| /* Copyright 2013 Google Inc. All Rights Reserved. |
| |
| Distributed under MIT license. |
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| */ |
| |
| /* Bit reading helpers */ |
| |
| #include "bit_reader.h" |
| |
| #include "../common/platform.h" |
| #include <brotli/types.h> |
| |
| #if defined(__cplusplus) || defined(c_plusplus) |
| extern "C" { |
| #endif |
| |
| const uint32_t kBrotliBitMask[33] = { 0x00000000, |
| 0x00000001, 0x00000003, 0x00000007, 0x0000000F, |
| 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF, |
| 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF, |
| 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, |
| 0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF, |
| 0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF, |
| 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF, |
| 0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF |
| }; |
| |
| void BrotliInitBitReader(BrotliBitReader* const br) { |
| br->val_ = 0; |
| br->bit_pos_ = sizeof(br->val_) << 3; |
| } |
| |
| BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* const br) { |
| size_t aligned_read_mask = (sizeof(br->val_) >> 1) - 1; |
| /* Fixing alignment after unaligned BrotliFillWindow would result accumulator |
| overflow. If unalignment is caused by BrotliSafeReadBits, then there is |
| enough space in accumulator to fix alignment. */ |
| if (!BROTLI_ALIGNED_READ) { |
| aligned_read_mask = 0; |
| } |
| if (BrotliGetAvailableBits(br) == 0) { |
| if (!BrotliPullByte(br)) { |
| return BROTLI_FALSE; |
| } |
| } |
| |
| while ((((size_t)br->next_in) & aligned_read_mask) != 0) { |
| if (!BrotliPullByte(br)) { |
| /* If we consumed all the input, we don't care about the alignment. */ |
| return BROTLI_TRUE; |
| } |
| } |
| return BROTLI_TRUE; |
| } |
| |
| BROTLI_BOOL BrotliSafeReadBits32Slow(BrotliBitReader* const br, |
| uint32_t n_bits, uint32_t* val) { |
| uint32_t low_val; |
| uint32_t high_val; |
| BrotliBitReaderState memento; |
| BROTLI_DCHECK(n_bits <= 32); |
| BROTLI_DCHECK(n_bits > 24); |
| BrotliBitReaderSaveState(br, &memento); |
| if (!BrotliSafeReadBits(br, 16, &low_val) || |
| !BrotliSafeReadBits(br, n_bits - 16, &high_val)) { |
| BrotliBitReaderRestoreState(br, &memento); |
| return BROTLI_FALSE; |
| } |
| *val = low_val | (high_val << 16); |
| return BROTLI_TRUE; |
| } |
| |
| #if defined(__cplusplus) || defined(c_plusplus) |
| } /* extern "C" */ |
| #endif |