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godotengine
GitHub Repository: godotengine/godot
 Path: blob/master/thirdparty/brotli/dec/bit_reader.c
21318 views
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/* Copyright 2013 Google Inc. All Rights Reserved.

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   Distributed under MIT license.

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   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT

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*/

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/* Bit reading helpers */

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#include "bit_reader.h"

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#include "../common/platform.h"

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#if defined(__cplusplus) || defined(c_plusplus)

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extern "C" {

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#endif

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const BROTLI_MODEL("small")

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brotli_reg_t kBrotliBitMask[33] = {     0x00000000,

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    0x00000001, 0x00000003, 0x00000007, 0x0000000F,

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    0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,

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    0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,

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    0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF,

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    0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF,

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    0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF,

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    0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF,

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    0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF

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};

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void BrotliInitBitReader(BrotliBitReader* const br) {

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  br->val_ = 0;

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  br->bit_pos_ = 0;

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}

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BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* const br) {

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  size_t aligned_read_mask = (sizeof(br->val_) >> 1) - 1;

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  /* Fixing alignment after unaligned BrotliFillWindow would result accumulator

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     overflow. If unalignment is caused by BrotliSafeReadBits, then there is

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     enough space in accumulator to fix alignment. */

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  if (BROTLI_UNALIGNED_READ_FAST) {

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    aligned_read_mask = 0;

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  }

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  if (BrotliGetAvailableBits(br) == 0) {

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    br->val_ = 0;

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    if (!BrotliPullByte(br)) {

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      return BROTLI_FALSE;

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    }

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  }

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  while ((((size_t)br->next_in) & aligned_read_mask) != 0) {

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    if (!BrotliPullByte(br)) {

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      /* If we consumed all the input, we don't care about the alignment. */

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      return BROTLI_TRUE;

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    }

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  }

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  return BROTLI_TRUE;

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}

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BROTLI_BOOL BrotliSafeReadBits32Slow(BrotliBitReader* const br,

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    brotli_reg_t n_bits, brotli_reg_t* val) {

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  brotli_reg_t low_val;

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  brotli_reg_t high_val;

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  BrotliBitReaderState memento;

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  BROTLI_DCHECK(n_bits <= 32);

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  BROTLI_DCHECK(n_bits > 24);

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  BrotliBitReaderSaveState(br, &memento);

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  if (!BrotliSafeReadBits(br, 16, &low_val) ||

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      !BrotliSafeReadBits(br, n_bits - 16, &high_val)) {

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    BrotliBitReaderRestoreState(br, &memento);

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    return BROTLI_FALSE;

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  }

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  *val = low_val | (high_val << 16);

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  return BROTLI_TRUE;

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}

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#if defined(__cplusplus) || defined(c_plusplus)

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}  /* extern "C" */

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#endif

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