v8/src/conversions.h

// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_CONVERSIONS_H_
#define V8_CONVERSIONS_H_

#include <limits>

#include "src/base/logging.h"
#include "src/handles.h"
#include "src/objects.h"
#include "src/utils.h"

namespace v8 {
namespace internal {

class UnicodeCache;

// 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;


inline 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);
}


inline bool isBinaryDigit(int x) {
  return x == '0' || x == '1';
}


// The fast double-to-(unsigned-)int conversion routine does not guarantee
// rounding towards zero.
// If x is NaN, the result is INT_MIN.  Otherwise the result is the argument x,
// clamped to [INT_MIN, INT_MAX] and then rounded to an integer.
inline int FastD2IChecked(double x) {
  if (!(x >= INT_MIN)) return INT_MIN;  // Negation to catch NaNs.
  if (x > INT_MAX) return INT_MAX;
  return static_cast<int>(x);
}


// 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.
inline int FastD2I(double x) {
  return static_cast<int32_t>(x);
}

inline unsigned int FastD2UI(double x);


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);
}


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.
inline double DoubleToInteger(double x);


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


// This function should match the exact semantics of ECMA-262 9.6.
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_OCTAL = 2,
  ALLOW_IMPLICIT_OCTAL = 4,
  ALLOW_BINARY = 8,
  ALLOW_TRAILING_JUNK = 16
};


// Converts a string into a double value according to ECMA-262 9.3.1
double StringToDouble(UnicodeCache* unicode_cache,
                      Vector<const uint8_t> 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 string into an integer.
double StringToInt(UnicodeCache* unicode_cache,
                   Vector<const uint8_t> vector,
                   int radix);


double StringToInt(UnicodeCache* unicode_cache,
                   Vector<const uc16> vector,
                   int radix);

const int kDoubleToCStringMinBufferSize = 100;

// 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);


static inline bool IsMinusZero(double value) {
  static const DoubleRepresentation minus_zero(-0.0);
  return DoubleRepresentation(value) == minus_zero;
}


static inline bool IsSmiDouble(double value) {
  return !IsMinusZero(value) && value >= Smi::kMinValue &&
         value <= Smi::kMaxValue && value == FastI2D(FastD2I(value));
}


// Integer32 is an integer that can be represented as a signed 32-bit
// integer. It has to be in the range [-2^31, 2^31 - 1].
// We also have to check for negative 0 as it is not an Integer32.
static inline bool IsInt32Double(double value) {
  return !IsMinusZero(value) &&
         value >= kMinInt &&
         value <= kMaxInt &&
         value == FastI2D(FastD2I(value));
}


// UInteger32 is an integer that can be represented as an unsigned 32-bit
// integer. It has to be in the range [0, 2^32 - 1].
// We also have to check for negative 0 as it is not a UInteger32.
static inline bool IsUint32Double(double value) {
  return !IsMinusZero(value) &&
         value >= 0 &&
         value <= kMaxUInt32 &&
         value == FastUI2D(FastD2UI(value));
}


// Convert from Number object to C integer.
inline int32_t NumberToInt32(Object* number) {
  if (number->IsSmi()) return Smi::cast(number)->value();
  return DoubleToInt32(number->Number());
}


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


double StringToDouble(UnicodeCache* unicode_cache,
                      String* string,
                      int flags,
                      double empty_string_val = 0.0);


inline bool TryNumberToSize(Isolate* isolate,
                            Object* number, size_t* result) {
  SealHandleScope shs(isolate);
  if (number->IsSmi()) {
    int value = Smi::cast(number)->value();
    DCHECK(static_cast<unsigned>(Smi::kMaxValue)
           <= std::numeric_limits<size_t>::max());
    if (value >= 0) {
      *result = static_cast<size_t>(value);
      return true;
    }
    return false;
  } else {
    DCHECK(number->IsHeapNumber());
    double value = HeapNumber::cast(number)->value();
    if (value >= 0 &&
        value <= std::numeric_limits<size_t>::max()) {
      *result = static_cast<size_t>(value);
      return true;
    } else {
      return false;
    }
  }
}

// Converts a number into size_t.
inline size_t NumberToSize(Isolate* isolate,
                           Object* number) {
  size_t result = 0;
  bool is_valid = TryNumberToSize(isolate, number, &result);
  CHECK(is_valid);
  return result;
}

} }  // namespace v8::internal

#endif  // V8_CONVERSIONS_H_