(function() { 
  let shistory = gBrowser.selectedBrowser.browsingContext.sessionHistory;
  let index = shistory.index;
  let requestedIndex = shistory.requestedIndex;
  let count = shistory.count;

  function encode(uri) {
    if (!uri) {
      return null;
    }
    let u = encodeURIComponent(uri);
    if (u.length > 100) {
      u = u.substr(0, 100) + "...";
    }
    return u;
  }

  function entryToString(entry, i) {
    return "Entry[" + i + "],  originalURI: " + encode(entry.originalURI?.spec) + ", uri: " + encode(entry.URI?.spec) + ", ID: " + entry.ID + "<br>";
  }

  function childToString(entry, index, nested) {
    let out = "";
    for (let n = 0; n < nested; ++n) {
      out += "&nbsp;&nbsp;";
    }

    if (!entry) {
      return out + "Entry[" + index + "](null entry)";
    }

    out = out + entryToString(entry, index);

    for (let i = 0; i < entry.childCount; ++i) {
      out += childToString(entry.GetChildAt(i), i, nested + 1);
    }

    return out;
  }

  let entries = "";
  for (let i = 0; i < count; ++i) {
    let entry = shistory.getEntryAtIndex(i);
    entries += entryToString(entry, i);
    for (let j = 0; j < entry.childCount; ++j) {
      entries += childToString(entry.GetChildAt(j), j, 1);
    } 
  }

  let uri = "data:text/html," +
    "index: " + index + "<br>" +
    "requestedIndex: " + requestedIndex + "<br>" +
    "count: " + count + "<br>" + 
    entries;
  
  gBrowser.addAdjacentNewTab("about:blank"); gBrowser.selectedBrowser.loadURI(uri, {triggeringPrincipal:  document.nodePrincipal});

 } )();