Adding io::{Read, Write} traits in libcore? #68315
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Jan 20, 2020
1548: Add kernel::debug::IoWrite trait and remove unsound str::from_utf8_unchecked (fix #1449) r=ppannuto a=gendx ### Pull Request Overview This pull request adds a new `IoWrite` trait in the kernel, to write arbitrary bytes instead of UTF-8 strings (fixes #1449). Until now, the `flush` function was using `str::from_utf8_unchecked`, even though the bytes are actually not UTF-8 (even with only UTF-8 input, the underlying ring buffer may wrap-around in the middle on a UTF-8 character). In practice, the underlying implementations work byte-by-byte to send debug output, so a more general trait to write byte slices can be plugged in. This `IoWrite` trait is similar to `std::io::Write`, except that the latter doesn't exist in `no_std` (because `std::io::Error` isn't compatible - see rust-lang/rust#68315 and rust-lang/rfcs#2262). ### Testing Strategy This pull request was tested by Travis. ### TODO or Help Wanted This pull request still needs support for byte-by-byte writing on the arty-e21 board. I'm not even sure the current `debug!` macro is what we want to do in a panic handler. ### Documentation Updated - [x] Updated the relevant files in `/docs`, or no updates are required. ### Formatting - [x] Ran `make formatall`. Co-authored-by: Guillaume Endignoux <[email protected]>
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Currently, libcore contains
core::fmt::Writebut (as far as I understand) nothing of thestd::io::namespace.However,
core::fmt::Writeis more constrained thanstd::io::Write, in that it only allows to write UTF-8 strings, as opposed to slices of bytes in general. It seems to me thatstd::io::Writeas a trait doesn't require any specific OS support (contrary toFile,Stdout, etc.), and as such would be useful in libcore and would integrate well there.For an example where it would be useful in a
no_stdcontext, see tock/tock#1449. In this case, one could essentially re-write theio::Writetrait, but this seems quite redundant (and wouldn't inter-operate with crates that require a genuineio::Writein their API).In general, it seems to me that
std::io::{Read, Write}, as well as a other utilities such asCursororBufReaderwould have their place in libcore, to be able to use them inno_stdcontexts. Or is there any technical difficultly that I missed?The text was updated successfully, but these errors were encountered: