html/scripting-parser/parser.html

<!DOCTYPE HTML>
<html lang=en>
<head>
<title>Live Scripting HTML Parser</title>
<style>
  h1, h2 {
    margin: 0;
    font-size: 100%;
  }
  p, pre {
    margin: 0;
  }
  textarea {
    width: 100%;
    -width: 99%;
    height: 10em;
  }
  output {
    display: block;
    font-family: monospace;
    white-space: -moz-pre-wrap;
    white-space: pre-wrap;
  }
</style>
<script>
  var delayedUpdater = 0;

  function update () {
    if (delayedUpdater) {
      clearTimeout (delayedUpdater);
      delayedUpdater = 0;
    }
    delayedUpdater = setTimeout (update2, 100);
  } // update

  function update2 () {
    var v = document.sourceElement.value;
    if (v != document.previousSourceText) {
      document.previousSourceText = v;
      document.links['permalink'].href
          = location.pathname + '?s=' + encodeURIComponent (v);
      document.links['ldvlink'].href
          = 'http://software.hixie.ch/utilities/js/live-dom-viewer/?'
          + encodeURIComponent (v);

      document.logElement.textContent = '';
      var p = new Parser (new InputStream (v));
      var doc = p.doc;
      p.parse ();
      
      log (dumpTree (doc, ''));
      
      if (p.hasAsyncScript) {
        log ('Some script codes are executed asynchronously; it means that the document might be rendered in different ways depending on the network condition and other factors');
      }
    }
  } // update2

  var logIndentLevel = 0;
  function log (s) {
    for (var i = 0; i < logIndentLevel; i++) {
      s = '  ' + s;
    }
    document.logElement.appendChild (document.createTextNode (s + "\n"));
  } // log

  function InputStream (s) {
    this.s = s;
  } // InputStream

  function Parser (i, doc) {
    this.parseMode = 'pcdata';
    if (!doc) {
      doc = new JSDocument (this);
      doc.manakaiIsHTML = true;
    }
    this.doc = doc;
    this.openElements = [doc];
    this.input = i;
    this.scriptsExecutedAfterParsing = [];
    this.scriptsExecutedSoon = [];
  } // Parser

  Parser.prototype.getNextToken = function () {
    var p = this;
    var i = this.input;
    if (this.parseMode == 'script') {
      var token;
      if (p.insertionPoint <= 0) {
        return {type: 'abort'};
      }
      i.s = i.s.replace (/^([^<]+)/,
      function (s, t) {
        if (0 < p.insertionPoint && p.insertionPoint < t.length) {
          token = {type: 'char', value: t.substring (0, p.insertionPoint)};
          var ip = p.insertionPoint;
          p.insertionPoint = 0;
          return t.substring (ip, t.length);
        }
        token = {type: 'char', value: t};
        p.insertionPoint -= t.length;
        return '';
      });
      if (token) return token;
      i.s = i.s.replace (/^<\/[Ss][Cc][Rr][Ii][Pp][Tt]>/, function (s) {
        if (p.insertionPoint < s.length) {
          token = {type: 'abort'};
          return s;
        }
        token = {type: 'end-tag', value: 'script'};
        p.insertionPoint -= s.length;
        return '';
      });
      if (token) return token;
      var m;
      if ((p.insertionPoint < '</script'.length) &&
          (m = i.s.match (/^<\/([SCRIPTscript]+)/))) {
        var v = m[1].substring (0, p.insertionPoint).toLowerCase ();
        if (v == 'script'.substring (0, p.insertionPoint - '</'.length)) {
          return {type: 'abort'};
        }
      }
      i.s = i.s.replace (/^</,
      function (s) {
        token = {type: 'char', value: s};
        p.insertionPoint -= s.length;
        return '';
      });
      if (token) return token;
      return {type: 'eof'};
    }

