io: implement [Read|Write]Volatile for &File and co #321
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| @@ -175,7 +205,7 @@ impl_read_write_volatile_for_raw_fd!(std::os::fd::BorrowedFd<'_>); | |||
| /// Returns the numbers of bytes read. | |||
| #[cfg(feature = "rawfd")] | |||
| fn read_volatile_raw_fd<Fd: AsRawFd>( | |||
| raw_fd: &mut Fd, | |||
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I think &mut is more appropriate since you change the seek position into the file, or consume data from a pipe/socket.
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Right, and I think that's why originally I didn't do this. But today I ended up checking the standard library, and they have impl Read for &File, e.g. advancing the seek position/consuming data through an immutable reference is possible for the stdlib version of these traits. I suppose this is considered okay because read-ing from a File doesn't change any Rust state (e.g. the File object itself remains unmodified), only kernel internal state.
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So, I've changed the signature of this function to just take a RawFd instead of any kind of reference, but that doesn't really address your feedback, as it just moves the as_raw_fd() call up to the caller.
But since the standard library has impl Read for &File, do you still have any concerns about providing the same kind of impls here?
src/io.rs
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| @@ -206,7 +236,7 @@ fn read_volatile_raw_fd<Fd: AsRawFd>( | |||
| /// Returns the numbers of bytes written. | |||
| #[cfg(feature = "rawfd")] | |||
| fn write_volatile_raw_fd<Fd: AsRawFd>( | |||
| raw_fd: &mut Fd, | |||
| raw_fd: &Fd, | |||
Implement these traits for references to types that implement them, e.g. &File, &TcpStream, &UnixStream, &Stdout, etc. This mirrors the standard library implementations and allows calling read/write methods from contexts where no mutable reference is available. Signed-off-by: Patrick Roy <[email protected]>
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| #[cfg(feature = "rawfd")] | ||
| impl WriteVolatile for &Stdout { | ||
| fn write_volatile<B: BitmapSlice>( | ||
| &mut self, | ||
| buf: &VolatileSlice<B>, | ||
| ) -> Result<usize, VolatileMemoryError> { | ||
| write_volatile_raw_fd(self.as_raw_fd(), buf) |
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why do we need WriteVolatile for Stdout?
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vm-virtio is using this for virtio-console
Signed-off-by: Patrick Roy <[email protected]>
Implement these traits for references to types that implement them, e.g. &File, &TcpStream, &UnixStream, &Stdout, etc. This mirrors the standard library implementations and allows calling read/write methods from contexts where no mutable reference is available.
There's probably something more clever we can do with the traits to avoid some repetition, but really, isn't not that bad imo.
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test.
Release" section of CHANGELOG.md (if no such section exists, please create one).
unsafecode is properly documented.