// toPrecision converts a number to a string, takeing an argument specifying a
// number of significant figures to round the significand to. For positive
// exponent, all values that can be represented using a decimal fraction will
// be, e.g. when rounding to 3 s.f. any value up to 999 will be formated as a
// decimal, whilst 1000 is converted to the exponential representation 1.00e+3.
// For negative exponents values >= 1e-6 are formated as decimal fractions,
// with smaller values converted to exponential representation.
EncodedTiValue JSC_HOST_CALL numberProtoFuncToPrecision(TiExcState* exec)
{
// Get x (the double value of this, which should be a Number).
TiValue thisValue = exec->hostThisValue();
TiValue v = thisValue.getJSNumber();
if (!v)
return throwVMTypeError(exec);
double x = v.uncheckedGetNumber();
// Get the argument.
int significantFigures;
bool isUndefined;
if (!getIntegerArgumentInRange(exec, 1, 21, significantFigures, isUndefined))
return throwVMError(exec, createRangeError(exec, "toPrecision() argument must be between 1 and 21"));
// To precision called with no argument is treated as ToString.
if (isUndefined)
return TiValue::encode(jsString(exec, UString::number(x)));
// Handle NaN and Infinity.
if (isnan(x) || isinf(x))
return TiValue::encode(jsString(exec, UString::number(x)));
// Convert to decimal with rounding.
DecimalNumber number(x, RoundingSignificantFigures, significantFigures);
// If number is in the range 1e-6 <= x < pow(10, significantFigures) then format
// as decimal. Otherwise, format the number as an exponential. Decimal format
// demands a minimum of (exponent + 1) digits to represent a number, for example
// 1234 (1.234e+3) requires 4 digits. (See ECMA-262 15.7.4.7.10.c)
NumberToStringBuffer buffer;
unsigned length = number.exponent() >= -6 && number.exponent() < significantFigures
? number.toStringDecimal(buffer, WTI::NumberToStringBufferLength)
: number.toStringExponential(buffer, WTI::NumberToStringBufferLength);
return TiValue::encode(jsString(exec, UString(buffer, length)));
}
// toFixed converts a number to a string, always formatting as an a decimal fraction.
// This method takes an argument specifying a number of decimal places to round the
// significand to. However when converting large values (1e+21 and above) this
// method will instead fallback to calling ToString.
EncodedTiValue JSC_HOST_CALL numberProtoFuncToFixed(TiExcState* exec)
{
// Get x (the double value of this, which should be a Number).
TiValue thisValue = exec->hostThisValue();
TiValue v = thisValue.getJSNumber();
if (!v)
return throwVMTypeError(exec);
double x = v.uncheckedGetNumber();
// Get the argument.
int decimalPlaces;
bool isUndefined; // This is ignored; undefined treated as 0.
if (!getIntegerArgumentInRange(exec, 0, 20, decimalPlaces, isUndefined))
return throwVMError(exec, createRangeError(exec, "toFixed() argument must be between 0 and 20"));
// 15.7.4.5.7 states "If x >= 10^21, then let m = ToString(x)"
// This also covers Ininity, and structure the check so that NaN
// values are also handled by numberToString
if (!(fabs(x) < 1e+21))
return TiValue::encode(jsString(exec, UString::number(x)));
// The check above will return false for NaN or Infinity, these will be
// handled by numberToString.
ASSERT(!isnan(x) && !isinf(x));
// Convert to decimal with rounding, and format as decimal.
NumberToStringBuffer buffer;
unsigned length = DecimalNumber(x, RoundingDecimalPlaces, decimalPlaces).toStringDecimal(buffer, WTI::NumberToStringBufferLength);
return TiValue::encode(jsString(exec, UString(buffer, length)));
}
static ALWAYS_INLINE bool toThisNumber(TiValue thisValue, double &x)
{
TiValue v = thisValue.getJSNumber();
if (UNLIKELY(!v))
return false;
x = v.uncheckedGetNumber();
return true;
}
EncodedTiValue JSC_HOST_CALL numberProtoFuncToString(TiExcState* exec)
{
TiValue thisValue = exec->hostThisValue();
TiValue v = thisValue.getJSNumber();
if (!v)
return throwVMTypeError(exec);
TiValue radixValue = exec->argument(0);
int radix;
if (radixValue.isInt32())
radix = radixValue.asInt32();
else if (radixValue.isUndefined())
radix = 10;
else
radix = static_cast<int>(radixValue.toInteger(exec)); // nan -> 0
if (radix == 10)
return TiValue::encode(jsString(exec, v.toString(exec)));
static const char* const digits = "0123456789abcdefghijklmnopqrstuvwxyz";
// Fast path for number to character conversion.
if (radix == 36) {
if (v.isInt32()) {
int x = v.asInt32();
if (static_cast<unsigned>(x) < 36) { // Exclude negatives
TiGlobalData* globalData = &exec->globalData();
return TiValue::encode(globalData->smallStrings.singleCharacterString(globalData, digits[x]));
}
}
}
if (radix < 2 || radix > 36)
return throwVMError(exec, createRangeError(exec, "toString() radix argument must be between 2 and 36"));
// INT_MAX results in 1024 characters left of the dot with radix 2
// give the same space on the right side. safety checks are in place
// unless someone finds a precise rule.
char s[2048 + 3];
const char* lastCharInString = s + sizeof(s) - 1;
double x = v.uncheckedGetNumber();
if (isnan(x) || isinf(x))
return TiValue::encode(jsString(exec, UString::number(x)));
bool isNegative = x < 0.0;
if (isNegative)
x = -x;
double integerPart = floor(x);
char* decimalPoint = s + sizeof(s) / 2;
// convert integer portion
char* p = decimalPoint;
double d = integerPart;
do {
int remainderDigit = static_cast<int>(fmod(d, radix));
*--p = digits[remainderDigit];
d /= radix;
} while ((d <= -1.0 || d >= 1.0) && s < p);
if (isNegative)
*--p = '-';
char* startOfResultString = p;
ASSERT(s <= startOfResultString);
d = x - integerPart;
p = decimalPoint;
const double epsilon = 0.001; // TODO: guessed. base on radix ?
bool hasFractionalPart = (d < -epsilon || d > epsilon);
if (hasFractionalPart) {
*p++ = '.';
do {
d *= radix;
const int digit = static_cast<int>(d);
*p++ = digits[digit];
d -= digit;
} while ((d < -epsilon || d > epsilon) && p < lastCharInString);
}
*p = '\0';
ASSERT(p < s + sizeof(s));
return TiValue::encode(jsString(exec, startOfResultString));
}