@thi.ng/transducers-binary/partition-bits.js

Binary data related transducers & reducers

import { iterator, __iter } from "@thi.ng/transducers/iterator";
import { isReduced } from "@thi.ng/transducers/reduced";
function partitionBits(...args) {
  return __iter(partitionBits, args, iterator) || ((rfn) => {
    const destSize = args[0];
    const srcSize = args[1] || 8;
    return destSize < srcSize ? __small(rfn, destSize, srcSize) : destSize > srcSize ? __large(rfn, destSize, srcSize) : rfn;
  });
}
const __small = ([init, complete, reduce], n, wordSize) => {
  const maxb = wordSize - n;
  const m1 = (1 << wordSize) - 1;
  const m2 = (1 << n) - 1;
  let r = 0;
  let y = 0;
  return [
    init,
    (acc) => complete(r > 0 ? reduce(acc, y) : acc),
    (acc, x) => {
      let b = 0;
      do {
        acc = reduce(acc, y + (x >>> maxb + r & m2));
        b += n - r;
        x = x << n - r & m1;
        y = 0;
        r = 0;
      } while (b <= maxb && !isReduced(acc));
      r = wordSize - b;
      y = r > 0 ? x >>> maxb & m2 : 0;
      return acc;
    }
  ];
};
const __large = ([init, complete, reduce], n, wordSize) => {
  const m1 = (1 << wordSize) - 1;
  let r = 0;
  let y = 0;
  return [
    init,
    (acc) => complete(r > 0 ? reduce(acc, y) : acc),
    (acc, x) => {
      if (r + wordSize <= n) {
        y |= (x & m1) << n - wordSize - r;
        r += wordSize;
        if (r === n) {
          acc = reduce(acc, y);
          y = 0;
          r = 0;
        }
      } else {
        const k = n - r;
        r = wordSize - k;
        acc = reduce(acc, y | x >>> r & (1 << k) - 1);
        y = (x & (1 << r) - 1) << n - r;
      }
      return acc;
    }
  ];
};
export {
  partitionBits
};