一尘不染

int.TryParse实际如何工作

c#

我一直在寻找int.TryParse方法的实现,它实际上是如何工作的,但是我没有找到。我必须知道有关a的信息string,它是否是数字值,但是我现在不想转换它。

所以我只需要bool来自的结果int.TryParse。所以问题是:

  1. 是否有任何功能只能提供bool结果,

  1. 我想知道int.TryParse实际的工作方式(是否在try ... catch内部或通过input的字符进行迭代string)?

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2020-05-19

共1个答案

一尘不染

如果仅需要bool结果,则使用返回值并忽略该out参数。

bool successfullyParsed = int.TryParse(str, out ignoreMe);
if (successfullyParsed){
    // ...
}

编辑
:同时,您也可以看一下原始源代码

System.Int32.TryParse


如果我想知道实际上是如何实现的,我正在使用 ILSpy 反编译.NET代码。

结果如下:

// int
/// <summary>Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the operation succeeded.</summary>
/// <returns>true if s was converted successfully; otherwise, false.</returns>
/// <param name="s">A string containing a number to convert. </param>
/// <param name="result">When this method returns, contains the 32-bit signed integer value equivalent to the number contained in s, if the conversion succeeded, or zero if the conversion failed. The conversion fails if the s parameter is null, is not of the correct format, or represents a number less than <see cref="F:System.Int32.MinValue"></see> or greater than <see cref="F:System.Int32.MaxValue"></see>. This parameter is passed uninitialized. </param>
/// <filterpriority>1</filterpriority>
public static bool TryParse(string s, out int result)
{
    return Number.TryParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
}


// System.Number
internal unsafe static bool TryParseInt32(string s, NumberStyles style, NumberFormatInfo info, out int result)
{
    byte* stackBuffer = stackalloc byte[1 * 114 / 1];
    Number.NumberBuffer numberBuffer = new Number.NumberBuffer(stackBuffer);
    result = 0;
    if (!Number.TryStringToNumber(s, style, ref numberBuffer, info, false))
    {
        return false;
    }
    if ((style & NumberStyles.AllowHexSpecifier) != NumberStyles.None)
    {
        if (!Number.HexNumberToInt32(ref numberBuffer, ref result))
        {
            return false;
        }
    }
    else
    {
        if (!Number.NumberToInt32(ref numberBuffer, ref result))
        {
            return false;
        }
    }
    return true;
}

不,我Try-Catchs在路上看不到任何东西:

// System.Number
private unsafe static bool TryStringToNumber(string str, NumberStyles options, ref Number.NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
{
    if (str == null)
    {
        return false;
    }
    fixed (char* ptr = str)
    {
        char* ptr2 = ptr;
        if (!Number.ParseNumber(ref ptr2, options, ref number, numfmt, parseDecimal) || ((ptr2 - ptr / 2) / 2 < str.Length && !Number.TrailingZeros(str, (ptr2 - ptr / 2) / 2)))
        {
            return false;
        }
    }
    return true;
}

