Hadris I/O

No-std I/O abstraction layer for the Hadris filesystem crates.

Overview

This crate provides Read, Write, and Seek traits that work in no-std environments, enabling filesystem implementations to run on bare-metal systems, bootloaders, and embedded devices.

When the std feature is enabled, traits re-export from std::io. In no_std mode, a minimal custom trait surface is provided. The no-std Error type is intentionally smaller than std::io::Error (no OS error codes; message storage requires alloc).

Features

No-std Compatible - Works without the standard library
Familiar API - Trait signatures mirror std::io where practical
Zero-copy helpers - ReadExt structured reads via bytemuck
In-memory Cursor - Byte-slice reader/seeker for parsing

Sector-aligned wrappers such as SectorCursor live in hadris-fat, not in this crate.

Feature Flags

Feature	Description	Default
`std`	Standard library support (implies `sync`, `alloc`)	Yes
`sync`	Synchronous I/O traits	Yes
`async`	Asynchronous I/O traits	No
`alloc`	Heap allocation (dynamic error messages in no-std)	via `std`

Usage

With std (default)

[dependencies]
hadris-io = "2.0.0-rc.2"

No-std

[dependencies]
hadris-io = { version = "2.0.0-rc.2", default-features = false, features = ["sync"] }

Quick Start

use hadris_io::{Cursor, SeekFrom, Read, Seek};

let data = [0x48, 0x44, 0x52, 0x53]; // "HDRS"
let mut cursor = Cursor::new(&data);

let mut buf = [0u8; 2];
cursor.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"HD");

cursor.seek(SeekFrom::Start(0)).unwrap();
cursor.read_exact(&mut buf).unwrap();
assert_eq!(&buf, b"HD");

Core Traits

With std, these are std::io::{Read, Write, Seek}. Without std, this crate defines compatible traits returning hadris_io::Result:

pub trait Read {
    fn read(&mut self, buf: &mut [u8]) -> Result<usize>;
    fn read_exact(&mut self, buf: &mut [u8]) -> Result<()>;
}

pub trait Write {
    fn write(&mut self, buf: &[u8]) -> Result<usize>;
    fn write_all(&mut self, buf: &[u8]) -> Result<()>;
    fn flush(&mut self) -> Result<()>;
}

pub trait Seek {
    fn seek(&mut self, pos: SeekFrom) -> Result<u64>;
}

License

Licensed under the MIT license.

hadris-io 2.0.0-rc.2