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240 lines
8.5 KiB
C
240 lines
8.5 KiB
C
/*
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Copyright 2016 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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Author: lode.vandevenne@gmail.com (Lode Vandevenne)
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Author: jyrki.alakuijala@gmail.com (Jyrki Alakuijala)
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*/
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/*
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Utilities for using the lz77 symbols of the deflate spec.
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*/
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#ifndef ZOPFLI_SYMBOLS_H_
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#define ZOPFLI_SYMBOLS_H_
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/* __has_builtin available in clang */
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#ifdef __has_builtin
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# if __has_builtin(__builtin_clz)
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# define ZOPFLI_HAS_BUILTIN_CLZ
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# endif
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/* __builtin_clz available beginning with GCC 3.4 */
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#elif __GNUC__ * 100 + __GNUC_MINOR__ >= 304
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# define ZOPFLI_HAS_BUILTIN_CLZ
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#endif
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/* Gets the amount of extra bits for the given dist, cfr. the DEFLATE spec. */
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static int ZopfliGetDistExtraBits(int dist) {
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#ifdef ZOPFLI_HAS_BUILTIN_CLZ
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if (dist < 5) return 0;
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return (31 ^ __builtin_clz(dist - 1)) - 1; /* log2(dist - 1) - 1 */
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#else
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if (dist < 5) return 0;
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else if (dist < 9) return 1;
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else if (dist < 17) return 2;
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else if (dist < 33) return 3;
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else if (dist < 65) return 4;
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else if (dist < 129) return 5;
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else if (dist < 257) return 6;
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else if (dist < 513) return 7;
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else if (dist < 1025) return 8;
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else if (dist < 2049) return 9;
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else if (dist < 4097) return 10;
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else if (dist < 8193) return 11;
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else if (dist < 16385) return 12;
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else return 13;
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#endif
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}
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/* Gets value of the extra bits for the given dist, cfr. the DEFLATE spec. */
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static int ZopfliGetDistExtraBitsValue(int dist) {
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#ifdef ZOPFLI_HAS_BUILTIN_CLZ
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if (dist < 5) {
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return 0;
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} else {
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int l = 31 ^ __builtin_clz(dist - 1); /* log2(dist - 1) */
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return (dist - (1 + (1 << l))) & ((1 << (l - 1)) - 1);
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}
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#else
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if (dist < 5) return 0;
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else if (dist < 9) return (dist - 5) & 1;
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else if (dist < 17) return (dist - 9) & 3;
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else if (dist < 33) return (dist - 17) & 7;
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else if (dist < 65) return (dist - 33) & 15;
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else if (dist < 129) return (dist - 65) & 31;
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else if (dist < 257) return (dist - 129) & 63;
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else if (dist < 513) return (dist - 257) & 127;
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else if (dist < 1025) return (dist - 513) & 255;
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else if (dist < 2049) return (dist - 1025) & 511;
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else if (dist < 4097) return (dist - 2049) & 1023;
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else if (dist < 8193) return (dist - 4097) & 2047;
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else if (dist < 16385) return (dist - 8193) & 4095;
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else return (dist - 16385) & 8191;
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#endif
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}
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/* Gets the symbol for the given dist, cfr. the DEFLATE spec. */
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static int ZopfliGetDistSymbol(int dist) {
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#ifdef ZOPFLI_HAS_BUILTIN_CLZ
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if (dist < 5) {
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return dist - 1;
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} else {
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int l = (31 ^ __builtin_clz(dist - 1)); /* log2(dist - 1) */
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int r = ((dist - 1) >> (l - 1)) & 1;
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return l * 2 + r;
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}
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#else
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if (dist < 193) {
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if (dist < 13) { /* dist 0..13. */
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if (dist < 5) return dist - 1;
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else if (dist < 7) return 4;
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else if (dist < 9) return 5;
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else return 6;
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} else { /* dist 13..193. */
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if (dist < 17) return 7;
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else if (dist < 25) return 8;
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else if (dist < 33) return 9;
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else if (dist < 49) return 10;
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else if (dist < 65) return 11;
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else if (dist < 97) return 12;
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else if (dist < 129) return 13;
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else return 14;
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}
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} else {
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if (dist < 2049) { /* dist 193..2049. */
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if (dist < 257) return 15;
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else if (dist < 385) return 16;
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else if (dist < 513) return 17;
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else if (dist < 769) return 18;
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else if (dist < 1025) return 19;
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else if (dist < 1537) return 20;
