
| <span class="comment">// Don't visit states we've already added. |
| </span><span class="kw">if </span>q.contains(ip <span class="kw">as </span>usize) { |
| <span class="kw">break</span>; |
| } |
| q.insert(ip <span class="kw">as </span>usize); |
| <span class="kw">match </span><span class="self">self</span>.prog[ip <span class="kw">as </span>usize] { |
| Char(<span class="kw">_</span>) | Ranges(<span class="kw">_</span>) => <span class="macro">unreachable!</span>(), |
| Match(<span class="kw">_</span>) | Bytes(<span class="kw">_</span>) => { |
| <span class="kw">break</span>; |
| } |
| EmptyLook(<span class="kw-2">ref </span>inst) => { |
| <span class="comment">// Only follow empty assertion states if our flags |
| // satisfy the assertion. |
| </span><span class="kw">match </span>inst.look { |
| StartLine <span class="kw">if </span>flags.start_line => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| EndLine <span class="kw">if </span>flags.end_line => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| StartText <span class="kw">if </span>flags.start => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| EndText <span class="kw">if </span>flags.end => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| WordBoundaryAscii <span class="kw">if </span>flags.word_boundary => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| NotWordBoundaryAscii |
| <span class="kw">if </span>flags.not_word_boundary => |
| { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| WordBoundary <span class="kw">if </span>flags.word_boundary => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| NotWordBoundary <span class="kw">if </span>flags.not_word_boundary => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| StartLine | EndLine | StartText | EndText |
| | WordBoundaryAscii | NotWordBoundaryAscii |
| | WordBoundary | NotWordBoundary => { |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| Save(<span class="kw-2">ref </span>inst) => { |
| ip = inst.goto <span class="kw">as </span>InstPtr; |
| } |
| Split(<span class="kw-2">ref </span>inst) => { |
| <span class="self">self</span>.cache.stack.push(inst.goto2 <span class="kw">as </span>InstPtr); |
| ip = inst.goto1 <span class="kw">as </span>InstPtr; |
| } |
| } |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Find a previously computed state matching the given set of instructions |
| /// and is_match bool. |
| /// |
| /// The given set of instructions should represent a single state in the |
| /// NFA along with all states reachable without consuming any input. |
| /// |
| /// The is_match bool should be true if and only if the preceding DFA state |
| /// contains an NFA matching state. The cached state produced here will |
| /// then signify a match. (This enables us to delay a match by one byte, |
| /// in order to account for the EOF sentinel byte.) |
| /// |
| /// If the cache is full, then it is wiped before caching a new state. |
| /// |
| /// The current state should be specified if it exists, since it will need |
| /// to be preserved if the cache clears itself. (Start states are |
| /// always saved, so they should not be passed here.) It takes a mutable |
| /// pointer to the index because if the cache is cleared, the state's |
| /// location may change. |
| </span><span class="kw">fn </span>cached_state( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| q: <span class="kw-2">&</span>SparseSet, |
| <span class="kw-2">mut </span>state_flags: StateFlags, |
| current_state: <span class="prelude-ty">Option</span><<span class="kw-2">&mut </span>StatePtr>, |
| ) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="comment">// If we couldn't come up with a non-empty key to represent this state, |
| // then it is dead and can never lead to a match. |
| // |
| // Note that inst_flags represent the set of empty width assertions |
| // in q. We use this as an optimization in exec_byte to determine when |
| // we should follow epsilon transitions at the empty string preceding |
| // the current byte. |
| </span><span class="kw">let </span>key = <span class="kw">match </span><span class="self">self</span>.cached_state_key(q, <span class="kw-2">&mut </span>state_flags) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">Some</span>(STATE_DEAD), |
| <span class="prelude-val">Some</span>(v) => v, |
| }; |
| <span class="comment">// In the cache? Cool. Done. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(si) = <span class="self">self</span>.cache.compiled.get_ptr(<span class="kw-2">&</span>key) { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(si); |
| } |
| <span class="comment">// If the cache has gotten too big, wipe it. |
| </span><span class="kw">if </span><span class="self">self</span>.approximate_size() > <span class="self">self</span>.prog.dfa_size_limit |
| && !<span class="self">self</span>.clear_cache_and_save(current_state) |
| { |
| <span class="comment">// Ooops. DFA is giving up. |
| </span><span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="comment">// Allocate room for our state and add it. |
| </span><span class="self">self</span>.add_state(key) |
| } |
| |
| <span class="doccomment">/// Produces a key suitable for describing a state in the DFA cache. |
| /// |
| /// The key invariant here is that equivalent keys are produced for any two |
| /// sets of ordered NFA states (and toggling of whether the previous NFA |
| /// states contain a match state) that do not discriminate a match for any |
| /// input. |
| /// |
| /// Specifically, q should be an ordered set of NFA states and is_match |
| /// should be true if and only if the previous NFA states contained a match |
| /// state. |
| </span><span class="kw">fn </span>cached_state_key( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| q: <span class="kw-2">&</span>SparseSet, |
| state_flags: <span class="kw-2">&mut </span>StateFlags, |
