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