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Add brotli decoder and WOFF2 support.
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| Copyright (c) 2009, 2010, 2013-2016 by the Brotli Authors. | ||
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| Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| of this software and associated documentation files (the "Software"), to deal | ||
| in the Software without restriction, including without limitation the rights | ||
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| copies of the Software, and to permit persons to whom the Software is | ||
| furnished to do so, subject to the following conditions: | ||
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| The above copyright notice and this permission notice shall be included in | ||
| all copies or substantial portions of the Software. | ||
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| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
| THE SOFTWARE. |
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| /* Copyright 2013 Google Inc. All Rights Reserved. | ||
| Distributed under MIT license. | ||
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT | ||
| */ | ||
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| #include "constants.h" | ||
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| const BrotliPrefixCodeRange | ||
| _kBrotliPrefixCodeRanges[BROTLI_NUM_BLOCK_LEN_SYMBOLS] = { | ||
| {1, 2}, {5, 2}, {9, 2}, {13, 2}, {17, 3}, {25, 3}, | ||
| {33, 3}, {41, 3}, {49, 4}, {65, 4}, {81, 4}, {97, 4}, | ||
| {113, 5}, {145, 5}, {177, 5}, {209, 5}, {241, 6}, {305, 6}, | ||
| {369, 7}, {497, 8}, {753, 9}, {1265, 10}, {2289, 11}, {4337, 12}, | ||
| {8433, 13}, {16625, 24}}; |
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| /* Copyright 2016 Google Inc. All Rights Reserved. | ||
| Distributed under MIT license. | ||
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT | ||
| */ | ||
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| /** | ||
| * @file | ||
| * Common constants used in decoder and encoder API. | ||
| */ | ||
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| #ifndef BROTLI_COMMON_CONSTANTS_H_ | ||
| #define BROTLI_COMMON_CONSTANTS_H_ | ||
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| #include "platform.h" | ||
| #include <brotli/port.h> | ||
| #include <brotli/types.h> | ||
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| /* Specification: 7.3. Encoding of the context map */ | ||
| #define BROTLI_CONTEXT_MAP_MAX_RLE 16 | ||
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| /* Specification: 2. Compressed representation overview */ | ||
| #define BROTLI_MAX_NUMBER_OF_BLOCK_TYPES 256 | ||
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| /* Specification: 3.3. Alphabet sizes: insert-and-copy length */ | ||
| #define BROTLI_NUM_LITERAL_SYMBOLS 256 | ||
| #define BROTLI_NUM_COMMAND_SYMBOLS 704 | ||
| #define BROTLI_NUM_BLOCK_LEN_SYMBOLS 26 | ||
| #define BROTLI_MAX_CONTEXT_MAP_SYMBOLS (BROTLI_MAX_NUMBER_OF_BLOCK_TYPES + \ | ||
| BROTLI_CONTEXT_MAP_MAX_RLE) | ||
| #define BROTLI_MAX_BLOCK_TYPE_SYMBOLS (BROTLI_MAX_NUMBER_OF_BLOCK_TYPES + 2) | ||
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| /* Specification: 3.5. Complex prefix codes */ | ||
| #define BROTLI_REPEAT_PREVIOUS_CODE_LENGTH 16 | ||
| #define BROTLI_REPEAT_ZERO_CODE_LENGTH 17 | ||
| #define BROTLI_CODE_LENGTH_CODES (BROTLI_REPEAT_ZERO_CODE_LENGTH + 1) | ||
| /* "code length of 8 is repeated" */ | ||
| #define BROTLI_INITIAL_REPEATED_CODE_LENGTH 8 | ||
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| /* "Large Window Brotli" */ | ||
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| /** | ||
| * The theoretical maximum number of distance bits specified for large window | ||
| * brotli, for 64-bit encoders and decoders. Even when in practice 32-bit | ||
