HttpValidationHelpers.cs

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namespace System.Net;
 
internal static class HttpValidationHelpers
{
    private static readonly char[] s_httpTrimCharacters = new char[6] { '\t', '\n', '\v', '\f', '\r', ' ' };
 
    internal static bool ContainsNonAsciiChars(string token)
    {
        for (int i = 0; i < token.Length; i++)
        {
            if (token[i] < ' ' || token[i] > '~')
            {
                return true;
            }
        }
        return false;
    }
 
    internal static bool IsValidToken(string token)
    {
        if (token.Length > 0 && !IsInvalidMethodOrHeaderString(token))
        {
            return !ContainsNonAsciiChars(token);
        }
        return false;
    }
 
    public static string CheckBadHeaderValueChars(string value)
    {
        if (string.IsNullOrEmpty(value))
        {
            return string.Empty;
        }
        value = value.Trim(s_httpTrimCharacters);
        int num = 0;
        for (int i = 0; i < value.Length; i++)
        {
            char c = (char)(0xFFu & value[i]);
            switch (num)
            {
            case 0:
                if (c == '\r')
                {
                    num = 1;
                }
                else if (c == '\n')
                {
                    num = 2;
                }
                else if (c == '\u007f' || (c < ' ' && c != '\t'))
                {
                    throw new ArgumentException(System.SR.net_WebHeaderInvalidControlChars, "value");
                }
                break;
            case 1:
                if (c == '\n')
                {
                    num = 2;
                    break;
                }
                throw new ArgumentException(System.SR.net_WebHeaderInvalidCRLFChars, "value");
            case 2:
                if (c == ' ' || c == '\t')
                {
                    num = 0;
                    break;
                }
                throw new ArgumentException(System.SR.net_WebHeaderInvalidControlChars, "value");
            }
        }
        if (num != 0)
        {
            throw new ArgumentException(System.SR.net_WebHeaderInvalidCRLFChars, "value");
        }
        return value;
    }
 
    public static bool IsInvalidMethodOrHeaderString(string stringValue)
    {
        for (int i = 0; i < stringValue.Length; i++)
        {
            switch (stringValue[i])
            {
            case '\t':
            case '\n':
            case '\r':
            case ' ':
            case '"':
            case '\'':
            case '(':
            case ')':
            case ',':
            case '/':
            case ':':
            case ';':
            case '<':
            case '=':
            case '>':
            case '?':
            case '@':
            case '[':
            case '\\':
            case ']':
            case '{':
            case '}':
                return true;
            }
        }
        return false;
    }
}