    var token;
    i.s = i.s.replace (/^<\/([^>]+)(?:>|$)/, function (s, e) {
      if (p.insertionPoint < s.length ||
          (p.insertionPoint <= s.length &&
           s.substring (s.length - 1, 1) != '>')) {
        token = {type: 'abort'};
        return s;
      }
      token = {type: 'end-tag', value: e.toLowerCase ()};
      p.insertionPoint -= s.length;
      return '';
    });
    if (token) return token;
    i.s = i.s.replace (/^<([^>]+)(?:>|$)/, function (s, e) {
      if (p.insertionPoint < s.length ||
          (p.insertionPoint <= s.length &&
           s.substring (s.length - 1, 1) != '>')) {
        token = {type: 'abort'};
        return s;
      }
      var tagName;
      var attrs = {};
      e = e.replace (/^[\S]+/, function (v) {
        tagName = v.toLowerCase ();
        return '';
      });
      while (true) {
        var m = false;
        e = e.replace (/^\s*([^\s=]+)\s*(?:=\s*(?:"([^"]*)"|'([^']*)'|([^"'\s]*)))?/,
        function (x, attrName, attrValue1, attrValue2, attrValue3) {
          v = attrValue1 || attrValue2 || attrValue3;
          v = v.replace (/&quot;/g, '"').replace (/&apos;/g, "'")
              .replace (/&amp;/g, '&');
          attrs[attrName.toLowerCase ()] = v;
          m = true;
          return '';
        });
        if (!m) break;
      }
      if (e.length) {
        log ('Broken start tag: "' + e + '"');
      }
      token = {type: 'start-tag', value: tagName, attrs: attrs};
      p.insertionPoint -= s.length;
      return '';
    });
    if (token) return token;
    if (p.insertionPoint <= 0) {
      return {type: 'abort'};
    }
    i.s = i.s.replace (/^[^<]+/, function (s) {
      if (p.insertionPoint < s.length) {
        token = {type: 'char', value: s.substring (0, p.insertionPoint)};
        var ip = p.insertionPoint;
        p.insertionPoint = 0;
        return s.substring (ip, s.length);
      }
      token = {type: 'char', value: s};
      p.insertionPoint -= s.length;
      return '';
    });
    if (token) return token;
    i.s = i.s.replace (/^[\s\S]/, function (s) {
      token = {type: 'char', value: s};
      p.insertionPoint -= s.length;
      return '';
    });
    if (token) return token;
    return {type: 'eof'};
  } // getNextToken

  Parser.prototype.parse = function () {
    logIndentLevel++;
    log ('parse: start');

    while (true) {
      var token = this.getNextToken ();
      log ('token: ' + token.type + ' "' + token.value + '"');

      if (token.type == 'start-tag') {
        if (token.value == 'script') {
          // 1. Create an element for the token in the HTML namespace.
          var el = new JSElement (this.doc, token.value);
          if (token.attrs.async != null) el.async = true;
          if (token.attrs.defer != null) el.defer = true;
          if (token.attrs.src != null) el.src = token.attrs.src;

          // 2. Mark the element as being "parser-inserted".
          el.manakaiParserInserted = true;

          // 3. Switch the tokeniser's content model flag to the CDATA state.
          this.parseMode = 'script';

          // 4.1. Collect all the character tokens.
          while (true) {
            var token = this.getNextToken ();
            log ('token: ' + token.type + ' "' + token.value + '"');

            if (token.type == 'char') {
              // 5. Append a single Text node to the script element node.
              el.manakaiAppendText (token.value);

            // 4.2. Until it returns a token that is not a character token, or
            // until it stops tokenising.
            } else if (token.type == 'eof' ||
                       (token.type == 'end-tag' && token.value == 'script') ||
                       token.type == 'abort') {
              // 6. Switched back to the PCDATA state.
              this.parseMode = 'pcdata';

              // 7.1. If the next token is not an end tag token with ...
              if (token.type != 'end-tag') {
                // 7.2. This is a parse error.
                log ('Parse error: no </' + 'script>');

                // 7.3. Mark the script element as "already executed".
                el.manakaiAlreadyExecuted = true;
              } else {
                // 7.4. Ignore it.
                //
              }
              break;
            }
          }

          // 8.1. If the parser were originally created for the ...
          if (this.fragmentParsingMode) {
            // 8.2. Mark the script element as "already executed" and ...
            el.alreadyExecuted = true;
            continue;
          }

          // 9.1. Let the old insertion point have the same value as the ...
          var oldInsertionPoint = this.insertionPoint;
          // 9.2. Let the insertion point be just before the next input ...
          this.setInsertionPoint (0);