| ) -> <span class="prelude-ty">Option</span><State> { |
| <span class="kw">use </span><span class="kw">crate</span>::prog::Inst::<span class="kw-2">*</span>; |
| |
| <span class="comment">// We need to build up enough information to recognize pre-built states |
| // in the DFA. Generally speaking, this includes every instruction |
| // except for those which are purely epsilon transitions, e.g., the |
| // Save and Split instructions. |
| // |
| // Empty width assertions are also epsilon transitions, but since they |
| // are conditional, we need to make them part of a state's key in the |
| // cache. |
| |
| </span><span class="kw">let </span><span class="kw-2">mut </span>insts = |
| mem::replace(<span class="kw-2">&mut </span><span class="self">self</span>.cache.insts_scratch_space, <span class="macro">vec!</span>[]); |
| insts.clear(); |
| <span class="comment">// Reserve 1 byte for flags. |
| </span>insts.push(<span class="number">0</span>); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>prev = <span class="number">0</span>; |
| <span class="kw">for </span><span class="kw-2">&</span>ip <span class="kw">in </span>q { |
| <span class="kw">let </span>ip = usize_to_u32(ip); |
| <span class="kw">match </span><span class="self">self</span>.prog[ip <span class="kw">as </span>usize] { |
| Char(<span class="kw">_</span>) | Ranges(<span class="kw">_</span>) => <span class="macro">unreachable!</span>(), |
| Save(<span class="kw">_</span>) | Split(<span class="kw">_</span>) => {} |
| Bytes(<span class="kw">_</span>) => push_inst_ptr(<span class="kw-2">&mut </span>insts, <span class="kw-2">&mut </span>prev, ip), |
| EmptyLook(<span class="kw">_</span>) => { |
| state_flags.set_empty(); |
| push_inst_ptr(<span class="kw-2">&mut </span>insts, <span class="kw-2">&mut </span>prev, ip) |
| } |
| Match(<span class="kw">_</span>) => { |
| push_inst_ptr(<span class="kw-2">&mut </span>insts, <span class="kw-2">&mut </span>prev, ip); |
| <span class="kw">if </span>!<span class="self">self</span>.continue_past_first_match() { |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| } |
| <span class="comment">// If we couldn't transition to any other instructions and we didn't |
| // see a match when expanding NFA states previously, then this is a |
| // dead state and no amount of additional input can transition out |
| // of this state. |
| </span><span class="kw">let </span>opt_state = <span class="kw">if </span>insts.len() == <span class="number">1 </span>&& !state_flags.is_match() { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="kw">let </span>StateFlags(f) = <span class="kw-2">*</span>state_flags; |
| insts[<span class="number">0</span>] = f; |
| <span class="prelude-val">Some</span>(State { data: Arc::from(<span class="kw-2">&*</span>insts) }) |
| }; |
| <span class="self">self</span>.cache.insts_scratch_space = insts; |
| opt_state |
| } |
| |
| <span class="doccomment">/// Clears the cache, but saves and restores current_state if it is not |
| /// none. |
| /// |
| /// The current state must be provided here in case its location in the |
| /// cache changes. |
| /// |
| /// This returns false if the cache is not cleared and the DFA should |
| /// give up. |
| </span><span class="kw">fn </span>clear_cache_and_save( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| current_state: <span class="prelude-ty">Option</span><<span class="kw-2">&mut </span>StatePtr>, |
| ) -> bool { |
| <span class="kw">if </span><span class="self">self</span>.cache.compiled.is_empty() { |
| <span class="comment">// Nothing to clear... |
| </span><span class="kw">return </span><span class="bool-val">true</span>; |
| } |
| <span class="kw">match </span>current_state { |
| <span class="prelude-val">None </span>=> <span class="self">self</span>.clear_cache(), |
| <span class="prelude-val">Some</span>(si) => { |
| <span class="kw">let </span>cur = <span class="self">self</span>.state(<span class="kw-2">*</span>si).clone(); |
| <span class="kw">if </span>!<span class="self">self</span>.clear_cache() { |
| <span class="kw">return </span><span class="bool-val">false</span>; |
| } |
| <span class="comment">// The unwrap is OK because we just cleared the cache and |
| // therefore know that the next state pointer won't exceed |
| // STATE_MAX. |
| </span><span class="kw-2">*</span>si = <span class="self">self</span>.restore_state(cur).unwrap(); |
| <span class="bool-val">true |
| </span>} |
| } |
| } |
| |
| <span class="doccomment">/// Wipes the state cache, but saves and restores the current start state. |
| /// |
| /// This returns false if the cache is not cleared and the DFA should |
| /// give up. |
| </span><span class="kw">fn </span>clear_cache(<span class="kw-2">&mut </span><span class="self">self</span>) -> bool { |
| <span class="comment">// Bail out of the DFA if we're moving too "slowly." |
| // A heuristic from RE2: assume the DFA is too slow if it is processing |
| // 10 or fewer bytes per state. |
| // Additionally, we permit the cache to be flushed a few times before |
| // caling it quits. |
| </span><span class="kw">let </span>nstates = <span class="self">self</span>.cache.compiled.len(); |
| <span class="kw">if </span><span class="self">self</span>.cache.flush_count >= <span class="number">3 |
| </span>&& <span class="self">self</span>.at >= <span class="self">self</span>.last_cache_flush |
| && (<span class="self">self</span>.at - <span class="self">self</span>.last_cache_flush) <= <span class="number">10 </span>* nstates |
| { |
| <span class="kw">return </span><span class="bool-val">false</span>; |
| } |
| <span class="comment">// Update statistics tracking cache flushes. |
| </span><span class="self">self</span>.last_cache_flush = <span class="self">self</span>.at; |
| <span class="self">self</span>.cache.flush_count += <span class="number">1</span>; |
