Castflip

This crate is a Rust library for encoding and decoding numeric variables, arrays and structures in little-endian and big-endian.

More precisely, this crate provides several traits

• to encast a byte representation of a type as a value of the type,
• to decast a value of a type as a byte representation of the type, and
• to flip the endianness of a value of a type as required.

The supported types include

1. primitive numeric types, and
2. array types, struct types and union types consisting of the supported types.

For more information, please see the documentation of this crate. It includes some examples and summaries as well as the descriptions of its types and its traits.

A Simple Example

In this example, a byte representation of the UDP header in big-endian is encasted as a value of a struct type in native-endian.

use castflip::{BE, Cast, EncastMem, Flip};

//
// Step 1: Define struct `UdpHdr` and test data.
//
#[repr(C)]            // to make it possible to apply #[derive(Cast)]
#[derive(Cast, Flip)] // to implement trait Cast and trait Flip
struct UdpHdr {  // UDP: See https://www.rfc-editor.org/rfc/rfc768.txt
    sport: u16,  // UDP Source Port
    dport: u16,  // UDP Destination Port
    len:   u16,  // UDP Length in Bytes (header plus data)
    sum:   u16,  // UDP Checksum
}

// Test data: A sample byte representation of the UDP header (8 bytes)
const BYTES1: [u8; 8] = [0xc3, 0xc9, 0x00, 0x35, 0x00, 0x32, 0x82, 0x3f];

fn my_main() -> Option<()> {
    //
    // Step 2: Encast a byte representation of the UDP header in
    // big-endian stored in const `BYTES1` as a value of struct
    // `UdpHdr` in native-endian and save it to variable `udp_hdr2`.
    //
    let udp_hdr2: UdpHdr = BYTES1.encastf(BE)?;

    // Check if all fields in variable `udp_hdr2` are as expected.
    assert_eq!(udp_hdr2.sport, 0xc3c9); // = 50121 (Ephemeral Port)
    assert_eq!(udp_hdr2.dport, 0x0035); // = 53 (DNS Port)
    assert_eq!(udp_hdr2.len,   0x0032); // = 50 (Length in Bytes)
    assert_eq!(udp_hdr2.sum,   0x823f); // = 0x823f (Checksum)

    Some(())
}

fn main() { my_main(); }

To use this crate, add the following lines to your Cargo.toml:

[dependencies]
castflip = "0.1"