Crate vlq_rust 

Algorithm

Value-length quantity encoding is an implementation of variable-length integers.

Each byte is encoded into 7 bits, with the highest bit of the byte used to indicate if there are any further bytes to read. Reading will continue until the highest bit is 1, or will result in an error if the number is too large to fit in the desired type.

For example, the number 60000 (or 0xEA60 in hexadecimal):

         11101010 01100000  [as u16]
      11  1010100  1100000  [as separated into 7-bit groups]
 1100000  1010100       11  [re-organized so least significant byte first]
11100000 11010100 00000011  [as VLQ-encoded variable-length integer]

Usage

Add this to your Cargo.toml:

[dependencies]
vlq = { package = "vlq-rust", version = "0.2" }

Use ReadVlqExt and WriteVlqExt to get the read_vlq and write_vlq functions on every std::io::Read and std::io::Write implementation.

Example

use vlq::{ReadVlqExt, WriteVlqExt};

let mut data = std::io::Cursor::new(vec![]);
data.write_vlq(std::u64::MAX).unwrap();
data.set_position(0);

let x: u64 = data.read_vlq().unwrap();
assert_eq!(x, std::u64::MAX);

let mut data = std::io::Cursor::new(vec![]);
data.write_vlq(std::i64::MIN).unwrap();
data.set_position(0);

let x: i64 = data.read_vlq().unwrap();
assert_eq!(x, std::i64::MIN);

Traits

ReadVlqExt

Vlq

Trait applied to all types that can be encoded as VLQ’s.

WriteVlqExt