| |
| <span class="comment">// OK, actually flush the cache. |
| </span><span class="kw">let </span>start = <span class="self">self</span>.state(<span class="self">self</span>.start & !STATE_START).clone(); |
| <span class="kw">let </span>last_match = <span class="kw">if </span><span class="self">self</span>.last_match_si <= STATE_MAX { |
| <span class="prelude-val">Some</span>(<span class="self">self</span>.state(<span class="self">self</span>.last_match_si).clone()) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>}; |
| <span class="self">self</span>.cache.reset_size(); |
| <span class="self">self</span>.cache.trans.clear(); |
| <span class="self">self</span>.cache.compiled.clear(); |
| <span class="kw">for </span>s <span class="kw">in </span><span class="kw-2">&mut </span><span class="self">self</span>.cache.start_states { |
| <span class="kw-2">*</span>s = STATE_UNKNOWN; |
| } |
| <span class="comment">// The unwraps are OK because we just cleared the cache and therefore |
| // know that the next state pointer won't exceed STATE_MAX. |
| </span><span class="kw">let </span>start_ptr = <span class="self">self</span>.restore_state(start).unwrap(); |
| <span class="self">self</span>.start = <span class="self">self</span>.start_ptr(start_ptr); |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(last_match) = last_match { |
| <span class="self">self</span>.last_match_si = <span class="self">self</span>.restore_state(last_match).unwrap(); |
| } |
| <span class="bool-val">true |
| </span>} |
| |
| <span class="doccomment">/// Restores the given state back into the cache, and returns a pointer |
| /// to it. |
| </span><span class="kw">fn </span>restore_state(<span class="kw-2">&mut </span><span class="self">self</span>, state: State) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="comment">// If we've already stored this state, just return a pointer to it. |
| // None will be the wiser. |
| </span><span class="kw">if let </span><span class="prelude-val">Some</span>(si) = <span class="self">self</span>.cache.compiled.get_ptr(<span class="kw-2">&</span>state) { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(si); |
| } |
| <span class="self">self</span>.add_state(state) |
| } |
| |
| <span class="doccomment">/// Returns the next state given the current state si and current byte |
| /// b. {qcur,qnext} are used as scratch space for storing ordered NFA |
| /// states. |
| /// |
| /// This tries to fetch the next state from the cache, but if that fails, |
| /// it computes the next state, caches it and returns a pointer to it. |
| /// |
| /// The pointer can be to a real state, or it can be STATE_DEAD. |
| /// STATE_UNKNOWN cannot be returned. |
| /// |
| /// None is returned if a new state could not be allocated (i.e., the DFA |
| /// ran out of space and thinks it's running too slowly). |
| </span><span class="kw">fn </span>next_state( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| qcur: <span class="kw-2">&mut </span>SparseSet, |
| qnext: <span class="kw-2">&mut </span>SparseSet, |
| si: StatePtr, |
| b: Byte, |
| ) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="kw">if </span>si == STATE_DEAD { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(STATE_DEAD); |
| } |
| <span class="kw">match </span><span class="self">self</span>.cache.trans.next(si, <span class="self">self</span>.byte_class(b)) { |
| STATE_UNKNOWN => <span class="self">self</span>.exec_byte(qcur, qnext, si, b), |
| STATE_QUIT => <span class="prelude-val">None</span>, |
| nsi => <span class="prelude-val">Some</span>(nsi), |
| } |
| } |
| |
| <span class="doccomment">/// Computes and returns the start state, where searching begins at |
| /// position `at` in `text`. If the state has already been computed, |
| /// then it is pulled from the cache. If the state hasn't been cached, |
| /// then it is computed, cached and a pointer to it is returned. |
| /// |
| /// This may return STATE_DEAD but never STATE_UNKNOWN. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">fn </span>start_state( |
| <span class="kw-2">&mut </span><span class="self">self</span>, |
| q: <span class="kw-2">&mut </span>SparseSet, |
| empty_flags: EmptyFlags, |
| state_flags: StateFlags, |
| ) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="comment">// Compute an index into our cache of start states based on the set |
| // of empty/state flags set at the current position in the input. We |
| // don't use every flag since not all flags matter. For example, since |
| // matches are delayed by one byte, start states can never be match |
| // states. |
| </span><span class="kw">let </span>flagi = { |
| (((empty_flags.start <span class="kw">as </span>u8) << <span class="number">0</span>) |
| | ((empty_flags.end <span class="kw">as </span>u8) << <span class="number">1</span>) |
| | ((empty_flags.start_line <span class="kw">as </span>u8) << <span class="number">2</span>) |
| | ((empty_flags.end_line <span class="kw">as </span>u8) << <span class="number">3</span>) |
| | ((empty_flags.word_boundary <span class="kw">as </span>u8) << <span class="number">4</span>) |
| | ((empty_flags.not_word_boundary <span class="kw">as </span>u8) << <span class="number">5</span>) |
| | ((state_flags.is_word() <span class="kw">as </span>u8) << <span class="number">6</span>)) <span class="kw">as </span>usize |
| }; |
| <span class="kw">match </span><span class="self">self</span>.cache.start_states[flagi] { |
| STATE_UNKNOWN => {} |
| si => <span class="kw">return </span><span class="prelude-val">Some</span>(si), |
| } |
| q.clear(); |
| <span class="kw">let </span>start = usize_to_u32(<span class="self">self</span>.prog.start); |
| <span class="self">self</span>.follow_epsilons(start, q, empty_flags); |
| <span class="comment">// Start states can never be match states because we delay every match |
