canonicalCodeTable static method

void canonicalCodeTable(List<int> hcode)

Implementation

static void canonicalCodeTable(List<int> hcode) {
  final n = List<int>.filled(59, 0);

  // For each i from 0 through 58, count the
  // number of different codes of length i, and
  // store the count in n[i].

  for (var i = 0; i < HUF_ENCSIZE; ++i) {
    n[hcode[i]] += 1;
  }

  // For each i from 58 through 1, compute the
  // numerically lowest code with length i, and
  // store that code in n[i].

  var c = 0;

  for (var i = 58; i > 0; --i) {
    final nc = ((c + n[i]) >> 1);
    n[i] = c;
    c = nc;
  }

  // hcode[i] contains the length, l, of the
  // code for symbol i. Assign the next available
  // code of length l to the symbol and store both
  // l and the code in hcode[i].

  for (var i = 0; i < HUF_ENCSIZE; ++i) {
    final l = hcode[i];
    if (l > 0) {
      hcode[i] = l | (n[l]++ << 6);
    }
  }
}