@thi.ng/rle-pack/simple.js

Binary run-length encoding packer w/ flexible repeat bit widths and a naive RLE encoder/decoder for arrays of arbitrary typed values

import { illegalArgs } from "@thi.ng/errors/illegal-arguments";
const encodeSimple = (src, equiv = (a, b) => a === b) => {
  const result = [];
  const n = src.length;
  if (!n) return result;
  let val = src[0];
  let start = 0;
  for (let i = 1; i < n; i++) {
    if (!equiv(src[i], val)) {
      result.push(val, i - start);
      val = src[i];
      start = i;
    }
  }
  result.push(val, n - start);
  return result;
};
const decodeSimple = (src) => {
  const n = src.length;
  if (n & 1) illegalArgs(`input length must be even`);
  const result = [];
  for (let i = 0; i < n; i += 2) {
    const val = src[i];
    const count = src[i + 1];
    for (let j = 0; j < count; j++) result.push(val);
  }
  return result;
};
export {
  decodeSimple,
  encodeSimple
};