//
// Reads a domain literal in reverse
//
// Preconditions:
// - Index must be within the bounds of the data string.
// - The char at the given index is the initial bracket. (data[index] == EndSquareBracket)
//
// Return value:
// - The next index past the terminating bracket (data[index + 1] == StartSquareBracket).
// e.g. In (user@[domain]), starting at index=12 (]) returns index=4 (@).
//
// A FormatException will be thrown if:
// - A non-escaped character is encountered that is not valid in a domain literal, including Unicode.
// - The final bracket is not found.
//
internal static int ReadReverse(string data, int index)
{
Debug.Assert(0 <= index && index < data.Length, "index was outside the bounds of the string: " + index);
Debug.Assert(data[index] == MailBnfHelper.EndSquareBracket, "data did not end with a square bracket");
// Skip the end bracket
index--;
do
{
// Check for valid whitespace
index = WhitespaceReader.ReadFwsReverse(data, index);
if (index < 0)
{
break;
}
// Check for escaped characters
int quotedCharCount = QuotedPairReader.CountQuotedChars(data, index, false);
if (quotedCharCount > 0)
{
// Skip quoted pairs
index = index - quotedCharCount;
}
// Check for the terminating bracket
else if (data[index] == MailBnfHelper.StartSquareBracket)
{
// We're done parsing
return(index - 1);
}
// Check for invalid characters
else if (data[index] > MailBnfHelper.Ascii7bitMaxValue || !MailBnfHelper.Dtext[data[index]])
{
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter, data[index]));
}
// Valid char
else
{
index--;
}
}while (index >= 0);
// We didn't find a matching '[', throw.
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter,
MailBnfHelper.EndSquareBracket));
}
//
// This method attempts reading quoted-string formatted data when the bounding quotes were omitted.
// This is common for e-mail display-names.
//
// Precondition: The index must be within the bounds of the data string.
//
// Return value:
// - The index of the special delimiter provided.
// e.g. In ([email protected], billy box [email protected]), starting at index=19 (x) returns index=9 (,).
// - -1 if the terminating character was not found.
// e.g. In (my name username@domain), starting at index=5 (e) returns index=-1.
//
// A FormatException will be thrown if:
// - A non-escaped character is encountered that is not valid in a quoted string. This includes double quotes.
// - A Unicode character is encountered and Unicode has not been allowed.
//
internal static int ReadReverseUnQuoted(string data, int index, bool permitUnicode, bool expectCommaDelimiter)
{
Debug.Assert(0 <= index && index < data.Length, "Index out of range: " + index + ", " + data.Length);
do
{
// Check for valid whitespace
index = WhitespaceReader.ReadFwsReverse(data, index);
if (index < 0)
{
break;
}
// Check for escaped characters
int quotedCharCount = QuotedPairReader.CountQuotedChars(data, index, permitUnicode);
if (quotedCharCount > 0)
{
index = index - quotedCharCount;
}
// Check for the terminating char
else if (expectCommaDelimiter && data[index] == MailBnfHelper.Comma)
{
break;
}
// Check invalid characters
else if (!IsValidQtext(permitUnicode, data[index]))
{
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter, data[index]));
}
// Valid char
else
{
index--;
}
}while (index >= 0);
return(index);
}
// This method functions similarly to ReadFwsReverse but will also skip any comments.
//
// Comments are text within '(' and ')' and may be nested. There may also be consecutive comments. Unicode is
// allowed, as the comments are not transmitted.
//
// This method was explicitly written in a non-recursive fashion to avoid malicious or accidental
// stack-overflows from user input.
//
// Preconditions:
// - The data string must not be null or empty
// - The index must be within the upper bounds of the data string.
//
// Return value:
// - The given index if it data[index] was not a ')' or white space
// - The index of the next non comment or white space character
// e.g. " d ( ( c o mment) )" returns index 1
// - -1 if skipping the comments and/or whitespace moves you to the beginning of the data string.
// e.g. " (comment) " returns -1
//
// Throws a FormatException for mismatched '(' and ')', or for unescaped characters not allowed in comments.
internal static int ReadCfwsReverse(string data, int index)
{
Debug.Assert(!String.IsNullOrEmpty(data), "data was null or empty");
Debug.Assert(index < data.Length, "index was outside the bounds of the string");
int commentDepth = 0;
// Check for valid whitespace
index = ReadFwsReverse(data, index);
while (index >= 0)
{
// Check for escaped characters. They must be within comments.
int quotedCharCount = QuotedPairReader.CountQuotedChars(data, index, true);
if (commentDepth > 0 && quotedCharCount > 0)
{
index = index - quotedCharCount;
}
// Start a new comment
else if (data[index] == MailBnfHelper.EndComment)
{
commentDepth++;
index--;
}
// Finish a comment
else if (data[index] == MailBnfHelper.StartComment)
{
commentDepth--;
if (commentDepth < 0)
{
// Mismatched '('
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter,
MailBnfHelper.StartComment));
}
index--;
}
// Check for valid characters within comments. Allow Unicode, as we won't transmit any comments.
else if (commentDepth > 0 &&
(data[index] > MailBnfHelper.Ascii7bitMaxValue || MailBnfHelper.Ctext[data[index]]))
{
index--;
}
// If we're still in a comment, this must be an invalid char
else if (commentDepth > 0)
{
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter, data[index]));
}
// We must no longer be in a comment, and this is not a whitespace char, return
else
{
break;
}
// Check for valid whitespace
index = ReadFwsReverse(data, index);
}
if (commentDepth > 0)
{
// Mismatched ')', throw
throw new FormatException(string.Format(SR.MailHeaderFieldInvalidCharacter, MailBnfHelper.EndComment));
}
return(index);
}