/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim:expandtab:shiftwidth=4:tabstop=4:
 */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/ArrayUtils.h"

#include "nsArrayUtils.h"
#include "nsClipboard.h"
#include "nsClipboardX11.h"
#if defined(MOZ_WAYLAND)
#include "nsClipboardWayland.h"
#endif
#include "HeadlessClipboard.h"
#include "nsSupportsPrimitives.h"
#include "nsString.h"
#include "nsReadableUtils.h"
#include "nsPrimitiveHelpers.h"
#include "nsIServiceManager.h"
#include "nsImageToPixbuf.h"
#include "nsStringStream.h"
#include "nsIObserverService.h"
#include "mozilla/Services.h"
#include "mozilla/RefPtr.h"
#include "mozilla/TimeStamp.h"

#include "imgIContainer.h"

#include <gtk/gtk.h>
#include <gtk/gtkx.h>

#include "mozilla/Encoding.h"

using namespace mozilla;

// Idle timeout for receiving selection and property notify events (microsec)
const int kClipboardTimeout = 500000;

// Callback when someone asks us for the data
void clipboard_get_cb(GtkClipboard *aGtkClipboard,
                      GtkSelectionData *aSelectionData, guint info,
                      gpointer user_data);

// Callback when someone asks us to clear a clipboard
void clipboard_clear_cb(GtkClipboard *aGtkClipboard, gpointer user_data);

static void ConvertHTMLtoUCS2(const char *data, int32_t dataLength,
                              char16_t **unicodeData, int32_t &outUnicodeLen);

static void GetHTMLCharset(const char *data, int32_t dataLength,
                           nsCString &str);

GdkAtom GetSelectionAtom(int32_t aWhichClipboard) {
  if (aWhichClipboard == nsIClipboard::kGlobalClipboard)
    return GDK_SELECTION_CLIPBOARD;

  return GDK_SELECTION_PRIMARY;
}

nsClipboard::nsClipboard() {}

nsClipboard::~nsClipboard() {
  // We have to clear clipboard before gdk_display_close() call.
  // See bug 531580 for details.
  if (mGlobalTransferable) {
    gtk_clipboard_clear(gtk_clipboard_get(GDK_SELECTION_CLIPBOARD));
  }
  if (mSelectionTransferable) {
    gtk_clipboard_clear(gtk_clipboard_get(GDK_SELECTION_PRIMARY));
  }
}

NS_IMPL_ISUPPORTS(nsClipboard, nsIClipboard)

nsresult nsClipboard::Init(void) {
  GdkDisplay *display = gdk_display_get_default();

  // Create a nsRetrievalContext. If there's no default display
  // create the X11 one as a fallback.
  if (!display || GDK_IS_X11_DISPLAY(display)) {
    mContext = new nsRetrievalContextX11();
#if defined(MOZ_WAYLAND)
  } else {
    mContext = new nsRetrievalContextWayland();
#endif
  }
  NS_ASSERTION(mContext, "Missing nsRetrievalContext for nsClipboard!");

  nsCOMPtr<nsIObserverService> os = mozilla::services::GetObserverService();
  if (os) {
    os->AddObserver(this, "quit-application", false);
    os->AddObserver(this, "xpcom-shutdown", false);
  }

  return NS_OK;
}

nsresult nsClipboard::Store(void) {
  if (mGlobalTransferable) {
    GtkClipboard *clipboard = gtk_clipboard_get(GDK_SELECTION_CLIPBOARD);
    gtk_clipboard_store(clipboard);
  }
  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::Observe(nsISupports *aSubject, const char *aTopic,
                     const char16_t *aData) {
  Store();
  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::SetData(nsITransferable *aTransferable, nsIClipboardOwner *aOwner,
                     int32_t aWhichClipboard) {
  // See if we can short cut
  if ((aWhichClipboard == kGlobalClipboard &&
       aTransferable == mGlobalTransferable.get() &&
       aOwner == mGlobalOwner.get()) ||
      (aWhichClipboard == kSelectionClipboard &&
       aTransferable == mSelectionTransferable.get() &&
       aOwner == mSelectionOwner.get())) {
    return NS_OK;
  }

