This project is part of the @thi.ng/umbrella monorepo.

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Binary run-length encoding packer/unpacker with support for customizable input word sizes (1 - 32 bits) and repeat count (run-length) bit sizes (1 - 16 bits). The encoder uses 4 different repeat group sizes (thresholds) to minimize the number of bits used to store the run lengths. The range of supported run lengths is 16 bits (i.e. 65536 repetitions). If a value is repeated more often than that, the remainder will be encoded using additional RLE chunks...

• 32 bits - original number of words
• 5 bits - word size
• 16 bits - 4x RLE repeat group / chunk sizes (in bits)

The default group sizes are: 3, 4, 8, 16, i.e. 8, 16, 256, 65536 repetitions

Then per value:

• 1 bit - encoding flag (1 = RLE encoded, 0 = single occurrence)
• 2 bits - repeat or chunk class ID
• m bits - repeat count or chunk size (if greater than max group size then split into chunks...)
• n bits - value(s)

STABLE - used in production

Search or submit any issues for this package

• @thi.ng/binary - 100+ assorted binary / bitwise operations, conversions, utilities, lookup tables
• @thi.ng/bitstream - ES6 iterator based read/write bit streams with support for variable word widths
• @thi.ng/range-coder - Binary data range encoder / decoder

yarn add @thi.ng/rle-pack

ES module import:

<script type="module" src="https://cdn.skypack.dev/@thi.ng/rle-pack"></script>

Skypack documentation

For Node.js REPL:

# with flag only for < v16
node --experimental-repl-await

> const rlePack = await import("@thi.ng/rle-pack");

Package sizes (gzipped, pre-treeshake): ESM: 696 bytes

• @thi.ng/bitstream
• @thi.ng/errors

Generated API docs

import { encode, decode } from "@thi.ng/rle-pack";

// prepare dummy data
src = new Uint8Array(1024);
src.set([1,1,1,1,1,2,2,2,2,3,3,3,4,4,5,4,4,3,3,3,2,2,2,2,1,1,1,1,1], 512);

// pack data
packed = encode(src, src.length);
packed.length
// 30 => 2.93% of original

// pack with custom word size (3 bits, i.e. our value range is only 0-7)
// and use custom repeat group sizes suitable for our data
alt = encode(src, src.length, 3, [1, 2, 3, 9]);
alt.length
// 20 => 1.95% of original, 66% of default config

// unpack
unpacked = new Uint8Array(decode(alt));

Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-rle-pack,
  title = "@thi.ng/rle-pack",
  author = "Karsten Schmidt",
  note = "https://thi.ng/rle-pack",
  year = 2017
}

© 2017 - 2021 Karsten Schmidt // Apache Software License 2.0