| // by one byte. Given an empty string and an empty match, the match |
| // won't actually occur until the DFA processes the special EOF |
| // sentinel byte. |
| </span><span class="kw">let </span>sp = <span class="kw">match </span><span class="self">self</span>.cached_state(q, state_flags, <span class="prelude-val">None</span>) { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>(sp) => <span class="self">self</span>.start_ptr(sp), |
| }; |
| <span class="self">self</span>.cache.start_states[flagi] = sp; |
| <span class="prelude-val">Some</span>(sp) |
| } |
| |
| <span class="doccomment">/// Computes the set of starting flags for the given position in text. |
| /// |
| /// This should only be used when executing the DFA forwards over the |
| /// input. |
| </span><span class="kw">fn </span>start_flags(<span class="kw-2">&</span><span class="self">self</span>, text: <span class="kw-2">&</span>[u8], at: usize) -> (EmptyFlags, StateFlags) { |
| <span class="kw">let </span><span class="kw-2">mut </span>empty_flags = EmptyFlags::default(); |
| <span class="kw">let </span><span class="kw-2">mut </span>state_flags = StateFlags::default(); |
| empty_flags.start = at == <span class="number">0</span>; |
| empty_flags.end = text.is_empty(); |
| empty_flags.start_line = at == <span class="number">0 </span>|| text[at - <span class="number">1</span>] == <span class="string">b'\n'</span>; |
| empty_flags.end_line = text.is_empty(); |
| |
| <span class="kw">let </span>is_word_last = at > <span class="number">0 </span>&& Byte::byte(text[at - <span class="number">1</span>]).is_ascii_word(); |
| <span class="kw">let </span>is_word = at < text.len() && Byte::byte(text[at]).is_ascii_word(); |
| <span class="kw">if </span>is_word_last { |
| state_flags.set_word(); |
| } |
| <span class="kw">if </span>is_word == is_word_last { |
| empty_flags.not_word_boundary = <span class="bool-val">true</span>; |
| } <span class="kw">else </span>{ |
| empty_flags.word_boundary = <span class="bool-val">true</span>; |
| } |
| (empty_flags, state_flags) |
| } |
| |
| <span class="doccomment">/// Computes the set of starting flags for the given position in text. |
| /// |
| /// This should only be used when executing the DFA in reverse over the |
| /// input. |
| </span><span class="kw">fn </span>start_flags_reverse( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| text: <span class="kw-2">&</span>[u8], |
| at: usize, |
| ) -> (EmptyFlags, StateFlags) { |
| <span class="kw">let </span><span class="kw-2">mut </span>empty_flags = EmptyFlags::default(); |
| <span class="kw">let </span><span class="kw-2">mut </span>state_flags = StateFlags::default(); |
| empty_flags.start = at == text.len(); |
| empty_flags.end = text.is_empty(); |
| empty_flags.start_line = at == text.len() || text[at] == <span class="string">b'\n'</span>; |
| empty_flags.end_line = text.is_empty(); |
| |
| <span class="kw">let </span>is_word_last = |
| at < text.len() && Byte::byte(text[at]).is_ascii_word(); |
| <span class="kw">let </span>is_word = at > <span class="number">0 </span>&& Byte::byte(text[at - <span class="number">1</span>]).is_ascii_word(); |
| <span class="kw">if </span>is_word_last { |
| state_flags.set_word(); |
| } |
| <span class="kw">if </span>is_word == is_word_last { |
| empty_flags.not_word_boundary = <span class="bool-val">true</span>; |
| } <span class="kw">else </span>{ |
| empty_flags.word_boundary = <span class="bool-val">true</span>; |
| } |
| (empty_flags, state_flags) |
| } |
| |
| <span class="doccomment">/// Returns a reference to a State given a pointer to it. |
| </span><span class="kw">fn </span>state(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr) -> <span class="kw-2">&</span>State { |
| <span class="self">self</span>.cache.compiled.get_state(si).unwrap() |
| } |
| |
| <span class="doccomment">/// Adds the given state to the DFA. |
| /// |
| /// This allocates room for transitions out of this state in |
| /// self.cache.trans. The transitions can be set with the returned |
| /// StatePtr. |
| /// |
| /// If None is returned, then the state limit was reached and the DFA |
| /// should quit. |
| </span><span class="kw">fn </span>add_state(<span class="kw-2">&mut </span><span class="self">self</span>, state: State) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="comment">// This will fail if the next state pointer exceeds STATE_PTR. In |
| // practice, the cache limit will prevent us from ever getting here, |
| // but maybe callers will set the cache size to something ridiculous... |
| </span><span class="kw">let </span>si = <span class="kw">match </span><span class="self">self</span>.cache.trans.add() { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">None</span>, |
| <span class="prelude-val">Some</span>(si) => si, |
| }; |
| <span class="comment">// If the program has a Unicode word boundary, then set any transitions |
| // for non-ASCII bytes to STATE_QUIT. If the DFA stumbles over such a |
| // transition, then it will quit and an alternative matching engine |
| // will take over. |
| </span><span class="kw">if </span><span class="self">self</span>.prog.has_unicode_word_boundary { |
| <span class="kw">for </span>b <span class="kw">in </span><span class="number">128</span>..<span class="number">256 </span>{ |
| <span class="kw">let </span>cls = <span class="self">self</span>.byte_class(Byte::byte(b <span class="kw">as </span>u8)); |
| <span class="self">self</span>.cache.trans.set_next(si, cls, STATE_QUIT); |
| } |
| } |
| <span class="comment">// Finally, put our actual state on to our heap of states and index it |
| // so we can find it later. |
| </span><span class="self">self</span>.cache.size += <span class="self">self</span>.cache.trans.state_heap_size() |
| + state.data.len() |
| + (<span class="number">2 </span>* mem::size_of::<State>()) |
| + mem::size_of::<StatePtr>(); |
