prefix.c (2529B)
1 /* Copyright 2025 Google Inc. All Rights Reserved. 2 3 Distributed under MIT license. 4 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT 5 */ 6 7 #include "prefix.h" 8 9 #include "../common/platform.h" /* IWYU pragma: keep */ 10 #include "../common/static_init.h" 11 12 #if (BROTLI_STATIC_INIT != BROTLI_STATIC_INIT_NONE) 13 #include "../common/constants.h" 14 #endif 15 16 #if defined(__cplusplus) || defined(c_plusplus) 17 extern "C" { 18 #endif 19 20 #if (BROTLI_STATIC_INIT == BROTLI_STATIC_INIT_NONE) 21 /* Embed kCmdLut. */ 22 #include "prefix_inc.h" 23 #else 24 BROTLI_COLD BROTLI_BOOL BrotliDecoderInitCmdLut(CmdLutElement* items) { 25 static const uint8_t kInsertLengthExtraBits[24] = { 26 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x02, 0x02, 0x03, 0x03, 27 0x04, 0x04, 0x05, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0C, 0x0E, 0x18}; 28 static const uint8_t kCopyLengthExtraBits[24] = { 29 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x02, 0x02, 30 0x03, 0x03, 0x04, 0x04, 0x05, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x18}; 31 static const uint8_t kCellPos[11] = {0, 1, 0, 1, 8, 9, 2, 16, 10, 17, 18}; 32 33 uint16_t insert_length_offsets[24]; 34 uint16_t copy_length_offsets[24]; 35 insert_length_offsets[0] = 0; 36 copy_length_offsets[0] = 2; 37 for (size_t i = 0; i < 23; ++i) { 38 insert_length_offsets[i + 1] = 39 insert_length_offsets[i] + (uint16_t)(1u << kInsertLengthExtraBits[i]); 40 copy_length_offsets[i + 1] = 41 copy_length_offsets[i] + (uint16_t)(1u << kCopyLengthExtraBits[i]); 42 } 43 44 for (size_t symbol = 0; symbol < BROTLI_NUM_COMMAND_SYMBOLS; ++symbol) { 45 CmdLutElement* item = items + symbol; 46 const size_t cell_idx = symbol >> 6; 47 const size_t cell_pos = kCellPos[cell_idx]; 48 const size_t copy_code = ((cell_pos << 3) & 0x18) + (symbol & 0x7); 49 const uint16_t copy_len_offset = copy_length_offsets[copy_code]; 50 const size_t insert_code = (cell_pos & 0x18) + ((symbol >> 3) & 0x7); 51 item->copy_len_extra_bits = kCopyLengthExtraBits[copy_code]; 52 item->context = (copy_len_offset > 4) ? 3 : ((uint8_t)copy_len_offset - 2); 53 item->copy_len_offset = copy_len_offset; 54 item->distance_code = (cell_idx >= 2) ? -1 : 0; 55 item->insert_len_extra_bits = kInsertLengthExtraBits[insert_code]; 56 item->insert_len_offset = insert_length_offsets[insert_code]; 57 } 58 return BROTLI_TRUE; 59 } 60 61 BROTLI_MODEL("small") 62 CmdLutElement kCmdLut[BROTLI_NUM_COMMAND_SYMBOLS]; 63 #endif /* BROTLI_STATIC_INIT */ 64 65 #if defined(__cplusplus) || defined(c_plusplus) 66 } /* extern "C" */ 67 #endif