v8/src/conversions-inl.h

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#ifndef V8_CONVERSIONS_INL_H_
#define V8_CONVERSIONS_INL_H_

#include <math.h>
#include <float.h>         // required for DBL_MAX and on Win32 for finite()
#include <stdarg.h>

// ----------------------------------------------------------------------------
// Extra POSIX/ANSI functions for Win32/MSVC.

#include "conversions.h"
#include "platform.h"

namespace v8 {
namespace internal {

// The fast double-to-unsigned-int conversion routine does not guarantee
// rounding towards zero, or any reasonable value if the argument is larger
// than what fits in an unsigned 32-bit integer.
static inline unsigned int FastD2UI(double x) {
  // There is no unsigned version of lrint, so there is no fast path
  // in this function as there is in FastD2I. Using lrint doesn't work
  // for values of 2^31 and above.

  // Convert "small enough" doubles to uint32_t by fixing the 32
  // least significant non-fractional bits in the low 32 bits of the
  // double, and reading them from there.
  const double k2Pow52 = 4503599627370496.0;
  bool negative = x < 0;
  if (negative) {
    x = -x;
  }
  if (x < k2Pow52) {
    x += k2Pow52;
    uint32_t result;
#ifdef BIG_ENDIAN_FLOATING_POINT
    Address mantissa_ptr = reinterpret_cast<Address>(&x) + kIntSize;
#else
    Address mantissa_ptr = reinterpret_cast<Address>(&x);
#endif
    // Copy least significant 32 bits of mantissa.
    memcpy(&result, mantissa_ptr, sizeof(result));
    return negative ? ~result + 1 : result;
  }
  // Large number (outside uint32 range), Infinity or NaN.
  return 0x80000000u;  // Return integer indefinite.
}


static inline double DoubleToInteger(double x) {
  if (isnan(x)) return 0;
  if (!isfinite(x) || x == 0) return x;
  return (x >= 0) ? floor(x) : ceil(x);
}


int32_t NumberToInt32(Object* number) {
  if (number->IsSmi()) return Smi::cast(number)->value();
  return DoubleToInt32(number->Number());
}


uint32_t NumberToUint32(Object* number) {
  if (number->IsSmi()) return Smi::cast(number)->value();
  return DoubleToUint32(number->Number());
}


int32_t DoubleToInt32(double x) {
  int32_t i = FastD2I(x);
  if (FastI2D(i) == x) return i;
  static const double two32 = 4294967296.0;
  static const double two31 = 2147483648.0;
  if (!isfinite(x) || x == 0) return 0;
  if (x < 0 || x >= two32) x = modulo(x, two32);
  x = (x >= 0) ? floor(x) : ceil(x) + two32;
  return (int32_t) ((x >= two31) ? x - two32 : x);
}


} }  // namespace v8::internal

#endif  // V8_CONVERSIONS_INL_H_