| <span class="self">self</span>.cache.compiled.insert(state, si); |
| <span class="comment">// Transition table and set of states and map should all be in sync. |
| </span><span class="macro">debug_assert!</span>( |
| <span class="self">self</span>.cache.compiled.len() == <span class="self">self</span>.cache.trans.num_states() |
| ); |
| <span class="prelude-val">Some</span>(si) |
| } |
| |
| <span class="doccomment">/// Quickly finds the next occurrence of any literal prefixes in the regex. |
| /// If there are no literal prefixes, then the current position is |
| /// returned. If there are literal prefixes and one could not be found, |
| /// then None is returned. |
| /// |
| /// This should only be called when the DFA is in a start state. |
| </span><span class="kw">fn </span>prefix_at(<span class="kw-2">&</span><span class="self">self</span>, text: <span class="kw-2">&</span>[u8], at: usize) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="self">self</span>.prog.prefixes.find(<span class="kw-2">&</span>text[at..]).map(|(s, <span class="kw">_</span>)| at + s) |
| } |
| |
| <span class="doccomment">/// Returns the number of byte classes required to discriminate transitions |
| /// in each state. |
| /// |
| /// invariant: num_byte_classes() == len(State.next) |
| </span><span class="kw">fn </span>num_byte_classes(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="comment">// We add 1 to account for the special EOF byte. |
| </span>(<span class="self">self</span>.prog.byte_classes[<span class="number">255</span>] <span class="kw">as </span>usize + <span class="number">1</span>) + <span class="number">1 |
| </span>} |
| |
| <span class="doccomment">/// Given an input byte or the special EOF sentinel, return its |
| /// corresponding byte class. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">fn </span>byte_class(<span class="kw-2">&</span><span class="self">self</span>, b: Byte) -> usize { |
| <span class="kw">match </span>b.as_byte() { |
| <span class="prelude-val">None </span>=> <span class="self">self</span>.num_byte_classes() - <span class="number">1</span>, |
| <span class="prelude-val">Some</span>(b) => <span class="self">self</span>.u8_class(b), |
| } |
| } |
| |
| <span class="doccomment">/// Like byte_class, but explicitly for u8s. |
| </span><span class="attribute">#[cfg_attr(feature = <span class="string">"perf-inline"</span>, inline(always))] |
| </span><span class="kw">fn </span>u8_class(<span class="kw-2">&</span><span class="self">self</span>, b: u8) -> usize { |
| <span class="self">self</span>.prog.byte_classes[b <span class="kw">as </span>usize] <span class="kw">as </span>usize |
| } |
| |
| <span class="doccomment">/// Returns true if the DFA should continue searching past the first match. |
| /// |
| /// Leftmost first semantics in the DFA are preserved by not following NFA |
| /// transitions after the first match is seen. |
| /// |
| /// On occasion, we want to avoid leftmost first semantics to find either |
| /// the longest match (for reverse search) or all possible matches (for |
| /// regex sets). |
| </span><span class="kw">fn </span>continue_past_first_match(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.prog.is_reverse || <span class="self">self</span>.prog.matches.len() > <span class="number">1 |
| </span>} |
| |
| <span class="doccomment">/// Returns true if there is a prefix we can quickly search for. |
| </span><span class="kw">fn </span>has_prefix(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| !<span class="self">self</span>.prog.is_reverse |
| && !<span class="self">self</span>.prog.prefixes.is_empty() |
| && !<span class="self">self</span>.prog.is_anchored_start |
| } |
| |
| <span class="doccomment">/// Sets the STATE_START bit in the given state pointer if and only if |
| /// we have a prefix to scan for. |
| /// |
| /// If there's no prefix, then it's a waste to treat the start state |
| /// specially. |
| </span><span class="kw">fn </span>start_ptr(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr) -> StatePtr { |
| <span class="kw">if </span><span class="self">self</span>.has_prefix() { |
| si | STATE_START |
| } <span class="kw">else </span>{ |
| si |
| } |
| } |
| |
| <span class="doccomment">/// Approximate size returns the approximate heap space currently used by |
| /// the DFA. It is used to determine whether the DFA's state cache needs to |
| /// be wiped. Namely, it is possible that for certain regexes on certain |
| /// inputs, a new state could be created for every byte of input. (This is |
| /// bad for memory use, so we bound it with a cache.) |
| </span><span class="kw">fn </span>approximate_size(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.cache.size |
| } |
| } |
| |
| <span class="doccomment">/// An abstraction for representing a map of states. The map supports two |
| /// different ways of state lookup. One is fast constant time access via a |
| /// state pointer. The other is a hashmap lookup based on the DFA's |
| /// constituent NFA states. |
| /// |
| /// A DFA state internally uses an Arc such that we only need to store the |
| /// set of NFA states on the heap once, even though we support looking up |
| /// states by two different means. A more natural way to express this might |
| /// use raw pointers, but an Arc is safe and effectively achieves the same |
| /// thing. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>StateMap { |
| <span class="doccomment">/// The keys are not actually static but rely on always pointing to a |
| /// buffer in `states` which will never be moved except when clearing |
| /// the map or on drop, in which case the keys of this map will be |
| /// removed before |
| </span>map: HashMap<State, StatePtr>, |
| <span class="doccomment">/// Our set of states. Note that `StatePtr / num_byte_classes` indexes |
