bitsandbytes 0.1.0

An owned, bit-aware binary codec: fast bit/byte field types and the unified #[bin] macro.
Documentation 
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//! `big`/`little` byte order (ROADMAP Phase 2). Byte order is applied to
//! byte-multiple field values (binrw applies it only to byte-multiple types); the
//! default is big-endian (network order). Sub-byte fields are unaffected.

use bnb::{bin, u4, u12};

#[bin(big)]
#[derive(Debug, PartialEq, Eq, Clone)]
struct BeWord {
    value: u16,
    big: u32,
}

#[bin(little)]
#[derive(Debug, PartialEq, Eq, Clone)]
struct LeWord {
    value: u16,
    big: u32,
}

#[test]
fn byte_order_visible_on_the_wire() {
    let be = BeWord {
        value: 0x1234,
        big: 0xAABB_CCDD,
    };
    assert_eq!(be.to_bytes().unwrap(), [0x12, 0x34, 0xAA, 0xBB, 0xCC, 0xDD]);

    let le = LeWord {
        value: 0x1234,
        big: 0xAABB_CCDD,
    };
    assert_eq!(le.to_bytes().unwrap(), [0x34, 0x12, 0xDD, 0xCC, 0xBB, 0xAA]);

    assert_eq!(BeWord::decode_exact(&be.to_bytes().unwrap()).unwrap(), be);
    assert_eq!(LeWord::decode_exact(&le.to_bytes().unwrap()).unwrap(), le);
}

// Little-endian with a sub-byte lead field (so multi-byte values straddle bytes).
#[bin(little)]
#[derive(Debug, PartialEq, Eq, Clone)]
struct LeStraddle {
    tag: u4,
    value: u16,
    word: u32,
}

#[test]
fn little_endian_straddling_round_trips() {
    let f = LeStraddle {
        tag: u4::new(0x5),
        value: 0x1234,
        word: 0xAABB_CCDD,
    };
    assert_eq!(LeStraddle::decode_exact(&f.to_bytes().unwrap()).unwrap(), f);
}

// Sub-byte (non-byte-multiple) widths are not byte-swapped, regardless of order.
#[bin(little)]
#[derive(Debug, PartialEq, Eq, Clone)]
struct SubByte {
    a: u4,
    b: u12,
}

#[test]
fn sub_byte_fields_unaffected() {
    let f = SubByte {
        a: u4::new(0xA),
        b: u12::new(0x123),
    };
    assert_eq!(SubByte::decode_exact(&f.to_bytes().unwrap()).unwrap(), f);
}