| * encoders and decoders only support up to 30 max distance bits, the value is | ||
| * set to 62 because it affects the large window brotli file format. | ||
| * Specifically, it affects the encoding of simple huffman tree for distances, | ||
| * see Specification RFC 7932 chapter 3.4. | ||
| */ | ||
| #define BROTLI_LARGE_MAX_DISTANCE_BITS 62U | ||
| #define BROTLI_LARGE_MIN_WBITS 10 | ||
| /** | ||
| * The maximum supported large brotli window bits by the encoder and decoder. | ||
| * Large window brotli allows up to 62 bits, however the current encoder and | ||
| * decoder, designed for 32-bit integers, only support up to 30 bits maximum. | ||
| */ | ||
| #define BROTLI_LARGE_MAX_WBITS 30 | ||
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| /* Specification: 4. Encoding of distances */ | ||
| #define BROTLI_NUM_DISTANCE_SHORT_CODES 16 | ||
| /** | ||
| * Maximal number of "postfix" bits. | ||
| * | ||
| * Number of "postfix" bits is stored as 2 bits in meta-block header. | ||
| */ | ||
| #define BROTLI_MAX_NPOSTFIX 3 | ||
| #define BROTLI_MAX_NDIRECT 120 | ||
| #define BROTLI_MAX_DISTANCE_BITS 24U | ||
| #define BROTLI_DISTANCE_ALPHABET_SIZE(NPOSTFIX, NDIRECT, MAXNBITS) ( \ | ||
| BROTLI_NUM_DISTANCE_SHORT_CODES + (NDIRECT) + \ | ||
| ((MAXNBITS) << ((NPOSTFIX) + 1))) | ||
| /* BROTLI_NUM_DISTANCE_SYMBOLS == 1128 */ | ||
| #define BROTLI_NUM_DISTANCE_SYMBOLS \ | ||
| BROTLI_DISTANCE_ALPHABET_SIZE( \ | ||
| BROTLI_MAX_NDIRECT, BROTLI_MAX_NPOSTFIX, BROTLI_LARGE_MAX_DISTANCE_BITS) | ||
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| /* ((1 << 26) - 4) is the maximal distance that can be expressed in RFC 7932 | ||
| brotli stream using NPOSTFIX = 0 and NDIRECT = 0. With other NPOSTFIX and | ||
| NDIRECT values distances up to ((1 << 29) + 88) could be expressed. */ | ||
| #define BROTLI_MAX_DISTANCE 0x3FFFFFC | ||
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| /* ((1 << 31) - 4) is the safe distance limit. Using this number as a limit | ||
| allows safe distance calculation without overflows, given the distance | ||
| alphabet size is limited to corresponding size | ||
| (see kLargeWindowDistanceCodeLimits). */ | ||
| #define BROTLI_MAX_ALLOWED_DISTANCE 0x7FFFFFFC | ||
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| /* Specification: 4. Encoding of Literal Insertion Lengths and Copy Lengths */ | ||
| #define BROTLI_NUM_INS_COPY_CODES 24 | ||
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| /* 7.1. Context modes and context ID lookup for literals */ | ||
| /* "context IDs for literals are in the range of 0..63" */ | ||
| #define BROTLI_LITERAL_CONTEXT_BITS 6 | ||
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| /* 7.2. Context ID for distances */ | ||
| #define BROTLI_DISTANCE_CONTEXT_BITS 2 | ||
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| /* 9.1. Format of the Stream Header */ | ||
| /* Number of slack bytes for window size. Don't confuse | ||
| with BROTLI_NUM_DISTANCE_SHORT_CODES. */ | ||
| #define BROTLI_WINDOW_GAP 16 | ||
| #define BROTLI_MAX_BACKWARD_LIMIT(W) (((size_t)1 << (W)) - BROTLI_WINDOW_GAP) | ||
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| typedef struct BrotliDistanceCodeLimit { | ||
| uint32_t max_alphabet_size; | ||
| uint32_t max_distance; | ||
| } BrotliDistanceCodeLimit; | ||
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| /* This function calculates maximal size of distance alphabet, such that the | ||
| distances greater than the given values can not be represented. | ||
| This limits are designed to support fast and safe 32-bit decoders. | ||
| "32-bit" means that signed integer values up to ((1 << 31) - 1) could be | ||
| safely expressed. | ||
| Brotli distance alphabet symbols do not represent consecutive distance | ||
| ranges. Each distance alphabet symbol (excluding direct distances and short | ||
| codes), represent interleaved (for NPOSTFIX > 0) range of distances. | ||