| /// this Vec rather than just a `StatePtr`. |
| </span>states: Vec<State>, |
| <span class="doccomment">/// The number of byte classes in the DFA. Used to index `states`. |
| </span>num_byte_classes: usize, |
| } |
| |
| <span class="kw">impl </span>StateMap { |
| <span class="kw">fn </span>new(num_byte_classes: usize) -> StateMap { |
| StateMap { map: HashMap::new(), states: <span class="macro">vec!</span>[], num_byte_classes } |
| } |
| |
| <span class="kw">fn </span>len(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.states.len() |
| } |
| |
| <span class="kw">fn </span>is_empty(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.states.is_empty() |
| } |
| |
| <span class="kw">fn </span>get_ptr(<span class="kw-2">&</span><span class="self">self</span>, state: <span class="kw-2">&</span>State) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="self">self</span>.map.get(state).cloned() |
| } |
| |
| <span class="kw">fn </span>get_state(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span>State> { |
| <span class="self">self</span>.states.get(si <span class="kw">as </span>usize / <span class="self">self</span>.num_byte_classes) |
| } |
| |
| <span class="kw">fn </span>insert(<span class="kw-2">&mut </span><span class="self">self</span>, state: State, si: StatePtr) { |
| <span class="self">self</span>.map.insert(state.clone(), si); |
| <span class="self">self</span>.states.push(state); |
| } |
| |
| <span class="kw">fn </span>clear(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.map.clear(); |
| <span class="self">self</span>.states.clear(); |
| } |
| } |
| |
| <span class="kw">impl </span>Transitions { |
| <span class="doccomment">/// Create a new transition table. |
| /// |
| /// The number of byte classes corresponds to the stride. Every state will |
| /// have `num_byte_classes` slots for transitions. |
| </span><span class="kw">fn </span>new(num_byte_classes: usize) -> Transitions { |
| Transitions { table: <span class="macro">vec!</span>[], num_byte_classes } |
| } |
| |
| <span class="doccomment">/// Returns the total number of states currently in this table. |
| </span><span class="kw">fn </span>num_states(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.table.len() / <span class="self">self</span>.num_byte_classes |
| } |
| |
| <span class="doccomment">/// Allocates room for one additional state and returns a pointer to it. |
| /// |
| /// If there's no more room, None is returned. |
| </span><span class="kw">fn </span>add(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><StatePtr> { |
| <span class="kw">let </span>si = <span class="self">self</span>.table.len(); |
| <span class="kw">if </span>si > STATE_MAX <span class="kw">as </span>usize { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| <span class="self">self</span>.table.extend(repeat(STATE_UNKNOWN).take(<span class="self">self</span>.num_byte_classes)); |
| <span class="prelude-val">Some</span>(usize_to_u32(si)) |
| } |
| |
| <span class="doccomment">/// Clears the table of all states. |
| </span><span class="kw">fn </span>clear(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.table.clear(); |
| } |
| |
| <span class="doccomment">/// Sets the transition from (si, cls) to next. |
| </span><span class="kw">fn </span>set_next(<span class="kw-2">&mut </span><span class="self">self</span>, si: StatePtr, cls: usize, next: StatePtr) { |
| <span class="self">self</span>.table[si <span class="kw">as </span>usize + cls] = next; |
| } |
| |
| <span class="doccomment">/// Returns the transition corresponding to (si, cls). |
| </span><span class="kw">fn </span>next(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr, cls: usize) -> StatePtr { |
| <span class="self">self</span>.table[si <span class="kw">as </span>usize + cls] |
| } |
| |
| <span class="doccomment">/// The heap size, in bytes, of a single state in the transition table. |
| </span><span class="kw">fn </span>state_heap_size(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.num_byte_classes * mem::size_of::<StatePtr>() |
| } |
| |
| <span class="doccomment">/// Like `next`, but uses unchecked access and is therefore not safe. |
| </span><span class="kw">unsafe fn </span>next_unchecked(<span class="kw-2">&</span><span class="self">self</span>, si: StatePtr, cls: usize) -> StatePtr { |
| <span class="macro">debug_assert!</span>((si <span class="kw">as </span>usize) < <span class="self">self</span>.table.len()); |
| <span class="macro">debug_assert!</span>(cls < <span class="self">self</span>.num_byte_classes); |
| <span class="kw-2">*</span><span class="self">self</span>.table.get_unchecked(si <span class="kw">as </span>usize + cls) |
| } |
| } |
| |
| <span class="kw">impl </span>StateFlags { |
| <span class="kw">fn </span>is_match(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& <span class="number">0b0000_0001 </span>> <span class="number">0 |
| </span>} |
| |
| <span class="kw">fn </span>set_match(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= <span class="number">0b0000_0001</span>; |
| } |
| |
| <span class="kw">fn </span>is_word(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& <span class="number">0b0000_0010 </span>> <span class="number">0 |
| </span>} |
| |
| <span class="kw">fn </span>set_word(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= <span class="number">0b0000_0010</span>; |
| } |
| |
| <span class="kw">fn </span>has_empty(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& <span class="number">0b0000_0100 </span>> <span class="number">0 |
| </span>} |
| |
| <span class="kw">fn </span>set_empty(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= <span class="number">0b0000_0100</span>; |
| } |
| } |
| |
| <span class="kw">impl </span>Byte { |
| <span class="kw">fn </span>byte(b: u8) -> <span class="self">Self </span>{ |
| Byte(b <span class="kw">as </span>u16) |
| } |
