odirect

Minimal cross-platform direct I/O abstraction for Rust.

Features

• Linux: O_DIRECT
• macOS: F_NOCACHE
• Windows: FILE_FLAG_NO_BUFFERING

Installation

[dependencies]
odirect = "0.5.0"

Usage

use odirect::{open_direct_file, AccessMode};

fn main() {
    let file = open_direct_file(
        "data.bin",
        AccessMode::ReadWrite,
    );

    match file {
        Ok(_) => println!("opened successfully"),
        Err(e) => println!("error: {}", e),
    }
}

Supported Access Modes

AccessMode::Read
AccessMode::Write
AccessMode::ReadWrite

Platform Notes

Direct/unbuffered I/O behavior differs across operating systems:

• Linux: Uses O_DIRECT to bypass the page cache.
• macOS: Uses F_NOCACHE to disable file caching.
• Windows: Uses FILE_FLAG_NO_BUFFERING for unbuffered I/O.

All platforms may require aligned buffers and aligned reads/writes (typically 512 or 4096 bytes, depending on the underlying device) when performing direct I/O operations. Durability guarantees (fsync, F_FULLFSYNC, FlushFileBuffers) must be handled separately by the caller after writes.