| /* |
| * 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 __cplusplus |
| extern "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_ |