RLE

A rust library for run-length encoded (RLE) sequences. This library is still a work-in-progress and not ready for any sort of public use yet, as I may still mess around with breaking API changes.

Run-length encoding on Wikipedia

Usage

First, you create a Table, which serves as a lookup table for all the possible values you'll be encoding.

use rle::Table;

let mut table = Table::default();
table.extend_from_slice(&['A', 'B', 'C']);

Now, you can run-length encode sequences of those values...

let str: Vec<char> = "AAAAABBBBBBBBBBCCCAAAAAAAAAA".chars().collect();

for (ind, len) in table.encode(&str).unwrap() {
    print!("{}{} ", len, table[ind]);
}
println!();

// 5A 10B 3C 10A

Rather than a series of runs, you can also encode the values into a run-length encoded byte sequence. Here, we are also using encode_bytes_mut, instead of encode_bytes, which will build the table as it encodes the sequence.

let str: Vec<char> = "AAAAABBBBBBBBBBCCCAAAAAAAAAA".chars().collect();

let mut table = Table::default();
for byte in table.encode_bytes_mut(&str).unwrap().flatten() {
    print!("{:02X} ", byte);
}
println!();

// 01 05 03 0A 05 03 01 0A

Here's an example of a large sequence full of lots of runs being compressed into an RLE sequence of bytes...

let input = "................................................................
..........................XXXXXXXXXXXX..........................
......................XXXXXXXXXXXXXXXXXXXX......................
....................XXXXXXXXXXXXXXXXXXXXXXXX....................
.................XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.................
................XXXXXXXXXXX..........XXXXXXXXXXX................
..............XXXXXXXXX..................XXXXXXXXX..............
.............XXXXXXX........................XXXXXXX.............
...........XXXXXXX............................XXXXXXX...........
..........XXXXXXX..............................XXXXXXX..........
.........XXXXXX..................................XXXXXX.........
........XXXXXX....................................XXXXXX........
.......XXXXXX......................................XXXXXX.......
.......XXXXX........................................XXXXX.......
......XXXXX..........................................XXXXX......
.....XXXXX............................................XXXXX.....
.....XXXX..............................................XXXX.....
....XXXXX...........XXXX................XXXX...........XXXXX....
...XXXXX..........XXXXXXXX............XXXXXXXX..........XXXXX...
...XXXX..........XXXXXXXXXX..........XXXXXXXXXX..........XXXX...
...XXXX..........XXXXXXXXXX..........XXXXXXXXXX..........XXXX...
..XXXX..........XXXXXXXXXXXX........XXXXXXXXXXXX..........XXXX..
..XXXX..........XXXXXXXXXXXX........XXXXXXXXXXXX..........XXXX..
.XXXXX..........XXXXXXXXXXXX........XXXXXXXXXXXX..........XXXXX.
.XXXX...........XXXXXXXXXXXX........XXXXXXXXXXXX...........XXXX.
.XXXX............XXXXXXXXXX..........XXXXXXXXXX............XXXX.
.XXXX............XXXXXXXXXX..........XXXXXXXXXX............XXXX.
XXXXX.............XXXXXXXX............XXXXXXXX.............XXXXX
XXXX................XXXX................XXXX................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXX........................................................XXXX
XXXXX......................................................XXXXX
.XXXX......................................................XXXX.
.XXXX........XX..................................XX........XXXX.
.XXXX........XXX................................XXX........XXXX.
.XXXXX.......XXXX..............................XXXX.......XXXXX.
..XXXX........XXXX............................XXXX........XXXX..
..XXXX........XXXXXX........................XXXXXX........XXXX..
...XXXX........XXXXXXXX..................XXXXXXXX........XXXX...
...XXXX.........XXXXXXXXXXX..........XXXXXXXXXXX.........XXXX...
...XXXXX.........XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.........XXXXX...
....XXXXX...........XXXXXXXXXXXXXXXXXXXXXXXX...........XXXXX....
.....XXXX.............XXXXXXXXXXXXXXXXXXXX.............XXXX.....
.....XXXXX................XXXXXXXXXXXX................XXXXX.....
......XXXXX..........................................XXXXX......
.......XXXXX........................................XXXXX.......
.......XXXXXX......................................XXXXXX.......
........XXXXXX....................................XXXXXX........
.........XXXXXX..................................XXXXXX.........
..........XXXXXXX..............................XXXXXXX..........
...........XXXXXXX............................XXXXXXX...........
.............XXXXXXX........................XXXXXXX.............
..............XXXXXXXXX..................XXXXXXXXX..............
................XXXXXXXXXXX..........XXXXXXXXXXX................
.................XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.................
....................XXXXXXXXXXXXXXXXXXXXXXXX....................
......................XXXXXXXXXXXXXXXXXXXX......................
..........................XXXXXXXXXXXX..........................";

let chars: Vec<char> = input.chars().collect();

// Create an RLE table with an entry for each unique character
let mut table = Table::default();

// Encode the ASCII image into a sequence of RLE bytes
let encoded: Vec<u8> = table.encode_bytes_mut(&chars).unwrap().flatten().collect();

// Decode the bytes back into a string
let decoded: String = table.decode_bytes(&encoded).collect();

// Make sure we decoded properly
assert_eq!(input, decoded);

println!("Number of chars in input string ...... {}", chars.len());
println!("Number of unique symbols ............. {}", table.len());
println!("Number of bytes, encoded ............. {}", encoded.len());
println!("Number of chars in decoded string .... {}", decoded.len());

// Number of chars in input string ...... 4160
// Number of unique symbols ............. 2
// Number of bytes, encoded ............. 604
// Number of chars in decoded string .... 4160

ChevyRay/rle

RLE

Usage