78 lines
2.1 KiB
C
78 lines
2.1 KiB
C
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/*
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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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#include "vp8/common/common.h"
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#include "vpx_dsp/vpx_dsp_common.h"
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int vp8dx_start_decode(BOOL_DECODER *br,
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const unsigned char *source,
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unsigned int source_sz,
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vpx_decrypt_cb decrypt_cb,
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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 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 - CHAR_BIT - (count + CHAR_BIT);
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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 = shift + CHAR_BIT - (int)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 = VPXMIN(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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{
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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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{
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while(shift >= loop_end)
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{
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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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