          // 10. Append the new element to the current node.
          this.openElements[this.openElements.length - 1].appendChild (el);

          // 11. Let the insertion point have the value of the old ...

          oldInsertionPoint += this.insertionPoint;
          this.setInsertionPoint (oldInsertionPoint);

          // 12. If there is a script that will execute as soon as ...
          while (this.scriptExecutedWhenParserResumes) {
            // 12.1. If the tree construction stage is being called reentrantly
            if (this.reentrant) {
              log ('parse: abort (reentrance)');
              logIndentLevel--;
              return;

            // 12.2. Otherwise
            } else {
              // 1.
              var script = this.scriptExecutedWhenParserResumes;
              this.scriptExecutedWhenParserResumes = null;

              // 2. Pause until the script has completed loading.
              // 

              // 3. Let the insertion point to just before the next input char.
              this.setInsertionPoint (0);

              // 4. Execute the script.
              executeScript (this.doc, script);

              // 5. Let the insertion point be undefined again.
              this.setInsertionPoint (undefined);

              // 6. If there is once again a script that will execute ...
              //
            }
          }
        } else {
          var el = new JSElement (this.doc, token.value);
          this.openElements[this.openElements.length - 1].appendChild (el);
          this.openElements.push (el);
        }
      } else if (token.type == 'end-tag') {
        if (this.openElements[this.openElements.length - 1].localName ==
            token.value) {
          this.openElements.pop ();
        } else {
          log ('parse error: unmatched end tag: ' + token.value);
        }
      } else if (token.type == 'char') {
        this.openElements[this.openElements.length - 1].manakaiAppendText
            (token.value);
      } else if (token.type == 'eof') {
        break;
      } else if (token.type == 'abort') {
        log ('parse: abort');
        logIndentLevel--;
        return;
      }
    }

    log ('stop parsing');

    // readyState = 'interactive'

    // "When a script completes loading" rules start applying.

    // List of scripts that will execute as soon as possible
    for (var i = 0; i < this.scriptsExecutedSoon.length; i++) {
      var e = this.scriptsExecutedSoon[i];

      // If it has completed loading
      log ('Execute an external script not inserted by parser...');
      executeScript (this.doc, e);

      // NOTE: It MAY be executed before the end of the parsing, according
      // to the spec.
      this.hasAsyncScript = true;
    }

    // TODO: Handles
    // "list of scripts that will execute asynchronously"

    // Handle "list of scripts that will execute when the document has finished
    // parsing".
    var list = this.scriptsExecutedAfterParsing;
    while (list.length > 0) {
      // TODO: break unless completed loading

      // Step 1.
      //

      // Step 2. and Step 3.
      log ('Executing a |defer|red script...');
      executeScript (this.doc, list.shift ());

      // Step 4.
    }

    log ('DOMContentLoaded event fired');

    // "delays tha load event" things has completed:
    // readyState = 'complete'
    log ('load event fired');

    logIndentLevel--;
  } // parse

  Parser.prototype.setInsertionPoint = function (ip) {
    if (ip == undefined || ip == null || isNaN (ip)) {
      log ('insertion point: set to undefined');
      this.insertionPoint = undefined;
    } else if (ip == this.input.s.length) {
      log ('insertion point: end of file');
      this.insertionPoint = ip;
    } else {
      log ('insertion point: set to ' + ip +
           ' (before "' + this.input.s.substring (0, 10) + '")');
      this.insertionPoint = ip;
    }
  }; // setInsertionPoint

  function JSDocument (p) {
    this.childNodes = [];
    this._parser = p;
  } // JSDocument

  function JSElement (doc, localName) {
    this.localName = localName;
    this.ownerDocument = doc;
    this.childNodes = [];
  } // JSElement

  JSDocument.prototype.appendChild = JSElement.prototype.appendChild =
  function (e) {
    this.childNodes.push (e);
    e.parentNode = this;

    if (e.localName == 'script') {
      logIndentLevel++;
      log ('Running a script: start');

      var doc = this.ownerDocument || this;
      var p = doc._parser;