// System.Number
private unsafe static bool ParseNumber(ref char* str, NumberStyles options, ref Number.NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
{
    number.scale = 0;
    number.sign = false;
    string text = null;
    string text2 = null;
    string str2 = null;
    string str3 = null;
    bool flag = false;
    string str4;
    string str5;
    if ((options & NumberStyles.AllowCurrencySymbol) != NumberStyles.None)
    {
        text = numfmt.CurrencySymbol;
        if (numfmt.ansiCurrencySymbol != null)
        {
            text2 = numfmt.ansiCurrencySymbol;
        }
        str2 = numfmt.NumberDecimalSeparator;
        str3 = numfmt.NumberGroupSeparator;
        str4 = numfmt.CurrencyDecimalSeparator;
        str5 = numfmt.CurrencyGroupSeparator;
        flag = true;
    }
    else
    {
        str4 = numfmt.NumberDecimalSeparator;
        str5 = numfmt.NumberGroupSeparator;
    }
    int num = 0;
    char* ptr = str;
    char c = *ptr;
    while (true)
    {
        if (!Number.IsWhite(c) || (options & NumberStyles.AllowLeadingWhite) == NumberStyles.None || ((num & 1) != 0 && ((num & 1) == 0 || ((num & 32) == 0 && numfmt.numberNegativePattern != 2))))
        {
            bool flag2;
            char* ptr2;
            if ((flag2 = ((options & NumberStyles.AllowLeadingSign) != NumberStyles.None && (num & 1) == 0)) && (ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
            {
                num |= 1;
                ptr = ptr2 - (IntPtr)2 / 2;
            }
            else
            {
                if (flag2 && (ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
                {
                    num |= 1;
                    number.sign = true;
                    ptr = ptr2 - (IntPtr)2 / 2;
                }
                else
                {
                    if (c == '(' && (options & NumberStyles.AllowParentheses) != NumberStyles.None && (num & 1) == 0)
                    {
                        num |= 3;
                        number.sign = true;
                    }
                    else
                    {
                        if ((text == null || (ptr2 = Number.MatchChars(ptr, text)) == null) && (text2 == null || (ptr2 = Number.MatchChars(ptr, text2)) == null))
                        {
                            break;
                        }
                        num |= 32;
                        text = null;
                        text2 = null;
                        ptr = ptr2 - (IntPtr)2 / 2;
                    }
                }
            }
        }
        c = *(ptr += (IntPtr)2 / 2);
    }
    int num2 = 0;
    int num3 = 0;
    while (true)
    {
        if ((c >= '0' && c <= '9') || ((options & NumberStyles.AllowHexSpecifier) != NumberStyles.None && ((c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))))
        {
            num |= 4;
            if (c != '0' || (num & 8) != 0)
            {
                if (num2 < 50)
                {
                    number.digits[(IntPtr)(num2++)] = c;
                    if (c != '0' || parseDecimal)
                    {
                        num3 = num2;
                    }
                }
                if ((num & 16) == 0)
                {
                    number.scale++;
                }
                num |= 8;
            }
            else
            {
                if ((num & 16) != 0)
                {
                    number.scale--;
                }
            }
        }
        else
        {
            char* ptr2;
            if ((options & NumberStyles.AllowDecimalPoint) != NumberStyles.None && (num & 16) == 0 && ((ptr2 = Number.MatchChars(ptr, str4)) != null || (flag && (num & 32) == 0 && (ptr2 = Number.MatchChars(ptr, str2)) != null)))
            {
                num |= 16;
                ptr = ptr2 - (IntPtr)2 / 2;
            }
            else
            {
                if ((options & NumberStyles.AllowThousands) == NumberStyles.None || (num & 4) == 0 || (num & 16) != 0 || ((ptr2 = Number.MatchChars(ptr, str5)) == null && (!flag || (num & 32) != 0 || (ptr2 = Number.MatchChars(ptr, str3)) == null)))
                {
                    break;
                }
                ptr = ptr2 - (IntPtr)2 / 2;
            }
        }
        c = *(ptr += (IntPtr)2 / 2);
    }
    bool flag3 = false;
    number.precision = num3;
    number.digits[(IntPtr)num3] = '\0';
    if ((num & 4) != 0)
    {
        if ((c == 'E' || c == 'e') && (options & NumberStyles.AllowExponent) != NumberStyles.None)
        {
            char* ptr3 = ptr;
            c = *(ptr += (IntPtr)2 / 2);
            char* ptr2;
            if ((ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
            {
                c = *(ptr = ptr2);
            }
            else
            {
                if ((ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
                {
                    c = *(ptr = ptr2);
                    flag3 = true;
                }
            }
            if (c >= '0' && c <= '9')
            {
                int num4 = 0;
                do
                {
                    num4 = num4 * 10 + (int)(c - '0');
                    c = *(ptr += (IntPtr)2 / 2);
                    if (num4 > 1000)
                    {
                        num4 = 9999;
                        while (c >= '0' && c <= '9')
                        {
                            c = *(ptr += (IntPtr)2 / 2);
                        }
                    }
                }
                while (c >= '0' && c <= '9');
                if (flag3)
                {
                    num4 = -num4;
                }
                number.scale += num4;
            }
            else
            {
                ptr = ptr3;
                c = *ptr;
            }
        }
        while (true)
        {
            if (!Number.IsWhite(c) || (options & NumberStyles.AllowTrailingWhite) == NumberStyles.None)
            {
                bool flag2;
                char* ptr2;
                if ((flag2 = ((options & NumberStyles.AllowTrailingSign) != NumberStyles.None && (num & 1) == 0)) && (ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
                {
                    num |= 1;
                    ptr = ptr2 - (IntPtr)2 / 2;
                }
                else
                {
                    if (flag2 && (ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
                    {
                        num |= 1;
                        number.sign = true;
                        ptr = ptr2 - (IntPtr)2 / 2;
                    }
                    else
                    {
                        if (c == ')' && (num & 2) != 0)
                        {
                            num &= -3;
                        }
                        else
                        {
                            if ((text == null || (ptr2 = Number.MatchChars(ptr, text)) == null) && (text2 == null || (ptr2 = Number.MatchChars(ptr, text2)) == null))
                            {
                                break;
                            }
                            text = null;
                            text2 = null;
                            ptr = ptr2 - (IntPtr)2 / 2;
                        }
                    }
                }
            }
            c = *(ptr += (IntPtr)2 / 2);
        }
        if ((num & 2) == 0)
        {
            if ((num & 8) == 0)
            {
                if (!parseDecimal)
                {
                    number.scale = 0;
                }
                if ((num & 16) == 0)
                {
                    number.sign = false;
                }
            }
            str = ptr;
            return true;
        }
    }
    str = ptr;
    return false;
}
2020-05-19