/* *  Copyright (c) 2010 The WebM project authors. All Rights Reserved. * *  Use of this source code is governed by a BSD-style license *  that can be found in the LICENSE file in the root of the source *  tree. An additional intellectual property rights grant can be found *  in the file PATENTS.  All contributing project authors may *  be found in the AUTHORS file in the root of the source tree. */ #ifndef VPX_VPX_DSP_BITREADER_H_#define VPX_VPX_DSP_BITREADER_H_ #include <stddef.h>#include <stdio.h>#include <limits.h> #include "./vpx_config.h"#include "vpx_ports/mem.h"#include "vpx/vp8dx.h"#include "vpx/vpx_integer.h"#include "vpx_dsp/prob.h"#if CONFIG_BITSTREAM_DEBUG#include "vpx_util/vpx_debug_util.h"#endif  // CONFIG_BITSTREAM_DEBUG #ifdef __cplusplusextern "C" {#endif typedef size_t BD_VALUE; #define BD_VALUE_SIZE ((int)sizeof(BD_VALUE) * CHAR_BIT) // This is meant to be a large, positive constant that can still be efficiently// loaded as an immediate (on platforms like ARM, for example).// Even relatively modest values like 100 would work fine.#define LOTS_OF_BITS 0x40000000 typedef struct {  // Be careful when reordering this struct, it may impact the cache negatively.  BD_VALUE value;  unsigned int range;  int count;  const uint8_t *buffer_end;  const uint8_t *buffer;  vpx_decrypt_cb decrypt_cb;  void *decrypt_state;  uint8_t clear_buffer[sizeof(BD_VALUE) + 1];} vpx_reader; int vpx_reader_init(vpx_reader *r, const uint8_t *buffer, size_t size,                    vpx_decrypt_cb decrypt_cb, void *decrypt_state); void vpx_reader_fill(vpx_reader *r); const uint8_t *vpx_reader_find_end(vpx_reader *r); static INLINE int vpx_reader_has_error(vpx_reader *r) {  // Check if we have reached the end of the buffer.  //  // Variable 'count' stores the number of bits in the 'value' buffer, minus  // 8. The top byte is part of the algorithm, and the remainder is buffered  // to be shifted into it. So if count == 8, the top 16 bits of 'value' are  // occupied, 8 for the algorithm and 8 in the buffer.  //  // When reading a byte from the user's buffer, count is filled with 8 and  // one byte is filled into the value buffer. When we reach the end of the  // data, count is additionally filled with LOTS_OF_BITS. So when  // count == LOTS_OF_BITS - 1, the user's data has been exhausted.  //  // 1 if we have tried to decode bits after the end of stream was encountered.  // 0 No error.  return r->count > BD_VALUE_SIZE && r->count < LOTS_OF_BITS;} static INLINE int vpx_read(vpx_reader *r, int prob) {  unsigned int bit = 0;  BD_VALUE value;  BD_VALUE bigsplit;  int count;  unsigned int range;  unsigned int split = (r->range * prob + (256 - prob)) >> CHAR_BIT;   if (r->count < 0) vpx_reader_fill(r);   value = r->value;  count = r->count;   bigsplit = (BD_VALUE)split << (BD_VALUE_SIZE - CHAR_BIT);   range = split;   if (value >= bigsplit) {    range = r->range - split;    value = value - bigsplit;    bit = 1;  }   {    const unsigned char shift = vpx_norm[(unsigned char)range];    range <<= shift;    value <<= shift;    count -= shift;  }  r->value = value;  r->count = count;  r->range = range; #if CONFIG_BITSTREAM_DEBUG  {    const int queue_r = bitstream_queue_get_read();    const int frame_idx = bitstream_queue_get_frame_read();    int ref_result, ref_prob;    bitstream_queue_pop(&ref_result, &ref_prob);    if ((int)bit != ref_result) {      fprintf(stderr,              "\n *** [bit] result error, frame_idx_r %d bit %d ref_result %d "              "queue_r %d\n",              frame_idx, bit, ref_result, queue_r);       assert(0);    }    if (prob != ref_prob) {      fprintf(stderr,              "\n *** [bit] prob error, frame_idx_r %d prob %d ref_prob %d "              "queue_r %d\n",              frame_idx, prob, ref_prob, queue_r);       assert(0);    }  }#endif   return bit;} static INLINE int vpx_read_bit(vpx_reader *r) {  return vpx_read(r, 128);  // vpx_prob_half} static INLINE int vpx_read_literal(vpx_reader *r, int bits) {  int literal = 0, bit;   for (bit = bits - 1; bit >= 0; bit--) literal |= vpx_read_bit(r) << bit;   return literal;} static INLINE int vpx_read_tree(vpx_reader *r, const vpx_tree_index *tree,                                const vpx_prob *probs) {  vpx_tree_index i = 0;   while ((i = tree[i + vpx_read(r, probs[i >> 1])]) > 0) continue;   return -i;} #ifdef __cplusplus}  // extern "C"#endif #endif  // VPX_VPX_DSP_BITREADER_H_