IPv6AddressHelper.cs

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namespace System;
 
internal static class IPv6AddressHelper
{
    internal static string ParseCanonicalName(string str, int start, ref bool isLoopback, ref string scopeId)
    {
        Span<ushort> span = stackalloc ushort[8];
        span.Clear();
        Parse(str, span, start, ref scopeId);
        isLoopback = IsLoopback(span);
        (int longestSequenceStart, int longestSequenceLength) tuple = FindCompressionRange(span);
        int item = tuple.longestSequenceStart;
        int item2 = tuple.longestSequenceLength;
        bool flag = ShouldHaveIpv4Embedded(span);
        Span<char> span2 = stackalloc char[48];
        span2[0] = '[';
        int num = 1;
        for (int i = 0; i < 8; i++)
        {
            int charsWritten;
            if (flag && i == 6)
            {
                span2[num++] = ':';
                bool flag2 = (span[i] >> 8).TryFormat(span2.Slice(num), out charsWritten);
                num += charsWritten;
                span2[num++] = '.';
                flag2 = (span[i] & 0xFF).TryFormat(span2.Slice(num), out charsWritten);
                num += charsWritten;
                span2[num++] = '.';
                flag2 = (span[i + 1] >> 8).TryFormat(span2.Slice(num), out charsWritten);
                num += charsWritten;
                span2[num++] = '.';
                flag2 = (span[i + 1] & 0xFF).TryFormat(span2.Slice(num), out charsWritten);
                num += charsWritten;
                break;
            }
            if (item == i)
            {
                span2[num++] = ':';
            }
            if (item <= i && item2 == 8)
            {
                span2[num++] = ':';
                break;
            }
            if (item > i || i >= item2)
            {
                if (i != 0)
                {
                    span2[num++] = ':';
                }
                bool flag2 = span[i].TryFormat(span2.Slice(num), out charsWritten, "x");
                num += charsWritten;
            }
        }
        span2[num++] = ']';
        return new string(span2.Slice(0, num));
    }
 
    private static bool IsLoopback(ReadOnlySpan<ushort> numbers)
    {
        if (numbers[0] == 0 && numbers[1] == 0 && numbers[2] == 0 && numbers[3] == 0 && numbers[4] == 0)
        {
            if (numbers[5] != 0 || numbers[6] != 0 || numbers[7] != 1)
            {
                if (numbers[6] == 32512 && numbers[7] == 1)
                {
                    if (numbers[5] != 0)
                    {
                        return numbers[5] == ushort.MaxValue;
                    }
                    return true;
                }
                return false;
            }
            return true;
        }
        return false;
    }
 
    private unsafe static bool InternalIsValid(char* name, int start, ref int end, bool validateStrictAddress)
    {
        int num = 0;
        int num2 = 0;
        bool flag = false;
        bool flag2 = false;
        bool flag3 = false;
        bool flag4 = true;
        int start2 = 1;
        if (name[start] == ':' && (start + 1 >= end || name[start + 1] != ':'))
        {
            return false;
        }
        int i;
        for (i = start; i < end; i++)
        {
            bool num3;
            if (!flag3)
            {
                num3 = Uri.IsHexDigit(name[i]);
            }
            else
            {
                if (name[i] < '0')
                {
                    goto IL_0079;
                }
                num3 = name[i] <= '9';
            }
            if (num3)
            {
                num2++;
                flag4 = false;
                continue;
            }
            goto IL_0079;
            IL_0079:
            if (num2 > 4)
            {
                return false;
            }
            if (num2 != 0)
            {
                num++;
                start2 = i - num2;
            }
            char c = name[i];
            if ((uint)c <= 46u)
            {
                if (c == '%')
                {
                    while (true)
                    {
                        if (++i == end)
                        {
                            return false;
                        }
                        if (name[i] == ']')
                        {
                            break;
                        }
                        if (name[i] != '/')
                        {
                            continue;
                        }
                        goto IL_011c;
                    }
                    goto IL_00ee;
                }
                if (c != '.')
                {
                    goto IL_015c;
                }
                if (flag2)
                {
                    return false;
                }
                i = end;
                if (!IPv4AddressHelper.IsValid(name, start2, ref i, allowIPv6: true, notImplicitFile: false, unknownScheme: false))
                {
                    return false;
                }
                num++;
                flag2 = true;
                i--;
            }
            else
            {
                if (c == '/')
                {
                    goto IL_011c;
                }
                if (c != ':')
                {
                    if (c == ']')
                    {
                        goto IL_00ee;
                    }
                    goto IL_015c;
                }
                if (i > 0 && name[i - 1] == ':')
                {
                    if (flag)
                    {
                        return false;
                    }
                    flag = true;
                    flag4 = false;
                }
                else
                {
                    flag4 = true;
                }
            }
            goto IL_015e;
            IL_015c:
            return false;
            IL_011c:
            if (validateStrictAddress)
            {
                return false;
            }
            if (num == 0 || flag3)
            {
                return false;
            }
            flag3 = true;
            flag4 = true;
            goto IL_015e;
            IL_015e:
            num2 = 0;
            continue;
            IL_00ee:
            start = i;
            i = end;
        }
        if (flag3 && (num2 < 1 || num2 > 2))
        {
            return false;
        }
        int num4 = 8 + (flag3 ? 1 : 0);
        if (!flag4 && num2 <= 4 && (flag ? (num < num4) : (num == num4)))
        {
            if (i == end + 1)
            {
                end = start + 1;
                return true;
            }
            return false;
        }
        return false;
    }
 
