Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Net / System / Net / Mail / WhitespaceReader.cs / 1305376 / WhitespaceReader.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.Net.Mail { using System; using System.Text; using System.Net.Mime; using System.Globalization; using System.Collections; using System.Diagnostics; // FWS, CFWS, and Comments are defined in RFC 2822 section 3.2.3. // // FWS is a Folding White Space, or a series of spaces and tabs that may also contain a CRLF. // // CFWS is a FWS that also allows for nested comments enclosed in parenthesis. (comment (nested)) // // Valid values for these are declared in MailBnfHelper.cs and are explained in MailBNF.cs. // internal static class WhitespaceReader { // // This skips all folding and whitespace characters // // 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 index of the next character that is NOT a whitespace character. // - -1 if the beginning of the data string is reached. // // A FormatException will be thrown if a CR or LF is found NOT in the sequence CRLF. internal static int ReadFwsReverse(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"); bool expectCR = false; for ( ; index >= 0; index--) { // Check for a valid CRLF pair if (data[index] == MailBnfHelper.CR && expectCR) { expectCR = false; // valid pair } // LF without CR, or CR without LF, invalid else if (data[index] == MailBnfHelper.CR || expectCR) { throw new FormatException(SR.GetString(SR.MailAddressInvalidFormat)); } // LF is only valid if preceded by a CR. // Skip both if they're found together. else if (data[index] == MailBnfHelper.LF) { expectCR = true; } // Skip whitespace else if (data[index] == MailBnfHelper.Space || data[index] == MailBnfHelper.Tab) { // No-op } else { // Neither check hit so we must be on something that is not whitespace break; } } if (expectCR) { // We found a LF without an immediately preceding CR, invalid. throw new FormatException(SR.GetString(SR.MailAddressInvalidFormat)); } 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(SR.GetString(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(SR.GetString(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(SR.GetString(SR.MailHeaderFieldInvalidCharacter, MailBnfHelper.EndComment)); } return index; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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