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/*
* bitstream.h
* Copyright (C) 2000-2001 Michel Lespinasse <walken@zoy.org>
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
*
* This file is part of a52dec, a free ATSC A-52 stream decoder.
* See http://liba52.sourceforge.net/ for updates.
*
* a52dec 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.
*
* a52dec 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
*/
#if defined(__sparc__) || defined(hpux)
/*
* the alt bitstream reader performs unaligned memory accesses; that doesn't work
* on sparc/hpux. For now, disable ALT_BITSTREAM_READER.
*/
#undef ALT_BITSTREAM_READER
#else
// alternative (faster) bitstram reader (reades upto 3 bytes over the end of the input)
#define ALT_BITSTREAM_READER
/* used to avoid missaligned exceptions on some archs (alpha, ...) */
#if defined (ARCH_X86) || defined(ARCH_ARMV4L)
# define unaligned32(a) (*(uint32_t*)(a))
#else
# ifdef __GNUC__
static inline uint32_t unaligned32(const void *v) {
struct Unaligned {
uint32_t i;
} __attribute__((packed));
return ((const struct Unaligned *) v)->i;
}
# elif defined(__DECC)
static inline uint32_t unaligned32(const void *v) {
return *(const __unaligned uint32_t *) v;
}
# else
static inline uint32_t unaligned32(const void *v) {
return *(const uint32_t *) v;
}
# endif
#endif //!ARCH_X86
#endif
/* (stolen from the kernel) */
#ifdef WORDS_BIGENDIAN
# define swab32(x) (x)
#else
# if defined (__i386__)
# define swab32(x) __i386_swab32(x)
static inline const uint32_t __i386_swab32(uint32_t x)
{
__asm__("bswap %0" : "=r" (x) : "0" (x));
return x;
}
# else
# define swab32(x)\
((((uint8_t*)&x)[0] << 24) | (((uint8_t*)&x)[1] << 16) | \
(((uint8_t*)&x)[2] << 8) | (((uint8_t*)&x)[3]))
# endif
#endif
#ifdef ALT_BITSTREAM_READER
extern uint32_t *buffer_start;
extern int indx;
#else
extern uint32_t bits_left;
extern uint32_t current_word;
#endif
void bitstream_set_ptr (uint8_t * buf);
uint32_t bitstream_get_bh(uint32_t num_bits);
int32_t bitstream_get_bh_2(uint32_t num_bits);
static inline uint32_t
bitstream_get(uint32_t num_bits) // note num_bits is practically a constant due to inlineing
{
#ifdef ALT_BITSTREAM_READER
uint32_t result= swab32( unaligned32(((uint8_t *)buffer_start)+(indx>>3)) );
result<<= (indx&0x07);
result>>= 32 - num_bits;
indx+= num_bits;
return result;
#else
uint32_t result;
if(num_bits < bits_left) {
result = (current_word << (32 - bits_left)) >> (32 - num_bits);
bits_left -= num_bits;
return result;
}
return bitstream_get_bh(num_bits);
#endif
}
static inline void bitstream_skip(int num_bits)
{
#ifdef ALT_BITSTREAM_READER
indx+= num_bits;
#else
bitstream_get(num_bits);
#endif
}
static inline int32_t
bitstream_get_2(uint32_t num_bits)
{
#ifdef ALT_BITSTREAM_READER
int32_t result= swab32( unaligned32(((uint8_t *)buffer_start)+(indx>>3)) );
result<<= (indx&0x07);
result>>= 32 - num_bits;
indx+= num_bits;
return result;
#else
int32_t result;
if(num_bits < bits_left) {
result = (((int32_t)current_word) << (32 - bits_left)) >> (32 - num_bits);
bits_left -= num_bits;
return result;
}
return bitstream_get_bh_2(num_bits);
#endif
}
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