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Matthias Krüger
458095aa17
Override default `Write` methods for cursor-like types Override the default `io::Write` methods for cursor-like types to provide more efficient versions. Writes to resizable containers already write everything, so implement `write_all` and `write_all_vectored` in terms of those. For fixed-sized containers, cut out unnecessary error checking and looping for those same methods. | `impl Write for T` | `vectored` | `all` | `all_vectored` | `fmt` | | ------------------------------- | ---------- | ----- | -------------- | ------- | | `&mut [u8]` | Y | Y | new | | | `Vec<u8>` | Y | Y | new | #137762 | | `VecDeque<u8>` | Y | Y | new | #137762 | | `std::io::Cursor<&mut [u8]>` | Y | new | new | | | `std::io::Cursor<&mut Vec<u8>>` | Y | new | new | #137762 | | `std::io::Cursor<Vec<u8>>` | Y | new | new | #137762 | | `std::io::Cursor<Box<[u8]>>` | Y | new | new | | | `std::io::Cursor<[u8; N]>` | Y | new | new | | | `core::io::BorrowedCursor<'_>` | new | new | new | | Tracked in https://github.com/rust-lang/rust/issues/136756. # Open questions Is it guaranteed by `Write::write_all` that the maximal write is performed when not everything can be written? Its documentation describes the behavior of the default implementation, which writes until a 0-length write is encountered, thus implying that a maximal write is expected. In contrast, `Read::read_exact` declares that the contents of the buffer are unspecified for short reads. If it were allowed, these cursor-like types could bail on the write altogether if it has insufficient capacity.