xref: /aosp_15_r20/external/zopfli/src/zopfli/symbols.h (revision e47783fd9ac7e78d0523d35be12ee382df490d63)

/*
Copyright 2016 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Author: [email protected] (Lode Vandevenne)
Author: [email protected] (Jyrki Alakuijala)
*/

/*
Utilities for using the lz77 symbols of the deflate spec.
*/

#ifndef ZOPFLI_SYMBOLS_H_
#define ZOPFLI_SYMBOLS_H_

/* __has_builtin available in clang */
#ifdef __has_builtin
# if __has_builtin(__builtin_clz)
#   define ZOPFLI_HAS_BUILTIN_CLZ
# endif
/* __builtin_clz available beginning with GCC 3.4 */
#elif __GNUC__ * 100 + __GNUC_MINOR__ >= 304
# define ZOPFLI_HAS_BUILTIN_CLZ
#endif

/* Gets the amount of extra bits for the given dist, cfr. the DEFLATE spec. */
static int ZopfliGetDistExtraBits(int dist) {
#ifdef ZOPFLI_HAS_BUILTIN_CLZ
  if (dist < 5) return 0;
  return (31 ^ __builtin_clz(dist - 1)) - 1; /* log2(dist - 1) - 1 */
#else
  if (dist < 5) return 0;
  else if (dist < 9) return 1;
  else if (dist < 17) return 2;
  else if (dist < 33) return 3;
  else if (dist < 65) return 4;
  else if (dist < 129) return 5;
  else if (dist < 257) return 6;
  else if (dist < 513) return 7;
  else if (dist < 1025) return 8;
  else if (dist < 2049) return 9;
  else if (dist < 4097) return 10;
  else if (dist < 8193) return 11;
  else if (dist < 16385) return 12;
  else return 13;
#endif
}

/* Gets value of the extra bits for the given dist, cfr. the DEFLATE spec. */
static int ZopfliGetDistExtraBitsValue(int dist) {
#ifdef ZOPFLI_HAS_BUILTIN_CLZ
  if (dist < 5) {
    return 0;
  } else {
    int l = 31 ^ __builtin_clz(dist - 1); /* log2(dist - 1) */
    return (dist - (1 + (1 << l))) & ((1 << (l - 1)) - 1);
  }
#else
  if (dist < 5) return 0;
  else if (dist < 9) return (dist - 5) & 1;
  else if (dist < 17) return (dist - 9) & 3;
  else if (dist < 33) return (dist - 17) & 7;
  else if (dist < 65) return (dist - 33) & 15;
  else if (dist < 129) return (dist - 65) & 31;
  else if (dist < 257) return (dist - 129) & 63;
  else if (dist < 513) return (dist - 257) & 127;
  else if (dist < 1025) return (dist - 513) & 255;
  else if (dist < 2049) return (dist - 1025) & 511;
  else if (dist < 4097) return (dist - 2049) & 1023;
  else if (dist < 8193) return (dist - 4097) & 2047;
  else if (dist < 16385) return (dist - 8193) & 4095;
  else return (dist - 16385) & 8191;
#endif
}

/* Gets the symbol for the given dist, cfr. the DEFLATE spec. */
static int ZopfliGetDistSymbol(int dist) {
#ifdef ZOPFLI_HAS_BUILTIN_CLZ
  if (dist < 5) {
    return dist - 1;
  } else {
    int l = (31 ^ __builtin_clz(dist - 1)); /* log2(dist - 1) */
    int r = ((dist - 1) >> (l - 1)) & 1;
    return l * 2 + r;
  }
#else
  if (dist < 193) {
    if (dist < 13) {  /* dist 0..13. */
      if (dist < 5) return dist - 1;
      else if (dist < 7) return 4;
      else if (dist < 9) return 5;
      else return 6;
    } else {  /* dist 13..193. */
      if (dist < 17) return 7;
      else if (dist < 25) return 8;
      else if (dist < 33) return 9;
      else if (dist < 49) return 10;
      else if (dist < 65) return 11;
      else if (dist < 97) return 12;
      else if (dist < 129) return 13;
      else return 14;
    }
  } else {
    if (dist < 2049) {  /* dist 193..2049. */
      if (dist < 257) return 15;
      else if (dist < 385) return 16;
      else if (dist < 513) return 17;
      else if (dist < 769) return 18;
      else if (dist < 1025) return 19;
      else if (dist < 1537) return 20;
      else return 21;
    } else {  /* dist 2049..32768. */
      if (dist < 3073) return 22;
      else if (dist < 4097) return 23;
      else if (dist < 6145) return 24;
      else if (dist < 8193) return 25;
      else if (dist < 12289) return 26;
      else if (dist < 16385) return 27;
      else if (dist < 24577) return 28;
      else return 29;
    }
  }
#endif
}

