| <!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/git/checkouts/tokio-377c595163f99a10/dfe252d/tokio/src/io/stdio_common.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>stdio_common.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="doccomment">//! Contains utilities for stdout and stderr. |
| </span><span class="kw">use </span><span class="kw">crate</span>::io::AsyncWrite; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| <span class="doccomment">/// # Windows |
| /// AsyncWrite adapter that finds last char boundary in given buffer and does not write the rest, |
| /// if buffer contents seems to be utf8. Otherwise it only trims buffer down to MAX_BUF. |
| /// That's why, wrapped writer will always receive well-formed utf-8 bytes. |
| /// # Other platforms |
| /// Passes data to `inner` as is. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>SplitByUtf8BoundaryIfWindows<W> { |
| inner: W, |
| } |
| |
| <span class="kw">impl</span><W> SplitByUtf8BoundaryIfWindows<W> { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(inner: W) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ inner } |
| } |
| } |
| |
| <span class="comment">// this constant is defined by Unicode standard. |
| </span><span class="kw">const </span>MAX_BYTES_PER_CHAR: usize = <span class="number">4</span>; |
| |
| <span class="comment">// Subject for tweaking here |
| </span><span class="kw">const </span>MAGIC_CONST: usize = <span class="number">8</span>; |
| |
| <span class="kw">impl</span><W> <span class="kw">crate</span>::io::AsyncWrite <span class="kw">for </span>SplitByUtf8BoundaryIfWindows<W> |
| <span class="kw">where |
| </span>W: AsyncWrite + Unpin, |
| { |
| <span class="kw">fn </span>poll_write( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| <span class="kw-2">mut </span>buf: <span class="kw-2">&</span>[u8], |
| ) -> Poll<<span class="prelude-ty">Result</span><usize, std::io::Error>> { |
| <span class="comment">// just a closure to avoid repetitive code |
| </span><span class="kw">let </span><span class="kw-2">mut </span>call_inner = <span class="kw">move </span>|buf| Pin::new(<span class="kw-2">&mut </span><span class="self">self</span>.inner).poll_write(cx, buf); |
| |
| <span class="comment">// 1. Only windows stdio can suffer from non-utf8. |
| // We also check for `test` so that we can write some tests |
| // for further code. Since `AsyncWrite` can always shrink |
| // buffer at its discretion, excessive (i.e. in tests) shrinking |
| // does not break correctness. |
| // 2. If buffer is small, it will not be shrunk. |
| // That's why, it's "textness" will not change, so we don't have |
| // to fixup it. |
| </span><span class="kw">if </span><span class="macro">cfg!</span>(not(any(target_os = <span class="string">"windows"</span>, test))) || buf.len() <= <span class="kw">crate</span>::io::blocking::MAX_BUF |
| { |
| <span class="kw">return </span>call_inner(buf); |
| } |
| |
| buf = <span class="kw-2">&</span>buf[..<span class="kw">crate</span>::io::blocking::MAX_BUF]; |
| |
| <span class="comment">// Now there are two possibilities. |
| // If caller gave is binary buffer, we **should not** shrink it |
| // anymore, because excessive shrinking hits performance. |
| // If caller gave as binary buffer, we **must** additionally |
| // shrink it to strip incomplete char at the end of buffer. |
| // that's why check we will perform now is allowed to have |
| // false-positive. |
| |
| // Now let's look at the first MAX_BYTES_PER_CHAR * MAGIC_CONST bytes. |
| // if they are (possibly incomplete) utf8, then we can be quite sure |
| // that input buffer was utf8. |
| |
| </span><span class="kw">let </span>have_to_fix_up = <span class="kw">match </span>std::str::from_utf8(<span class="kw-2">&</span>buf[..MAX_BYTES_PER_CHAR * MAGIC_CONST]) { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => <span class="bool-val">true</span>, |
| <span class="prelude-val">Err</span>(err) => { |
| <span class="kw">let </span>incomplete_bytes = MAX_BYTES_PER_CHAR * MAGIC_CONST - err.valid_up_to(); |
| incomplete_bytes < MAX_BYTES_PER_CHAR |
| } |
| }; |
| |
| <span class="kw">if </span>have_to_fix_up { |
| <span class="comment">// We must pop several bytes at the end which form incomplete |
| // character. To achieve it, we exploit UTF8 encoding: |
| // for any code point, all bytes except first start with 0b10 prefix. |
| // see https://en.wikipedia.org/wiki/UTF-8#Encoding for details |
| </span><span class="kw">let </span>trailing_incomplete_char_size = buf |
| .iter() |
| .rev() |
| .take(MAX_BYTES_PER_CHAR) |
| .position(|byte| <span class="kw-2">*</span>byte < <span class="number">0b1000_0000 </span>|| <span class="kw-2">*</span>byte >= <span class="number">0b1100_0000</span>) |
| .unwrap_or(<span class="number">0</span>) |
| + <span class="number">1</span>; |
| buf = <span class="kw-2">&</span>buf[..buf.len() - trailing_incomplete_char_size]; |
| } |
| |
| call_inner(buf) |
| } |
| |
| <span class="kw">fn </span>poll_flush( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| ) -> Poll<<span class="prelude-ty">Result</span><(), std::io::Error>> { |
| Pin::new(<span class="kw-2">&mut </span><span class="self">self</span>.inner).poll_flush(cx) |
| } |
| |
| <span class="kw">fn </span>poll_shutdown( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| ) -> Poll<<span class="prelude-ty">Result</span><(), std::io::Error>> { |