  // Clear out the clipboard in order to set the new data
  EmptyClipboard(aWhichClipboard);

  // List of suported targets
  GtkTargetList *list = gtk_target_list_new(nullptr, 0);

  // Get the types of supported flavors
  nsCOMPtr<nsIArray> flavors;

  nsresult rv =
      aTransferable->FlavorsTransferableCanExport(getter_AddRefs(flavors));
  if (!flavors || NS_FAILED(rv)) return NS_ERROR_FAILURE;

  // Add all the flavors to this widget's supported type.
  bool imagesAdded = false;
  uint32_t count;
  flavors->GetLength(&count);
  for (uint32_t i = 0; i < count; i++) {
    nsCOMPtr<nsISupportsCString> flavor = do_QueryElementAt(flavors, i);

    if (flavor) {
      nsCString flavorStr;
      flavor->ToString(getter_Copies(flavorStr));

      // special case text/unicode since we can handle all of
      // the string types
      if (flavorStr.EqualsLiteral(kUnicodeMime)) {
        gtk_target_list_add(list, gdk_atom_intern("UTF8_STRING", FALSE), 0, 0);
        gtk_target_list_add(list, gdk_atom_intern("COMPOUND_TEXT", FALSE), 0,
                            0);
        gtk_target_list_add(list, gdk_atom_intern("TEXT", FALSE), 0, 0);
        gtk_target_list_add(list, GDK_SELECTION_TYPE_STRING, 0, 0);
        continue;
      }

      if (flavorStr.EqualsLiteral(kNativeImageMime) ||
          flavorStr.EqualsLiteral(kPNGImageMime) ||
          flavorStr.EqualsLiteral(kJPEGImageMime) ||
          flavorStr.EqualsLiteral(kJPGImageMime) ||
          flavorStr.EqualsLiteral(kGIFImageMime)) {
        // don't bother adding image targets twice
        if (!imagesAdded) {
          // accept any writable image type
          gtk_target_list_add_image_targets(list, 0, TRUE);
          imagesAdded = true;
        }
        continue;
      }

      // Add this to our list of valid targets
      GdkAtom atom = gdk_atom_intern(flavorStr.get(), FALSE);
      gtk_target_list_add(list, atom, 0, 0);
    }
  }

  // Get GTK clipboard (CLIPBOARD or PRIMARY)
  GtkClipboard *gtkClipboard =
      gtk_clipboard_get(GetSelectionAtom(aWhichClipboard));

  gint numTargets;
  GtkTargetEntry *gtkTargets =
      gtk_target_table_new_from_list(list, &numTargets);

  // Set getcallback and request to store data after an application exit
  if (gtkTargets &&
      gtk_clipboard_set_with_data(gtkClipboard, gtkTargets, numTargets,
                                  clipboard_get_cb, clipboard_clear_cb, this)) {
    // We managed to set-up the clipboard so update internal state
    // We have to set it now because gtk_clipboard_set_with_data() calls
    // clipboard_clear_cb() which reset our internal state
    if (aWhichClipboard == kSelectionClipboard) {
      mSelectionOwner = aOwner;
      mSelectionTransferable = aTransferable;
    } else {
      mGlobalOwner = aOwner;
      mGlobalTransferable = aTransferable;
      gtk_clipboard_set_can_store(gtkClipboard, gtkTargets, numTargets);
    }

    rv = NS_OK;
  } else {
    rv = NS_ERROR_FAILURE;
  }

  gtk_target_table_free(gtkTargets, numTargets);
  gtk_target_list_unref(list);

  return rv;
}

void nsClipboard::SetTransferableData(nsITransferable *aTransferable,
                                      nsCString &aFlavor,
                                      const char *aClipboardData,
                                      uint32_t aClipboardDataLength) {
  nsCOMPtr<nsISupports> wrapper;
  nsPrimitiveHelpers::CreatePrimitiveForData(
      aFlavor, aClipboardData, aClipboardDataLength, getter_AddRefs(wrapper));
  aTransferable->SetTransferData(aFlavor.get(), wrapper, aClipboardDataLength);
}

