| <!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/io/util/buf_writer.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>buf_writer.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>::io::util::DEFAULT_BUF_SIZE; |
| <span class="kw">use </span><span class="kw">crate</span>::io::{AsyncBufRead, AsyncRead, AsyncSeek, AsyncWrite, ReadBuf}; |
| |
| <span class="kw">use </span>pin_project_lite::pin_project; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::io::{<span class="self">self</span>, IoSlice, SeekFrom, Write}; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// Wraps a writer and buffers its output. |
| /// |
| /// It can be excessively inefficient to work directly with something that |
| /// implements [`AsyncWrite`]. A `BufWriter` keeps an in-memory buffer of data and |
| /// writes it to an underlying writer in large, infrequent batches. |
| /// |
| /// `BufWriter` can improve the speed of programs that make *small* and |
| /// *repeated* write calls to the same file or network socket. It does not |
| /// help when writing very large amounts at once, or writing just one or a few |
| /// times. It also provides no advantage when writing to a destination that is |
| /// in memory, like a `Vec<u8>`. |
| /// |
| /// When the `BufWriter` is dropped, the contents of its buffer will be |
| /// discarded. Creating multiple instances of a `BufWriter` on the same |
| /// stream can cause data loss. If you need to write out the contents of its |
| /// buffer, you must manually call flush before the writer is dropped. |
| /// |
| /// [`AsyncWrite`]: AsyncWrite |
| /// [`flush`]: super::AsyncWriteExt::flush |
| /// |
| </span><span class="attribute">#[cfg_attr(docsrs, doc(cfg(feature = <span class="string">"io-util"</span>)))] |
| </span><span class="kw">pub struct </span>BufWriter<W> { |
| <span class="attribute">#[pin] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) inner: W, |
| <span class="kw">pub</span>(<span class="kw">super</span>) buf: Vec<u8>, |
| <span class="kw">pub</span>(<span class="kw">super</span>) written: usize, |
| <span class="kw">pub</span>(<span class="kw">super</span>) seek_state: SeekState, |
| } |
| } |
| |
| <span class="kw">impl</span><W: AsyncWrite> BufWriter<W> { |
| <span class="doccomment">/// Creates a new `BufWriter` with a default buffer capacity. The default is currently 8 KB, |
| /// but may change in the future. |
| </span><span class="kw">pub fn </span>new(inner: W) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::with_capacity(DEFAULT_BUF_SIZE, inner) |
| } |
| |
| <span class="doccomment">/// Creates a new `BufWriter` with the specified buffer capacity. |
| </span><span class="kw">pub fn </span>with_capacity(cap: usize, inner: W) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| inner, |
| buf: Vec::with_capacity(cap), |
| written: <span class="number">0</span>, |
| seek_state: SeekState::Init, |
| } |
| } |
| |
| <span class="kw">fn </span>flush_buf(<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<io::Result<()>> { |
| <span class="kw">let </span><span class="kw-2">mut </span>me = <span class="self">self</span>.project(); |
| |
| <span class="kw">let </span>len = me.buf.len(); |
| <span class="kw">let </span><span class="kw-2">mut </span>ret = <span class="prelude-val">Ok</span>(()); |
| <span class="kw">while </span><span class="kw-2">*</span>me.written < len { |
| <span class="kw">match </span><span class="macro">ready!</span>(me.inner.as_mut().poll_write(cx, <span class="kw-2">&</span>me.buf[<span class="kw-2">*</span>me.written..])) { |
| <span class="prelude-val">Ok</span>(<span class="number">0</span>) => { |
| ret = <span class="prelude-val">Err</span>(io::Error::new( |
| io::ErrorKind::WriteZero, |
| <span class="string">"failed to write the buffered data"</span>, |
| )); |
| <span class="kw">break</span>; |
| } |
| <span class="prelude-val">Ok</span>(n) => <span class="kw-2">*</span>me.written += n, |
| <span class="prelude-val">Err</span>(e) => { |
| ret = <span class="prelude-val">Err</span>(e); |
| <span class="kw">break</span>; |
| } |
| } |
| } |
| <span class="kw">if </span><span class="kw-2">*</span>me.written > <span class="number">0 </span>{ |
| me.buf.drain(..<span class="kw-2">*</span>me.written); |
| } |
| <span class="kw-2">*</span>me.written = <span class="number">0</span>; |
| Poll::Ready(ret) |
| } |
| |
| <span class="doccomment">/// Gets a reference to the underlying writer. |
| </span><span class="kw">pub fn </span>get_ref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>W { |
| <span class="kw-2">&</span><span class="self">self</span>.inner |
| } |
| |
| <span class="doccomment">/// Gets a mutable reference to the underlying writer. |
| /// |
| /// It is inadvisable to directly write to the underlying writer. |
| </span><span class="kw">pub fn </span>get_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>W { |
| <span class="kw-2">&mut </span><span class="self">self</span>.inner |
| } |
| |
| <span class="doccomment">/// Gets a pinned mutable reference to the underlying writer. |
| /// |