      // 1. Script type
      //

      // 2.1. If scripting is disabled
      //
      // 2.2. If the script element was created by an XML ... innerHTML ...
      //
      // 2.3. If the user agent does not support the scripting language ...
      //
      // 2.4. If the script element has its "already executed" flag set
      if (e.manakaiAlreadyExecuted) {
        // 2.5. Abort these steps at this point.
        log ('Running a script: aborted');
        logIndentLevel--;
        return e;
      }

      // 3. Set the element's "already executed" flag.
      e.manakaiAlreadyExecuted = true;

      // 4. If the element has a src attribute, then a load for ...
      // TODO: load an external resource

      // 5. The first of the following options:

      // 5.1. 
      if (/* TODO: If the document is still being parsed && */
          e.defer && !e.async) {
        p.scriptsExecutedAfterParsing.push (e);
        log ('Running a script: aborted (defer)');
      } else if (e.async && e.src != null) {
        // TODO
      } else if (e.async && e.src == null
                 /* && list of scripts that will execute asynchronously is not empty */) {
        // TODO
      } else if (e.src != null && e.manakaiParserInserted) {
        if (p.scriptExecutedWhenParserResumes) {
          log ('Error: There is a script that will execute as soon as the parser resumes.');
        }
        p.scriptExecutedWhenParserResumes = e;
        log ('Running a script: aborted (src parser-inserted)');
      } else if (e.src != null) {
        p.scriptsExecutedSoon.push (e);
        log ('Running a script: aborted (src)');
      } else {
        executeScript (doc, e); // even if other scripts are already executing.
      }

      log ('Running a script: end');
      logIndentLevel--;
    }

    return e;
  }; // appendChild

  function executeScript (doc, e) {
    log ('executing a script block: start');

    var s;
    if (e.src != null) {
      s = getExternalScript (e.src);

      // If the load resulted in an error, then ... firing an error event ...
      if (s == null) {
        log ('error event fired at the script element');
        return;
      }

      log ('External script loaded: "' + s + '"');
    } else {
      s = e.text;
    }

    // If the load was successful
    log ('load event fired at the script element');

    if (true) {
    // Scripting is enabled, Document.designMode is disabled,
    // Document is the active document in its browsing context

      parseAndRunScript (doc, s);
    }

    log ('executing a script block: end');
  } // executeScript

  function getExternalScript (uri) {
    if (uri.match (/^javascript:/i)) {
      var m;
      if (m = uri.match (/^javascript:\s*(?:'([^']*)'|"([^"]+)")\s*$/i)) {
        if (m[1]) {
          return unescapeJSLiteral (m[1]);
        } else if (m[2]) {
          return unescapeJSLiteral (m[2]);
        } else {
          return null;
        }
      } else {
        log ('Complex javascript: URI is not supported: <' + uri + '>');
        return null;
      }
    } else {
      log ('URI scheme not supported: <' + uri + '>');
      return null;
    }
  } // getExternalScript

  function parseAndRunScript (doc, s) {
    while (true) {
      var matched = false;
      s = s.replace (/^\s*document\.write\s*\(((?:'[^']*'|"[^"]*")\s*(?:,\s*(?:'[^']*'|"[^"]*"))*)\)\s*;\s*/, function (s, t) {
        matched = true;
        var args = [];
        t.replace (/('[^']*'|"[^"]*")/g, function (s, v) {
          args.push (unescapeJSLiteral (v.substring (1, v.length - 1)));
          return '';
        });
        doc.write.apply (doc, args);
        return '';
      });
      s = s.replace (/^\s*var\s+s\s*=\s*document\.createElement\s*\(\s*['"]script['"]\s*\)\s*;\s*s\.src\s*=\s*(?:'(javascript:[^']*)'|"(javascript:[^"]*)")\s*;\s*document\.documentElement\.appendChild\s*\(\s*s\s*\)\s*;\s*/,
      function (s, t, u) {
        matched = true;
        var args = [unescapeJSLiteral (t ? t : u)];
        doc._insertExternalScript.apply (doc, args);
        return '';
      });
      if (s == '') break;
      if (!matched) {
        log ('Script parse error: "' + s + '"');
        break;
      }
    }
  } // parseAndRunScript

