| /* |
| * 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. |
| */ |
| |
| #include "vpx_ports/mem.h" |
| #include "vpx_mem/vpx_mem.h" |
| |
| #include "vp9/decoder/vp9_dboolhuff.h" |
| |
| int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) { |
| int marker_bit; |
| |
| r->buffer_end = buffer + size; |
| r->buffer = buffer; |
| r->value = 0; |
| r->count = -8; |
| r->range = 255; |
| |
| if (size && !buffer) |
| return 1; |
| |
| vp9_reader_fill(r); |
| marker_bit = vp9_read_bit(r); |
| return marker_bit != 0; |
| } |
| |
| void vp9_reader_fill(vp9_reader *r) { |
| const uint8_t *const buffer_end = r->buffer_end; |
| const uint8_t *buffer = r->buffer; |
| VP9_BD_VALUE value = r->value; |
| int count = r->count; |
| int shift = VP9_BD_VALUE_SIZE - 8 - (count + 8); |
| int loop_end = 0; |
| const int bits_left = (int)((buffer_end - buffer)*CHAR_BIT); |
| const int x = shift + CHAR_BIT - bits_left; |
| |
| if (x >= 0) { |
| count += VP9_LOTS_OF_BITS; |
| loop_end = x; |
| } |
| |
| if (x < 0 || bits_left) { |
| while (shift >= loop_end) { |
| count += CHAR_BIT; |
| value |= (VP9_BD_VALUE)*buffer++ << shift; |
| shift -= CHAR_BIT; |
| } |
| } |
| |
| r->buffer = buffer; |
| r->value = value; |
| r->count = count; |
| } |
| |
| const uint8_t *vp9_reader_find_end(vp9_reader *r) { |
| // Find the end of the coded buffer |
| while (r->count > CHAR_BIT && r->count < VP9_BD_VALUE_SIZE) { |
| r->count -= CHAR_BIT; |
| r->buffer--; |
| } |
| return r->buffer; |
| } |
| |