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//! Encoding and decoding of little-endian format. //! //! This was created out of fustration with the `byteorder` crate, which I felt had a heavy API, so //! I created this crate. #![feature(i128_type)] /// Write some integer into a buffer. /// /// This writes `from` into `buf` through the methods in `T`'s implementation of `Encode`. pub fn write<T: Encode>(buf: &mut [u8], from: T) { from.write_le(buf) } /// Read an integer from a buffer. /// /// This writes `buf` through the methods in `T`'s implementation of `Encode`. pub fn read<T: Encode>(buf: &[u8]) -> T { T::read_le(buf) } /// An encodable/decodable type. pub trait Encode { /// Read an integer in little-endian format. /// /// This reads the first n bytes (depending on the size of `Self`) of `from` in little-endian /// (least significant byte first). /// /// # Panics /// /// This will potentially panic if `from` is not large enough. fn read_le(from: &[u8]) -> Self; /// Write an integer in little-endian format. /// /// This writes `self` into the first n bytes (depending on the size of `Self`) of `into` in /// little-endian format (least significant byte first). /// /// # Panics /// /// This will potentially panic if `into` is not large enough. fn write_le(self, into: &mut [u8]); } impl Encode for u8 { fn read_le(from: &[u8]) -> u8 { from[0] } fn write_le(self, into: &mut [u8]) { into[0] = self; } } impl Encode for u16 { fn read_le(from: &[u8]) -> u16 { from[0] as u16 | (from[1] as u16) << 8 } fn write_le(self, into: &mut [u8]) { into[0] = self as u8; into[1] = (self >> 8) as u8; } } impl Encode for u32 { fn read_le(from: &[u8]) -> u32 { from[0] as u32 | (from[1] as u32) << 8 | (from[2] as u32) << 16 | (from[3] as u32) << 24 } fn write_le(self, into: &mut [u8]) { into[0] = self as u8; into[1] = (self >> 8) as u8; into[2] = (self >> 16) as u8; into[3] = (self >> 24) as u8; } } impl Encode for u64 { fn read_le(from: &[u8]) -> u64 { from[0] as u64 | (from[1] as u64) << 8 | (from[2] as u64) << 16 | (from[3] as u64) << 24 | (from[4] as u64) << 32 | (from[5] as u64) << 40 | (from[6] as u64) << 48 | (from[7] as u64) << 56 } fn write_le(self, into: &mut [u8]) { into[0] = self as u8; into[1] = (self >> 8) as u8; into[2] = (self >> 16) as u8; into[3] = (self >> 24) as u8; into[4] = (self >> 32) as u8; into[5] = (self >> 40) as u8; into[6] = (self >> 48) as u8; into[7] = (self >> 56) as u8; } } impl Encode for u128 { fn read_le(from: &[u8]) -> u128 { from[0] as u128 | (from[1] as u128) << 8 | (from[2] as u128) << 16 | (from[3] as u128) << 24 | (from[4] as u128) << 32 | (from[5] as u128) << 40 | (from[6] as u128) << 48 | (from[7] as u128) << 56 | (from[8] as u128) << 64 | (from[9] as u128) << 72 | (from[10] as u128) << 80 | (from[11] as u128) << 88 | (from[12] as u128) << 96 | (from[13] as u128) << 104 | (from[14] as u128) << 112 | (from[15] as u128) << 120 } fn write_le(self, into: &mut [u8]) { into[0] = self as u8; into[1] = (self >> 8) as u8; into[2] = (self >> 16) as u8; into[3] = (self >> 24) as u8; into[4] = (self >> 32) as u8; into[5] = (self >> 40) as u8; into[6] = (self >> 48) as u8; into[7] = (self >> 56) as u8; into[8] = (self >> 64) as u8; into[9] = (self >> 72) as u8; into[10] = (self >> 80) as u8; into[11] = (self >> 88) as u8; into[12] = (self >> 96) as u8; into[13] = (self >> 104) as u8; into[14] = (self >> 112) as u8; into[15] = (self >> 120) as u8; } } #[cfg(test)] mod tests { use super::*; use std::{ops, mem, fmt}; fn test_int<T>(n: T) where T: Encode + Copy + PartialEq + ops::BitAnd<T, Output = T> + ops::Shr<T, Output = T> + From<u8> + fmt::Debug { let len = mem::size_of::<T>(); let mut buf = [0; 32]; write(&mut buf, n); for i in 0..len { assert_eq!(T::from(buf[i]), (n >> T::from(i as u8 * 8)) & T::from(0xFF)); } assert_eq!(read(&buf), n); } #[test] fn u8() { test_int(12u8); test_int(1u8); test_int(0u8); } #[test] fn u16() { test_int::<u16>(0xAB); test_int::<u16>(0xBA); test_int::<u16>(0); } #[test] fn u32() { test_int::<u32>(0xABCD); test_int::<u32>(0xDCBA); test_int::<u32>(0); } #[test] fn u64() { test_int::<u64>(0xABCDEF0); test_int::<u64>(0x0FEDCBA); test_int::<u64>(0); } #[test] fn u128() { test_int::<u128>(0xABCDEF012345678); test_int::<u128>(0x876543210FEDCBA); test_int::<u128>(0); } }