1/* 2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved. 3 * 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. 9 */ 10 11 12#include "dboolhuff.h" 13#include "vp8/common/common.h" 14#include "vpx_dsp/vpx_dsp_common.h" 15 16int vp8dx_start_decode(BOOL_DECODER *br, 17 const unsigned char *source, 18 unsigned int source_sz, 19 vpx_decrypt_cb decrypt_cb, 20 void *decrypt_state) 21{ 22 br->user_buffer_end = source+source_sz; 23 br->user_buffer = source; 24 br->value = 0; 25 br->count = -8; 26 br->range = 255; 27 br->decrypt_cb = decrypt_cb; 28 br->decrypt_state = decrypt_state; 29 30 if (source_sz && !source) 31 return 1; 32 33 /* Populate the buffer */ 34 vp8dx_bool_decoder_fill(br); 35 36 return 0; 37} 38 39void vp8dx_bool_decoder_fill(BOOL_DECODER *br) 40{ 41 const unsigned char *bufptr = br->user_buffer; 42 VP8_BD_VALUE value = br->value; 43 int count = br->count; 44 int shift = VP8_BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT); 45 size_t bytes_left = br->user_buffer_end - bufptr; 46 size_t bits_left = bytes_left * CHAR_BIT; 47 int x = (int)(shift + CHAR_BIT - bits_left); 48 int loop_end = 0; 49 unsigned char decrypted[sizeof(VP8_BD_VALUE) + 1]; 50 51 if (br->decrypt_cb) { 52 size_t n = VPXMIN(sizeof(decrypted), bytes_left); 53 br->decrypt_cb(br->decrypt_state, bufptr, decrypted, (int)n); 54 bufptr = decrypted; 55 } 56 57 if(x >= 0) 58 { 59 count += VP8_LOTS_OF_BITS; 60 loop_end = x; 61 } 62 63 if (x < 0 || bits_left) 64 { 65 while(shift >= loop_end) 66 { 67 count += CHAR_BIT; 68 value |= (VP8_BD_VALUE)*bufptr << shift; 69 ++bufptr; 70 ++br->user_buffer; 71 shift -= CHAR_BIT; 72 } 73 } 74 75 br->value = value; 76 br->count = count; 77} 78