| /// It is inadvisable to directly write to the underlying writer. |
| </span><span class="kw">pub fn </span>get_pin_mut(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>) -> Pin<<span class="kw-2">&mut </span>W> { |
| <span class="self">self</span>.project().inner |
| } |
| |
| <span class="doccomment">/// Consumes this `BufWriter`, returning the underlying writer. |
| /// |
| /// Note that any leftover data in the internal buffer is lost. |
| </span><span class="kw">pub fn </span>into_inner(<span class="self">self</span>) -> W { |
| <span class="self">self</span>.inner |
| } |
| |
| <span class="doccomment">/// Returns a reference to the internally buffered data. |
| </span><span class="kw">pub fn </span>buffer(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>[u8] { |
| <span class="kw-2">&</span><span class="self">self</span>.buf |
| } |
| } |
| |
| <span class="kw">impl</span><W: AsyncWrite> AsyncWrite <span class="kw">for </span>BufWriter<W> { |
| <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<io::Result<usize>> { |
| <span class="kw">if </span><span class="self">self</span>.buf.len() + buf.len() > <span class="self">self</span>.buf.capacity() { |
| <span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| } |
| |
| <span class="kw">let </span>me = <span class="self">self</span>.project(); |
| <span class="kw">if </span>buf.len() >= me.buf.capacity() { |
| me.inner.poll_write(cx, buf) |
| } <span class="kw">else </span>{ |
| Poll::Ready(me.buf.write(buf)) |
| } |
| } |
| |
| <span class="kw">fn </span>poll_write_vectored( |
| <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>bufs: <span class="kw-2">&</span>[IoSlice<<span class="lifetime">'_</span>>], |
| ) -> Poll<io::Result<usize>> { |
| <span class="kw">if </span><span class="self">self</span>.inner.is_write_vectored() { |
| <span class="kw">let </span>total_len = bufs |
| .iter() |
| .fold(<span class="number">0usize</span>, |acc, b| acc.saturating_add(b.len())); |
| <span class="kw">if </span>total_len > <span class="self">self</span>.buf.capacity() - <span class="self">self</span>.buf.len() { |
| <span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| } |
| <span class="kw">let </span>me = <span class="self">self</span>.as_mut().project(); |
| <span class="kw">if </span>total_len >= me.buf.capacity() { |
| <span class="comment">// It's more efficient to pass the slices directly to the |
| // underlying writer than to buffer them. |
| // The case when the total_len calculation saturates at |
| // usize::MAX is also handled here. |
| </span>me.inner.poll_write_vectored(cx, bufs) |
| } <span class="kw">else </span>{ |
| bufs.iter().for_each(|b| me.buf.extend_from_slice(b)); |
| Poll::Ready(<span class="prelude-val">Ok</span>(total_len)) |
| } |
| } <span class="kw">else </span>{ |
| <span class="comment">// Remove empty buffers at the beginning of bufs. |
| </span><span class="kw">while </span>bufs.first().map(|buf| buf.len()) == <span class="prelude-val">Some</span>(<span class="number">0</span>) { |
| bufs = <span class="kw-2">&</span>bufs[<span class="number">1</span>..]; |
| } |
| <span class="kw">if </span>bufs.is_empty() { |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(<span class="number">0</span>)); |
| } |
| <span class="comment">// Flush if the first buffer doesn't fit. |
| </span><span class="kw">let </span>first_len = bufs[<span class="number">0</span>].len(); |
| <span class="kw">if </span>first_len > <span class="self">self</span>.buf.capacity() - <span class="self">self</span>.buf.len() { |
| <span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| <span class="macro">debug_assert!</span>(<span class="self">self</span>.buf.is_empty()); |
| } |
| <span class="kw">let </span>me = <span class="self">self</span>.as_mut().project(); |
| <span class="kw">if </span>first_len >= me.buf.capacity() { |
| <span class="comment">// The slice is at least as large as the buffering capacity, |
| // so it's better to write it directly, bypassing the buffer. |
| </span><span class="macro">debug_assert!</span>(me.buf.is_empty()); |
| <span class="kw">return </span>me.inner.poll_write(cx, <span class="kw-2">&</span>bufs[<span class="number">0</span>]); |
| } <span class="kw">else </span>{ |
| me.buf.extend_from_slice(<span class="kw-2">&</span>bufs[<span class="number">0</span>]); |
| bufs = <span class="kw-2">&</span>bufs[<span class="number">1</span>..]; |
| } |
| <span class="kw">let </span><span class="kw-2">mut </span>total_written = first_len; |
| <span class="macro">debug_assert!</span>(total_written != <span class="number">0</span>); |
| <span class="comment">// Append the buffers that fit in the internal buffer. |
| </span><span class="kw">for </span>buf <span class="kw">in </span>bufs { |
| <span class="kw">if </span>buf.len() > me.buf.capacity() - me.buf.len() { |
| <span class="kw">break</span>; |
| } <span class="kw">else </span>{ |
| me.buf.extend_from_slice(buf); |
| total_written += buf.len(); |
| } |
| } |
| Poll::Ready(<span class="prelude-val">Ok</span>(total_written)) |
| } |
| } |
| |
| <span class="kw">fn </span>is_write_vectored(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="bool-val">true |
