Castflip

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

In this crate, the term encast means decoding a number of bytes to one or more values, the term decast means encoding one or more variables to a number of bytes, and the term endian-flip means flipping the endianness of value(s).

Here we show an example below. For more examples and documentation, please see https://docs.rs/castflip/.

Example 1

In the example below, method encastf decodes bytes in bytes1 in big-endian ([BE]) to variable udp_hdr2 of type UdpHdr. Then, method decastf encodes the resulting value in udp_hdr2 to bytes in big-endian ([BE]) and stores them in bytes3.

```rust use castflip::{Cast, Flip, EncastMem, DecastMem, BE};

[repr(C)]

[derive(Cast, Flip)]

struct UdpHdr { // UDP: https://www.rfc-editor.org/rfc/rfc768.txt sport: u16, // UDP Source Port dport: u16, // UDP Destination Port len: u16, // UDP Length sum: u16, // UDP Checksum }

// Input data: UDP header (8 bytes) let bytes1: [u8; 8] = [0xC3, 0xC9, 0x00, 0x35, 0x00, 0x32, 0x82, 0x3F];

// Decode bytes bytes1 to variable udp_hdr2. let udp_hdr2 = bytes1.encastf::(BE)?; // BE = Big-Endian

// Encode the resulting UDP header udp_hdr2 to bytes bytes3. let mut bytes3 = [0u8; 8]; let bytes3size = bytes3.decastf::(&udp_hdr2, BE)?;

// Check the results. asserteq!(udphdr2.sport, 0xC3C9); // = 50121 asserteq!(udphdr2.dport, 0x0035); // = 53 (DNS) asserteq!(udphdr2.len, 0x0032); // = 50 asserteq!(udphdr2.sum, 0x823F); asserteq!(bytes3size, 8); assert_eq!(bytes3, bytes1); ```

In the example above, #[derive([Cast])] makes the value of UdpHdr encastable / decastable, and #[derive([Flip])] makes the value of UdpHdr endian-flippable.

Trait [EncastMem] provides methods to encast from memory, and trait [DecastMem] provides methods to decast to memory. The generic type parameters of their methods can be omitted where the Rust compiler can infer them. Their methods whose names end with 'f' flip the endianness of the results. The endianness of bytes is specified in their argument. [BE] is an alias of [Endian]::Big, which means Big-Endian.

In addition to these traits, this crate has trait [EncastIO] providing methods to encast from I/O, and trait [DecastIO] providing methods to decast to I/O.

Note: [UDP] is one of the fundamental protocols in the internet protocol suite.