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73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "dboolhuff.h"
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int
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vp8dx_start_decode (BOOL_DECODER * br,
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const unsigned char *source,
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unsigned int source_sz, vp8_decrypt_cb * decrypt_cb, void *decrypt_state)
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{
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br->user_buffer_end = source + source_sz;
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br->user_buffer = source;
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br->value = 0;
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br->count = -8;
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br->range = 255;
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br->decrypt_cb = decrypt_cb;
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br->decrypt_state = decrypt_state;
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if (source_sz && !source)
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return 1;
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/* Populate the buffer */
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vp8dx_bool_decoder_fill (br);
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return 0;
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}
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void
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vp8dx_bool_decoder_fill (BOOL_DECODER * br)
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{
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const unsigned char *bufptr = br->user_buffer;
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VP8_BD_VALUE value = br->value;
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int count = br->count;
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int shift = VP8_BD_VALUE_SIZE - 8 - (count + 8);
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size_t bytes_left = br->user_buffer_end - bufptr;
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size_t bits_left = bytes_left * CHAR_BIT;
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int x = (int) (shift + CHAR_BIT - bits_left);
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int loop_end = 0;
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unsigned char decrypted[sizeof (VP8_BD_VALUE) + 1];
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if (br->decrypt_cb) {
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size_t n =
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bytes_left > sizeof (decrypted) ? sizeof (decrypted) : bytes_left;
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br->decrypt_cb (br->decrypt_state, bufptr, decrypted, (int) n);
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bufptr = decrypted;
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}
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if (x >= 0) {
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count += VP8_LOTS_OF_BITS;
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loop_end = x;
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}
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if (x < 0 || bits_left) {
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while (shift >= loop_end) {
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count += CHAR_BIT;
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value |= (VP8_BD_VALUE) * bufptr << shift;
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++bufptr;
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++br->user_buffer;
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shift -= CHAR_BIT;
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}
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}
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br->value = value;
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br->count = count;
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}
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