| A "group" of consecutive (1 << NPOSTFIX) symbols represent non-interleaved | ||
| range. Two consecutive groups require the same amount of "extra bits". | ||
| It is important that distance alphabet represents complete "groups". | ||
| To avoid complex logic on encoder side about interleaved ranges | ||
| it was decided to restrict both sides to complete distance code "groups". | ||
| */ | ||
| BROTLI_UNUSED_FUNCTION BrotliDistanceCodeLimit BrotliCalculateDistanceCodeLimit( | ||
| uint32_t max_distance, uint32_t npostfix, uint32_t ndirect) { | ||
| BrotliDistanceCodeLimit result; | ||
| /* Marking this function as unused, because not all files | ||
| including "constants.h" use it -> compiler warns about that. */ | ||
| BROTLI_UNUSED(&BrotliCalculateDistanceCodeLimit); | ||
| if (max_distance <= ndirect) { | ||
| /* This case never happens / exists only for the sake of completeness. */ | ||
| result.max_alphabet_size = max_distance + BROTLI_NUM_DISTANCE_SHORT_CODES; | ||
| result.max_distance = max_distance; | ||
| return result; | ||
| } else { | ||
| /* The first prohibited value. */ | ||
| uint32_t forbidden_distance = max_distance + 1; | ||
| /* Subtract "directly" encoded region. */ | ||
| uint32_t offset = forbidden_distance - ndirect - 1; | ||
| uint32_t ndistbits = 0; | ||
| uint32_t tmp; | ||
| uint32_t half; | ||
| uint32_t group; | ||
| /* Postfix for the last dcode in the group. */ | ||
| uint32_t postfix = (1u << npostfix) - 1; | ||
| uint32_t extra; | ||
| uint32_t start; | ||
| /* Remove postfix and "head-start". */ | ||
| offset = (offset >> npostfix) + 4; | ||
| /* Calculate the number of distance bits. */ | ||
| tmp = offset / 2; | ||
| /* Poor-man's log2floor, to avoid extra dependencies. */ | ||
| while (tmp != 0) {ndistbits++; tmp = tmp >> 1;} | ||
| /* One bit is covered with subrange addressing ("half"). */ | ||
| ndistbits--; | ||
| /* Find subrange. */ | ||
| half = (offset >> ndistbits) & 1; | ||
| /* Calculate the "group" part of dcode. */ | ||
| group = ((ndistbits - 1) << 1) | half; | ||
| /* Calculated "group" covers the prohibited distance value. */ | ||
| if (group == 0) { | ||
| /* This case is added for correctness; does not occur for limit > 128. */ | ||
| result.max_alphabet_size = ndirect + BROTLI_NUM_DISTANCE_SHORT_CODES; | ||
| result.max_distance = ndirect; | ||
| return result; | ||
| } | ||
| /* Decrement "group", so it is the last permitted "group". */ | ||
| group--; | ||
| /* After group was decremented, ndistbits and half must be recalculated. */ | ||
| ndistbits = (group >> 1) + 1; | ||
| /* The last available distance in the subrange has all extra bits set. */ | ||
| extra = (1u << ndistbits) - 1; | ||
| /* Calculate region start. NB: ndistbits >= 1. */ | ||
| start = (1u << (ndistbits + 1)) - 4; | ||
| /* Move to subregion. */ | ||
| start += (group & 1) << ndistbits; | ||
| /* Calculate the alphabet size. */ | ||
| result.max_alphabet_size = ((group << npostfix) | postfix) + ndirect + | ||
| BROTLI_NUM_DISTANCE_SHORT_CODES + 1; | ||
| /* Calculate the maximal distance representable by alphabet. */ | ||
| result.max_distance = ((start + extra) << npostfix) + postfix + ndirect + 1; | ||
| return result; | ||
| } | ||
| } | ||
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| /* Represents the range of values belonging to a prefix code: | ||
| [offset, offset + 2^nbits) */ | ||
| typedef struct { | ||
| uint16_t offset; | ||
| uint8_t nbits; | ||
| } BrotliPrefixCodeRange; | ||
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| /* "Soft-private", it is exported, but not "advertised" as API. */ | ||
| BROTLI_COMMON_API extern const BrotliPrefixCodeRange | ||
| _kBrotliPrefixCodeRanges[BROTLI_NUM_BLOCK_LEN_SYMBOLS]; | ||
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| #endif /* BROTLI_COMMON_CONSTANTS_H_ */ |
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