| <!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/tokio-1.28.2/src/sync/mpsc/block.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>block.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="../../../../tokio/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="../../../../tokio/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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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">crate</span>::loom::cell::UnsafeCell; |
| <span class="kw">use </span><span class="kw">crate</span>::loom::sync::atomic::{AtomicPtr, AtomicUsize}; |
| |
| <span class="kw">use </span>std::alloc::Layout; |
| <span class="kw">use </span>std::mem::MaybeUninit; |
| <span class="kw">use </span>std::ops; |
| <span class="kw">use </span>std::ptr::{<span class="self">self</span>, NonNull}; |
| <span class="kw">use </span>std::sync::atomic::Ordering::{<span class="self">self</span>, AcqRel, Acquire, Release}; |
| |
| <span class="doccomment">/// A block in a linked list. |
| /// |
| /// Each block in the list can hold up to `BLOCK_CAP` messages. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Block<T> { |
| <span class="doccomment">/// The header fields. |
| </span>header: BlockHeader<T>, |
| |
| <span class="doccomment">/// Array containing values pushed into the block. Values are stored in a |
| /// continuous array in order to improve cache line behavior when reading. |
| /// The values must be manually dropped. |
| </span>values: Values<T>, |
| } |
| |
| <span class="doccomment">/// Extra fields for a `Block<T>`. |
| </span><span class="kw">struct </span>BlockHeader<T> { |
| <span class="doccomment">/// The start index of this block. |
| /// |
| /// Slots in this block have indices in `start_index .. start_index + BLOCK_CAP`. |
| </span>start_index: usize, |
| |
| <span class="doccomment">/// The next block in the linked list. |
| </span>next: AtomicPtr<Block<T>>, |
| |
| <span class="doccomment">/// Bitfield tracking slots that are ready to have their values consumed. |
| </span>ready_slots: AtomicUsize, |
| |
| <span class="doccomment">/// The observed `tail_position` value *after* the block has been passed by |
| /// `block_tail`. |
| </span>observed_tail_position: UnsafeCell<usize>, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>Read<T> { |
| Value(T), |
| Closed, |
| } |
| |
| <span class="attribute">#[repr(transparent)] |
| </span><span class="kw">struct </span>Values<T>([UnsafeCell<MaybeUninit<T>>; BLOCK_CAP]); |
| |
| <span class="kw">use </span><span class="kw">super</span>::BLOCK_CAP; |
| |
| <span class="doccomment">/// Masks an index to get the block identifier. |
| </span><span class="kw">const </span>BLOCK_MASK: usize = !(BLOCK_CAP - <span class="number">1</span>); |
| |
| <span class="doccomment">/// Masks an index to get the value offset in a block. |
| </span><span class="kw">const </span>SLOT_MASK: usize = BLOCK_CAP - <span class="number">1</span>; |
| |
| <span class="doccomment">/// Flag tracking that a block has gone through the sender's release routine. |
| /// |
| /// When this is set, the receiver may consider freeing the block. |
| </span><span class="kw">const </span>RELEASED: usize = <span class="number">1 </span><< BLOCK_CAP; |
| |
| <span class="doccomment">/// Flag tracking all senders dropped. |
| /// |
| /// When this flag is set, the send half of the channel has closed. |
| </span><span class="kw">const </span>TX_CLOSED: usize = RELEASED << <span class="number">1</span>; |
| |
| <span class="doccomment">/// Mask covering all bits used to track slot readiness. |
| </span><span class="kw">const </span>READY_MASK: usize = RELEASED - <span class="number">1</span>; |
| |
| <span class="doccomment">/// Returns the index of the first slot in the block referenced by `slot_index`. |
| </span><span class="attribute">#[inline(always)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>start_index(slot_index: usize) -> usize { |
| BLOCK_MASK & slot_index |
| } |
| |
| <span class="doccomment">/// Returns the offset into the block referenced by `slot_index`. |
| </span><span class="attribute">#[inline(always)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>offset(slot_index: usize) -> usize { |
| SLOT_MASK & slot_index |
| } |
| |
