restruct is used to interpret binary data stored in files or other sources or convert
between C structs and Rust types and when using a parser-generator is considered
disproportionate.
It is a brainchild of Python's struct-module.
The library uses Format Strings as compact descriptions of the binary data and the intended conversion to/from Rust-types. The Format Strings are interpreted at compile-time to generate a type whose functions can be used to convert between unstructured and structured data.
// Generate a parser in little-endian for two 32bit integers, a float and a bool.
#[derive(restruct_derive::Struct)]
#[fmt="<2if?"]
struct FooParser;
// Pack a tuple of two integers, a float and a bool into a [u8; _]-buffer.
let packed = FooParser::pack((1, 2, 3.0, false));
assert_eq!(packed, [1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 64, 64, 0]);
assert_eq!(packed.len(), FooParser::SIZE);
// Packing and unpacking can't fail at runtime.
let unpacked = FooParser::unpack(packed);
assert_eq!(unpacked, (1, 2, 3.0, false));
// Any `io::Read` can be used directly.
let unpacked = FooParser::read_from(&mut &packed[..]).expect("i/o failed");
assert_eq!(unpacked, (1, 2, 3.0, false));
// Any `io::Write` can be used directly.
let mut buffer = Vec::with_capacity(FooParser::SIZE);
FooParser::write_to((1, 2, 3.0, false), &mut buffer).expect("i/o failed");
assert_eq!(&buffer, &packed);// Because packing and unpacking is const we can use these functions to initialize other consts
const TEAPOT: <Tea as restruct::Struct>::Unpacked = Tea::unpack(*include_bytes!("teapot.bin"));
const TEAPOT_TEMPERATURE: i32 = TEAPOT.0;
const TEAPOT_FILL_STATUS: f32 = TEAPOT.2;
const TEAPOT_ACTIVE: bool = TEAPOT.3;