os.h

fix point版本的Ogg Vorbis decoder

#ifndef _OS_H
#define _OS_H
/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2001             *
 * by the XIPHOPHORUS Company http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

 function: #ifdef jail to whip a few platforms into the UNIX ideal.
 last mod: $Id: os.h,v 1.29 2002/03/18 03:30:23 segher Exp $

 ********************************************************************/

#include <math.h>
#include "ogg_os_types.h"

#ifndef _V_IFDEFJAIL_H_
#  define _V_IFDEFJAIL_H_

#  ifdef __GNUC__
#    define STIN static __inline__
#  elif _WIN32
#    define STIN static __inline
#else
#  define STIN static
#endif

#ifndef M_PI
#  define M_PI (3.1415926536f)
#endif

#ifdef _WIN32
#  include <malloc.h>
#  define rint(x)   (floor((x)+0.5f)) 
#  define NO_FLOAT_MATH_LIB
#  define FAST_HYPOT(a, b) sqrt((a)*(a) + (b)*(b))
#endif

#ifdef HAVE_SQRTF
#  define sqrt sqrtf
#endif
#ifdef HAVE_LOGF
#  define log logf
#endif
#ifdef HAVE_EXPF
#  define exp expf
#endif
#ifdef HAVE_ACOSF
#  define acos acosf
#endif
#ifdef HAVE_ATANF
#  define atan atanf
#endif
#ifdef HAVE_FREXPF
#  define frexp frexpf
#endif
#ifdef HAVE_RINTF
#  define rint rintf
#endif
#ifdef HAVE_FLOORF
#  define floor floorf
#endif

#ifndef FAST_HYPOT
#  define FAST_HYPOT hypot
#endif

#endif

#ifdef HAVE_ALLOCA_H
#  include <alloca.h>
#endif

#ifdef USE_MEMORY_H
#  include <memory.h>
#endif

#ifndef min
#  define min(x,y)  ((x)>(y)?(y):(x))
#endif

#ifndef max
#  define max(x,y)  ((x)<(y)?(y):(x))
#endif

#if defined(__i386__) && defined(__GNUC__) && !defined(__BEOS__)
#  define VORBIS_FPU_CONTROL
/* both GCC and MSVC are kinda stupid about rounding/casting to int.
   Because of encapsulation constraints (GCC can't see inside the asm
   block and so we end up doing stupid things like a store/load that
   is collectively a noop), we do it this way */

/* we must set up the fpu before this works!! */

typedef ogg_int16_t vorbis_fpu_control;

static inline void vorbis_fpu_setround(vorbis_fpu_control *fpu){
  ogg_int16_t ret;
  ogg_int16_t temp;
  __asm__ __volatile__("fnstcw %0\n\t"
	  "movw %0,%%dx\n\t"
	  "orw $62463,%%dx\n\t"
	  "movw %%dx,%1\n\t"
	  "fldcw %1\n\t":"=m"(ret):"m"(temp): "dx");
  *fpu=ret;
}

static inline void vorbis_fpu_restore(vorbis_fpu_control fpu){
  __asm__ __volatile__("fldcw %0":: "m"(fpu));
}

/* assumes the FPU is in round mode! */
static inline int vorbis_ftoi(double f){  /* yes, double!  Otherwise,
                                             we get extra fst/fld to
                                             truncate precision */
  int i;
  __asm__("fistl %0": "=m"(i) : "t"(f));
  return(i);
}
#endif


#if defined(_WIN32) && !defined(__GNUC__)
#  define VORBIS_FPU_CONTROL

typedef ogg_int16_t vorbis_fpu_control;

static __inline int vorbis_ftoi(double f){
	int i;
	__asm{
		fld f
		fistp i
	}
	return i;
}

static __inline void vorbis_fpu_setround(vorbis_fpu_control *fpu){
}

static __inline void vorbis_fpu_restore(vorbis_fpu_control fpu){
}

#endif


#ifndef VORBIS_FPU_CONTROL

typedef int vorbis_fpu_control;

#define vorbis_ftoi(f) (int)((f)+.5)

/* We don't have special code for this compiler/arch, so do it the slow way */
#  define vorbis_fpu_setround(vorbis_fpu_control) {}
#  define vorbis_fpu_restore(vorbis_fpu_control) {}

#endif

#endif /* _OS_H */