| <span class="macro">generate_addr_of_methods! </span>{ |
| <span class="kw">impl</span><T> Block<T> { |
| <span class="kw">unsafe fn </span>addr_of_header(<span class="self">self</span>: NonNull<<span class="self">Self</span>>) -> NonNull<BlockHeader<T>> { |
| <span class="kw-2">&</span><span class="self">self</span>.header |
| } |
| |
| <span class="kw">unsafe fn </span>addr_of_values(<span class="self">self</span>: NonNull<<span class="self">Self</span>>) -> NonNull<Values<T>> { |
| <span class="kw-2">&</span><span class="self">self</span>.values |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T> Block<T> { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(start_index: usize) -> Box<Block<T>> { |
| <span class="kw">unsafe </span>{ |
| <span class="comment">// Allocate the block on the heap. |
| // SAFETY: The size of the Block<T> is non-zero, since it is at least the size of the header. |
| </span><span class="kw">let </span>block = std::alloc::alloc(Layout::new::<Block<T>>()) <span class="kw">as </span><span class="kw-2">*mut </span>Block<T>; |
| <span class="kw">let </span>block = <span class="kw">match </span>NonNull::new(block) { |
| <span class="prelude-val">Some</span>(block) => block, |
| <span class="prelude-val">None </span>=> std::alloc::handle_alloc_error(Layout::new::<Block<T>>()), |
| }; |
| |
| <span class="comment">// Write the header to the block. |
| </span>Block::addr_of_header(block).as_ptr().write(BlockHeader { |
| <span class="comment">// The absolute index in the channel of the first slot in the block. |
| </span>start_index, |
| |
| <span class="comment">// Pointer to the next block in the linked list. |
| </span>next: AtomicPtr::new(ptr::null_mut()), |
| |
| ready_slots: AtomicUsize::new(<span class="number">0</span>), |
| |
| observed_tail_position: UnsafeCell::new(<span class="number">0</span>), |
| }); |
| |
| <span class="comment">// Initialize the values array. |
| </span>Values::initialize(Block::addr_of_values(block)); |
| |
| <span class="comment">// Convert the pointer to a `Box`. |
| // Safety: The raw pointer was allocated using the global allocator, and with |
| // the layout for a `Block<T>`, so it's valid to convert it to box. |
| </span>Box::from_raw(block.as_ptr()) |
| } |
| } |
| |
| <span class="doccomment">/// Returns `true` if the block matches the given index. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>is_at_index(<span class="kw-2">&</span><span class="self">self</span>, index: usize) -> bool { |
| <span class="macro">debug_assert!</span>(offset(index) == <span class="number">0</span>); |
| <span class="self">self</span>.header.start_index == index |
| } |
| |
| <span class="doccomment">/// Returns the number of blocks between `self` and the block at the |
| /// specified index. |
| /// |
| /// `start_index` must represent a block *after* `self`. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>distance(<span class="kw-2">&</span><span class="self">self</span>, other_index: usize) -> usize { |
| <span class="macro">debug_assert!</span>(offset(other_index) == <span class="number">0</span>); |
| other_index.wrapping_sub(<span class="self">self</span>.header.start_index) / BLOCK_CAP |
| } |
| |
| <span class="doccomment">/// Reads the value at the given offset. |
| /// |
| /// Returns `None` if the slot is empty. |
| /// |
| /// # Safety |
| /// |
| /// To maintain safety, the caller must ensure: |
| /// |
| /// * No concurrent access to the slot. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>read(<span class="kw-2">&</span><span class="self">self</span>, slot_index: usize) -> <span class="prelude-ty">Option</span><Read<T>> { |
| <span class="kw">let </span>offset = offset(slot_index); |
| |
| <span class="kw">let </span>ready_bits = <span class="self">self</span>.header.ready_slots.load(Acquire); |
| |
| <span class="kw">if </span>!is_ready(ready_bits, offset) { |
| <span class="kw">if </span>is_tx_closed(ready_bits) { |
| <span class="kw">return </span><span class="prelude-val">Some</span>(Read::Closed); |
| } |
| |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| |
| <span class="comment">// Get the value |
| </span><span class="kw">let </span>value = <span class="self">self</span>.values[offset].with(|ptr| ptr::read(ptr)); |
| |
