ref: 197ef67eeb327d79abb961fa0dfd8de9df24d691
dir: /vp8/decoder/dboolhuff.c/
/* * 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" #include "vp8/common/common.h" #include "vpx_dsp/vpx_dsp_common.h" int vp8dx_start_decode(BOOL_DECODER *br, const unsigned char *source, unsigned int source_sz, vpx_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 - CHAR_BIT - (count + CHAR_BIT); size_t bytes_left = br->user_buffer_end - bufptr; size_t bits_left = bytes_left * CHAR_BIT; int x = shift + CHAR_BIT - (int)bits_left; int loop_end = 0; unsigned char decrypted[sizeof(VP8_BD_VALUE) + 1]; if (br->decrypt_cb) { size_t n = VPXMIN(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; }