| </span>} |
| |
| <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<io::Result<()>> { |
| <span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| <span class="self">self</span>.get_pin_mut().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<io::Result<()>> { |
| <span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| <span class="self">self</span>.get_pin_mut().poll_shutdown(cx) |
| } |
| } |
| |
| <span class="attribute">#[derive(Debug, Clone, Copy)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>SeekState { |
| <span class="doccomment">/// start_seek has not been called. |
| </span>Init, |
| <span class="doccomment">/// start_seek has been called, but poll_complete has not yet been called. |
| </span>Start(SeekFrom), |
| <span class="doccomment">/// Waiting for completion of poll_complete. |
| </span>Pending, |
| } |
| |
| <span class="doccomment">/// Seek to the offset, in bytes, in the underlying writer. |
| /// |
| /// Seeking always writes out the internal buffer before seeking. |
| </span><span class="kw">impl</span><W: AsyncWrite + AsyncSeek> AsyncSeek <span class="kw">for </span>BufWriter<W> { |
| <span class="kw">fn </span>start_seek(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, pos: SeekFrom) -> io::Result<()> { |
| <span class="comment">// We need to flush the internal buffer before seeking. |
| // It receives a `Context` and returns a `Poll`, so it cannot be called |
| // inside `start_seek`. |
| </span><span class="kw-2">*</span><span class="self">self</span>.project().seek_state = SeekState::Start(pos); |
| <span class="prelude-val">Ok</span>(()) |
| } |
| |
| <span class="kw">fn </span>poll_complete(<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<io::Result<u64>> { |
| <span class="kw">let </span>pos = <span class="kw">match </span><span class="self">self</span>.seek_state { |
| SeekState::Init => { |
| <span class="kw">return </span><span class="self">self</span>.project().inner.poll_complete(cx); |
| } |
| SeekState::Start(pos) => <span class="prelude-val">Some</span>(pos), |
| SeekState::Pending => <span class="prelude-val">None</span>, |
| }; |
| |
| <span class="comment">// Flush the internal buffer before seeking. |
| </span><span class="macro">ready!</span>(<span class="self">self</span>.as_mut().flush_buf(cx))<span class="question-mark">?</span>; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>me = <span class="self">self</span>.project(); |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(pos) = pos { |
| <span class="comment">// Ensure previous seeks have finished before starting a new one |
| </span><span class="macro">ready!</span>(me.inner.as_mut().poll_complete(cx))<span class="question-mark">?</span>; |
| <span class="kw">if let </span><span class="prelude-val">Err</span>(e) = me.inner.as_mut().start_seek(pos) { |
| <span class="kw-2">*</span>me.seek_state = SeekState::Init; |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Err</span>(e)); |
| } |
| } |
| <span class="kw">match </span>me.inner.poll_complete(cx) { |
| Poll::Ready(res) => { |
| <span class="kw-2">*</span>me.seek_state = SeekState::Init; |
| Poll::Ready(res) |
| } |
| Poll::Pending => { |
| <span class="kw-2">*</span>me.seek_state = SeekState::Pending; |
| Poll::Pending |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><W: AsyncWrite + AsyncRead> AsyncRead <span class="kw">for </span>BufWriter<W> { |
| <span class="kw">fn </span>poll_read( |
| <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">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>> { |
| <span class="self">self</span>.get_pin_mut().poll_read(cx, buf) |
| } |
| } |
| |
| <span class="kw">impl</span><W: AsyncWrite + AsyncBufRead> AsyncBufRead <span class="kw">for </span>BufWriter<W> { |
| <span class="kw">fn </span>poll_fill_buf(<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<io::Result<<span class="kw-2">&</span>[u8]>> { |
| <span class="self">self</span>.get_pin_mut().poll_fill_buf(cx) |
| } |
| |
| <span class="kw">fn </span>consume(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, amt: usize) { |
| <span class="self">self</span>.get_pin_mut().consume(amt) |
| } |
| } |
| |
| <span class="kw">impl</span><W: fmt::Debug> fmt::Debug <span class="kw">for </span>BufWriter<W> { |
| <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">"BufWriter"</span>) |
| .field(<span class="string">"writer"</span>, <span class="kw-2">&</span><span class="self">self</span>.inner) |
| .field( |
| <span class="string">"buffer"</span>, |
| <span class="kw-2">&</span><span class="macro">format_args!</span>(<span class="string">"{}/{}"</span>, <span class="self">self</span>.buf.len(), <span class="self">self</span>.buf.capacity()), |
| ) |
| .field(<span class="string">"written"</span>, <span class="kw-2">&</span><span class="self">self</span>.written) |
| .finish() |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>assert_unpin() { |
| <span class="kw">crate</span>::is_unpin::<BufWriter<()>>(); |
| } |
| } |
| </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> |