Crate castflip

Crate castflip is a Rust library for encoding and decoding numeric variables, arrays and structures in little-endian and big-endian. It provides methods to convert between a byte representation of a format and a value of a Rust type with endian handling.

Introduction

Crate castflip 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.

The alignment of the addresses of byte representations need not be considered because data are copied when being encasted or decasted.

For more information, please see the documentation of crate castflip. 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`.
//
#[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
}

//
// Step 2: Encast a byte representation of the UDP header in big-endian
// (`BE`) stored in variable `in_bytes` as a value of struct `UdpHdr` in
// native-endian and save it to variable `out_hdr`.
//

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

// Encast a byte representation in big-endian (`BE`) as a value.
let out_hdr: UdpHdr = in_bytes.encastf(BE).unwrap();

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

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

[dependencies]
castflip = "0.1"