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//------------------------------------------------------------------------------
// <copyright file="LinkGrep.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
namespace System.Web.Services.Discovery {
using System;
using System.IO;
using System.Text.RegularExpressions;
using System.Web.Services.Protocols;
using System.Globalization;
internal class LinkGrep {
private LinkGrep() { }
private static string ReadEntireStream(TextReader input) {
char[] buffer = new char[4096];
int bufferpos = 0;
int delta;
//
for (;;) {
delta = input.Read(buffer, bufferpos, buffer.Length - bufferpos);
if (delta == 0)
break;
bufferpos += delta;
if (bufferpos == buffer.Length) {
char[] newbuf = new char[buffer.Length * 2];
System.Array.Copy(buffer, 0, newbuf, 0, buffer.Length);
buffer = newbuf;
}
}
return new string(buffer, 0, bufferpos);
}
internal static string SearchForLink(Stream stream) {
string text = null;
text = ReadEntireStream(new StreamReader(stream));
int textpos = 0;
Match match;
if ((match = doctypeDirectiveRegex.Match(text, textpos)).Success) {
textpos += match.Length;
}
bool oneMatch;
for (;;) {
// Reset match flag
oneMatch = false;
// 1: scan for text up to the next tag.
// First case: check for whitespace going all the way to the next tag
if ((match = whitespaceRegex.Match(text, textpos)).Success) {
oneMatch = true;
}
// Second case: there may be some nonwhitespace; scan it
else if ((match = textRegex.Match(text, textpos)).Success) {
oneMatch = true;
}
// we might be done now
textpos += match.Length;
if (textpos == text.Length)
break;
// 2: handle constructs that start with <
// First, check to see if it's a tag
if ((match = tagRegex.Match(text, textpos)).Success)
{
oneMatch = true;
string tag = match.Groups["tagname"].Value;
if (String.Compare(tag, "link", StringComparison.OrdinalIgnoreCase) == 0) {
CaptureCollection attrnames = match.Groups["attrname"].Captures;
CaptureCollection attrvalues = match.Groups["attrval"].Captures;
int count = attrnames.Count;
bool rightType = false;
bool rightRel = false;
string href = null;
for (int i = 0; i < count; i++) {
string attrName = attrnames[i].ToString();
string attrValue = attrvalues[i].ToString();
if (String.Compare(attrName, "type", StringComparison.OrdinalIgnoreCase) == 0 &&
ContentType.MatchesBase(attrValue, ContentType.TextXml)) {
rightType = true;
}
else if (String.Compare(attrName, "rel", StringComparison.OrdinalIgnoreCase) == 0 &&
String.Compare(attrValue, "alternate", StringComparison.OrdinalIgnoreCase) == 0) {
rightRel = true;
}
else if (String.Compare(attrName, "href", StringComparison.OrdinalIgnoreCase) == 0) {
href = attrValue;
}
if (rightType && rightRel && href != null) {
// Got a link to a disco file!
return href;
}
}
}
else if (tag == "body") {
// If body begins, get out, since link tags should only be defined in the head
break;
}
}
// check to see if it's an end tag
else if ((match = endtagRegex.Match(text, textpos)).Success) {
oneMatch = true;
}
// check to see if it's a comment
else if ((match = commentRegex.Match(text, textpos)).Success) {
oneMatch = true;
}
// we might be done now
textpos += match.Length;
if (textpos == text.Length)
break;
// If we couldn't get one single match, it means that it's probably not HTML, so bail
if (!oneMatch) {
break;
}
}
return null;
}
private readonly static Regex tagRegex = new Regex
(
"\\G<" + // leading <
"(?<prefix>[\\w:.-]+(?=:)|):?" + // optional prefix:
"(?<tagname>[\\w.-]+)" + // tagname
"(?:\\s+" + // zero or more attributes
"(?<attrprefix>[\\w:.-]+(?=:)|):?" + // optional attrprefix:
"(?<attrname>[\\w.-]+)" + // attrname
"\\s*=\\s*" + // required equals
"(?:" + // quoted value
"\"(?<attrval>[^\"]*)\"" + // double quoted attrval
"|'(?<attrval>[^\']*)'" + // single quoted attrval
"|(?<attrval>[a-zA-Z0-9\\-._:]+)" + // attrval with no quotes (SGML-approved chars)
")" + // end quoted value
")*" + // end attribute
"\\s*(?<empty>/)?>" // optional trailing /, and trailing >
);
private readonly static Regex doctypeDirectiveRegex = new Regex
(
@"\G<!doctype\b(([\s\w]+)|("".*""))*>",
RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.IgnorePatternWhitespace
);
private readonly static Regex endtagRegex = new Regex
(
"\\G</" + // leading </
"(?<prefix>[\\w:-]+(?=:)|):?" + // optional prefix:
"(?<tagname>[\\w-]+)\\s*>" // tagname
);
private readonly static Regex commentRegex = new Regex
(
"\\G<!--" + // leading <!--
"(?>[^-]*-)+?" + // one or more chunks of text ending with -, minimal
"->" // trailing ->
);
private readonly static Regex whitespaceRegex = new Regex
(
"\\G\\s+" + // at least one char of whitespace
"(?=<|\\Z)" // ending with either '<' or the end of the string
);
private readonly static Regex textRegex = new Regex
(
"\\G[^<]+" // at least one char on non-'<', maximal
);
}
}
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