IPv4AddressHelper.cs

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using System.Buffers.Binary;
 
namespace System;
 
internal static class IPv4AddressHelper
{
    internal static int ParseHostNumber(ReadOnlySpan<char> str, int start, int end)
    {
        Span<byte> span = stackalloc byte[4];
        for (int i = 0; i < span.Length; i++)
        {
            int num = 0;
            char c;
            while (start < end && (c = str[start]) != '.' && c != ':')
            {
                num = num * 10 + c - 48;
                start++;
            }
            span[i] = (byte)num;
            start++;
        }
        return BinaryPrimitives.ReadInt32BigEndian(span);
    }
 
    internal unsafe static bool IsValid(char* name, int start, ref int end, bool allowIPv6, bool notImplicitFile, bool unknownScheme)
    {
        if (allowIPv6 || unknownScheme)
        {
            return IsValidCanonical(name, start, ref end, allowIPv6, notImplicitFile);
        }
        return ParseNonCanonical(name, start, ref end, notImplicitFile) != -1;
    }
 
    internal unsafe static bool IsValidCanonical(char* name, int start, ref int end, bool allowIPv6, bool notImplicitFile)
    {
        int num = 0;
        int num2 = 0;
        bool flag = false;
        bool flag2 = false;
        while (start < end)
        {
            char c = name[start];
            if (allowIPv6)
            {
                if (c == ']' || c == '/' || c == '%')
                {
                    break;
                }
            }
            else if (c == '/' || c == '\\' || (notImplicitFile && (c == ':' || c == '?' || c == '#')))
            {
                break;
            }
            if (c <= '9' && c >= '0')
            {
                if (!flag && c == '0')
                {
                    if (start + 1 < end && name[start + 1] == '0')
                    {
                        return false;
                    }
                    flag2 = true;
                }
                flag = true;
                num2 = num2 * 10 + (name[start] - 48);
                if (num2 > 255)
                {
                    return false;
                }
            }
            else
            {
                if (c != '.')
                {
                    return false;
                }
                if (!flag || (num2 > 0 && flag2))
                {
                    return false;
                }
                num++;
                flag = false;
                num2 = 0;
                flag2 = false;
            }
            start++;
        }
        bool flag3 = num == 3 && flag;
        if (flag3)
        {
            end = start;
        }
        return flag3;
    }
 
    internal unsafe static long ParseNonCanonical(char* name, int start, ref int end, bool notImplicitFile)
    {
        int num = 10;
        long* ptr = stackalloc long[4];
        long num2 = 0L;
        bool flag = false;
        int num3 = 0;
        int i;
        for (i = start; i < end; i++)
        {
            char c = name[i];
            num2 = 0L;
            num = 10;
            if (c == '0')
            {
                num = 8;
                i++;
                flag = true;
                if (i < end)
                {
                    c = name[i];
                    if (c == 'x' || c == 'X')
                    {
                        num = 16;
                        i++;
                        flag = false;
                    }
                }
            }
            for (; i < end; i++)
            {
                c = name[i];
                int num4;
                if ((num == 10 || num == 16) && '0' <= c && c <= '9')
                {
                    num4 = c - 48;
                }
                else if (num == 8 && '0' <= c && c <= '7')
                {
                    num4 = c - 48;
                }
                else if (num == 16 && 'a' <= c && c <= 'f')
                {
                    num4 = c + 10 - 97;
                }
                else
                {
                    if (num != 16 || 'A' > c || c > 'F')
                    {
                        break;
                    }
                    num4 = c + 10 - 65;
                }
                num2 = num2 * num + num4;
                if (num2 > uint.MaxValue)
                {
                    return -1L;
                }
                flag = true;
            }
            if (i >= end || name[i] != '.')
            {
                break;
            }
            if (num3 >= 3 || !flag || num2 > 255)
            {
                return -1L;
            }
            ptr[num3] = num2;
            num3++;
            flag = false;
        }
        if (!flag)
        {
            return -1L;
        }
        if (i < end)
        {
            char c;
            if ((c = name[i]) != '/' && c != '\\' && (!notImplicitFile || (c != ':' && c != '?' && c != '#')))
            {
                return -1L;
            }
            end = i;
        }
        ptr[num3] = num2;
        switch (num3)
        {
        case 0:
            if (*ptr > uint.MaxValue)
            {
                return -1L;
            }
            return *ptr;
        case 1:
            if (ptr[1] > 16777215)
            {
                return -1L;
            }
            return (*ptr << 24) | (ptr[1] & 0xFFFFFF);
        case 2:
            if (ptr[2] > 65535)
            {
                return -1L;
            }
            return (*ptr << 24) | ((ptr[1] & 0xFF) << 16) | (ptr[2] & 0xFFFF);
        case 3:
            if (ptr[3] > 255)
            {
                return -1L;
            }
            return (*ptr << 24) | ((ptr[1] & 0xFF) << 16) | ((ptr[2] & 0xFF) << 8) | (ptr[3] & 0xFF);
        default:
            return -1L;
        }
    }
}