This project is part of the @thi.ng/umbrella monorepo.
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
- @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-packPackage sizes (gzipped, pre-treeshake): ESM: 673 bytes / CJS: 727 bytes / UMD: 825 bytes
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
© 2017 - 2020 Karsten Schmidt // Apache Software License 2.0