NS_IMETHODIMP
nsClipboard::GetData(nsITransferable *aTransferable, int32_t aWhichClipboard) {
  if (!aTransferable) return NS_ERROR_FAILURE;

  // Get a list of flavors this transferable can import
  nsCOMPtr<nsIArray> flavors;
  nsresult rv;
  rv = aTransferable->FlavorsTransferableCanImport(getter_AddRefs(flavors));
  if (!flavors || NS_FAILED(rv)) return NS_ERROR_FAILURE;

  uint32_t count;
  flavors->GetLength(&count);
  for (uint32_t i = 0; i < count; i++) {
    nsCOMPtr<nsISupportsCString> currentFlavor;
    currentFlavor = do_QueryElementAt(flavors, i);
    if (!currentFlavor) continue;

    nsCString flavorStr;
    currentFlavor->ToString(getter_Copies(flavorStr));

    if (flavorStr.EqualsLiteral(kJPEGImageMime) ||
        flavorStr.EqualsLiteral(kJPGImageMime) ||
        flavorStr.EqualsLiteral(kPNGImageMime) ||
        flavorStr.EqualsLiteral(kGIFImageMime)) {
      // Emulate support for image/jpg
      if (flavorStr.EqualsLiteral(kJPGImageMime)) {
        flavorStr.Assign(kJPEGImageMime);
      }

      uint32_t clipboardDataLength;
      const char *clipboardData = mContext->GetClipboardData(
          flavorStr.get(), aWhichClipboard, &clipboardDataLength);
      if (!clipboardData) continue;

      nsCOMPtr<nsIInputStream> byteStream;
      NS_NewByteInputStream(getter_AddRefs(byteStream), clipboardData,
                            clipboardDataLength, NS_ASSIGNMENT_COPY);
      aTransferable->SetTransferData(flavorStr.get(), byteStream,
                                     sizeof(nsIInputStream *));

      mContext->ReleaseClipboardData(clipboardData);
      return NS_OK;
    }

    // Special case text/unicode since we can convert any
    // string into text/unicode
    if (flavorStr.EqualsLiteral(kUnicodeMime)) {
      const char *clipboardData = mContext->GetClipboardText(aWhichClipboard);
      if (!clipboardData) {
        // If the type was text/unicode and we couldn't get
        // text off the clipboard, run the next loop
        // iteration.
        continue;
      }

      // Convert utf-8 into our unicode format.
      NS_ConvertUTF8toUTF16 ucs2string(clipboardData);
      const char *unicodeData = (const char *)ToNewUnicode(ucs2string);
      uint32_t unicodeDataLength = ucs2string.Length() * 2;
      SetTransferableData(aTransferable, flavorStr, unicodeData,
                          unicodeDataLength);
      free((void *)unicodeData);

      mContext->ReleaseClipboardData(clipboardData);
      return NS_OK;
    }

    uint32_t clipboardDataLength;
    const char *clipboardData = mContext->GetClipboardData(
        flavorStr.get(), aWhichClipboard, &clipboardDataLength);

    if (clipboardData) {
      // Special case text/html since we can convert into UCS2
      if (flavorStr.EqualsLiteral(kHTMLMime)) {
        char16_t *htmlBody = nullptr;
        int32_t htmlBodyLen = 0;
        // Convert text/html into our unicode format
        ConvertHTMLtoUCS2(clipboardData, clipboardDataLength, &htmlBody,
                          htmlBodyLen);

        // Try next data format?
        if (!htmlBodyLen) {
          mContext->ReleaseClipboardData(clipboardData);
          continue;
        }

