bitstuff.h
上传用户:zhongxx05
上传日期:2007-06-06
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文件大小:6k
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: RCSL 1.0/RPSL 1.0
- *
- * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
- *
- * The contents of this file, and the files included with this file, are
- * subject to the current version of the RealNetworks Public Source License
- * Version 1.0 (the "RPSL") available at
- * http://www.helixcommunity.org/content/rpsl unless you have licensed
- * the file under the RealNetworks Community Source License Version 1.0
- * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl,
- * in which case the RCSL will apply. You may also obtain the license terms
- * directly from RealNetworks. You may not use this file except in
- * compliance with the RPSL or, if you have a valid RCSL with RealNetworks
- * applicable to this file, the RCSL. Please see the applicable RPSL or
- * RCSL for the rights, obligations and limitations governing use of the
- * contents of the file.
- *
- * This file is part of the Helix DNA Technology. RealNetworks is the
- * developer of the Original Code and owns the copyrights in the portions
- * it created.
- *
- * This file, and the files included with this file, is distributed and made
- * available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- *
- * Technology Compatibility Kit Test Suite(s) Location:
- * http://www.helixcommunity.org/content/tck
- *
- * Contributor(s):
- *
- * ***** END LICENSE BLOCK ***** */
- typedef struct TAG_LD {
- /* bit input */
- unsigned char *rdbfr;
- unsigned char *rdptr;
- int incnt;
- int bitcnt;
- } LD;
- #if defined _AIX || defined _OSF1 || (defined _SOLARIS && !defined __GNUC__)
- #define INLINE static inline
- #else
- #define INLINE static __inline
- #endif
- /*
- * Initializes bit-buffer.
- * Use:
- * void initbuffer (char *buffer, void *bufinfo);
- * Input:
- * buffer - pointer to the input buffer to use
- * bufinfo - pointer to the buffer information
- * Returns:
- * none
- */
- INLINE void initbuffer (unsigned char *buffer, void *bufinfo)
- {
- LD * ld = (LD*)bufinfo;
- ld->rdptr = buffer;
- ld->rdbfr = buffer;
- ld->incnt = 0;
- ld->bitcnt = 0;
- }
- /*
- * Fills pre-load buffer.
- * Use:
- * void fillbfr (void *inst);
- * Input:
- * inst - decoder instance
- * Returns:
- * none
- */
- INLINE void fillbfr (void *inst) {/* obsolete */}
- /*
- * Returns next n bits (right adjusted) without advancing.
- * Use:
- * unsigned int showbits(int n, void *inst);
- * Input:
- * n - the number of bits to retrieve
- * inst - decoder instance
- * Note:
- * len must be less than 24
- * Returns:
- * the bit vector
- */
- #ifdef _M_IX86
- #pragma warning(disable:4035)
- INLINE unsigned int showbits (int n, void *inst)
- {
- __asm mov eax,inst
- __asm mov edx,/* LD */ [eax].rdptr
- __asm mov ecx,/* LD */ [eax].incnt
- __asm mov eax,dword ptr [edx]
- __asm mov edx,32
- __asm bswap eax
- __asm sub edx,n
- __asm shl eax,cl
- __asm mov ecx,edx
- __asm shr eax,cl
- }
- #else
- /* I guess it should be portable: */
- INLINE unsigned int showbits (int n, void *inst)
- {
- LD * ld = (LD*)inst;
- unsigned char *p = ld->rdptr;
- unsigned int a, c = ld->incnt;
- /* load in big-Endian order: */
- a = (unsigned int)(p[0]<<24) + (p[1]<<16) + (p[2]<<8) + (p[3]);
- return (a << c) >> (32-n);
- }
- #endif
- /*
- * Advance by n bits.
- * Use:
- * void flushbits(int n, void *inst);
- * Input:
- * n - the number of bits to throw away
- * inst - decoder instance
- * Returns:
- * none
- */
- INLINE void flushbits (int n, void *inst)
- {
- LD * ld = (LD*)inst;
- ld->incnt += n;
- ld->bitcnt+= n;
- ld->rdptr += ld->incnt >> 3;
- ld->incnt &= 0x07;
- }
- /*
- * Returns next n bits (right adjusted)
- * Use:
- * unsigned int getbits(int n, void *inst);
- * Input:
- * n - the number of bits to retrieve
- * inst - decoder instance
- * Note:
- * len must be less than 24
- * Returns:
- * the bit vector
- */
- INLINE unsigned int getbits(int n, void *inst)
- {
- unsigned int l = showbits(n, inst);
- flushbits(n, inst);
- return l;
- }
- /*
- * Returns next bit from the bitstream.
- * Use:
- * unsigned int getbits1 (void * inst);
- * Input:
- * inst - decoder instance
- * Returns:
- * bit value
- */
- #if 1
- INLINE unsigned int getbits1 (void * inst)
- {
- LD * ld = (LD*)inst;
- unsigned int a = ld->rdptr[0];
- unsigned int c = ld->incnt + 1;
- ld->bitcnt ++;
- ld->incnt = c & 7;
- ld->rdptr += c >> 3;
- return (a >> (8 - c)) & 1;
- }
- #else
- /* 'lazy' version */
- INLINE unsigned int getbits1 (void * inst)
- {
- return getbits(1, inst);
- }
- #endif
- /*
- * Returns current byte number.
- * Use:
- * unsigned int getbytes (void *bufinfo);
- * bufinfo - pointer to the buffer information
- * Returns:
- * none
- */
- INLINE unsigned int getbytes (void *bufinfo)
- {
- LD * ld = (LD*)ld;
- return ld->bitcnt >> 3;
- }
- /*
- * Seek to a certain position in the bitstream:
- * Use:
- * unsigned char *gotoByte (int byteInPacket, void *bufinfo);
- * Input:
- * byteInPacket - target byte position
- * bufinfo - pointer to the buffer information
- * Returns
- * pointer to the requested position in the bistream
- */
- INLINE unsigned char *gotoByte (int byteInPacket, void *bufinfo)
- {
- LD * ld = (LD*)bufinfo;
- unsigned char * newPtrLocation = ld->rdbfr + byteInPacket;
- ld->rdptr = newPtrLocation;
- ld->bitcnt = byteInPacket << 3;
- ld->incnt= 0;
- return newPtrLocation;
- }