/eio

Read and write numbers in big-endian and little-endian

Primary LanguageRustApache License 2.0Apache-2.0

eio

Read and write numbers in big-endian and little-endian.

🚀 Getting started

Add the following to your Cargo manifest.

[dependencies]
eio = "0.1"

And bring the ReadExt and/or WriteExt traits into scope.

use eio::{ReadExt, WriteExt};

🤸 Usage

The most common usage is parsing numbers from a source. You can do this using the read_le() and read_be() methods on anything that implements Read.

use eio::ReadExt;

// `Cursor` implements `Read`
let mut rdr = std::io::Cursor::new([
  0x37, 0x13,
  0x12, 0x34, 0x56, 0x78,
  0x00, 0x09, 0x10,
]);

// Read a two byte `u16` in little-endian order
let i: u16 = rdr.read_le()?;
assert_eq!(i, 0x1337);

// Read a four byte `i32` in big-endian order
let i: i32 = rdr.read_be()?;
assert_eq!(i, 0x12345678);

// Read a three byte array
let a: [u8; 3] = rdr.read_array()?;
assert_eq!(a, [0x00, 0x09, 0x10]);

Serialization of numbers can be done using the write_le() and write_be(). This can be done on anything that implements Write.

use eio::WriteExt;

// `&mut [u8]` implements `Write`.
let mut wtr = Vec::new();

// Write a four byte `f32` in little-endian order
wtr.write_le(1_f32)?;
// Write a one byte `u8`
wtr.write_be(7_u8)?;

assert_eq!(wtr, &[0, 0, 0x80, 0x3f, 0x07]);

In no_std contexts the FromBytes and ToBytes traits can be used directly.

use eio::{FromBytes, ToBytes};

let x: u32 = FromBytes::from_be_bytes([0, 0, 0, 7]);
assert_eq!(x, 7);

let data = ToBytes::to_le_bytes(x);
assert_eq!(data, [7, 0, 0, 0]);

💡 Prior art

eio provides the same capabilities as the popular byteorder crate but with a very different API. The advantages of eio are the following:

  • It is extendible, anyone can implement FromBytes or ToBytes for their own integer types.
  • Uses the core/std {from,to}_{le,be}_bytes functions to do the conversion for floats and integers. byteorder reimplements these.
  • Doesn't require turbofish type annotations all the time. 
    // byteorder
let i = rdr.read_u16::<BigEndian>()?;
// eio
let i: u16 = rdr.read_be()?;

License

Licensed under either of

at your option.