function prettyPrint(opt_whenDone) {
    var isIE6 = PR_isIE6();
    
    // fetch a list of nodes to rewrite
    var codeSegments = [
        document.getElementsByTagName('pre'),
        document.getElementsByTagName('code'),
        document.getElementsByTagName('xmp') ];
    var elements = [];
    for (var i = 0; i < codeSegments.length; ++i) {
      for (var j = 0; j < codeSegments[i].length; ++j) {
        elements.push(codeSegments[i][j]);
      }
    }
    codeSegments = null;
  
    // the loop is broken into a series of continuations to make sure that we
    // don't make the browser unresponsive when rewriting a large page.
    var k = 0;
  
    function doWork() {
      var endTime = (PR_SHOULD_USE_CONTINUATION
                     ? new Date().getTime() + 250
                     : Infinity);
      for (; k < elements.length && new Date().getTime() < endTime; k++) {
        var cs = elements[k];
        if (cs.className && cs.className.indexOf('prettyprint') >= 0) {
  
          // make sure this is not nested in an already prettified element
          var nested = false;
          for (var p = cs.parentNode; p != null; p = p.parentNode) {
            if ((p.tagName == 'pre' || p.tagName == 'code' ||
                 p.tagName == 'xmp') &&
                p.className && p.className.indexOf('prettyprint') >= 0) {
              nested = true;
              break;
            }
          }
          if (!nested) {
            // fetch the content as a snippet of properly escaped HTML.
            // Firefox adds newlines at the end.
            var content = PR_getInnerHtml(cs);
            content = content.replace(/(?:\r\n?|\n)/, '');
  
            // do the pretty printing
            var newContent = prettyPrintOne(content);
  
            // push the prettified html back into the tag.
            if (!PR_isRawContent(cs)) {
              // just replace the old html with the new
              cs.innerHTML = newContent;
            } else {
              // we need to change the tag to a <pre> since <xmp>s do not allow
              // embedded tags such as the span tags used to attach styles to
              // sections of source code.
              var pre = document.createElement('PRE');
              for (var i = 0; i < cs.attributes.length; ++i) {
                var a = cs.attributes[i];
                if (a.specified) {
                  pre.setAttribute(a.name, a.value);
                }
              }
              pre.innerHTML = newContent;
  
              // remove the old
              cs.parentNode.replaceChild(pre, cs);
              pre = cs;
            }
  
            // Replace <br>s with line-feeds so that copying and pasting works on
            // IE 6.
            // Doing this on other browsers breaks lots of stuff since \r\n is
            // treated as two newlines on Firefox, and doing this also slows down
            // rendering.
            if (isIE6 && cs.tagName === 'PRE') {
              var lineBreaks = cs.getElementsByTagName('br');
              for (var i = lineBreaks.length; --i >= 0;) {
                var lineBreak = lineBreaks[i];
                lineBreak.parentNode.replaceChild(
                    document.createTextNode('\r\n'), lineBreak);
              }
            }
          }
        }
      }
      if (k < elements.length) {
        // finish up in a continuation
        setTimeout(doWork, 250);
      } else if (opt_whenDone) {
        opt_whenDone();
      }
    }
  
    doWork();
  }