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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
*/
/* Bit reading helpers */
#include "bit_reader.h"
#include <brotli/types.h>
#include "../common/platform.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
const brotli_reg_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_ = 0;
}
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_UNALIGNED_READ_FAST) {
aligned_read_mask = 0;
}
if (BrotliGetAvailableBits(br) == 0) {
br->val_ = 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,
brotli_reg_t n_bits, brotli_reg_t* val) {
brotli_reg_t low_val;
brotli_reg_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
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