| Pin::new(<span class="kw-2">&mut </span><span class="self">self</span>.inner).poll_shutdown(cx) |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| #[cfg(not(loom))] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span><span class="kw">crate</span>::io::AsyncWriteExt; |
| <span class="kw">use </span>std::io; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::Context; |
| <span class="kw">use </span>std::task::Poll; |
| |
| <span class="kw">const </span>MAX_BUF: usize = <span class="number">16 </span>* <span class="number">1024</span>; |
| |
| <span class="kw">struct </span>TextMockWriter; |
| |
| <span class="kw">impl </span><span class="kw">crate</span>::io::AsyncWrite <span class="kw">for </span>TextMockWriter { |
| <span class="kw">fn </span>poll_write( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&</span>[u8], |
| ) -> Poll<<span class="prelude-ty">Result</span><usize, io::Error>> { |
| <span class="macro">assert!</span>(buf.len() <= MAX_BUF); |
| <span class="macro">assert!</span>(std::str::from_utf8(buf).is_ok()); |
| Poll::Ready(<span class="prelude-val">Ok</span>(buf.len())) |
| } |
| |
| <span class="kw">fn </span>poll_flush(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), io::Error>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| |
| <span class="kw">fn </span>poll_shutdown( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| ) -> Poll<<span class="prelude-ty">Result</span><(), io::Error>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| |
| <span class="kw">struct </span>LoggingMockWriter { |
| write_history: Vec<usize>, |
| } |
| |
| <span class="kw">impl </span>LoggingMockWriter { |
| <span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| LoggingMockWriter { |
| write_history: Vec::new(), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span><span class="kw">crate</span>::io::AsyncWrite <span class="kw">for </span>LoggingMockWriter { |
| <span class="kw">fn </span>poll_write( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&</span>[u8], |
| ) -> Poll<<span class="prelude-ty">Result</span><usize, io::Error>> { |
| <span class="macro">assert!</span>(buf.len() <= MAX_BUF); |
| <span class="self">self</span>.write_history.push(buf.len()); |
| Poll::Ready(<span class="prelude-val">Ok</span>(buf.len())) |
| } |
| |
| <span class="kw">fn </span>poll_flush(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), io::Error>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| |
| <span class="kw">fn </span>poll_shutdown( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| ) -> Poll<<span class="prelude-ty">Result</span><(), io::Error>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_splitter() { |
| <span class="kw">let </span>data = str::repeat(<span class="string">"█"</span>, MAX_BUF); |
| <span class="kw">let </span><span class="kw-2">mut </span>wr = <span class="kw">super</span>::SplitByUtf8BoundaryIfWindows::new(TextMockWriter); |
| <span class="kw">let </span>fut = <span class="kw">async move </span>{ |
| wr.write_all(data.as_bytes()).<span class="kw">await</span>.unwrap(); |
| }; |
| <span class="kw">crate</span>::runtime::Builder::new_current_thread() |
| .build() |
| .unwrap() |
| .block_on(fut); |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_pseudo_text() { |
| <span class="comment">// In this test we write a piece of binary data, whose beginning is |
| // text though. We then validate that even in this corner case buffer |
| // was not shrunk too much. |
| </span><span class="kw">let </span>checked_count = <span class="kw">super</span>::MAGIC_CONST * <span class="kw">super</span>::MAX_BYTES_PER_CHAR; |
| <span class="kw">let </span><span class="kw-2">mut </span>data: Vec<u8> = str::repeat(<span class="string">"a"</span>, checked_count).into(); |
| data.extend(std::iter::repeat(<span class="number">0b1010_1010</span>).take(MAX_BUF - checked_count + <span class="number">1</span>)); |
| <span class="kw">let </span><span class="kw-2">mut </span>writer = LoggingMockWriter::new(); |
| <span class="kw">let </span><span class="kw-2">mut </span>splitter = <span class="kw">super</span>::SplitByUtf8BoundaryIfWindows::new(<span class="kw-2">&mut </span>writer); |
| <span class="kw">crate</span>::runtime::Builder::new_current_thread() |
| .build() |
| .unwrap() |
| .block_on(<span class="kw">async </span>{ |
| splitter.write_all(<span class="kw-2">&</span>data).<span class="kw">await</span>.unwrap(); |
| }); |
| <span class="comment">// Check that at most two writes were performed |
| </span><span class="macro">assert!</span>(writer.write_history.len() <= <span class="number">2</span>); |
| <span class="comment">// Check that all has been written |
| </span><span class="macro">assert_eq!</span>( |
| writer.write_history.iter().copied().sum::<usize>(), |
| data.len() |
| ); |
| <span class="comment">// Check that at most MAX_BYTES_PER_CHAR + 1 (i.e. 5) bytes were shrunk |
| // from the buffer: one because it was outside of MAX_BUF boundary, and |
| // up to one "utf8 code point". |
| </span><span class="macro">assert!</span>(data.len() - writer.write_history[<span class="number">0</span>] <= <span class="kw">super</span>::MAX_BYTES_PER_CHAR + <span class="number">1</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> |