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else return 21;
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} else { /* dist 2049..32768. */
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if (dist < 3073) return 22;
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else if (dist < 4097) return 23;
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else if (dist < 6145) return 24;
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else if (dist < 8193) return 25;
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else if (dist < 12289) return 26;
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else if (dist < 16385) return 27;
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else if (dist < 24577) return 28;
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else return 29;
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}
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}
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#endif
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}
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/* Gets the amount of extra bits for the given length, cfr. the DEFLATE spec. */
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static int ZopfliGetLengthExtraBits(int l) {
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static const int table[259] = {
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 0
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};
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return table[l];
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}
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/* Gets value of the extra bits for the given length, cfr. the DEFLATE spec. */
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static int ZopfliGetLengthExtraBitsValue(int l) {
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static const int table[259] = {
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 2, 3, 0,
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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,
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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,
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7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
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13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2,
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3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
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10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28,
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29, 30, 31, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
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18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 0, 1, 2, 3, 4, 5, 6,
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7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
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27, 28, 29, 30, 31, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
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16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 0
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};
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return table[l];
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}
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/*
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Gets the symbol for the given length, cfr. the DEFLATE spec.
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Returns the symbol in the range [257-285] (inclusive)
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*/
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static int ZopfliGetLengthSymbol(int l) {
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static const int table[259] = {
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0, 0, 0, 257, 258, 259, 260, 261, 262, 263, 264,
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265, 265, 266, 266, 267, 267, 268, 268,
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269, 269, 269, 269, 270, 270, 270, 270,
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271, 271, 271, 271, 272, 272, 272, 272,
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273, 273, 273, 273, 273, 273, 273, 273,
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274, 274, 274, 274, 274, 274, 274, 274,
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275, 275, 275, 275, 275, 275, 275, 275,
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276, 276, 276, 276, 276, 276, 276, 276,
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277, 277, 277, 277, 277, 277, 277, 277,
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277, 277, 277, 277, 277, 277, 277, 277,
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278, 278, 278, 278, 278, 278, 278, 278,
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278, 278, 278, 278, 278, 278, 278, 278,
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279, 279, 279, 279, 279, 279, 279, 279,
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279, 279, 279, 279, 279, 279, 279, 279,
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280, 280, 280, 280, 280, 280, 280, 280,
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280, 280, 280, 280, 280, 280, 280, 280,
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281, 281, 281, 281, 281, 281, 281, 281,
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281, 281, 281, 281, 281, 281, 281, 281,
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281, 281, 281, 281, 281, 281, 281, 281,
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281, 281, 281, 281, 281, 281, 281, 281,
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282, 282, 282, 282, 282, 282, 282, 282,
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282, 282, 282, 282, 282, 282, 282, 282,
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282, 282, 282, 282, 282, 282, 282, 282,
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282, 282, 282, 282, 282, 282, 282, 282,
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283, 283, 283, 283, 283, 283, 283, 283,
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283, 283, 283, 283, 283, 283, 283, 283,
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283, 283, 283, 283, 283, 283, 283, 283,
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283, 283, 283, 283, 283, 283, 283, 283,
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284, 284, 284, 284, 284, 284, 284, 284,
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284, 284, 284, 284, 284, 284, 284, 284,
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284, 284, 284, 284, 284, 284, 284, 284,
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284, 284, 284, 284, 284, 284, 284, 285
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};
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return table[l];
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}
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/* Gets the amount of extra bits for the given length symbol. */
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static int ZopfliGetLengthSymbolExtraBits(int s) {
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static const int table[29] = {
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0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
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3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
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};
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return table[s - 257];
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}
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/* Gets the amount of extra bits for the given distance symbol. */
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static int ZopfliGetDistSymbolExtraBits(int s) {
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static const int table[30] = {
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0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8,
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9, 9, 10, 10, 11, 11, 12, 12, 13, 13
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};
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return table[s];
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}
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#endif /* ZOPFLI_SYMBOLS_H_ */
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