int VP8RecordCoeffTokens()

in Extended/libwebp/src/enc/token_enc.c [113:193]
79 lines of code
16 McCabe index (conditional complexity)

int VP8RecordCoeffTokens(int ctx, const struct VP8Residual* const res,
                         VP8TBuffer* const tokens) {
  const int16_t* const coeffs = res->coeffs;
  const int coeff_type = res->coeff_type;
  const int last = res->last;
  int n = res->first;
  uint32_t base_id = TOKEN_ID(coeff_type, n, ctx);
  // should be stats[VP8EncBands[n]], but it's equivalent for n=0 or 1
  proba_t* s = res->stats[n][ctx];
  if (!AddToken(tokens, last >= 0, base_id + 0, s + 0)) {
    return 0;
  }

  while (n < 16) {
    const int c = coeffs[n++];
    const int sign = c < 0;
    const uint32_t v = sign ? -c : c;
    if (!AddToken(tokens, v != 0, base_id + 1, s + 1)) {
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 0);  // ctx=0
      s = res->stats[VP8EncBands[n]][0];
      continue;
    }
    if (!AddToken(tokens, v > 1, base_id + 2, s + 2)) {
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 1);  // ctx=1
      s = res->stats[VP8EncBands[n]][1];
    } else {
      if (!AddToken(tokens, v > 4, base_id + 3, s + 3)) {
        if (AddToken(tokens, v != 2, base_id + 4, s + 4)) {
          AddToken(tokens, v == 4, base_id + 5, s + 5);
        }
      } else if (!AddToken(tokens, v > 10, base_id + 6, s + 6)) {
        if (!AddToken(tokens, v > 6, base_id + 7, s + 7)) {
          AddConstantToken(tokens, v == 6, 159);
        } else {
          AddConstantToken(tokens, v >= 9, 165);
          AddConstantToken(tokens, !(v & 1), 145);
        }
      } else {
        int mask;
        const uint8_t* tab;
        uint32_t residue = v - 3;
        if (residue < (8 << 1)) {          // VP8Cat3  (3b)
          AddToken(tokens, 0, base_id + 8, s + 8);
          AddToken(tokens, 0, base_id + 9, s + 9);
          residue -= (8 << 0);
          mask = 1 << 2;
          tab = VP8Cat3;
        } else if (residue < (8 << 2)) {   // VP8Cat4  (4b)
          AddToken(tokens, 0, base_id + 8, s + 8);
          AddToken(tokens, 1, base_id + 9, s + 9);
          residue -= (8 << 1);
          mask = 1 << 3;
          tab = VP8Cat4;
        } else if (residue < (8 << 3)) {   // VP8Cat5  (5b)
          AddToken(tokens, 1, base_id + 8, s + 8);
          AddToken(tokens, 0, base_id + 10, s + 9);
          residue -= (8 << 2);
          mask = 1 << 4;
          tab = VP8Cat5;
        } else {                         // VP8Cat6 (11b)
          AddToken(tokens, 1, base_id + 8, s + 8);
          AddToken(tokens, 1, base_id + 10, s + 9);
          residue -= (8 << 3);
          mask = 1 << 10;
          tab = VP8Cat6;
        }
        while (mask) {
          AddConstantToken(tokens, !!(residue & mask), *tab++);
          mask >>= 1;
        }
      }
      base_id = TOKEN_ID(coeff_type, VP8EncBands[n], 2);  // ctx=2
      s = res->stats[VP8EncBands[n]][2];
    }
    AddConstantToken(tokens, sign, 128);
    if (n == 16 || !AddToken(tokens, n <= last, base_id + 0, s + 0)) {
      return 1;   // EOB
    }
  }
  return 1;
}