| <span class="prelude-val">Some</span>(Read::Value(value.assume_init())) |
| } |
| |
| <span class="doccomment">/// Writes a value to the block at the given offset. |
| /// |
| /// # Safety |
| /// |
| /// To maintain safety, the caller must ensure: |
| /// |
| /// * The slot is empty. |
| /// * No concurrent access to the slot. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>write(<span class="kw-2">&</span><span class="self">self</span>, slot_index: usize, value: T) { |
| <span class="comment">// Get the offset into the block |
| </span><span class="kw">let </span>slot_offset = offset(slot_index); |
| |
| <span class="self">self</span>.values[slot_offset].with_mut(|ptr| { |
| ptr::write(ptr, MaybeUninit::new(value)); |
| }); |
| |
| <span class="comment">// Release the value. After this point, the slot ref may no longer |
| // be used. It is possible for the receiver to free the memory at |
| // any point. |
| </span><span class="self">self</span>.set_ready(slot_offset); |
| } |
| |
| <span class="doccomment">/// Signal to the receiver that the sender half of the list is closed. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>tx_close(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.header.ready_slots.fetch_or(TX_CLOSED, Release); |
| } |
| |
| <span class="doccomment">/// Resets the block to a blank state. This enables reusing blocks in the |
| /// channel. |
| /// |
| /// # Safety |
| /// |
| /// To maintain safety, the caller must ensure: |
| /// |
| /// * All slots are empty. |
| /// * The caller holds a unique pointer to the block. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>reclaim(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.header.start_index = <span class="number">0</span>; |
| <span class="self">self</span>.header.next = AtomicPtr::new(ptr::null_mut()); |
| <span class="self">self</span>.header.ready_slots = AtomicUsize::new(<span class="number">0</span>); |
| } |
| |
| <span class="doccomment">/// Releases the block to the rx half for freeing. |
| /// |
| /// This function is called by the tx half once it can be guaranteed that no |
| /// more senders will attempt to access the block. |
| /// |
| /// # Safety |
| /// |
| /// To maintain safety, the caller must ensure: |
| /// |
| /// * The block will no longer be accessed by any sender. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>tx_release(<span class="kw-2">&</span><span class="self">self</span>, tail_position: usize) { |
| <span class="comment">// Track the observed tail_position. Any sender targeting a greater |
| // tail_position is guaranteed to not access this block. |
| </span><span class="self">self</span>.header |
| .observed_tail_position |
| .with_mut(|ptr| <span class="kw-2">*</span>ptr = tail_position); |
| |
| <span class="comment">// Set the released bit, signalling to the receiver that it is safe to |
| // free the block's memory as soon as all slots **prior** to |
| // `observed_tail_position` have been filled. |
| </span><span class="self">self</span>.header.ready_slots.fetch_or(RELEASED, Release); |
| } |
| |
| <span class="doccomment">/// Mark a slot as ready |
| </span><span class="kw">fn </span>set_ready(<span class="kw-2">&</span><span class="self">self</span>, slot: usize) { |
| <span class="kw">let </span>mask = <span class="number">1 </span><< slot; |
| <span class="self">self</span>.header.ready_slots.fetch_or(mask, Release); |
| } |
| |
| <span class="doccomment">/// Returns `true` when all slots have their `ready` bits set. |
| /// |
| /// This indicates that the block is in its final state and will no longer |
| /// be mutated. |
| /// |
| /// # Implementation |
| /// |
| /// The implementation walks each slot checking the `ready` flag. It might |
| /// be that it would make more sense to coalesce ready flags as bits in a |
| /// single atomic cell. However, this could have negative impact on cache |
| /// behavior as there would be many more mutations to a single slot. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>is_final(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.header.ready_slots.load(Acquire) & READY_MASK == READY_MASK |
| } |
| |
| <span class="doccomment">/// Returns the `observed_tail_position` value, if set |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>observed_tail_position(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><usize> { |
