v8/src/conversions.h

// Copyright 2011 the V8 project authors. All rights reserved.
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#ifndef V8_CONVERSIONS_H_
#define V8_CONVERSIONS_H_

#include <limits>

#include "scanner-base.h"

namespace v8 {
namespace internal {

// Maximum number of significant digits in decimal representation.
// The longest possible double in decimal representation is
// (2^53 - 1) * 2 ^ -1074 that is (2 ^ 53 - 1) * 5 ^ 1074 / 10 ^ 1074
// (768 digits). If we parse a number whose first digits are equal to a
// mean of 2 adjacent doubles (that could have up to 769 digits) the result
// must be rounded to the bigger one unless the tail consists of zeros, so
// we don't need to preserve all the digits.
const int kMaxSignificantDigits = 772;


static bool isDigit(int x, int radix) {
  return (x >= '0' && x <= '9' && x < '0' + radix)
      || (radix > 10 && x >= 'a' && x < 'a' + radix - 10)
      || (radix > 10 && x >= 'A' && x < 'A' + radix - 10);
}


static double SignedZero(bool negative) {
  return negative ? -0.0 : 0.0;
}


// The fast double-to-(unsigned-)int conversion routine does not guarantee
// rounding towards zero.
// The result is unspecified if x is infinite or NaN, or if the rounded
// integer value is outside the range of type int.
static inline int FastD2I(double x) {
  // The static_cast convertion from double to int used to be slow, but
  // as new benchmarks show, now it is much faster than lrint().
  return static_cast<int>(x);
}

static inline unsigned int FastD2UI(double x);


static inline double FastI2D(int x) {
  // There is no rounding involved in converting an integer to a
  // double, so this code should compile to a few instructions without
  // any FPU pipeline stalls.
  return static_cast<double>(x);
}


static inline double FastUI2D(unsigned x) {
  // There is no rounding involved in converting an unsigned integer to a
  // double, so this code should compile to a few instructions without
  // any FPU pipeline stalls.
  return static_cast<double>(x);
}


// This function should match the exact semantics of ECMA-262 9.4.
static inline double DoubleToInteger(double x);


// This function should match the exact semantics of ECMA-262 9.5.
static inline int32_t DoubleToInt32(double x);


// This function should match the exact semantics of ECMA-262 9.6.
static inline uint32_t DoubleToUint32(double x) {
  return static_cast<uint32_t>(DoubleToInt32(x));
}


// Enumeration for allowing octals and ignoring junk when converting
// strings to numbers.
enum ConversionFlags {
  NO_FLAGS = 0,
  ALLOW_HEX = 1,
  ALLOW_OCTALS = 2,
  ALLOW_TRAILING_JUNK = 4
};


// Converts a string into a double value according to ECMA-262 9.3.1
double StringToDouble(UnicodeCache* unicode_cache,
                      Vector<const char> str,
                      int flags,
                      double empty_string_val = 0);
double StringToDouble(UnicodeCache* unicode_cache,
                      Vector<const uc16> str,
                      int flags,
                      double empty_string_val = 0);
// This version expects a zero-terminated character array.
double StringToDouble(UnicodeCache* unicode_cache,
                      const char* str,
                      int flags,
                      double empty_string_val = 0);

// Converts a double to a string value according to ECMA-262 9.8.1.
// The buffer should be large enough for any floating point number.
// 100 characters is enough.
const char* DoubleToCString(double value, Vector<char> buffer);

// Convert an int to a null-terminated string. The returned string is
// located inside the buffer, but not necessarily at the start.
const char* IntToCString(int n, Vector<char> buffer);

// Additional number to string conversions for the number type.
// The caller is responsible for calling free on the returned pointer.
char* DoubleToFixedCString(double value, int f);
char* DoubleToExponentialCString(double value, int f);
char* DoubleToPrecisionCString(double value, int f);
char* DoubleToRadixCString(double value, int radix);

} }  // namespace v8::internal

#endif  // V8_CONVERSIONS_H_