2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved.
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
10 #include "./vp9_prob.h"
11 #include "./vp9_reader.h"
13 #include "vpx_ports/mem.h"
14 #include "vpx_mem/vpx_mem.h"
16 int vp9_reader_init(vp9_reader *r,
17 const uint8_t *buffer,
19 vpx_decrypt_cb decrypt_cb,
20 void *decrypt_state) {
21 if (size && !buffer) {
24 r->buffer_end = buffer + size;
29 r->decrypt_cb = decrypt_cb;
30 r->decrypt_state = decrypt_state;
32 return vp9_read_bit(r) != 0; // marker bit
36 void vp9_reader_fill(vp9_reader *r) {
37 const uint8_t *const buffer_end = r->buffer_end;
38 const uint8_t *buffer = r->buffer;
39 const uint8_t *buffer_start = buffer;
40 BD_VALUE value = r->value;
42 int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
44 const size_t bytes_left = buffer_end - buffer;
45 const size_t bits_left = bytes_left * CHAR_BIT;
46 const int x = (int)(shift + CHAR_BIT - bits_left);
49 size_t n = MIN(sizeof(r->clear_buffer), bytes_left);
50 r->decrypt_cb(r->decrypt_state, buffer, r->clear_buffer, (int)n);
51 buffer = r->clear_buffer;
52 buffer_start = r->clear_buffer;
56 count += LOTS_OF_BITS;
60 if (x < 0 || bits_left) {
61 while (shift >= loop_end) {
63 value |= (BD_VALUE)*buffer++ << shift;
68 // NOTE: Variable 'buffer' may not relate to 'r->buffer' after decryption,
69 // so we increase 'r->buffer' by the amount that 'buffer' moved, rather than
70 // assign 'buffer' to 'r->buffer'.
71 r->buffer += buffer - buffer_start;
76 const uint8_t *vp9_reader_find_end(vp9_reader *r) {
77 // Find the end of the coded buffer
78 while (r->count > CHAR_BIT && r->count < BD_VALUE_SIZE) {