1 files changed, 119 insertions, 0 deletions
diff --git a/src/lib/math/fp.c b/src/lib/math/fp.c
new file mode 100644
index 0000000000..d5989db637
--- /dev/null
+++ b/src/lib/math/fp.c
@@ -0,0 +1,119 @@
+/* Copyright (c) 2003, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, 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) && 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.
+*/
+#define PROBLEMATIC_FLOAT_CONVERSION_WARNING
+DISABLE_GCC_WARNING(float-conversion)
+#endif /* defined(MINGW_ANY) && 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(double-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(double-promotion)
+#endif
+#ifdef PROBLEMATIC_FLOAT_CONVERSION_WARNING
+ENABLE_GCC_WARNING(float-conversion)
+#endif
+}