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| </pre><pre class="rust"><code><span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::mem::MaybeUninit; |
| |
| <span class="doccomment">/// A wrapper around a byte buffer that is incrementally filled and initialized. |
| /// |
| /// This type is a sort of "double cursor". It tracks three regions in the |
| /// buffer: a region at the beginning of the buffer that has been logically |
| /// filled with data, a region that has been initialized at some point but not |
| /// yet logically filled, and a region at the end that may be uninitialized. |
| /// The filled region is guaranteed to be a subset of the initialized region. |
| /// |
| /// In summary, the contents of the buffer can be visualized as: |
| /// |
| /// ```not_rust |
| /// [ capacity ] |
| /// [ filled | unfilled ] |
| /// [ initialized | uninitialized ] |
| /// ``` |
| /// |
| /// It is undefined behavior to de-initialize any bytes from the uninitialized |
| /// region, since it is merely unknown whether this region is uninitialized or |
| /// not, and if part of it turns out to be initialized, it must stay initialized. |
| </span><span class="kw">pub struct </span>ReadBuf<<span class="lifetime">'a</span>> { |
| buf: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[MaybeUninit<u8>], |
| filled: usize, |
| initialized: usize, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> ReadBuf<<span class="lifetime">'a</span>> { |
| <span class="doccomment">/// Creates a new `ReadBuf` from a fully initialized buffer. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>new(buf: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[u8]) -> ReadBuf<<span class="lifetime">'a</span>> { |
| <span class="kw">let </span>initialized = buf.len(); |
| <span class="kw">let </span>buf = <span class="kw">unsafe </span>{ slice_to_uninit_mut(buf) }; |
| ReadBuf { |
| buf, |
| filled: <span class="number">0</span>, |
| initialized, |
| } |
| } |
| |
| <span class="doccomment">/// Creates a new `ReadBuf` from a fully uninitialized buffer. |
| /// |
| /// Use `assume_init` if part of the buffer is known to be already initialized. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>uninit(buf: <span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>[MaybeUninit<u8>]) -> ReadBuf<<span class="lifetime">'a</span>> { |
| ReadBuf { |
| buf, |
| filled: <span class="number">0</span>, |
| initialized: <span class="number">0</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Returns the total capacity of the buffer. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>capacity(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.buf.len() |
| } |
| |
| <span class="doccomment">/// Returns a shared reference to the filled portion of the buffer. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>filled(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>[u8] { |
| <span class="kw">let </span>slice = <span class="kw-2">&</span><span class="self">self</span>.buf[..<span class="self">self</span>.filled]; |
| <span class="comment">// safety: filled describes how far into the buffer that the |
| // user has filled with bytes, so it's been initialized. |
| </span><span class="kw">unsafe </span>{ slice_assume_init(slice) } |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the filled portion of the buffer. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>filled_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[u8] { |
| <span class="kw">let </span>slice = <span class="kw-2">&mut </span><span class="self">self</span>.buf[..<span class="self">self</span>.filled]; |
| <span class="comment">// safety: filled describes how far into the buffer that the |
| // user has filled with bytes, so it's been initialized. |
| </span><span class="kw">unsafe </span>{ slice_assume_init_mut(slice) } |
| } |
| |
| <span class="doccomment">/// Returns a new `ReadBuf` comprised of the unfilled section up to `n`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>take(<span class="kw-2">&mut </span><span class="self">self</span>, n: usize) -> ReadBuf<<span class="lifetime">'_</span>> { |
| <span class="kw">let </span>max = std::cmp::min(<span class="self">self</span>.remaining(), n); |
| <span class="comment">// Safety: We don't set any of the `unfilled_mut` with `MaybeUninit::uninit`. |
| </span><span class="kw">unsafe </span>{ ReadBuf::uninit(<span class="kw-2">&mut </span><span class="self">self</span>.unfilled_mut()[..max]) } |
| } |
| |
| <span class="doccomment">/// Returns a shared reference to the initialized portion of the buffer. |
| /// |
| /// This includes the filled portion. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>initialized(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>[u8] { |
| <span class="kw">let </span>slice = <span class="kw-2">&</span><span class="self">self</span>.buf[..<span class="self">self</span>.initialized]; |
| <span class="comment">// safety: initialized describes how far into the buffer that the |
| // user has at some point initialized with bytes. |
| </span><span class="kw">unsafe </span>{ slice_assume_init(slice) } |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the initialized portion of the buffer. |
| /// |
