trionan.c

一个C语言写的快速贝叶斯垃圾邮件过滤工具

/*************************************************************************
 *
 * $Id: trionan.c,v 1.33 2005/05/29 11:57:25 breese Exp $
 *
 * Copyright (C) 2001 Bjorn Reese <[e-mail]>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE AUTHORS AND
 * CONTRIBUTORS ACCEPT NO RESPONSIBILITY IN ANY CONCEIVABLE MANNER.
 *
 ************************************************************************
 *
 * Functions to handle special quantities in floating-point numbers
 * (that is, NaNs and infinity). They provide the capability to detect
 * and fabricate special quantities.
 *
 * Although written to be as portable as possible, it can never be
 * guaranteed to work on all platforms, as not all hardware supports
 * special quantities.
 *
 * The approach used here (approximately) is to:
 *
 *   1. Use C99 functionality when available.
 *   2. Use IEEE 754 bit-patterns if possible.
 *   3. Use platform-specific techniques.
 *
 ************************************************************************/

/*************************************************************************
 * Include files
 */
#include "triodef.h"
#include "trionan.h"

#include <math.h>
#include <string.h>
#include <limits.h>
#if !defined(TRIO_PLATFORM_SYMBIAN)
# include <float.h>
#endif
#if defined(TRIO_PLATFORM_UNIX)
# include <signal.h>
#endif
#if defined(TRIO_COMPILER_DECC)
# include <fp_class.h>
#endif
#include <assert.h>

#if defined(TRIO_DOCUMENTATION)
# include "doc/doc_nan.h"
#endif
/** @addtogroup SpecialQuantities
    @{
*/

/*************************************************************************
 * Definitions
 */

#if !defined(TRIO_PUBLIC_NAN)
# define TRIO_PUBLIC_NAN TRIO_PUBLIC
#endif
#if !defined(TRIO_PRIVATE_NAN)
# define TRIO_PRIVATE_NAN TRIO_PRIVATE
#endif

#define TRIO_TRUE (1 == 1)
#define TRIO_FALSE (0 == 1)

/*
 * We must enable IEEE floating-point on Alpha
 */
#if defined(__alpha) && !defined(_IEEE_FP)
# if defined(TRIO_COMPILER_DECC)
#  if defined(TRIO_PLATFORM_VMS)
#   error "Must be compiled with option /IEEE_MODE=UNDERFLOW_TO_ZERO/FLOAT=IEEE"
#  else
#   if !defined(_CFE)
#    error "Must be compiled with option -ieee"
#   endif
#  endif
# else
#  if defined(TRIO_COMPILER_GCC)
#   error "Must be compiled with option -mieee"
#  endif
# endif
#endif /* __alpha && ! _IEEE_FP */

/*
 * In ANSI/IEEE 754-1985 64-bits double format numbers have the
 * following properties (amoungst others)
 *
 *   o FLT_RADIX == 2: binary encoding
 *   o DBL_MAX_EXP == 1024: 11 bits exponent, where one bit is used
 *     to indicate special numbers (e.g. NaN and Infinity), so the
 *     maximum exponent is 10 bits wide (2^10 == 1024).
 *   o DBL_MANT_DIG == 53: The mantissa is 52 bits wide, but because
 *     numbers are normalized the initial binary 1 is represented
 *     implicitly (the so-called "hidden bit"), which leaves us with
 *     the ability to represent 53 bits wide mantissa.
 */
#if defined(__STDC_IEC_559__)
# define TRIO_IEEE_754
#else
# if (FLT_RADIX - 0 == 2) && (DBL_MAX_EXP - 0 == 1024) && (DBL_MANT_DIG - 0 == 53)
#  define TRIO_IEEE_754
# endif
#endif