        SetTransferableData(aTransferable, flavorStr, (const char *)htmlBody,
                            htmlBodyLen * 2);
        free(htmlBody);
      } else {
        SetTransferableData(aTransferable, flavorStr, clipboardData,
                            clipboardDataLength);
      }

      mContext->ReleaseClipboardData(clipboardData);
      return NS_OK;
    }
  }

  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::EmptyClipboard(int32_t aWhichClipboard) {
  if (aWhichClipboard == kSelectionClipboard) {
    if (mSelectionOwner) {
      mSelectionOwner->LosingOwnership(mSelectionTransferable);
      mSelectionOwner = nullptr;
    }
    mSelectionTransferable = nullptr;
  } else {
    if (mGlobalOwner) {
      mGlobalOwner->LosingOwnership(mGlobalTransferable);
      mGlobalOwner = nullptr;
    }
    mGlobalTransferable = nullptr;
  }

  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::HasDataMatchingFlavors(const char **aFlavorList, uint32_t aLength,
                                    int32_t aWhichClipboard, bool *_retval) {
  if (!aFlavorList || !_retval) return NS_ERROR_NULL_POINTER;

  *_retval = false;

  int targetNums;
  GdkAtom *targets = mContext->GetTargets(aWhichClipboard, &targetNums);
  if (!targets) return NS_OK;

  // Walk through the provided types and try to match it to a
  // provided type.
  for (uint32_t i = 0; i < aLength && !*_retval; i++) {
    // We special case text/unicode here.
    if (!strcmp(aFlavorList[i], kUnicodeMime) &&
        gtk_targets_include_text(targets, targetNums)) {
      *_retval = true;
      break;
    }

    for (int32_t j = 0; j < targetNums; j++) {
      gchar *atom_name = gdk_atom_name(targets[j]);
      if (!atom_name) continue;

      if (!strcmp(atom_name, aFlavorList[i])) *_retval = true;

      // X clipboard supports image/jpeg, but we want to emulate support
      // for image/jpg as well
      if (!strcmp(aFlavorList[i], kJPGImageMime) &&
          !strcmp(atom_name, kJPEGImageMime)) {
        *_retval = true;
      }

      g_free(atom_name);

      if (*_retval) break;
    }
  }

  g_free(targets);
  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::SupportsSelectionClipboard(bool *_retval) {
  *_retval = mContext->HasSelectionSupport();
  return NS_OK;
}

NS_IMETHODIMP
nsClipboard::SupportsFindClipboard(bool *_retval) {
  *_retval = false;
  return NS_OK;
}

nsITransferable *nsClipboard::GetTransferable(int32_t aWhichClipboard) {
  nsITransferable *retval;

  if (aWhichClipboard == kSelectionClipboard)
    retval = mSelectionTransferable.get();
  else
    retval = mGlobalTransferable.get();

  return retval;
}

void nsClipboard::SelectionGetEvent(GtkClipboard *aClipboard,
                                    GtkSelectionData *aSelectionData) {
  // Someone has asked us to hand them something.  The first thing
  // that we want to do is see if that something includes text.  If
  // it does, try to give it text/unicode after converting it to
  // utf-8.

  int32_t whichClipboard;

  // which clipboard?
  GdkAtom selection = gtk_selection_data_get_selection(aSelectionData);
  if (selection == GDK_SELECTION_PRIMARY)
    whichClipboard = kSelectionClipboard;
  else if (selection == GDK_SELECTION_CLIPBOARD)
    whichClipboard = kGlobalClipboard;
  else
    return;  // THAT AIN'T NO CLIPBOARD I EVER HEARD OF

  nsCOMPtr<nsITransferable> trans = GetTransferable(whichClipboard);
  if (!trans) {
  // We have nothing to serve
#ifdef DEBUG_CLIPBOARD
    printf("nsClipboard::SelectionGetEvent() - %s clipboard is empty!\n",
           whichClipboard == kSelectionClipboard ? "Selection" : "Global");
#endif
    return;
  }

  nsresult rv;
  nsCOMPtr<nsISupports> item;
  uint32_t len;

  GdkAtom selectionTarget = gtk_selection_data_get_target(aSelectionData);