| /// This includes the filled portion. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>initialized_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[u8] { |
| <span class="kw">let </span>slice = <span class="kw-2">&mut </span><span class="self">self</span>.buf[..<span class="self">self</span>.initialized]; |
| <span class="comment">// safety: initialized describes how far into the buffer that the |
| // user has at some point initialized with bytes. |
| </span><span class="kw">unsafe </span>{ slice_assume_init_mut(slice) } |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the entire buffer, without ensuring that it has been fully |
| /// initialized. |
| /// |
| /// The elements between 0 and `self.filled().len()` are filled, and those between 0 and |
| /// `self.initialized().len()` are initialized (and so can be converted to a `&mut [u8]`). |
| /// |
| /// The caller of this method must ensure that these invariants are upheld. For example, if the |
| /// caller initializes some of the uninitialized section of the buffer, it must call |
| /// [`assume_init`](Self::assume_init) with the number of bytes initialized. |
| /// |
| /// # Safety |
| /// |
| /// The caller must not de-initialize portions of the buffer that have already been initialized. |
| /// This includes any bytes in the region marked as uninitialized by `ReadBuf`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub unsafe fn </span>inner_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[MaybeUninit<u8>] { |
| <span class="self">self</span>.buf |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the unfilled part of the buffer without ensuring that it has been fully |
| /// initialized. |
| /// |
| /// # Safety |
| /// |
| /// The caller must not de-initialize portions of the buffer that have already been initialized. |
| /// This includes any bytes in the region marked as uninitialized by `ReadBuf`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub unsafe fn </span>unfilled_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[MaybeUninit<u8>] { |
| <span class="kw-2">&mut </span><span class="self">self</span>.buf[<span class="self">self</span>.filled..] |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the unfilled part of the buffer, ensuring it is fully initialized. |
| /// |
| /// Since `ReadBuf` tracks the region of the buffer that has been initialized, this is effectively "free" after |
| /// the first use. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>initialize_unfilled(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[u8] { |
| <span class="self">self</span>.initialize_unfilled_to(<span class="self">self</span>.remaining()) |
| } |
| |
| <span class="doccomment">/// Returns a mutable reference to the first `n` bytes of the unfilled part of the buffer, ensuring it is |
| /// fully initialized. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `self.remaining()` is less than `n`. |
| </span><span class="attribute">#[inline] |
| #[track_caller] |
| </span><span class="kw">pub fn </span>initialize_unfilled_to(<span class="kw-2">&mut </span><span class="self">self</span>, n: usize) -> <span class="kw-2">&mut </span>[u8] { |
| <span class="macro">assert!</span>(<span class="self">self</span>.remaining() >= n, <span class="string">"n overflows remaining"</span>); |
| |
| <span class="comment">// This can't overflow, otherwise the assert above would have failed. |
| </span><span class="kw">let </span>end = <span class="self">self</span>.filled + n; |
| |
| <span class="kw">if </span><span class="self">self</span>.initialized < end { |
| <span class="kw">unsafe </span>{ |
| <span class="self">self</span>.buf[<span class="self">self</span>.initialized..end] |
| .as_mut_ptr() |
| .write_bytes(<span class="number">0</span>, end - <span class="self">self</span>.initialized); |
| } |
| <span class="self">self</span>.initialized = end; |
| } |
| |
| <span class="kw">let </span>slice = <span class="kw-2">&mut </span><span class="self">self</span>.buf[<span class="self">self</span>.filled..end]; |
| <span class="comment">// safety: just above, we checked that the end of the buf has |
| // been initialized to some value. |
| </span><span class="kw">unsafe </span>{ slice_assume_init_mut(slice) } |
| } |
| |
| <span class="doccomment">/// Returns the number of bytes at the end of the slice that have not yet been filled. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>remaining(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.capacity() - <span class="self">self</span>.filled |
| } |
| |
| <span class="doccomment">/// Clears the buffer, resetting the filled region to empty. |
| /// |
| /// The number of initialized bytes is not changed, and the contents of the buffer are not modified. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>clear(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.filled = <span class="number">0</span>; |
| } |
| |
| <span class="doccomment">/// Advances the size of the filled region of the buffer. |
| /// |
| /// The number of initialized bytes is not changed. |
| /// |
| /// # Panics |
| /// |
| /// Panics if the filled region of the buffer would become larger than the initialized region. |
| </span><span class="attribute">#[inline] |
| #[track_caller] |
