fixed.h

完成MP3播放功能

/*
 * libmad - MPEG audio decoder library
 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
 *
 * This program 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.
 *
 * This program 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
 *
 * $Id: fixed.h,v 1.38 2004/02/17 02:02:03 rob Exp $
 */

# ifndef LIBMAD_FIXED_H
# define LIBMAD_FIXED_H

# if SIZEOF_INT >= 4
typedef   signed int mad_fixed_t;

typedef   signed int mad_fixed64hi_t;
typedef unsigned int mad_fixed64lo_t;
# else
typedef   signed long mad_fixed_t;

typedef   signed long mad_fixed64hi_t;
typedef unsigned long mad_fixed64lo_t;
# endif

# if defined(_MSC_VER)
#  define mad_fixed64_t  signed __int64
# elif 1 || defined(__GNUC__)
#  define mad_fixed64_t  signed long long
# endif

# if defined(FPM_FLOAT)
typedef double mad_sample_t;
# else
typedef mad_fixed_t mad_sample_t;
# endif

/*
 * Fixed-point format: 0xABBBBBBB
 * A == whole part      (sign + 3 bits)
 * B == fractional part (28 bits)
 *
 * Values are signed two's complement, so the effective range is:
 * 0x80000000 to 0x7fffffff
 *       -8.0 to +7.9999999962747097015380859375
 *
 * The smallest representable value is:
 * 0x00000001 == 0.0000000037252902984619140625 (i.e. about 3.725e-9)
 *
 * 28 bits of fractional accuracy represent about
 * 8.6 digits of decimal accuracy.
 *
 * Fixed-point numbers can be added or subtracted as normal
 * integers, but multiplication requires shifting the 64-bit result
 * from 56 fractional bits back to 28 (and rounding.)
 *
 * Changing the definition of MAD_F_FRACBITS is only partially
 * supported, and must be done with care.
 */

# define MAD_F_FRACBITS		28

# if MAD_F_FRACBITS == 28
#  define MAD_F(x)		((mad_fixed_t) (x##L))
# else
#  if MAD_F_FRACBITS < 28
#   warning "MAD_F_FRACBITS < 28"
#   define MAD_F(x)		((mad_fixed_t)  \
				 (((x##L) +  \
				   (1L << (28 - MAD_F_FRACBITS - 1))) >>  \
				  (28 - MAD_F_FRACBITS)))
#  elif MAD_F_FRACBITS > 28
#   error "MAD_F_FRACBITS > 28 not currently supported"
#   define MAD_F(x)		((mad_fixed_t)  \
				 ((x##L) << (MAD_F_FRACBITS - 28)))
#  endif
# endif

# define MAD_F_MIN		((mad_fixed_t) -0x80000000L)
# define MAD_F_MAX		((mad_fixed_t) +0x7fffffffL)

# define MAD_F_ONE		MAD_F(0x10000000)

# define mad_f_tofixed(x)	((mad_fixed_t)  \
				 ((x) * (double) (1L << MAD_F_FRACBITS) + 0.5))
# define mad_f_todouble(x)	((double)  \
				 ((x) / (double) (1L << MAD_F_FRACBITS)))

# define mad_f_intpart(x)	((x) >> MAD_F_FRACBITS)
# define mad_f_fracpart(x)	((x) & ((1L << MAD_F_FRACBITS) - 1))
				/* (x should be positive) */

