vu64 0.3.0

variable length encode/decode for a 64-bits integer
Documentation 
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# vu64

[![crate][crate-image]][crate-link]
[![Docs][docs-image]][docs-link]
![Rust Version][rustc-image]
![Apache2/MIT licensed][license-image]
[![Test ubu][test-ubuntu-image]][test-ubuntu-link]
[![Test mac][test-windows-image]][test-windows-link]
[![Test win][test-macos-image]][test-macos-link]

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`](https://crates.io/crates/vint64),
but 0x00 is represented by 0x00.

## Examples

### Encode

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

### Decode

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

### Encode and decode

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

### Read from buffer and decode

```rust
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

```rust
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());
```


# Changelogs

[This crate's changelog here.](https://github.com/aki-akaguma/vu64/blob/main/CHANGELOG.md)

# References

+ [vint64](https://crates.io/crates/vint64)
+ [varu64](https://crates.io/crates/varu64)
+ [varbincode](https://crates.io/crates/varbincode)

# License

This project is licensed under either of

 * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
   https://www.apache.org/licenses/LICENSE-2.0)
 * MIT license ([LICENSE-MIT](LICENSE-MIT) or
   https://opensource.org/licenses/MIT)

at your option.

[//]: # (badges)

[crate-image]: https://img.shields.io/crates/v/vu64.svg
[crate-link]: https://crates.io/crates/vu64
[docs-image]: https://docs.rs/vu64/badge.svg
[docs-link]: https://docs.rs/vu64/
[rustc-image]: https://img.shields.io/badge/rustc-1.58+-blue.svg
[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
[test-ubuntu-image]: https://github.com/aki-akaguma/vu64/actions/workflows/test-ubuntu.yml/badge.svg
[test-ubuntu-link]: https://github.com/aki-akaguma/vu64/actions/workflows/test-ubuntu.yml
[test-macos-image]: https://github.com/aki-akaguma/vu64/actions/workflows/test-macos.yml/badge.svg
[test-macos-link]: https://github.com/aki-akaguma/vu64/actions/workflows/test-macos.yml
[test-windows-image]: https://github.com/aki-akaguma/vu64/actions/workflows/test-windows.yml/badge.svg
[test-windows-link]: https://github.com/aki-akaguma/vu64/actions/workflows/test-windows.yml