/*
 * Determine which fpclassify_and_sign() function to use.
 */
#if defined(TRIO_FUNC_FPCLASSIFY_AND_SIGNBIT)
# if defined(PREDEF_STANDARD_C99) && defined(fpclassify)
#  define TRIO_FUNC_C99_FPCLASSIFY_AND_SIGNBIT
# else
#  if defined(TRIO_COMPILER_DECC)
#   define TRIO_FUNC_DECC_FPCLASSIFY_AND_SIGNBIT
#  else
#   if defined(TRIO_COMPILER_VISUALC) || defined(TRIO_COMPILER_BORLAND)
#    define TRIO_FUNC_MS_FPCLASSIFY_AND_SIGNBIT
#   else
#    if defined(TRIO_COMPILER_HP) && defined(FP_PLUS_NORM)
#     define TRIO_FUNC_HP_FPCLASSIFY_AND_SIGNBIT
#    else
#     if defined(TRIO_COMPILER_XLC) && defined(FP_PLUS_NORM)
#      define TRIO_FUNC_XLC_FPCLASSIFY_AND_SIGNBIT
#     else
#      define TRIO_FUNC_INTERNAL_FPCLASSIFY_AND_SIGNBIT
#     endif
#    endif
#   endif
#  endif
# endif
#endif

/*
 * Determine how to generate negative zero.
 */
#if defined(TRIO_FUNC_NZERO)
# if defined(TRIO_IEEE_754)
#  define TRIO_NZERO_IEEE_754
# else
#  define TRIO_NZERO_FALLBACK
# endif
#endif

/*
 * Determine how to generate positive infinity.
 */
#if defined(TRIO_FUNC_PINF)
# if defined(INFINITY) && defined(__STDC_IEC_559__)
#  define TRIO_PINF_C99_MACRO
# else
#  if defined(TRIO_IEEE_754)
#   define TRIO_PINF_IEEE_754
#  else
#   define TRIO_PINF_FALLBACK
#  endif
# endif
#endif

/*
 * Determine how to generate NaN.
 */
#if defined(TRIO_FUNC_NAN)
# if defined(PREDEF_STANDARD_C99) && !defined(TRIO_COMPILER_DECC)
#  define TRIO_NAN_C99_FUNCTION
# else
#  if defined(NAN) && defined(__STDC_IEC_559__)
#   define TRIO_NAN_C99_MACRO
#  else
#   if defined(TRIO_IEEE_754)
#    define TRIO_NAN_IEEE_754
#   else
#    define TRIO_NAN_FALLBACK
#   endif
#  endif
# endif
#endif

/*
 * Resolve internal dependencies.
 */
#if defined(TRIO_FUNC_INTERNAL_FPCLASSIFY_AND_SIGNBIT)
# define TRIO_FUNC_INTERNAL_ISNAN
# define TRIO_FUNC_INTERNAL_ISINF
# if defined(TRIO_IEEE_754)
#  define TRIO_FUNC_INTERNAL_IS_SPECIAL_QUANTITY
#  define TRIO_FUNC_INTERNAL_IS_NEGATIVE
# endif
#endif

#if defined(TRIO_NZERO_IEEE_754) \
 || defined(TRIO_PINF_IEEE_754) \
 || defined(TRIO_NAN_IEEE_754)
# define TRIO_FUNC_INTERNAL_MAKE_DOUBLE
#endif

#if defined(TRIO_FUNC_INTERNAL_ISNAN)
# if defined(PREDEF_STANDARD_XPG3)
#  define TRIO_INTERNAL_ISNAN_XPG3
# else
#  if defined(TRIO_IEEE_754)
#   define TRIO_INTERNAL_ISNAN_IEEE_754
#  else
#   define TRIO_INTERNAL_ISNAN_FALLBACK
#  endif
# endif
#endif

#if defined(TRIO_FUNC_INTERNAL_ISINF)
# if defined(TRIO_IEEE_754)
#  define TRIO_INTERNAL_ISINF_IEEE_754
# else
#  define TRIO_INTERNAL_ISINF_FALLBACK
# endif
#endif

/*************************************************************************
 * Constants
 */

#if !defined(TRIO_EMBED_NAN)
static TRIO_CONST char rcsid[] = "@(#)$Id: trionan.c,v 1.33 2005/05/29 11:57:25 breese Exp $";
#endif