    internal unsafe static bool IsValid(char* name, int start, ref int end)
    {
        return InternalIsValid(name, start, ref end, validateStrictAddress: false);
    }
 
    internal static (int longestSequenceStart, int longestSequenceLength) FindCompressionRange(ReadOnlySpan<ushort> numbers)
    {
        int num = 0;
        int num2 = -1;
        int num3 = 0;
        for (int i = 0; i < numbers.Length; i++)
        {
            if (numbers[i] == 0)
            {
                num3++;
                if (num3 > num)
                {
                    num = num3;
                    num2 = i - num3 + 1;
                }
            }
            else
            {
                num3 = 0;
            }
        }
        if (num <= 1)
        {
            return (longestSequenceStart: -1, longestSequenceLength: -1);
        }
        return (longestSequenceStart: num2, longestSequenceLength: num2 + num);
    }
 
    internal static bool ShouldHaveIpv4Embedded(ReadOnlySpan<ushort> numbers)
    {
        if (numbers[0] == 0 && numbers[1] == 0 && numbers[2] == 0 && numbers[3] == 0 && numbers[6] != 0)
        {
            if (numbers[4] == 0 && (numbers[5] == 0 || numbers[5] == ushort.MaxValue))
            {
                return true;
            }
            if (numbers[4] == ushort.MaxValue && numbers[5] == 0)
            {
                return true;
            }
        }
        if (numbers[4] == 0)
        {
            return numbers[5] == 24318;
        }
        return false;
    }
 
    internal static void Parse(ReadOnlySpan<char> address, Span<ushort> numbers, int start, ref string scopeId)
    {
        int num = 0;
        int num2 = 0;
        int num3 = -1;
        bool flag = true;
        int num4 = 0;
        if (address[start] == '[')
        {
            start++;
        }
        int i = start;
        while (i < address.Length && address[i] != ']')
        {
            switch (address[i])
            {
            case '%':
                if (flag)
                {
                    numbers[num2++] = (ushort)num;
                    flag = false;
                }
                start = i;
                for (i++; i < address.Length && address[i] != ']' && address[i] != '/'; i++)
                {
                }
                scopeId = new string(address.Slice(start, i - start));
                for (; i < address.Length && address[i] != ']'; i++)
                {
                }
                break;
            case ':':
            {
                numbers[num2++] = (ushort)num;
                num = 0;
                i++;
                if (address[i] == ':')
                {
                    num3 = num2;
                    i++;
                }
                else if (num3 < 0 && num2 < 6)
                {
                    break;
                }
                for (int j = i; j < address.Length && address[j] != ']' && address[j] != ':' && address[j] != '%' && address[j] != '/' && j < i + 4; j++)
                {
                    if (address[j] == '.')
                    {
                        for (; j < address.Length && address[j] != ']' && address[j] != '/' && address[j] != '%'; j++)
                        {
                        }
                        num = IPv4AddressHelper.ParseHostNumber(address, i, j);
                        numbers[num2++] = (ushort)(num >> 16);
                        numbers[num2++] = (ushort)num;
                        i = j;
                        num = 0;
                        flag = false;
                        break;
                    }
                }
                break;
            }
            case '/':
                if (flag)
                {
                    numbers[num2++] = (ushort)num;
                    flag = false;
                }
                for (i++; address[i] != ']'; i++)
                {
                    num4 = num4 * 10 + (address[i] - 48);
                }
                break;
            default:
                num = num * 16 + Uri.FromHex(address[i++]);
                break;
            }
        }
        if (flag)
        {
            numbers[num2++] = (ushort)num;
        }
        if (num3 <= 0)
        {
            return;
        }
        int num5 = 7;
        int num6 = num2 - 1;
        if (num6 != num5)
        {
            for (int num7 = num2 - num3; num7 > 0; num7--)
            {
                numbers[num5--] = numbers[num6];
                numbers[num6--] = 0;
            }
        }
    }
}