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/* Copyright (c) 2003, Roger Dingledine
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file fp.c
*
* \brief Basic floating-point compatibility and convenience code.
**/
#include "orconfig.h"
#include "lib/math/fp.h"
#include <math.h>
/**
* Returns the natural logarithm of d base e. We defined this wrapper here so
* to avoid conflicts with old versions of tor_log(), which were named log().
*/
double
tor_mathlog(double d)
{
return log(d);
}
/** Return the long integer closest to <b>d</b>. We define this wrapper
* here so that not all users of math.h need to use the right incantations
* to get the c99 functions. */
long
tor_lround(double d)
{
#if defined(HAVE_LROUND)
return lround(d);
#elif defined(HAVE_RINT)
return (long)rint(d);
#else
return (long)(d > 0 ? d + 0.5 : ceil(d - 0.5));
#endif /* defined(HAVE_LROUND) || ... */
}
/** Return the 64-bit integer closest to d. We define this wrapper here so
* that not all users of math.h need to use the right incantations to get the
* c99 functions. */
int64_t
tor_llround(double d)
{
#if defined(HAVE_LLROUND)
return (int64_t)llround(d);
#elif defined(HAVE_RINT)
return (int64_t)rint(d);
#else
return (int64_t)(d > 0 ? d + 0.5 : ceil(d - 0.5));
#endif /* defined(HAVE_LLROUND) || ... */
}
/** Cast a given double value to a int64_t. Return 0 if number is NaN.
* Returns either INT64_MIN or INT64_MAX if number is outside of the int64_t
* range. */
int64_t
clamp_double_to_int64(double number)
{
int exponent;
#if (defined(MINGW_ANY)||defined(__FreeBSD__)) && GCC_VERSION >= 409
/*
Mingw's math.h uses gcc's __builtin_choose_expr() facility to declare
isnan, isfinite, and signbit. But as implemented in at least some
versions of gcc, __builtin_choose_expr() can generate type warnings
even from branches that are not taken. So, suppress those warnings.
FreeBSD's math.h uses an __fp_type_select() macro, which dispatches
based on sizeof -- again, this can generate type warnings from
branches that are not taken.
*/
#define PROBLEMATIC_FLOAT_CONVERSION_WARNING
DISABLE_GCC_WARNING("-Wfloat-conversion")
#endif /* (defined(MINGW_ANY)||defined(__FreeBSD__)) && GCC_VERSION >= 409 */
/*
With clang 4.0 we apparently run into "double promotion" warnings here,
since clang thinks we're promoting a double to a long double.
*/
#if defined(__clang__)
#if __has_warning("-Wdouble-promotion")
#define PROBLEMATIC_DOUBLE_PROMOTION_WARNING
DISABLE_GCC_WARNING("-Wdouble-promotion")
#endif
#endif /* defined(__clang__) */
/* NaN is a special case that can't be used with the logic below. */
if (isnan(number)) {
return 0;
}
/* Time to validate if result can overflows a int64_t value. Fun with
* float! Find that exponent exp such that
* number == x * 2^exp
* for some x with abs(x) in [0.5, 1.0). Note that this implies that the
* magnitude of number is strictly less than 2^exp.
*
* If number is infinite, the call to frexp is legal but the contents of
* are exponent unspecified. */
frexp(number, &exponent);
/* If the magnitude of number is strictly less than 2^63, the truncated
* version of number is guaranteed to be representable. The only
* representable integer for which this is not the case is INT64_MIN, but
* it is covered by the logic below. */
if (isfinite(number) && exponent <= 63) {
return (int64_t)number;
}
/* Handle infinities and finite numbers with magnitude >= 2^63. */
return signbit(number) ? INT64_MIN : INT64_MAX;
#ifdef PROBLEMATIC_DOUBLE_PROMOTION_WARNING
ENABLE_GCC_WARNING("-Wdouble-promotion")
#endif
#ifdef PROBLEMATIC_FLOAT_CONVERSION_WARNING
ENABLE_GCC_WARNING("-Wfloat-conversion")
#endif
}
/* isinf() wrapper for tor */
int
tor_isinf(double x)
{
/* Same as above, work around the "double promotion" warnings */
#ifdef PROBLEMATIC_FLOAT_CONVERSION_WARNING
DISABLE_GCC_WARNING("-Wfloat-conversion")
#endif
#ifdef PROBLEMATIC_DOUBLE_PROMOTION_WARNING
DISABLE_GCC_WARNING("-Wdouble-promotion")
#endif
return isinf(x);
#ifdef PROBLEMATIC_DOUBLE_PROMOTION_WARNING
ENABLE_GCC_WARNING("-Wdouble-promotion")
#endif
#ifdef PROBLEMATIC_FLOAT_CONVERSION_WARNING
ENABLE_GCC_WARNING("-Wfloat-conversion")
#endif
}
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