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| 1 /* Copyright 2013 Google Inc. All Rights Reserved. |
| 2 |
| 3 Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 you may not use this file except in compliance with the License. |
| 5 You may obtain a copy of the License at |
| 6 |
| 7 http://www.apache.org/licenses/LICENSE-2.0 |
| 8 |
| 9 Unless required by applicable law or agreed to in writing, software |
| 10 distributed under the License is distributed on an "AS IS" BASIS, |
| 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 See the License for the specific language governing permissions and |
| 13 limitations under the License. |
| 14 |
| 15 Lookup tables to map prefix codes to value ranges. This is used during |
| 16 decoding of the block lengths, literal insertion lengths and copy lengths. |
| 17 */ |
| 18 |
| 19 #ifndef BROTLI_DEC_PREFIX_H_ |
| 20 #define BROTLI_DEC_PREFIX_H_ |
| 21 |
| 22 /* Represents the range of values belonging to a prefix code: */ |
| 23 /* [offset, offset + 2^nbits) */ |
| 24 struct PrefixCodeRange { |
| 25 int offset; |
| 26 int nbits; |
| 27 }; |
| 28 |
| 29 static const struct PrefixCodeRange kBlockLengthPrefixCode[] = { |
| 30 { 1, 2}, { 5, 2}, { 9, 2}, { 13, 2}, |
| 31 { 17, 3}, { 25, 3}, { 33, 3}, { 41, 3}, |
| 32 { 49, 4}, { 65, 4}, { 81, 4}, { 97, 4}, |
| 33 { 113, 5}, { 145, 5}, { 177, 5}, { 209, 5}, |
| 34 { 241, 6}, { 305, 6}, { 369, 7}, { 497, 8}, |
| 35 { 753, 9}, { 1265, 10}, {2289, 11}, {4337, 12}, |
| 36 {8433, 13}, {16625, 24} |
| 37 }; |
| 38 |
| 39 static const struct PrefixCodeRange kInsertLengthPrefixCode[] = { |
| 40 { 0, 0}, { 1, 0}, { 2, 0}, { 3, 0}, |
| 41 { 4, 0}, { 5, 0}, { 6, 1}, { 8, 1}, |
| 42 { 10, 2}, { 14, 2}, { 18, 3}, { 26, 3}, |
| 43 { 34, 4}, { 50, 4}, { 66, 5}, { 98, 5}, |
| 44 { 130, 6}, { 194, 7}, { 322, 8}, { 578, 9}, |
| 45 {1090, 10}, {2114, 12}, {6210, 14}, {22594, 24}, |
| 46 }; |
| 47 |
| 48 static const struct PrefixCodeRange kCopyLengthPrefixCode[] = { |
| 49 { 2, 0}, { 3, 0}, { 4, 0}, { 5, 0}, |
| 50 { 6, 0}, { 7, 0}, { 8, 0}, { 9, 0}, |
| 51 { 10, 1}, { 12, 1}, { 14, 2}, { 18, 2}, |
| 52 { 22, 3}, { 30, 3}, { 38, 4}, { 54, 4}, |
| 53 { 70, 5}, { 102, 5}, { 134, 6}, { 198, 7}, |
| 54 {326, 8}, { 582, 9}, {1094, 10}, {2118, 24}, |
| 55 }; |
| 56 |
| 57 static const int kInsertRangeLut[9] = { |
| 58 0, 0, 8, 8, 0, 16, 8, 16, 16, |
| 59 }; |
| 60 |
| 61 static const int kCopyRangeLut[9] = { |
| 62 0, 8, 0, 8, 16, 0, 16, 8, 16, |
| 63 }; |
| 64 |
| 65 #endif /* BROTLI_DEC_PREFIX_H_ */ |
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