From 899f471de500355b9dc7ef4ec424c05bae01ec31 Mon Sep 17 00:00:00 2001 From: Jonathan Date: Sun, 18 Dec 2022 13:17:04 +0000 Subject: [PATCH] feat: Safer poll timeout --- CHANGELOG.md | 2 + src/poll.rs | 191 ++++++++++++++++++++++++++++++++++++++++++++-- test/test_poll.rs | 6 +- 3 files changed, 189 insertions(+), 10 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index 8ff4176c87..4b3d9e5fb5 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -21,6 +21,8 @@ This project adheres to [Semantic Versioning](https://semver.org/). - With I/O-safe type applied in `pty::OpenptyResult` and `pty::ForkptyResult`, users no longer need to manually close the file descriptors in these types. ([#1921](https://github.com/nix-rust/nix/pull/1921)) +- The `timeout` argument of `poll::poll` is now of type `poll::PollTimeout`. + ([#1876](https://github.com/nix-rust/nix/pull/1876)) ### Fixed ### Removed diff --git a/src/poll.rs b/src/poll.rs index 9181bf7f30..be0a4f3c3f 100644 --- a/src/poll.rs +++ b/src/poll.rs @@ -1,9 +1,9 @@ //! Wait for events to trigger on specific file descriptors use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd}; +use std::time::Duration; use crate::errno::Errno; use crate::Result; - /// This is a wrapper around `libc::pollfd`. /// /// It's meant to be used as an argument to the [`poll`](fn.poll.html) and @@ -168,6 +168,180 @@ libc_bitflags! { } } +/// Timeout argument for [`poll`]. +#[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd)] +pub struct PollTimeout(i32); + +impl PollTimeout { + /// Blocks indefinitely. + /// + /// > Specifying a negative value in timeout means an infinite timeout. + pub const NONE: Self = Self(-1); + /// Returns immediately. + /// + /// > Specifying a timeout of zero causes poll() to return immediately, even if no file + /// > descriptors are ready. + pub const ZERO: Self = Self(0); + /// Blocks for at most [`std::i32::MAX`] milliseconds. + pub const MAX: Self = Self(i32::MAX); + /// Returns if `self` equals [`PollTimeout::NONE`]. + pub fn is_none(&self) -> bool { + // > Specifying a negative value in timeout means an infinite timeout. + *self <= Self::NONE + } + /// Returns if `self` does not equal [`PollTimeout::NONE`]. + pub fn is_some(&self) -> bool { + !self.is_none() + } + /// Returns the timeout in milliseconds if there is some, otherwise returns `None`. + pub fn timeout(&self) -> Option { + self.is_some().then_some(self.0) + } +} + +impl> From> for PollTimeout { + fn from(x: Option) -> Self { + x.map_or(Self::NONE, |x| x.into()) + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: Duration) -> std::result::Result { + Ok(Self(i32::try_from(x.as_millis())?)) + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: u128) -> std::result::Result { + Ok(Self(i32::try_from(x)?)) + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: u64) -> std::result::Result { + Ok(Self(i32::try_from(x)?)) + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: u32) -> std::result::Result { + Ok(Self(i32::try_from(x)?)) + } +} +impl From for PollTimeout { + fn from(x: u16) -> Self { + Self(i32::from(x)) + } +} +impl From for PollTimeout { + fn from(x: u8) -> Self { + Self(i32::from(x)) + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: i128) -> std::result::Result { + match x { + // > Specifying a negative value in timeout means an infinite timeout. + i128::MIN..=-1 => Ok(Self::NONE), + millis @ 0.. => Ok(Self(i32::try_from(millis)?)), + } + } +} +impl TryFrom for PollTimeout { + type Error = >::Error; + fn try_from(x: i64) -> std::result::Result { + match x { + i64::MIN..