  // Check to see if the selection data includes any of the string
  // types that we support.
  if (selectionTarget == gdk_atom_intern("STRING", FALSE) ||
      selectionTarget == gdk_atom_intern("TEXT", FALSE) ||
      selectionTarget == gdk_atom_intern("COMPOUND_TEXT", FALSE) ||
      selectionTarget == gdk_atom_intern("UTF8_STRING", FALSE)) {
    // Try to convert our internal type into a text string.  Get
    // the transferable for this clipboard and try to get the
    // text/unicode type for it.
    rv = trans->GetTransferData("text/unicode", getter_AddRefs(item), &len);
    if (!item || NS_FAILED(rv)) return;

    nsCOMPtr<nsISupportsString> wideString;
    wideString = do_QueryInterface(item);
    if (!wideString) return;

    nsAutoString ucs2string;
    wideString->GetData(ucs2string);
    char *utf8string = ToNewUTF8String(ucs2string);
    if (!utf8string) return;

    gtk_selection_data_set_text(aSelectionData, utf8string, strlen(utf8string));

    free(utf8string);
    return;
  }

  // Check to see if the selection data is an image type
  if (gtk_targets_include_image(&selectionTarget, 1, TRUE)) {
    // Look through our transfer data for the image
    static const char *const imageMimeTypes[] = {kNativeImageMime,
                                                 kPNGImageMime, kJPEGImageMime,
                                                 kJPGImageMime, kGIFImageMime};
    nsCOMPtr<nsISupports> imageItem;
    nsCOMPtr<nsISupportsInterfacePointer> ptrPrimitive;
    for (uint32_t i = 0; !ptrPrimitive && i < ArrayLength(imageMimeTypes);
         i++) {
      rv = trans->GetTransferData(imageMimeTypes[i], getter_AddRefs(imageItem),
                                  &len);
      ptrPrimitive = do_QueryInterface(imageItem);
    }
    if (!ptrPrimitive) return;

    nsCOMPtr<nsISupports> primitiveData;
    ptrPrimitive->GetData(getter_AddRefs(primitiveData));
    nsCOMPtr<imgIContainer> image(do_QueryInterface(primitiveData));
    if (!image)  // Not getting an image for an image mime type!?
      return;

    GdkPixbuf *pixbuf = nsImageToPixbuf::ImageToPixbuf(image);
    if (!pixbuf) return;

    gtk_selection_data_set_pixbuf(aSelectionData, pixbuf);
    g_object_unref(pixbuf);
    return;
  }

  // Try to match up the selection data target to something our
  // transferable provides.
  gchar *target_name = gdk_atom_name(selectionTarget);
  if (!target_name) return;

  rv = trans->GetTransferData(target_name, getter_AddRefs(item), &len);
  // nothing found?
  if (!item || NS_FAILED(rv)) {
    g_free(target_name);
    return;
  }

  void *primitive_data = nullptr;
  nsPrimitiveHelpers::CreateDataFromPrimitive(nsDependentCString(target_name),
                                              item, &primitive_data, len);

  if (primitive_data) {
    // Check to see if the selection data is text/html
    if (selectionTarget == gdk_atom_intern(kHTMLMime, FALSE)) {
      /*
       * "text/html" can be encoded UCS2. It is recommended that
       * documents transmitted as UCS2 always begin with a ZERO-WIDTH
       * NON-BREAKING SPACE character (hexadecimal FEFF, also called
       * Byte Order Mark (BOM)). Adding BOM can help other app to
       * detect mozilla use UCS2 encoding when copy-paste.
       */
      guchar *buffer =
          (guchar *)g_malloc((len * sizeof(guchar)) + sizeof(char16_t));
      if (!buffer) return;
      char16_t prefix = 0xFEFF;
      memcpy(buffer, &prefix, sizeof(prefix));
      memcpy(buffer + sizeof(prefix), primitive_data, len);
      g_free((guchar *)primitive_data);
      primitive_data = (guchar *)buffer;
      len += sizeof(prefix);
    }

    gtk_selection_data_set(aSelectionData, selectionTarget,
                           8, /* 8 bits in a unit */
                           (const guchar *)primitive_data, len);
    g_free(primitive_data);
  }

  g_free(target_name);
}

void nsClipboard::SelectionClearEvent(GtkClipboard *aGtkClipboard) {
  int32_t whichClipboard;