| <span class="kw">fn </span>eof() -> <span class="self">Self </span>{ |
| Byte(<span class="number">256</span>) |
| } |
| <span class="kw">fn </span>is_eof(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>== <span class="number">256 |
| </span>} |
| |
| <span class="kw">fn </span>is_ascii_word(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span>b = <span class="kw">match </span><span class="self">self</span>.as_byte() { |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="bool-val">false</span>, |
| <span class="prelude-val">Some</span>(b) => b, |
| }; |
| <span class="kw">match </span>b { |
| <span class="string">b'A'</span>..=<span class="string">b'Z' </span>| <span class="string">b'a'</span>..=<span class="string">b'z' </span>| <span class="string">b'0'</span>..=<span class="string">b'9' </span>| <span class="string">b'_' </span>=> <span class="bool-val">true</span>, |
| <span class="kw">_ </span>=> <span class="bool-val">false</span>, |
| } |
| } |
| |
| <span class="kw">fn </span>as_byte(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><u8> { |
| <span class="kw">if </span><span class="self">self</span>.is_eof() { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="prelude-val">Some</span>(<span class="self">self</span>.<span class="number">0 </span><span class="kw">as </span>u8) |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>State { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">let </span>ips: Vec<usize> = <span class="self">self</span>.inst_ptrs().collect(); |
| f.debug_struct(<span class="string">"State"</span>) |
| .field(<span class="string">"flags"</span>, <span class="kw-2">&</span><span class="self">self</span>.flags()) |
| .field(<span class="string">"insts"</span>, <span class="kw-2">&</span>ips) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Transitions { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">let </span><span class="kw-2">mut </span>fmtd = f.debug_map(); |
| <span class="kw">for </span>si <span class="kw">in </span><span class="number">0</span>..<span class="self">self</span>.num_states() { |
| <span class="kw">let </span>s = si * <span class="self">self</span>.num_byte_classes; |
| <span class="kw">let </span>e = s + <span class="self">self</span>.num_byte_classes; |
| fmtd.entry(<span class="kw-2">&</span>si.to_string(), <span class="kw-2">&</span>TransitionsRow(<span class="kw-2">&</span><span class="self">self</span>.table[s..e])); |
| } |
| fmtd.finish() |
| } |
| } |
| |
| <span class="kw">struct </span>TransitionsRow<<span class="lifetime">'a</span>>(<span class="kw-2">&</span><span class="lifetime">'a </span>[StatePtr]); |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> fmt::Debug <span class="kw">for </span>TransitionsRow<<span class="lifetime">'a</span>> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">let </span><span class="kw-2">mut </span>fmtd = f.debug_map(); |
| <span class="kw">for </span>(b, si) <span class="kw">in </span><span class="self">self</span>.<span class="number">0</span>.iter().enumerate() { |
| <span class="kw">match </span><span class="kw-2">*</span>si { |
| STATE_UNKNOWN => {} |
| STATE_DEAD => { |
| fmtd.entry(<span class="kw-2">&</span>vb(b <span class="kw">as </span>usize), <span class="kw-2">&</span><span class="string">"DEAD"</span>); |
| } |
| si => { |
| fmtd.entry(<span class="kw-2">&</span>vb(b <span class="kw">as </span>usize), <span class="kw-2">&</span>si.to_string()); |
| } |
| } |
| } |
| fmtd.finish() |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>StateFlags { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"StateFlags"</span>) |
| .field(<span class="string">"is_match"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_match()) |
| .field(<span class="string">"is_word"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_word()) |
| .field(<span class="string">"has_empty"</span>, <span class="kw-2">&</span><span class="self">self</span>.has_empty()) |
| .finish() |
| } |
| } |
| |
| <span class="doccomment">/// Helper function for formatting a byte as a nice-to-read escaped string. |
| </span><span class="kw">fn </span>vb(b: usize) -> String { |
| <span class="kw">use </span>std::ascii::escape_default; |
| |
| <span class="kw">if </span>b > ::std::u8::MAX <span class="kw">as </span>usize { |
| <span class="string">"EOF"</span>.to_owned() |
| } <span class="kw">else </span>{ |
| <span class="kw">let </span>escaped = escape_default(b <span class="kw">as </span>u8).collect::<Vec<u8>>(); |
| String::from_utf8_lossy(<span class="kw-2">&</span>escaped).into_owned() |
| } |
| } |
| |
| <span class="kw">fn </span>usize_to_u32(n: usize) -> u32 { |
| <span class="kw">if </span>(n <span class="kw">as </span>u64) > (::std::u32::MAX <span class="kw">as </span>u64) { |
| <span class="macro">panic!</span>(<span class="string">"BUG: {} is too big to fit into u32"</span>, n) |
| } |
| n <span class="kw">as </span>u32 |
| } |
| |
| <span class="attribute">#[allow(dead_code)] </span><span class="comment">// useful for debugging |
| </span><span class="kw">fn </span>show_state_ptr(si: StatePtr) -> String { |
| <span class="kw">let </span><span class="kw-2">mut </span>s = <span class="macro">format!</span>(<span class="string">"{:?}"</span>, si & STATE_MAX); |
| <span class="kw">if </span>si == STATE_UNKNOWN { |
| s = <span class="macro">format!</span>(<span class="string">"{} (unknown)"</span>, s); |
| } |
| <span class="kw">if </span>si == STATE_DEAD { |
| s = <span class="macro">format!</span>(<span class="string">"{} (dead)"</span>, s); |
| } |
| <span class="kw">if </span>si == STATE_QUIT { |
| s = <span class="macro">format!</span>(<span class="string">"{} (quit)"</span>, s); |
| } |
| <span class="kw">if </span>si & STATE_START > <span class="number">0 </span>{ |
| s = <span class="macro">format!</span>(<span class="string">"{} (start)"</span>, s); |
