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Improve parseFloat performance and number range #1396

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merged 1 commit into from
Jan 5, 2023
Merged

Improve parseFloat performance and number range #1396

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8 changes: 8 additions & 0 deletions Jint.Tests/Runtime/NumberTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,5 +55,13 @@ public void ToPrecision(int fractionDigits, string result)
var value = _engine.Evaluate($"(3).toPrecision({fractionDigits}).toString()").AsString();
Assert.Equal(result, value);
}

[Theory]
[InlineData("1.7976931348623157e+308", double.MaxValue)]
public void ParseFloat(string input, double result)
{
var value = _engine.Evaluate($"parseFloat('{input}')").AsNumber();
Assert.Equal(result, value);
}
}
}
174 changes: 72 additions & 102 deletions Jint/Native/Global/GlobalObject.cs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Text;
using Esprima;
using Jint.Collections;
using Jint.Native.Object;
using Jint.Native.String;
Expand Down Expand Up @@ -224,154 +225,124 @@ public static JsValue ParseInt(JsValue thisObject, JsValue[] arguments)
}

/// <summary>
/// http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.2.3
/// https://tc39.es/ecma262/#sec-parsefloat-string
/// </summary>
public static JsValue ParseFloat(JsValue thisObject, JsValue[] arguments)
{
var inputString = TypeConverter.ToString(arguments.At(0));
var trimmedString = StringPrototype.TrimStartEx(inputString);

var sign = 1;
if (trimmedString.Length > 0)
{
if (trimmedString[0] == '-')
{
sign = -1;
trimmedString = trimmedString.Substring(1);
}
else if (trimmedString[0] == '+')
{
trimmedString = trimmedString.Substring(1);
}
}

if (trimmedString.StartsWith("Infinity"))
{
return sign * double.PositiveInfinity;
}

if (trimmedString.StartsWith("NaN"))
if (string.IsNullOrWhiteSpace(trimmedString))
{
return JsNumber.DoubleNaN;
}

var separator = (char)0;

bool isNan = true;
decimal number = 0;
// start of string processing
var i = 0;
for (; i < trimmedString.Length; i++)

// check known string constants
if (!char.IsDigit(trimmedString[0]))
{
var c = trimmedString[i];
if (c == '.')
if (trimmedString[0] == '-')
{
i++;
separator = '.';
break;
if (trimmedString.Length > 1 && trimmedString[1] == 'I' && trimmedString.StartsWith("-Infinity"))
{
return JsNumber.DoubleNegativeInfinity;
}
}

if (c == 'e' || c == 'E')
if (trimmedString[0] == '+')
{
i++;
separator = 'e';
break;
if (trimmedString.Length > 1 && trimmedString[1] == 'I' && trimmedString.StartsWith("+Infinity"))
{
return JsNumber.DoublePositiveInfinity;
}
}

var digit = c - '0';

if (digit >= 0 && digit <= 9)
if (trimmedString.StartsWith("Infinity"))
{
isNan = false;
number = number * 10 + digit;
return JsNumber.DoublePositiveInfinity;
}
else

if (trimmedString.StartsWith("NaN"))
{
break;
return JsNumber.DoubleNaN;
}
}

decimal pow = 0.1m;
// find the starting part of string that is still acceptable JS number

if (separator == '.')
var dotFound = false;
var exponentFound = false;
while (i < trimmedString.Length)
{
for (; i < trimmedString.Length; i++)
{
var c = trimmedString[i];
var c = trimmedString[i];

var digit = c - '0';
if (Character.IsDecimalDigit(c))
{
i++;
continue;
}

if (digit >= 0 && digit <= 9)
{
isNan = false;
number += digit * pow;
pow *= 0.1m;
}
else if (c == 'e' || c == 'E')
{
i++;
separator = 'e';
break;
}
else
if (c == '.')
{
if (dotFound)
{
// does not look right
break;
}
}
}

var exp = 0;
var expSign = 1;
i++;
dotFound = true;
continue;
}

if (separator == 'e')
{
if (i < trimmedString.Length)
if (c is 'e' or 'E')
{
if (trimmedString[i] == '-')
{
expSign = -1;
i++;
}
else if (trimmedString[i] == '+')
if (exponentFound)
{
i++;
// does not look right
break;
}

i++;
exponentFound = true;
continue;
}

for (; i < trimmedString.Length; i++)
if (c is '+' or '-' && trimmedString[i - 1] is 'e' or 'E')
{
var c = trimmedString[i];

var digit = c - '0';

if (digit >= 0 && digit <= 9)
{
exp = exp * 10 + digit;
}
else
{
break;
}
// ok
i++;
continue;
}

break;
}

if (isNan)
while (exponentFound && i > 0 && !Character.IsDecimalDigit(trimmedString[i - 1]))
{
return JsNumber.DoubleNaN;
// we are missing required exponent number part info
i--;
}

for (var k = 1; k <= exp; k++)
// we should now have proper input part

#if NETSTANDARD2_1_OR_GREATER
var substring = trimmedString.AsSpan(0, i);
#else
var substring = trimmedString.Substring(0, i);
#endif

const NumberStyles Styles = NumberStyles.AllowDecimalPoint | NumberStyles.AllowExponent | NumberStyles.AllowLeadingSign;
if (double.TryParse(substring, Styles, CultureInfo.InvariantCulture, out var d))
{
if (expSign > 0)
{
number *= 10;
}
else
{
number /= 10;
}
return d;
}

return (double)(sign * number);
return JsNumber.DoubleNaN;
}

/// <summary>
Expand Down Expand Up @@ -550,11 +521,10 @@ private string Encode(string uriString, HashSet<char> unescapedUriSet)
};
}

for (var j = 0; j < octets.Length; j++)
foreach (var octet in octets)
{
var jOctet = octets[j];
var x1 = HexaMap[jOctet / 16];
var x2 = HexaMap[jOctet % 16];
var x1 = HexaMap[octet / 16];
var x2 = HexaMap[octet % 16];
_stringBuilder.Append('%').Append(x1).Append(x2);
}
}
Expand Down