refactor: buffered

[AsakuraMizu]

Depends: #8

This is the second stage of refactoring, extracted from #4.

Changes

• Reimplement BufReader
  • If alloc feature is enabled, use a Box<[MaybeUninit<u8>]> as buffer backend and use heapless::Vec which has a capacity limit if alloc feature is disabled.
• Add BufWriter and LineWriter
  • Similar to BufReader, use heapless::Vec instead of alloc::vec::Vec if alloc feature is disabled but the capacity is fixed.
• Use autocfg to check if maybe_uninit_slice is stabilized on current compiler

[Copilot]

Pull request overview

This PR refactors the buffered I/O implementation as the second stage of a larger refactoring effort. It reimplements BufReader with improved buffer management, adds BufWriter and LineWriter implementations, and reorganizes the module structure for better maintainability.

Key changes:

• Reorganized code into separate read, write, and seek modules for better separation of concerns
• Reimplemented BufReader to use Box<[MaybeUninit<u8>]> when alloc is enabled, and heapless::Vec with fixed capacity when disabled
• Added BufWriter and LineWriter with similar dual-mode buffer management
• Enhanced build configuration using autocfg to detect maybe_uninit_slice feature availability

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/lib.rs	Updated to use new module structure, bumped edition to 2024, added DEFAULT_BUF_SIZE constant
src/prelude.rs	Updated import paths to use crate:: instead of super::
src/read/mod.rs	Extracted Read trait and related functionality from lib.rs with additional helper functions
src/read/impls.rs	Implementations of Read/BufRead for standard types like slices, Box, VecDeque
src/write/mod.rs	New Write trait module with formatting support
src/write/impls.rs	Implementations of Write for standard types
src/seek/mod.rs	New Seek trait module extracted from lib.rs
src/seek/impls.rs	Forwarding implementations for &mut T and Box
src/buffered/mod.rs	Added exports for BufWriter, LineWriter, and IntoInnerError
src/buffered/bufreader/mod.rs	Reimplemented BufReader with new buffer abstraction
src/buffered/bufreader/buffer.rs	New internal buffer implementation supporting both alloc and no-alloc modes
src/buffered/bufwriter/mod.rs	New BufWriter implementation with dual-mode buffering
src/buffered/linewriter/mod.rs	New LineWriter wrapper around BufWriter
src/buffered/linewriter/shim.rs	Internal line-buffering logic implementation
build.rs	Added autocfg probe for maybe_uninit_slice feature
Cargo.toml	Updated axerrno to 0.2, added heapless and memchr dependencies, changed edition to 2024
README.md	Enhanced documentation with feature descriptions and limitations
rustfmt.toml	New formatting configuration file

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[AsakuraMizu]

Typos found by Copilot has been reported upstream.

[Copilot]

Pull request overview

Copilot reviewed 22 out of 22 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

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[Copilot]

Buffer::backshift updates pos/filled but (under cfg(borrowedbuf_init)) it does not update initialized. After shifting the underlying slice left, the first initialized bytes are no longer guaranteed to be initialized, so later BorrowedBuf::set_init(self.initialized) can over-report initialized bytes and cause UB for Read impls that don't fully initialize the buffer. Track the old pos and subtract it from initialized (or otherwise recompute it) when borrowedbuf_init is enabled.

Suggested change

	self.buf.copy_within(self.pos.., 0);
	self.filled -= self.pos;
	let old_pos = self.pos;
	self.buf.copy_within(old_pos.., 0);
	self.filled -= old_pos;
	#[cfg(borrowedbuf_init)]
	{
	self.initialized -= old_pos;
	}