#if defined(TRIO_FUNC_INTERNAL_MAKE_DOUBLE) \
 || defined(TRIO_FUNC_INTERNAL_IS_SPECIAL_QUANTITY) \
 || defined(TRIO_FUNC_INTERNAL_IS_NEGATIVE)
/*
 * Endian-agnostic indexing macro.
 *
 * The value of internalEndianMagic, when converted into a 64-bit
 * integer, becomes 0x0706050403020100 (we could have used a 64-bit
 * integer value instead of a double, but not all platforms supports
 * that type). The value is automatically encoded with the correct
 * endianess by the compiler, which means that we can support any
 * kind of endianess. The individual bytes are then used as an index
 * for the IEEE 754 bit-patterns and masks.
 */
#define TRIO_DOUBLE_INDEX(x) (((unsigned char *)&internalEndianMagic)[7-(x)])
static TRIO_CONST double internalEndianMagic = 7.949928895127363e-275;
#endif

#if defined(TRIO_FUNC_INTERNAL_IS_SPECIAL_QUANTITY)
/* Mask for the exponent */
static TRIO_CONST unsigned char ieee_754_exponent_mask[] = {
  0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

/* Mask for the mantissa */
static TRIO_CONST unsigned char ieee_754_mantissa_mask[] = {
  0x00, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
#endif

#if defined(TRIO_FUNC_INTERNAL_IS_NEGATIVE)
/* Mask for the sign bit */
static TRIO_CONST unsigned char ieee_754_sign_mask[] = {
  0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
#endif

#if defined(TRIO_NZERO_IEEE_754)
/* Bit-pattern for negative zero */
static TRIO_CONST unsigned char ieee_754_negzero_array[] = {
  0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
#endif

#if defined(TRIO_PINF_IEEE_754)
/* Bit-pattern for infinity */
static TRIO_CONST unsigned char ieee_754_infinity_array[] = {
  0x7F, 0xF0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
#endif

#if defined(TRIO_NAN_IEEE_754)
/* Bit-pattern for quiet NaN */
static TRIO_CONST unsigned char ieee_754_qnan_array[] = {
  0x7F, 0xF8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
#endif


/*************************************************************************
 * Internal functions
 */

/*
 * internal_make_double
 */
#if defined(TRIO_FUNC_INTERNAL_MAKE_DOUBLE)

TRIO_PRIVATE_NAN double
internal_make_double
TRIO_ARGS1((values),
	   TRIO_CONST unsigned char *values)
{
  TRIO_VOLATILE double result;
  int i;

  for (i = 0; i < (int)sizeof(double); i++) {
    ((TRIO_VOLATILE unsigned char *)&result)[TRIO_DOUBLE_INDEX(i)] = values[i];
  }
  return result;
}

#endif

/*
 * internal_is_special_quantity
 */
#if defined(TRIO_FUNC_INTERNAL_IS_SPECIAL_QUANTITY)

TRIO_PRIVATE_NAN int
internal_is_special_quantity
TRIO_ARGS2((number, has_mantissa),
	   double number,
	   int *has_mantissa)
{
  unsigned int i;
  unsigned char current;
  int is_special_quantity = TRIO_TRUE;

  *has_mantissa = 0;

  for (i = 0; i < (unsigned int)sizeof(double); i++) {
    current = ((unsigned char *)&number)[TRIO_DOUBLE_INDEX(i)];
    is_special_quantity
      &= ((current & ieee_754_exponent_mask[i]) == ieee_754_exponent_mask[i]);
    *has_mantissa |= (current & ieee_754_mantissa_mask[i]);
  }
  return is_special_quantity;
}

#endif

/*
 * internal_is_negative
 */
#if defined(TRIO_FUNC_INTERNAL_IS_NEGATIVE)