# define mad_f_fromint(x)	((x) << MAD_F_FRACBITS)

# define mad_f_add(x, y)	((x) + (y))
# define mad_f_sub(x, y)	((x) - (y))

# if defined(FPM_FLOAT)
#  error "FPM_FLOAT not yet supported"

#  undef MAD_F
#  define MAD_F(x)		mad_f_todouble(x)

#  define mad_f_mul(x, y)	((x) * (y))
#  define mad_f_scale64

#  undef ASO_ZEROCHECK

# elif defined(FPM_64BIT)

/*
 * This version should be the most accurate if 64-bit types are supported by
 * the compiler, although it may not be the most efficient.
 */
//#  if defined(OPT_ACCURACY)
//#   define mad_f_mul(x, y)  \
    ((mad_fixed_t)  \
     ((((mad_fixed64_t) (x) * (y)) +  \
       (1L << (MAD_F_SCALEBITS - 1))) >> MAD_F_SCALEBITS))
//#  else
#   define mad_f_mul(x, y)  \
    ((mad_fixed_t) (((mad_fixed64_t) (x) * (y)) >> MAD_F_SCALEBITS))
//#  endif

#  define MAD_F_SCALEBITS  MAD_F_FRACBITS

/* --- Intel --------------------------------------------------------------- */


#  define MAD_F_SCALEBITS  MAD_F_FRACBITS

/* --- Default ------------------------------------------------------------- */

# elif defined(FPM_DEFAULT)

/*
 * This version is the most portable but it loses significant accuracy.
 * Furthermore, accuracy is biased against the second argument, so care
 * should be taken when ordering operands.
 *
 * The scale factors are constant as this is not used with SSO.
 *
 * Pre-rounding is required to stay within the limits of compliance.
 */
//#  if defined(OPT_SPEED)***********************************
//#   define mad_f_mul(x, y)	(((x) >> 12) * ((y) >> 16))
//#  else
#   define mad_f_mul(x, y)	((((x) + (1L << 11)) >> 12) *  \
				 (((y) + (1L << 15)) >> 16))
//#  endif****************************************************

/* ------------------------------------------------------------------------- */

//# else******************************************************
//#  error "no FPM selected"**********************************
# endif

/* default implementations */
/**************************************************************
# if !defined(mad_f_mul)
#  define mad_f_mul(x, y)  \
    ({ register mad_fixed64hi_t __hi;  \
       register mad_fixed64lo_t __lo;  \
       MAD_F_MLX(__hi, __lo, (x), (y));  \
       mad_f_scale64(__hi, __lo);  \
    })
# endif
*/
# if !defined(MAD_F_MLA)
#  define MAD_F_ML0(hi, lo, x, y)	((lo)  = mad_f_mul((x), (y)))
#  define MAD_F_MLA(hi, lo, x, y)	((lo) += mad_f_mul((x), (y)))
#  define MAD_F_MLN(hi, lo)		((lo)  = -(lo))
#  define MAD_F_MLZ(hi, lo)		((void) (hi), (mad_fixed_t) (lo))
# endif

//# if !defined(MAD_F_ML0)********************************
//#  define MAD_F_ML0(hi, lo, x, y)	MAD_F_MLX((hi), (lo), (x), (y))
//# endif************************************************

# if !defined(MAD_F_MLN)
#  define MAD_F_MLN(hi, lo)		((hi) = ((lo) = -(lo)) ? ~(hi) : -(hi))
# endif

# if !defined(MAD_F_MLZ)
#  define MAD_F_MLZ(hi, lo)		mad_f_scale64((hi), (lo))
# endif

# if !defined(mad_f_scale64)
#  if defined(OPT_ACCURACY)
#   define mad_f_scale64(hi, lo)  \
    ((((mad_fixed_t)  \
       (((hi) << (32 - (MAD_F_SCALEBITS - 1))) |  \
	((lo) >> (MAD_F_SCALEBITS - 1)))) + 1) >> 1)
#  else
#   define mad_f_scale64(hi, lo)  \
    ((mad_fixed_t)  \
     (((hi) << (32 - MAD_F_SCALEBITS)) |  \
      ((lo) >> MAD_F_SCALEBITS)))
#  endif
#  define MAD_F_SCALEBITS  MAD_F_FRACBITS
# endif

/* C routines */

mad_fixed_t mad_f_abs(mad_fixed_t);
mad_fixed_t mad_f_div(mad_fixed_t, mad_fixed_t);

# endif