  function unescapeJSLiteral (s) {
    return s.replace (/\\u([0-9A-Fa-f]{4})/g, function (t, v) {
      return String.fromCharCode (parseInt ('0x' + v));
    });
  } // unescapeJSLiteral

  function JSText (data) {
    this.data = data;
  } // JSText

  JSDocument.prototype.manakaiAppendText =
  JSElement.prototype.manakaiAppendText =
  function (s) {
    if (this.childNodes.length > 0 &&
        this.childNodes[this.childNodes.length - 1] instanceof JSText) {
      this.childNodes[this.childNodes.length - 1].data += s;
    } else {
      this.childNodes.push (new JSText (s));
    }
  }; // manakaiAppendText

  JSDocument.prototype.open = function () {
    // Two or fewer arguments

    // Step 1.
    var type = arguments[0] || 'text/html';
    
    // Step 2.
    var replace = arguments[1] == 'replace';

    // Step 3.
    if (this._parser &&
        !this._parser.scriptCreated &&
        this._parser.input.insertionPoint != undefined) {
      log ('document.open () in parsing mode is ignored');
      return this;
    }

    // Step 4.
    log ('onbeforeunload event fired');
    log ('onunload event fired');

    // Step 5.
    if (this._parser) {
      // Discard the parser.
    }

    // Step 6.
    log ('document cleared by document.open ()');
    this.childNodes = [];

    // Step 7.
    this._parser = new Parser (new InputStream (''), this);
    this._parser.scriptCreated = true;

    // Step 8.
    this.manakaiIsHTML = true;

    // Step 9.
    // If not text/html, ...

    // Step 10.
    if (!replace) {
      // History      
    }

    // Step 11.
    this._parser.setInsertionPoint (this._parser.input.s.length);

    // Step 12.
    return this;
  }; // document.open

  JSDocument.prototype.write = function () {
    logIndentLevel++;

    var p = this._parser;

    // 1. If the insertion point is undefined, the open() method must be ...
    if (isNaN (p.insertionPoint) || p.insertionPoint == undefined) {
      this.open ();
      p = this._parser;
    }

    // 2. ... inserted into the input stream just before the insertion point.
    var s = Array.join (arguments, '');
    log ('document.write: insert "' + s + '"' +
         ' before "' +
         p.input.s.substring (p.insertionPoint, p.insertionPoint + 10) + '"');
    p.input.s = p.input.s.substring (0, p.insertionPoint) + s
        + p.input.s.substring (p.insertionPoint, p.input.s.length);
    p.insertionPoint += s.length;

    // 3. If there is a script that will execute as soon as the parser resumes
    if (p.scriptExecutedAfterParserResumes) {
      log ('document.write: processed later (there is an unprocessed <script src>)');
      logIndentLevel--;
      return;
    }

    // 4. Process the characters that were inserted, ...
    var originalReentrant = p.reentrant;
    p.reentrant = true;
    p.parse ();
    p.reentrant = originalReentrant;
    // TODO: "Abort the processing of any nested invokations of the tokeniser,
    // yielding control back to the caller." (<script> parsing).  Do we need
    // to do something here?

    // 5. Return
    log ('document.write: return');

    logIndentLevel--;
    return;
  }; // document.write

  JSDocument.prototype._insertExternalScript = function (uri) {
    var s = new JSElement (this, 'script');
    s.src = uri;
    this.documentElement.appendChild (s);
  }; // _insertExternalScript

  JSDocument.prototype.__defineGetter__ ('documentElement', function () {
    var cn = this.childNodes;
    for (var i = 0; i < cn.length; i++) {
      if (cn[i] instanceof JSElement) {
        return cn[i]
      }
    }
    return null;
  });

