The Castflip Repository

This repository contains three crates.

• Crate castflip
  Is a Rust library for encoding and decoding numeric variables, arrays and structures. It provides methods to convert between a byte representation of a fixed binary format and a value of a Rust type with endianness handling.

• Crate castflip_derive
  Provides five derive macros to implement the basic traits of crate castflip for their supported types.

• Crate castflip_test
  Is a test suite for the methods of crate castflip.

Crate castflip

Crate castflip provides several traits

• to encast a byte representation of a type as a value of the type with endianness handling,
• to decast a value of a type as a byte representation of the type with endianness handling, and
• to be used as bounds to determine which methods can be applied.

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 crate castflip. It includes a number of examples and summaries as well as the detailed descriptions of its types and its traits.

A Simple Example

The example below encasts a byte representation of the UDP header in big-endian as a value of struct UdpHdr in native-endian.

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

//
// Step 1: Define struct `UdpHdr` (The UDP header) 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
}

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

//
// Step 2: Encast a byte representation of the UDP header in big-endian
// (`BE`) at the head of variable `in_bytes` as a value of struct
// `UdpHdr` in native-endian and save it to variable `out_hdr`.
//
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 version 0.1, add the following lines to your Cargo.toml:

[dependencies]
castflip = "0.1"