text: // 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_NUMBERS_CONVERSIONS_H_
  #define V8_NUMBERS_CONVERSIONS_H_
  
  #include "src/base/export-template.h"
  #include "src/base/logging.h"
  #include "src/common/globals.h"
  #include "src/handles/handle-for.h"
  #include "src/utils/vector.h"
  
  namespace v8 {
  namespace internal {
  
  class BigInt;
  template <typename T>
  class Handle;
  
  // The limit for the the fractionDigits/precision for toFixed, toPrecision
  // and toExponential.
  const int kMaxFractionDigits = 100;
  
  // 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 undefined if x is infinite or NaN, or if the rounded
  // integer value is outside the range of type int.
  inline int FastD2I(double x) {
    DCHECK(x <= INT_MAX);
    DCHECK(x >= INT_MIN);
    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 20.2.2.17.
  inline float DoubleToFloat32(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);
  
  // 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(Vector<const uint8_t> str, int flags,
                        double empty_string_val = 0);
  double StringToDouble(Vector<const uc16> str, int flags,
                        double empty_string_val = 0);
  // This version expects a zero-terminated character array.
  double V8_EXPORT_PRIVATE StringToDouble(const char* str, int flags,
                                          double empty_string_val = 0);
  
  double StringToInt(Isolate* isolate, Handle<String> string, int radix);
  
  // This follows https://tc39.github.io/proposal-bigint/#sec-string-to-bigint
  // semantics: "" => 0n.
  MaybeHandle<BigInt> StringToBigInt(Isolate* isolate, Handle<String> string);
  
  // This version expects a zero-terminated character array. Radix will
  // be inferred from string prefix (case-insensitive):
  //   0x -> hex
  //   0o -> octal
  //   0b -> binary
  template <typename Isolate>
  EXPORT_TEMPLATE_DECLARE(V8_EXPORT_PRIVATE)
  MaybeHandleFor<Isolate, BigInt> BigIntLiteral(Isolate* isolate,
                                                const char* string);
  
  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.
  V8_EXPORT_PRIVATE 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.
  V8_EXPORT_PRIVATE 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) {
    return bit_cast<int64_t>(value) == bit_cast<int64_t>(-0.0);
  }
  
  // Returns true if value can be converted to a SMI, and returns the resulting
  // integer value of the SMI in |smi_int_value|.
  inline bool DoubleToSmiInteger(double value, int* smi_int_value);
  
  inline bool IsSmiDouble(double 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.
  inline bool IsInt32Double(double 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.
  inline bool IsUint32Double(double value);
  
  // Tries to convert |value| to a uint32, setting the result in |uint32_value|.
  // If the output does not compare equal to the input, returns false and the
  // value in |uint32_value| is left unspecified.
  // Used for conversions such as in ECMA-262 15.4.2.2, which check "ToUint32(len)
  // is equal to len".
  inline bool DoubleToUint32IfEqualToSelf(double value, uint32_t* uint32_value);
  
  // Convert from Number object to C integer.
  inline uint32_t PositiveNumberToUint32(Object number);
  inline int32_t NumberToInt32(Object number);
  inline uint32_t NumberToUint32(Object number);
  inline int64_t NumberToInt64(Object number);
  inline uint64_t PositiveNumberToUint64(Object number);
  
  double StringToDouble(Isolate* isolate, Handle<String> string, int flags,
                        double empty_string_val = 0.0);
  
  inline bool TryNumberToSize(Object number, size_t* result);
  
  // Converts a number into size_t.
  inline size_t NumberToSize(Object number);
  
  // returns DoubleToString(StringToDouble(string)) == string
  V8_EXPORT_PRIVATE bool IsSpecialIndex(String string);
  
  }  // namespace internal
  }  // namespace v8
  
  #endif  // V8_NUMBERS_CONVERSIONS_H_
  