  JSElement.prototype.__defineGetter__ ('text', function () {
    var r = '';
    for (var i = 0; i < this.childNodes.length; i++) {
      if (this.childNodes[i] instanceof JSText) {
        r += this.childNodes[i].data;
      }
    }
    return r;
  });

  function dumpTree (n, indent) {
    var r = '';
    for (var i = 0; i < n.childNodes.length; i++) {
      var node = n.childNodes[i];
      if (node instanceof JSElement) {
        r += '| ' + indent + node.localName + '\n';
        if (node.async) r += '| ' + indent + '  async=""\n';
        if (node.defer) r += '| ' + indent + '  defer=""\n';
        if (node.src != null) {
          r += '| ' + indent + '  src="' + node.src + '"\n';
        }
        r += dumpTree (node, indent + '  ');
      } else if (node instanceof JSText) {
        r += '| ' + indent + '"' + node.data + '"\n';
      } else {
        r += '| ' + indent + node + '\n';
      }
    }
    return r;
  } // dumpTree
</script>
</head>
<body onload="
  document.sourceElement = document.getElementsByTagName ('textarea')[0];

  var q = location.search;
  if (q != null) {
    q = q.substring (1).split (/;/);
    for (var i = 0; i < q.length; i++) {
      var v = q[i].split (/=/, 2);
      v[0] = decodeURIComponent (v[0]);
      v[1] = decodeURIComponent (v[1] || '');
      if (v[0] == 's') {
        document.sourceElement.value = v[1];
      }
    }
  }

  document.logElement = document.getElementsByTagName ('output')[0];
  update ();
">
<h1>Live Scripting <abbr title="Hypertext Markup Language">HTML</abbr>
Parser</h1>

<h2>Markup to test
(<a href=data:, id=permalink rel=bookmark>permalink</a>,
<a href="http://software.hixie.ch/utilities/js/live-dom-viewer/"
    id=ldvlink>Live <abbr title="Document Object Model">DOM</abbr>
    Viewer</a>)</h2>
<p>
<textarea onkeydown=" update () " onchange=" update () " oninput=" update () ">&lt;html>
&lt;head>&lt;/head>&lt;body>
&lt;p>
&lt;script>
document.write ('aaaaaaa&lt;/p>&lt;script>document.write("cccccc");&lt;/', 'script>bbbbbb');
&lt;/script>
&lt;p>
</textarea>

<h2 id=log>Log</h2>
<p><output></output>

<h2 id=notes>Notes</h2>

<p>This is a <em>simplified</em> implementation of 
<a href="http://www.whatwg.org/specs/web-apps/current-work/#parsing">HTML5 
Parsing Algorithm</a>.  It only implements script-related part of the 
algorithm.  Especially, this parser:
<ul>
<li>Does not support <code>DOCTYPE</code> and comment tokens.
<li>Does not support entities except for <code>&amp;quot;</code>,
<code>&amp;apos;</code>, and <code>&amp;amp;</code> in <code>script</code>
<code>src</code> attribute value.
<li>Does not support omissions of start or end tags, the <abbr>AAA</abbr>
algorithm, and so on.
<li>Does not raise parse errors for invalid attribute specifications in start 
or end tags.
<li>Does not support CDATA/PCDATA element other than <code>script</code>.
<li>Does not support <code>&lt;!--</code>..<code>--></code> parsing rule
in <code>script</code> element.
<li>Does not support foreign (SVG or MathML) elements.
<li>Only supports <code>script</code> <code>type</code>
<code>text/javascript</code>.  <code>type</code> and <code>language</code>
attributes are ignored.
<li>Only supports limited statements.  It must consist of zero or more
of statements looking similar to the following statements, possibly
introduced, followed, or separated by white space characters:
  <ul>
  <li><code>document.write ("<var>string</var>", ["<var>string</var>", ...]);</code>.
  <li><code>var s = document.createElement ("script");
            s.src = "<var>string</var>";
            document.documentElement.appendChild (s);</code>
  </ul>
Note that strings may be delimited by <code>'</code>s instead of
<code>"</code>s.
<li>Only supports <code>javascript:</code> 
<abbr title="Uniform Resourace Identifiers">URI</abbr> scheme in the 
<code>src</code> attribute of the <code>script</code> element.  In addition, 
the <abbr title="Uniform Resource Identifiers">URI</abbr> must be conform to 
the regular expression <code>^javascript:\s*(?:"[^"]*"|'[^']*')\s*$</code>.
<li>Only supports <code>\u<var>HHHH</var></code> escapes in JavaScript 
string literals.
</ul>

<p>For some reason, this parser does not work in browsers that do
not support JavaScript 1.5.

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