Crate vu64

Expand description

The variable length integer encoding of u64. This is a simple and fast encoder/decoder.

Features

integer value length compaction
minimum support rustc 1.58.1 (db9d1b20b 2022-01-20)

format pattern

Prefix	Precision	Total Bytes
`0xxxxxxx`	7 bits	1 byte
`10xxxxxx`	14 bits	2 bytes
`110xxxxx`	21 bits	3 bytes
`1110xxxx`	28 bits	4 bytes
`11110xxx`	35 bits	5 bytes
`111110xx`	42 bits	6 bytes
`1111110x`	49 bits	7 bytes
`11111110`	56 bits	8 bytes
`11111111`	64 bits	9 bytes

This format is a like vint64, but 0x00 is represented by 0x00.

Examples

Encode

use vu64::encode;
assert_eq!(encode(0x0f0f).as_ref(), &[0x8F, 0x3c]);

Decode

use vu64::decode;
let slice = [0x8F, 0x3c].as_ref();
assert_eq!(decode(slice).unwrap(), 0x0f0f);

Encode and decode

use vu64::{encode, decode};
let val = 1234;
assert_eq!(decode(encode(val).as_ref()).unwrap(), val);

Read from buffer and decode

use vu64::io::ReadVu64;
let vec: Vec<u8> = vec![0xFF, 0xf0, 0xf0, 0x0f, 0x0f, 0xf0, 0xf0, 0x0f, 0x0f];
let mut crsr = std::io::Cursor::new(vec);
let r = crsr.read_and_decode_vu64();
assert!(r.is_ok());
assert_eq!(r.unwrap(), 0x0f0f_f0f0_0f0f_f0f0);

Encode and write to buffer

use vu64::io::WriteVu64;
let vec_0: Vec<u8> = vec![0xFF, 0xf0, 0xf0, 0x0f, 0x0f, 0xf0, 0xf0, 0x0f, 0x0f];
let vec: Vec<u8> = Vec::new();
let mut crsr = std::io::Cursor::new(vec);
let r = crsr.encode_and_write_vu64(0x0f0f_f0f0_0f0f_f0f0);
assert!(r.is_ok());
assert_eq!(crsr.get_ref().as_slice(), vec_0.as_slice());