/* * bitstream.c * Copyright (C) 2004 Gildas Bazin * Copyright (C) 2000-2003 Michel Lespinasse * Copyright (C) 1999-2000 Aaron Holtzman * * This file is part of dtsdec, a free DTS Coherent Acoustics stream decoder. * See http://www.videolan.org/dtsdec.html for updates. * * dtsdec is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * dtsdec is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #include "config.h" #include #include "dts.h" #include "dts_internal.h" #include "bitstream.h" #define BUFFER_SIZE 4096 void dts_bitstream_init (dts_state_t * state, uint8_t * buf, int word_mode, int bigendian_mode) { intptr_t align; align = (uintptr_t)buf & 3; state->buffer_start = (uint32_t *) (buf - align); state->bits_left = 0; state->current_word = 0; state->word_mode = word_mode; state->bigendian_mode = bigendian_mode; bitstream_get (state, align * 8); } #include static inline void bitstream_fill_current (dts_state_t * state) { uint32_t tmp; tmp = *(state->buffer_start++); if (state->bigendian_mode) state->current_word = swab32 (tmp); else state->current_word = swable32 (tmp); if (!state->word_mode) { state->current_word = (state->current_word & 0x00003FFF) | ((state->current_word & 0x3FFF0000 ) >> 2); } } /* * The fast paths for _get is in the * bitstream.h header file so it can be inlined. * * The "bottom half" of this routine is suffixed _bh * * -ah */ uint32_t dts_bitstream_get_bh (dts_state_t * state, uint32_t num_bits) { uint32_t result; num_bits -= state->bits_left; result = ((state->current_word << (32 - state->bits_left)) >> (32 - state->bits_left)); if ( !state->word_mode && num_bits > 28 ) { bitstream_fill_current (state); result = (result << 28) | state->current_word; num_bits -= 28; } bitstream_fill_current (state); if ( state->word_mode ) { if (num_bits != 0) result = (result << num_bits) | (state->current_word >> (32 - num_bits)); state->bits_left = 32 - num_bits; } else { if (num_bits != 0) result = (result << num_bits) | (state->current_word >> (28 - num_bits)); state->bits_left = 28 - num_bits; } return result; }