=-1 => Ok(Self::NONE), + millis @ 0.. => Ok(Self(i32::try_from(millis)?)), + } + } +} +impl From for PollTimeout { + fn from(x: i32) -> Self { + Self(x) + } +} +impl From for PollTimeout { + fn from(x: i16) -> Self { + Self(i32::from(x)) + } +} +impl From for PollTimeout { + fn from(x: i8) -> Self { + Self(i32::from(x)) + } +} +impl TryFrom for Duration { + type Error = (); + fn try_from(x: PollTimeout) -> std::result::Result { + match x.timeout() { + // SAFETY: When `x.timeout()` returns `Some(a)`, `a` is always non-negative. + Some(millis) => Ok(Duration::from_millis(unsafe { + u64::try_from(millis).unwrap_unchecked() + })), + None => Err(()), + } + } +} +impl TryFrom for u128 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl TryFrom for u64 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl TryFrom for u32 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl TryFrom for u16 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl TryFrom for u8 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl From for i128 { + fn from(x: PollTimeout) -> Self { + Self::from(x.0) + } +} +impl From for i64 { + fn from(x: PollTimeout) -> Self { + Self::from(x.0) + } +} +impl From for i32 { + fn from(x: PollTimeout) -> Self { + x.0 + } +} +impl TryFrom for i16 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} +impl TryFrom for i8 { + type Error = >::Error; + fn try_from(x: PollTimeout) -> std::result::Result { + Self::try_from(x.0) + } +} + /// `poll` waits for one of a set of file descriptors to become ready to perform I/O. /// ([`poll(2)`](https://pubs.opengroup.org/onlinepubs/9699919799/functions/poll.html)) /// @@ -184,16 +358,19 @@ libc_bitflags! { /// /// Note that the timeout interval will be rounded up to the system clock /// granularity, and kernel scheduling delays mean that the blocking -/// interval may overrun by a small amount. Specifying a negative value -/// in timeout means an infinite timeout. Specifying a timeout of zero -/// causes `poll()` to return immediately, even if no file descriptors are -/// ready. -pub fn poll(fds: &mut [PollFd], timeout: libc::c_int) -> Result { +/// interval may overrun by a small amount. Specifying a [`PollTimeout::NONE`] +/// in timeout means an infinite timeout. Specifying a timeout of +/// [`PollTimeout::ZERO`] causes `poll()` to return immediately, even if no file +/// descriptors are ready. +pub fn poll>( + fds: &mut [PollFd], + timeout: T, +) -> Result { let res = unsafe { libc::poll( fds.as_mut_ptr() as *mut libc::pollfd, fds.len() as libc::nfds_t, - timeout, + i32::from(timeout.into()), ) }; diff --git a/test/test_poll.rs b/test/test_poll.rs index 045ccd3df1..c8cd43ef0d 100644 --- a/test/test_poll.rs +++ b/test/test_poll.rs @@ -1,6 +1,6 @@ use nix::{ errno::Errno, - poll::{poll, PollFd, PollFlags}, + poll::{poll, PollFd, PollFlags, PollTimeout}, unistd::{close, pipe, write}, }; use std::os::unix::io::{BorrowedFd, FromRawFd, OwnedFd}; @@ -24,14 +24,14 @@ fn test_poll() { let mut fds = [PollFd::new(&r, PollFlags::POLLIN)]; // Poll an idle pipe. Should timeout - let nfds = loop_while_eintr!(poll(&mut fds, 100)); + let nfds = loop_while_eintr!(poll(&mut fds, PollTimeout::from(100u8))); assert_eq!(nfds, 0); assert!(!fds[0].revents().unwrap().contains(PollFlags::POLLIN)); write(w, b".").unwrap(); // Poll a readable pipe. Should return an event. - let nfds = poll(&mut fds, 100).unwrap(); + let nfds = poll(&mut fds, PollTimeout::from(100u8)).unwrap(); assert_eq!(nfds, 1); assert!(fds[0].revents().unwrap().contains(PollFlags::POLLIN)); close(w).unwrap();