TRIO_PRIVATE_NAN int
internal_is_negative
TRIO_ARGS1((number),
	   double number)
{
  unsigned int i;
  int is_negative = TRIO_FALSE;

  for (i = 0; i < (unsigned int)sizeof(double); i++) {
    is_negative |= (((unsigned char *)&number)[TRIO_DOUBLE_INDEX(i)]
		    & ieee_754_sign_mask[i]);
  }
  return is_negative;
}

#endif

#if defined(TRIO_FUNC_C99_FPCLASSIFY_AND_SIGNBIT)

TRIO_PRIVATE_NAN TRIO_INLINE int
c99_fpclassify_and_signbit
TRIO_ARGS2((number, is_negative),
	   double number,
	   int *is_negative)
{
  *is_negative = signbit(number);
  switch (fpclassify(number)) {
  case FP_NAN:
    return TRIO_FP_NAN;
  case FP_INFINITE:
    return TRIO_FP_INFINITE;
  case FP_SUBNORMAL:
    return TRIO_FP_SUBNORMAL;
  case FP_ZERO:
    return TRIO_FP_ZERO;
  default:
    return TRIO_FP_NORMAL;
  }
}

#endif /* TRIO_FUNC_C99_FPCLASSIFY_AND_SIGNBIT */

#if defined(TRIO_FUNC_DECC_FPCLASSIFY_AND_SIGNBIT)

TRIO_PRIVATE_NAN TRIO_INLINE int
decc_fpclassify_and_signbit
TRIO_ARGS2((number, is_negative),
	  double number,
	  int *is_negative)
{
  switch (fp_class(number)) {
  case FP_QNAN:
  case FP_SNAN:
    *is_negative = TRIO_FALSE; /* NaN has no sign */
    return TRIO_FP_NAN;
  case FP_POS_INF:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_INFINITE;
  case FP_NEG_INF:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_INFINITE;
  case FP_POS_DENORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_SUBNORMAL;
  case FP_NEG_DENORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_SUBNORMAL;
  case FP_POS_ZERO:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_ZERO;
  case FP_NEG_ZERO:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_ZERO;
  case FP_POS_NORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_NORMAL;
  case FP_NEG_NORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_NORMAL;
  default:
    *is_negative = (number < 0.0);
    return TRIO_FP_NORMAL;
  }
}

#endif /* TRIO_FUNC_DECC_FPCLASSIFY_AND_SIGNBIT */

#if defined(TRIO_FUNC_MS_FPCLASSIFY_AND_SIGNBIT)

TRIO_PRIVATE_NAN int
ms_fpclassify_and_signbit
TRIO_ARGS2((number, is_negative),
	  double number,
	  int *is_negative)
{
  int result;
# if defined(TRIO_COMPILER_BORLAND)
  /*
   * The floating-point precision may be changed by the Borland _fpclass()
   * function, so we have to save and restore the floating-point control mask.
   */
  unsigned int mask;
  /* Remember the old mask */
  mask = _control87(0, 0);
# endif
  
  switch (_fpclass(number)) {
  case _FPCLASS_QNAN:
  case _FPCLASS_SNAN:
    *is_negative = TRIO_FALSE; /* NaN has no sign */
    result = TRIO_FP_NAN;
    break;
  case _FPCLASS_PINF:
    *is_negative = TRIO_FALSE;
    result = TRIO_FP_INFINITE;
    break;
  case _FPCLASS_NINF:
    *is_negative = TRIO_TRUE;
    result = TRIO_FP_INFINITE;
    break;
  case _FPCLASS_PD:
    *is_negative = TRIO_FALSE;
    result = TRIO_FP_SUBNORMAL;
    break;
  case _FPCLASS_ND:
    *is_negative = TRIO_TRUE;
    result = TRIO_FP_SUBNORMAL;
    break;
  case _FPCLASS_PZ:
    *is_negative = TRIO_FALSE;
    result = TRIO_FP_ZERO;
    break;
  case _FPCLASS_NZ:
    *is_negative = TRIO_TRUE;
    result = TRIO_FP_ZERO;
    break;
  case _FPCLASS_PN:
    *is_negative = TRIO_FALSE;
    result = TRIO_FP_NORMAL;
    break;
  case _FPCLASS_NN:
    *is_negative = TRIO_TRUE;
    result = TRIO_FP_NORMAL;
    break;
  default:
    *is_negative = (number < 0.0);
    result = TRIO_FP_NORMAL;
    break;
  }
  