| } |
| <span class="kw">if </span>si & STATE_MATCH > <span class="number">0 </span>{ |
| s = <span class="macro">format!</span>(<span class="string">"{} (match)"</span>, s); |
| } |
| s |
| } |
| |
| <span class="doccomment">/// https://developers.google.com/protocol-buffers/docs/encoding#varints |
| </span><span class="kw">fn </span>write_vari32(data: <span class="kw-2">&mut </span>Vec<u8>, n: i32) { |
| <span class="kw">let </span><span class="kw-2">mut </span>un = (n <span class="kw">as </span>u32) << <span class="number">1</span>; |
| <span class="kw">if </span>n < <span class="number">0 </span>{ |
| un = !un; |
| } |
| write_varu32(data, un) |
| } |
| |
| <span class="doccomment">/// https://developers.google.com/protocol-buffers/docs/encoding#varints |
| </span><span class="kw">fn </span>read_vari32(data: <span class="kw-2">&</span>[u8]) -> (i32, usize) { |
| <span class="kw">let </span>(un, i) = read_varu32(data); |
| <span class="kw">let </span><span class="kw-2">mut </span>n = (un >> <span class="number">1</span>) <span class="kw">as </span>i32; |
| <span class="kw">if </span>un & <span class="number">1 </span>!= <span class="number">0 </span>{ |
| n = !n; |
| } |
| (n, i) |
| } |
| |
| <span class="doccomment">/// https://developers.google.com/protocol-buffers/docs/encoding#varints |
| </span><span class="kw">fn </span>write_varu32(data: <span class="kw-2">&mut </span>Vec<u8>, <span class="kw-2">mut </span>n: u32) { |
| <span class="kw">while </span>n >= <span class="number">0b1000_0000 </span>{ |
| data.push((n <span class="kw">as </span>u8) | <span class="number">0b1000_0000</span>); |
| n >>= <span class="number">7</span>; |
| } |
| data.push(n <span class="kw">as </span>u8); |
| } |
| |
| <span class="doccomment">/// https://developers.google.com/protocol-buffers/docs/encoding#varints |
| </span><span class="kw">fn </span>read_varu32(data: <span class="kw-2">&</span>[u8]) -> (u32, usize) { |
| <span class="kw">let </span><span class="kw-2">mut </span>n: u32 = <span class="number">0</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>shift: u32 = <span class="number">0</span>; |
| <span class="kw">for </span>(i, <span class="kw-2">&</span>b) <span class="kw">in </span>data.iter().enumerate() { |
| <span class="kw">if </span>b < <span class="number">0b1000_0000 </span>{ |
| <span class="kw">return </span>(n | ((b <span class="kw">as </span>u32) << shift), i + <span class="number">1</span>); |
| } |
| n |= ((b <span class="kw">as </span>u32) & <span class="number">0b0111_1111</span>) << shift; |
| shift += <span class="number">7</span>; |
| } |
| (<span class="number">0</span>, <span class="number">0</span>) |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| |
| <span class="kw">use super</span>::{ |
| push_inst_ptr, read_vari32, read_varu32, write_vari32, write_varu32, |
| State, StateFlags, |
| }; |
| <span class="kw">use </span>quickcheck::{quickcheck, Gen, QuickCheck}; |
| <span class="kw">use </span>std::sync::Arc; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_state_encode_decode() { |
| <span class="kw">fn </span>p(<span class="kw-2">mut </span>ips: Vec<u32>, flags: u8) -> bool { |
| <span class="comment">// It looks like our encoding scheme can't handle instruction |
| // pointers at or above 2**31. We should fix that, but it seems |
| // unlikely to occur in real code due to the amount of memory |
| // required for such a state machine. So for now, we just clamp |
| // our test data. |
| </span><span class="kw">for </span>ip <span class="kw">in </span><span class="kw-2">&mut </span>ips { |
| <span class="kw">if </span><span class="kw-2">*</span>ip >= <span class="number">1 </span><< <span class="number">31 </span>{ |
| <span class="kw-2">*</span>ip = (<span class="number">1 </span><< <span class="number">31</span>) - <span class="number">1</span>; |
| } |
| } |
| <span class="kw">let </span><span class="kw-2">mut </span>data = <span class="macro">vec!</span>[flags]; |
| <span class="kw">let </span><span class="kw-2">mut </span>prev = <span class="number">0</span>; |
| <span class="kw">for </span><span class="kw-2">&</span>ip <span class="kw">in </span>ips.iter() { |
| push_inst_ptr(<span class="kw-2">&mut </span>data, <span class="kw-2">&mut </span>prev, ip); |
| } |
| <span class="kw">let </span>state = State { data: Arc::from(<span class="kw-2">&</span>data[..]) }; |
| |
| <span class="kw">let </span>expected: Vec<usize> = |
| ips.into_iter().map(|ip| ip <span class="kw">as </span>usize).collect(); |
| <span class="kw">let </span>got: Vec<usize> = state.inst_ptrs().collect(); |
| expected == got && state.flags() == StateFlags(flags) |
| } |
| QuickCheck::new() |
| .gen(Gen::new(<span class="number">10_000</span>)) |
| .quickcheck(p <span class="kw">as fn</span>(Vec<u32>, u8) -> bool); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_read_write_u32() { |
| <span class="kw">fn </span>p(n: u32) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>buf = <span class="macro">vec!</span>[]; |
| write_varu32(<span class="kw-2">&mut </span>buf, n); |
| <span class="kw">let </span>(got, nread) = read_varu32(<span class="kw-2">&</span>buf); |
| nread == buf.len() && got == n |
| } |
| quickcheck(p <span class="kw">as fn</span>(u32) -> bool); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>prop_read_write_i32() { |
| <span class="kw">fn </span>p(n: i32) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>buf = <span class="macro">vec!</span>[]; |
| write_vari32(<span class="kw-2">&mut </span>buf, n); |
| <span class="kw">let </span>(got, nread) = read_vari32(<span class="kw-2">&</span>buf); |
| nread == buf.len() && got == n |
| } |
| quickcheck(p <span class="kw">as fn</span>(i32) -> bool); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="regex" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |