odirect

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

Features

• Linux: O_DIRECT with optional O_DSYNC / O_SYNC
• macOS: F_NOCACHE
• Windows: FILE_FLAG_NO_BUFFERING with optional write-through

Installation

[dependencies]
odirect = "0.4.0"

Usage

use odirect::{open_direct_file, AccessMode, Integrity};

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

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

Supported Access Modes

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

Supported Integrity Levels

Controls durability guarantees when writing:

Integrity::Null   // No sync (default buffering behavior)
Integrity::Data   // Data integrity (Linux: O_DSYNC)
Integrity::File   // Full file integrity (Linux: O_SYNC)

Platform Notes

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

• Linux: Uses O_DIRECT. Integrity levels map to O_DSYNC and O_SYNC.
• macOS: Uses F_NOCACHE. Integrity levels are not applied at open time—handle durability separately with fsync / F_FULLFSYNC after writes.
• Windows: Uses FILE_FLAG_NO_BUFFERING. Integrity levels other than Null add write-through behavior.

Some platforms may require aligned buffers and aligned reads/writes when performing direct I/O operations.

The key changes:

• Added Integrity to the usage example since it's now a required parameter
• Added an "Integrity Levels" section
• Updated platform notes to accurately reflect how each OS handles integrity
• Kept the overall structure and simplicity intact