/* Gets the amount of extra bits for the given length, cfr. the DEFLATE spec. */
static int ZopfliGetLengthExtraBits(int l) {
  static const int table[259] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 0
  };
  return table[l];
}

/* Gets value of the extra bits for the given length, cfr. the DEFLATE spec. */
static int ZopfliGetLengthExtraBitsValue(int l) {
  static const int table[259] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 3, 0,
    1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5,
    6, 7, 0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5, 6,
    7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
    13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2,
    3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
    10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
    29, 30, 31, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
    18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 0, 1, 2, 3, 4, 5, 6,
    7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
    27, 28, 29, 30, 31, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
    16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 0
  };
  return table[l];
}

/*
Gets the symbol for the given length, cfr. the DEFLATE spec.
Returns the symbol in the range [257-285] (inclusive)
*/
static int ZopfliGetLengthSymbol(int l) {
  static const int table[259] = {
    0, 0, 0, 257, 258, 259, 260, 261, 262, 263, 264,
    265, 265, 266, 266, 267, 267, 268, 268,
    269, 269, 269, 269, 270, 270, 270, 270,
    271, 271, 271, 271, 272, 272, 272, 272,
    273, 273, 273, 273, 273, 273, 273, 273,
    274, 274, 274, 274, 274, 274, 274, 274,
    275, 275, 275, 275, 275, 275, 275, 275,
    276, 276, 276, 276, 276, 276, 276, 276,
    277, 277, 277, 277, 277, 277, 277, 277,
    277, 277, 277, 277, 277, 277, 277, 277,
    278, 278, 278, 278, 278, 278, 278, 278,
    278, 278, 278, 278, 278, 278, 278, 278,
    279, 279, 279, 279, 279, 279, 279, 279,
    279, 279, 279, 279, 279, 279, 279, 279,
    280, 280, 280, 280, 280, 280, 280, 280,
    280, 280, 280, 280, 280, 280, 280, 280,
    281, 281, 281, 281, 281, 281, 281, 281,
    281, 281, 281, 281, 281, 281, 281, 281,
    281, 281, 281, 281, 281, 281, 281, 281,
    281, 281, 281, 281, 281, 281, 281, 281,
    282, 282, 282, 282, 282, 282, 282, 282,
    282, 282, 282, 282, 282, 282, 282, 282,
    282, 282, 282, 282, 282, 282, 282, 282,
    282, 282, 282, 282, 282, 282, 282, 282,
    283, 283, 283, 283, 283, 283, 283, 283,
    283, 283, 283, 283, 283, 283, 283, 283,
    283, 283, 283, 283, 283, 283, 283, 283,
    283, 283, 283, 283, 283, 283, 283, 283,
    284, 284, 284, 284, 284, 284, 284, 284,
    284, 284, 284, 284, 284, 284, 284, 284,
    284, 284, 284, 284, 284, 284, 284, 284,
    284, 284, 284, 284, 284, 284, 284, 285
  };
  return table[l];
}

/* Gets the amount of extra bits for the given length symbol. */
static int ZopfliGetLengthSymbolExtraBits(int s) {
  static const int table[29] = {
    0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
    3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
  };
  return table[s - 257];
}

/* Gets the amount of extra bits for the given distance symbol. */
static int ZopfliGetDistSymbolExtraBits(int s) {
  static const int table[30] = {
    0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8,
    9, 9, 10, 10, 11, 11, 12, 12, 13, 13
  };
  return table[s];
}

#endif  /* ZOPFLI_SYMBOLS_H_ */