| <span class="kw">if </span><span class="number">0 </span>== RELEASED & <span class="self">self</span>.header.ready_slots.load(Acquire) { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="prelude-val">Some</span>( |
| <span class="self">self</span>.header |
| .observed_tail_position |
| .with(|ptr| <span class="kw">unsafe </span>{ <span class="kw-2">*</span>ptr }), |
| ) |
| } |
| } |
| |
| <span class="doccomment">/// Loads the next block |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>load_next(<span class="kw-2">&</span><span class="self">self</span>, ordering: Ordering) -> <span class="prelude-ty">Option</span><NonNull<Block<T>>> { |
| <span class="kw">let </span>ret = NonNull::new(<span class="self">self</span>.header.next.load(ordering)); |
| |
| <span class="macro">debug_assert!</span>(<span class="kw">unsafe </span>{ |
| ret.map(|block| { |
| block.as_ref().header.start_index == <span class="self">self</span>.header.start_index.wrapping_add(BLOCK_CAP) |
| }) |
| .unwrap_or(<span class="bool-val">true</span>) |
| }); |
| |
| ret |
| } |
| |
| <span class="doccomment">/// Pushes `block` as the next block in the link. |
| /// |
| /// Returns Ok if successful, otherwise, a pointer to the next block in |
| /// the list is returned. |
| /// |
| /// This requires that the next pointer is null. |
| /// |
| /// # Ordering |
| /// |
| /// This performs a compare-and-swap on `next` using AcqRel ordering. |
| /// |
| /// # Safety |
| /// |
| /// To maintain safety, the caller must ensure: |
| /// |
| /// * `block` is not freed until it has been removed from the list. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>try_push( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| block: <span class="kw-2">&mut </span>NonNull<Block<T>>, |
| success: Ordering, |
| failure: Ordering, |
| ) -> <span class="prelude-ty">Result</span><(), NonNull<Block<T>>> { |
| block.as_mut().header.start_index = <span class="self">self</span>.header.start_index.wrapping_add(BLOCK_CAP); |
| |
| <span class="kw">let </span>next_ptr = <span class="self">self |
| </span>.header |
| .next |
| .compare_exchange(ptr::null_mut(), block.as_ptr(), success, failure) |
| .unwrap_or_else(|x| x); |
| |
| <span class="kw">match </span>NonNull::new(next_ptr) { |
| <span class="prelude-val">Some</span>(next_ptr) => <span class="prelude-val">Err</span>(next_ptr), |
| <span class="prelude-val">None </span>=> <span class="prelude-val">Ok</span>(()), |
| } |
| } |
| |
| <span class="doccomment">/// Grows the `Block` linked list by allocating and appending a new block. |
| /// |
| /// The next block in the linked list is returned. This may or may not be |
| /// the one allocated by the function call. |
| /// |
| /// # Implementation |
| /// |
| /// It is assumed that `self.next` is null. A new block is allocated with |
| /// `start_index` set to be the next block. A compare-and-swap is performed |
| /// with AcqRel memory ordering. If the compare-and-swap is successful, the |
| /// newly allocated block is released to other threads walking the block |
| /// linked list. If the compare-and-swap fails, the current thread acquires |
| /// the next block in the linked list, allowing the current thread to access |
| /// the slots. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>grow(<span class="kw-2">&</span><span class="self">self</span>) -> NonNull<Block<T>> { |
| <span class="comment">// Create the new block. It is assumed that the block will become the |
| // next one after `&self`. If this turns out to not be the case, |
| // `start_index` is updated accordingly. |
| </span><span class="kw">let </span>new_block = Block::new(<span class="self">self</span>.header.start_index + BLOCK_CAP); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>new_block = <span class="kw">unsafe </span>{ NonNull::new_unchecked(Box::into_raw(new_block)) }; |
| |
| <span class="comment">// Attempt to store the block. The first compare-and-swap attempt is |
| // "unrolled" due to minor differences in logic |
| // |
| // `AcqRel` is used as the ordering **only** when attempting the |
| // compare-and-swap on self.next. |
| // |
| // If the compare-and-swap fails, then the actual value of the cell is |