# if defined(TRIO_COMPILER_BORLAND)
  /* Restore the old precision */
  (void)_control87(mask, MCW_PC);
# endif
  
  return result;
}

#endif /* TRIO_FUNC_MS_FPCLASSIFY_AND_SIGNBIT */

#if defined(TRIO_FUNC_HP_FPCLASSIFY_AND_SIGNBIT)

TRIO_PRIVATE_NAN TRIO_INLINE int
hp_fpclassify_and_signbit
TRIO_ARGS2((number, is_negative),
	  double number,
	  int *is_negative)
{
  /*
   * HP-UX 9.x and 10.x have an fpclassify() function, that is different
   * from the C99 fpclassify() macro supported on HP-UX 11.x.
   */
  switch (fpclassify(number)) {
  case FP_QNAN:
  case FP_SNAN:
    *is_negative = TRIO_FALSE; /* NaN has no sign */
    return TRIO_FP_NAN;
  case FP_PLUS_INF:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_INFINITE;
  case FP_MINUS_INF:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_INFINITE;
  case FP_PLUS_DENORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_SUBNORMAL;
  case FP_MINUS_DENORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_SUBNORMAL;
  case FP_PLUS_ZERO:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_ZERO;
  case FP_MINUS_ZERO:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_ZERO;
  case FP_PLUS_NORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_NORMAL;
  case FP_MINUS_NORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_NORMAL;
  default:
    *is_negative = (number < 0.0);
    return TRIO_FP_NORMAL;
  }
}

#endif /* TRIO_FUNC_HP_FPCLASSIFY_AND_SIGNBIT */

#if defined(TRIO_FUNC_XLC_FPCLASSIFY_AND_SIGNBIT)

TRIO_PRIVATE_NAN TRIO_INLINE int
xlc_fpclassify_and_signbit
TRIO_ARGS2((number, is_negative),
	  double number,
	  int *is_negative)
{
  /*
   * AIX has class() for C, and _class() for C++
   */
# if defined(__cplusplus)
#  define AIX_CLASS(n) _class(n)
# else
#  define AIX_CLASS(n) class(n)
# endif

  switch (AIX_CLASS(number)) {
  case FP_QNAN:
  case FP_SNAN:
    *is_negative = TRIO_FALSE; /* NaN has no sign */
    return TRIO_FP_NAN;
  case FP_PLUS_INF:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_INFINITE;
  case FP_MINUS_INF:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_INFINITE;
  case FP_PLUS_DENORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_SUBNORMAL;
  case FP_MINUS_DENORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_SUBNORMAL;
  case FP_PLUS_ZERO:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_ZERO;
  case FP_MINUS_ZERO:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_ZERO;
  case FP_PLUS_NORM:
    *is_negative = TRIO_FALSE;
    return TRIO_FP_NORMAL;
  case FP_MINUS_NORM:
    *is_negative = TRIO_TRUE;
    return TRIO_FP_NORMAL;
  default:
    *is_negative = (number < 0.0);
    return TRIO_FP_NORMAL;
  }
}

#endif /* TRIO_FUNC_XLC_FPCLASSIFY_AND_SIGNBIT */

#if defined(TRIO_FUNC_INTERNAL_ISNAN)

TRIO_PRIVATE_NAN TRIO_INLINE int
internal_isnan
TRIO_ARGS1((number),
	   double number)
{
# if defined(TRIO_INTERNAL_ISNAN_XPG3) || defined(TRIO_PLATFORM_SYMBIAN)
  /*
   * XPG3 defines isnan() as a function.
   */
  return isnan(number);

# endif
  
# if defined(TRIO_INTERNAL_ISNAN_IEEE_754)