| <!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/async_seek.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>async_seek.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>std::io::{<span class="self">self</span>, SeekFrom}; |
| <span class="kw">use </span>std::ops::DerefMut; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| |
| <span class="doccomment">/// Seek bytes asynchronously. |
| /// |
| /// This trait is analogous to the [`std::io::Seek`] trait, but integrates |
| /// with the asynchronous task system. In particular, the `start_seek` |
| /// method, unlike [`Seek::seek`], will not block the calling thread. |
| /// |
| /// Utilities for working with `AsyncSeek` values are provided by |
| /// [`AsyncSeekExt`]. |
| /// |
| /// [`std::io::Seek`]: std::io::Seek |
| /// [`Seek::seek`]: std::io::Seek::seek() |
| /// [`AsyncSeekExt`]: crate::io::AsyncSeekExt |
| </span><span class="kw">pub trait </span>AsyncSeek { |
| <span class="doccomment">/// Attempts to seek to an offset, in bytes, in a stream. |
| /// |
| /// A seek beyond the end of a stream is allowed, but behavior is defined |
| /// by the implementation. |
| /// |
| /// If this function returns successfully, then the job has been submitted. |
| /// To find out when it completes, call `poll_complete`. |
| /// |
| /// # Errors |
| /// |
| /// This function can return [`io::ErrorKind::Other`] in case there is |
| /// another seek in progress. To avoid this, it is advisable that any call |
| /// to `start_seek` is preceded by a call to `poll_complete` to ensure all |
| /// pending seeks have completed. |
| </span><span class="kw">fn </span>start_seek(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, position: SeekFrom) -> io::Result<()>; |
| |
| <span class="doccomment">/// Waits for a seek operation to complete. |
| /// |
| /// If the seek operation completed successfully, |
| /// this method returns the new position from the start of the stream. |
| /// That position can be used later with [`SeekFrom::Start`]. Repeatedly |
| /// calling this function without calling `start_seek` might return the |
| /// same result. |
| /// |
| /// # Errors |
| /// |
| /// Seeking to a negative offset is considered an error. |
| </span><span class="kw">fn </span>poll_complete(<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="macro">macro_rules! </span>deref_async_seek { |
| () => { |
| <span class="kw">fn </span>start_seek(<span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, pos: SeekFrom) -> io::Result<()> { |
| Pin::new(<span class="kw-2">&mut **</span><span class="self">self</span>).start_seek(pos) |
| } |
| |
| <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>> { |
| Pin::new(<span class="kw-2">&mut **</span><span class="self">self</span>).poll_complete(cx) |
| } |
| }; |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + AsyncSeek + Unpin> AsyncSeek <span class="kw">for </span>Box<T> { |
| <span class="macro">deref_async_seek!</span>(); |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + AsyncSeek + Unpin> AsyncSeek <span class="kw">for </span><span class="kw-2">&mut </span>T { |
| <span class="macro">deref_async_seek!</span>(); |
| } |
| |
| <span class="kw">impl</span><P> AsyncSeek <span class="kw">for </span>Pin<P> |
| <span class="kw">where |
| </span>P: DerefMut + Unpin, |
| P::Target: AsyncSeek, |
| { |
| <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="self">self</span>.get_mut().as_mut().start_seek(pos) |
| } |
| |
| <span class="kw">fn </span>poll_complete(<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="self">self</span>.get_mut().as_mut().poll_complete(cx) |
| } |
| } |
| |
| <span class="kw">impl</span><T: AsRef<[u8]> + Unpin> AsyncSeek <span class="kw">for </span>io::Cursor<T> { |
| <span class="kw">fn </span>start_seek(<span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, pos: SeekFrom) -> io::Result<()> { |
| io::Seek::seek(<span class="kw-2">&mut *</span><span class="self">self</span>, pos).map(drop) |
| } |
| <span class="kw">fn </span>poll_complete(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, <span class="kw">_</span>: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<io::Result<u64>> { |
| Poll::Ready(<span class="prelude-val">Ok</span>(<span class="self">self</span>.get_mut().position())) |
| } |
| } |
| </code></pre></div> |
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