| </span><span class="kw">pub fn </span>advance(<span class="kw-2">&mut </span><span class="self">self</span>, n: usize) { |
| <span class="kw">let </span>new = <span class="self">self</span>.filled.checked_add(n).expect(<span class="string">"filled overflow"</span>); |
| <span class="self">self</span>.set_filled(new); |
| } |
| |
| <span class="doccomment">/// Sets the size of the filled region of the buffer. |
| /// |
| /// The number of initialized bytes is not changed. |
| /// |
| /// Note that this can be used to *shrink* the filled region of the buffer in addition to growing it (for |
| /// example, by a `AsyncRead` implementation that compresses data in-place). |
| /// |
| /// # Panics |
| /// |
| /// Panics if the filled region of the buffer would become larger than the initialized region. |
| </span><span class="attribute">#[inline] |
| #[track_caller] |
| </span><span class="kw">pub fn </span>set_filled(<span class="kw-2">&mut </span><span class="self">self</span>, n: usize) { |
| <span class="macro">assert!</span>( |
| n <= <span class="self">self</span>.initialized, |
| <span class="string">"filled must not become larger than initialized" |
| </span>); |
| <span class="self">self</span>.filled = n; |
| } |
| |
| <span class="doccomment">/// Asserts that the first `n` unfilled bytes of the buffer are initialized. |
| /// |
| /// `ReadBuf` assumes that bytes are never de-initialized, so this method does nothing when called with fewer |
| /// bytes than are already known to be initialized. |
| /// |
| /// # Safety |
| /// |
| /// The caller must ensure that `n` unfilled bytes of the buffer have already been initialized. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub unsafe fn </span>assume_init(<span class="kw-2">&mut </span><span class="self">self</span>, n: usize) { |
| <span class="kw">let </span>new = <span class="self">self</span>.filled + n; |
| <span class="kw">if </span>new > <span class="self">self</span>.initialized { |
| <span class="self">self</span>.initialized = new; |
| } |
| } |
| |
| <span class="doccomment">/// Appends data to the buffer, advancing the written position and possibly also the initialized position. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `self.remaining()` is less than `buf.len()`. |
| </span><span class="attribute">#[inline] |
| #[track_caller] |
| </span><span class="kw">pub fn </span>put_slice(<span class="kw-2">&mut </span><span class="self">self</span>, buf: <span class="kw-2">&</span>[u8]) { |
| <span class="macro">assert!</span>( |
| <span class="self">self</span>.remaining() >= buf.len(), |
| <span class="string">"buf.len() must fit in remaining()" |
| </span>); |
| |
| <span class="kw">let </span>amt = buf.len(); |
| <span class="comment">// Cannot overflow, asserted above |
| </span><span class="kw">let </span>end = <span class="self">self</span>.filled + amt; |
| |
| <span class="comment">// Safety: the length is asserted above |
| </span><span class="kw">unsafe </span>{ |
| <span class="self">self</span>.buf[<span class="self">self</span>.filled..end] |
| .as_mut_ptr() |
| .cast::<u8>() |
| .copy_from_nonoverlapping(buf.as_ptr(), amt); |
| } |
| |
| <span class="kw">if </span><span class="self">self</span>.initialized < end { |
| <span class="self">self</span>.initialized = end; |
| } |
| <span class="self">self</span>.filled = end; |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>ReadBuf<<span class="lifetime">'_</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 { |
| f.debug_struct(<span class="string">"ReadBuf"</span>) |
| .field(<span class="string">"filled"</span>, <span class="kw-2">&</span><span class="self">self</span>.filled) |
| .field(<span class="string">"initialized"</span>, <span class="kw-2">&</span><span class="self">self</span>.initialized) |
| .field(<span class="string">"capacity"</span>, <span class="kw-2">&</span><span class="self">self</span>.capacity()) |
| .finish() |
| } |
| } |
| |
| <span class="kw">unsafe fn </span>slice_to_uninit_mut(slice: <span class="kw-2">&mut </span>[u8]) -> <span class="kw-2">&mut </span>[MaybeUninit<u8>] { |
| <span class="kw-2">&mut *</span>(slice <span class="kw">as </span><span class="kw-2">*mut </span>[u8] <span class="kw">as </span><span class="kw-2">*mut </span>[MaybeUninit<u8>]) |
| } |
| |
| <span class="comment">// TODO: This could use `MaybeUninit::slice_assume_init` when it is stable. |
| </span><span class="kw">unsafe fn </span>slice_assume_init(slice: <span class="kw-2">&</span>[MaybeUninit<u8>]) -> <span class="kw-2">&</span>[u8] { |
| <span class="kw-2">&*</span>(slice <span class="kw">as </span><span class="kw-2">*const </span>[MaybeUninit<u8>] <span class="kw">as </span><span class="kw-2">*const </span>[u8]) |
| } |
| |
| <span class="comment">// TODO: This could use `MaybeUninit::slice_assume_init_mut` when it is stable. |
| </span><span class="kw">unsafe fn </span>slice_assume_init_mut(slice: <span class="kw-2">&mut </span>[MaybeUninit<u8>]) -> <span class="kw-2">&mut </span>[u8] { |
| <span class="kw-2">&mut *</span>(slice <span class="kw">as </span><span class="kw-2">*mut </span>[MaybeUninit<u8>] <span class="kw">as </span><span class="kw-2">*mut </span>[u8]) |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
