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/*
* 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 "dboolhuff.h"
int
vp8dx_start_decode (BOOL_DECODER * br,
const unsigned char *source,
unsigned int source_sz, vp8_decrypt_cb * decrypt_cb, void *decrypt_state)
{
br->user_buffer_end = source + source_sz;
br->user_buffer = source;
br->value = 0;
br->count = -8;
br->range = 255;
br->decrypt_cb = decrypt_cb;
br->decrypt_state = decrypt_state;
if (source_sz && !source)
return 1;
/* Populate the buffer */
vp8dx_bool_decoder_fill (br);
return 0;
}
void
vp8dx_bool_decoder_fill (BOOL_DECODER * br)
{
const unsigned char *bufptr = br->user_buffer;
VP8_BD_VALUE value = br->value;
int count = br->count;
int shift = VP8_BD_VALUE_SIZE - 8 - (count + 8);
size_t bytes_left = br->user_buffer_end - bufptr;
size_t bits_left = bytes_left * CHAR_BIT;
int x = (int) (shift + CHAR_BIT - bits_left);
int loop_end = 0;
unsigned char decrypted[sizeof (VP8_BD_VALUE) + 1];
if (br->decrypt_cb) {
size_t n =
bytes_left > sizeof (decrypted) ? sizeof (decrypted) : bytes_left;
br->decrypt_cb (br->decrypt_state, bufptr, decrypted, (int) n);
bufptr = decrypted;
}
if (x >= 0) {
count += VP8_LOTS_OF_BITS;
loop_end = x;
}
if (x < 0 || bits_left) {
while (shift >= loop_end) {
count += CHAR_BIT;
value |= (VP8_BD_VALUE) * bufptr << shift;
++bufptr;
++br->user_buffer;
shift -= CHAR_BIT;
}
}
br->value = value;
br->count = count;
}
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