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