| // returned from this function and accessed by the caller. Given this, |
| // the memory must be acquired. |
| // |
| // `Release` ensures that the newly allocated block is available to |
| // other threads acquiring the next pointer. |
| </span><span class="kw">let </span>next = NonNull::new( |
| <span class="self">self</span>.header |
| .next |
| .compare_exchange(ptr::null_mut(), new_block.as_ptr(), AcqRel, Acquire) |
| .unwrap_or_else(|x| x), |
| ); |
| |
| <span class="kw">let </span>next = <span class="kw">match </span>next { |
| <span class="prelude-val">Some</span>(next) => next, |
| <span class="prelude-val">None </span>=> { |
| <span class="comment">// The compare-and-swap succeeded and the newly allocated block |
| // is successfully pushed. |
| </span><span class="kw">return </span>new_block; |
| } |
| }; |
| |
| <span class="comment">// There already is a next block in the linked list. The newly allocated |
| // block could be dropped and the discovered next block returned; |
| // however, that would be wasteful. Instead, the linked list is walked |
| // by repeatedly attempting to compare-and-swap the pointer into the |
| // `next` register until the compare-and-swap succeed. |
| // |
| // Care is taken to update new_block's start_index field as appropriate. |
| |
| </span><span class="kw">let </span><span class="kw-2">mut </span>curr = next; |
| |
| <span class="comment">// TODO: Should this iteration be capped? |
| </span><span class="kw">loop </span>{ |
| <span class="kw">let </span>actual = <span class="kw">unsafe </span>{ curr.as_ref().try_push(<span class="kw-2">&mut </span>new_block, AcqRel, Acquire) }; |
| |
| curr = <span class="kw">match </span>actual { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => { |
| <span class="kw">return </span>next; |
| } |
| <span class="prelude-val">Err</span>(curr) => curr, |
| }; |
| |
| <span class="kw">crate</span>::loom::thread::yield_now(); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Returns `true` if the specified slot has a value ready to be consumed. |
| </span><span class="kw">fn </span>is_ready(bits: usize, slot: usize) -> bool { |
| <span class="kw">let </span>mask = <span class="number">1 </span><< slot; |
| mask == mask & bits |
| } |
| |
| <span class="doccomment">/// Returns `true` if the closed flag has been set. |
| </span><span class="kw">fn </span>is_tx_closed(bits: usize) -> bool { |
| TX_CLOSED == bits & TX_CLOSED |
| } |
| |
| <span class="kw">impl</span><T> Values<T> { |
| <span class="doccomment">/// Initialize a `Values` struct from a pointer. |
| /// |
| /// # Safety |
| /// |
| /// The raw pointer must be valid for writing a `Values<T>`. |
| </span><span class="kw">unsafe fn </span>initialize(_value: NonNull<Values<T>>) { |
| <span class="comment">// When fuzzing, `UnsafeCell` needs to be initialized. |
| </span><span class="macro">if_loom! </span>{ |
| <span class="kw">let </span>p = _value.as_ptr() <span class="kw">as </span><span class="kw-2">*mut </span>UnsafeCell<MaybeUninit<T>>; |
| <span class="kw">for </span>i <span class="kw">in </span><span class="number">0</span>..BLOCK_CAP { |
| p.add(i) |
| .write(UnsafeCell::new(MaybeUninit::uninit())); |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T> ops::Index<usize> <span class="kw">for </span>Values<T> { |
| <span class="kw">type </span>Output = UnsafeCell<MaybeUninit<T>>; |
| |
| <span class="kw">fn </span>index(<span class="kw-2">&</span><span class="self">self</span>, index: usize) -> <span class="kw-2">&</span><span class="self">Self</span>::Output { |
| <span class="self">self</span>.<span class="number">0</span>.index(index) |
| } |
| } |
| |
| <span class="attribute">#[cfg(all(test, not(loom)))] |
| #[test] |
| </span><span class="kw">fn </span>assert_no_stack_overflow() { |
| <span class="comment">// https://github.com/tokio-rs/tokio/issues/5293 |
| |
| </span><span class="kw">struct </span>Foo { |
| _a: [u8; <span class="number">2_000_000</span>], |
| } |
| |
| <span class="macro">assert_eq!</span>( |
| Layout::new::<MaybeUninit<Block<Foo>>>(), |
| Layout::new::<Block<Foo>>() |
| ); |
| |
| <span class="kw">let </span>_block = Block::<Foo>::new(<span class="number">0</span>); |
| } |
| </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> |