QuotedPairReader.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Net / System / Net / Mail / QuotedPairReader.cs / 1305376 / QuotedPairReader.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Net.Mail 
{ 
    using System;
    using System.Text; 
    using System.Diagnostics;
    using System.Net.Mime;

    // RFC 2822 Section 3.2.2 - Quoted Characters 
    // As in C# strings, characters that would otherwise have special meaning should be ignored when quoted/escaped
    // by a backslash "\". Quoted characters (quoted-pair) are only allowed in the following contexts: Comments, 
    // quoted-string, domain-literal, and message-id. 
    //
    // Example: A quoted-string ("hello there") cannot contain a double quote, as it must be surrounded by them. 
    //  However, the double quote can be included as a quoted-pair: ("hello\"there") means (hello"there).
    //
    // Because backslashes themselves can be quoted-pairs (\\), this class's primary function is to verify what
    // character is being quoted. In "hi\\\\a", 'a' is not quoted because all of the backslashes are paired together. 
    // In "hi\\\a", 'a' is quoted.
    internal static class QuotedPairReader 
    { 
        //
        // Counts the number of consecutive quoted chars, including multiple preceding quoted backslashes 
        //
        // Preconditions: Index should be within the bounds of the data string.
        //
        // Return value: 
        // - 0 if the char at data[index] was not quoted
        //   e.g. (\\a) given index=2 returns 0 because 'a' is not quoted 
        // - The number of consecutive quoted chars, including multiple preceding quoted backslashes 
        //   e.g. (a\\\b) given index=4 returns 4, as 'b' is quoted, and so are the previous backslashes
        // 
        // Throws a FormatException if the an escaped Unicode character is found but was not permitted.
        internal static int CountQuotedChars(string data, int index, bool permitUnicodeEscaping)
        {
            Debug.Assert(0 <= index && index < data.Length, "Index out of range: " + index + ", " + data.Length); 

            if (index <= 0 || data[index - 1] != MailBnfHelper.Backslash) 
            { 
                return 0;
            } 

            // Count the preceding backslashes
            int backslashCount = CountBackslashes(data, index - 1);
 
            // For an even number of backslashes, the original character was NOT escaped/quoted
            if (backslashCount % 2 == 0) 
            { 
                return 0; // No quoted pair to skip
            } 
            else
            {
                if (!permitUnicodeEscaping && data[index] > MailBnfHelper.Ascii7bitMaxValue)
                { 
                    // Cannot accept quoted unicode
                    throw new FormatException(SR.GetString(SR.MailHeaderFieldInvalidCharacter, data[index])); 
                } 
                // Skip the quoted char, and the odd number of backslashes preceding it
                return backslashCount + 1; 
            }
        }

        // 
        // Counts the number of consecutive backslashes
        // 
        // Preconditions: 
        // - Index should be within the bounds of the data string.
        // - The initial data[index] must be a backslash. 
        //
        // Return value: The number of consecutive backslashes, including the initial one at data[index].
        private static int CountBackslashes(string data, int index)
        { 
            Debug.Assert(index >= 0 && data[index] == MailBnfHelper.Backslash, "index was not a backslash: " + index);
 
            // Find all the backslashes. It's possible that there are multiple escaped/quoted backslashes. 
            int backslashCount = 0;
            do 
            {
                backslashCount++;
                index--;
            } while (index >= 0 && data[index] == MailBnfHelper.Backslash); 

            // At this point data[index] should not be a backslash 
            Debug.Assert(index < 0 || data[index] != MailBnfHelper.Backslash, "index was a backslash: " + index); 

            return backslashCount; 
        }
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

Link Menu

Network programming in C#, Network Programming in VB.NET, Network Programming in .NET
This book is available now!
Buy at Amazon US or
Buy at Amazon UK