76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
/* 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
|