  // which clipboard?
  if (aGtkClipboard == gtk_clipboard_get(GDK_SELECTION_PRIMARY))
    whichClipboard = kSelectionClipboard;
  else if (aGtkClipboard == gtk_clipboard_get(GDK_SELECTION_CLIPBOARD))
    whichClipboard = kGlobalClipboard;
  else
    return;  // THAT AIN'T NO CLIPBOARD I EVER HEARD OF

  EmptyClipboard(whichClipboard);
}

void clipboard_get_cb(GtkClipboard *aGtkClipboard,
                      GtkSelectionData *aSelectionData, guint info,
                      gpointer user_data) {
  nsClipboard *aClipboard = static_cast<nsClipboard *>(user_data);
  aClipboard->SelectionGetEvent(aGtkClipboard, aSelectionData);
}

void clipboard_clear_cb(GtkClipboard *aGtkClipboard, gpointer user_data) {
  nsClipboard *aClipboard = static_cast<nsClipboard *>(user_data);
  aClipboard->SelectionClearEvent(aGtkClipboard);
}

/*
 * when copy-paste, mozilla wants data encoded using UCS2,
 * other app such as StarOffice use "text/html"(RFC2854).
 * This function convert data(got from GTK clipboard)
 * to data mozilla wanted.
 *
 * data from GTK clipboard can be 3 forms:
 *  1. From current mozilla
 *     "text/html", charset = utf-16
 *  2. From old version mozilla or mozilla-based app
 *     content("body" only), charset = utf-16
 *  3. From other app who use "text/html" when copy-paste
 *     "text/html", has "charset" info
 *
 * data      : got from GTK clipboard
 * dataLength: got from GTK clipboard
 * body      : pass to Mozilla
 * bodyLength: pass to Mozilla
 */
void ConvertHTMLtoUCS2(const char *data, int32_t dataLength,
                       char16_t **unicodeData, int32_t &outUnicodeLen) {
  nsAutoCString charset;
  GetHTMLCharset(data, dataLength, charset);  // get charset of HTML
  if (charset.EqualsLiteral("UTF-16")) {      // current mozilla
    outUnicodeLen = (dataLength / 2) - 1;
    *unicodeData = reinterpret_cast<char16_t *>(
        moz_xmalloc((outUnicodeLen + sizeof('\0')) * sizeof(char16_t)));
    if (*unicodeData) {
      memcpy(*unicodeData, data + sizeof(char16_t),
             outUnicodeLen * sizeof(char16_t));
      (*unicodeData)[outUnicodeLen] = '\0';
    }
  } else if (charset.EqualsLiteral("UNKNOWN")) {
    outUnicodeLen = 0;
    return;
  } else {
    // app which use "text/html" to copy&paste
    // get the decoder
    auto encoding = Encoding::ForLabelNoReplacement(charset);
    if (!encoding) {
#ifdef DEBUG_CLIPBOARD
      g_print("        get unicode decoder error\n");
#endif
      outUnicodeLen = 0;
      return;
    }
    auto decoder = encoding->NewDecoder();
    CheckedInt<size_t> needed = decoder->MaxUTF16BufferLength(dataLength);
    if (!needed.isValid() || needed.value() > INT32_MAX) {
      outUnicodeLen = 0;
      return;
    }

    outUnicodeLen = 0;
    if (needed.value()) {
      *unicodeData = reinterpret_cast<char16_t *>(
          moz_xmalloc((needed.value() + 1) * sizeof(char16_t)));
      if (*unicodeData) {
        uint32_t result;
        size_t read;
        size_t written;
        bool hadErrors;
        Tie(result, read, written, hadErrors) = decoder->DecodeToUTF16(
            AsBytes(MakeSpan(data, dataLength)),
            MakeSpan(*unicodeData, needed.value()), true);
        MOZ_ASSERT(result == kInputEmpty);
        MOZ_ASSERT(read == size_t(dataLength));
        MOZ_ASSERT(written <= needed.value());
        Unused << hadErrors;
#ifdef DEBUG_CLIPBOARD
        if (read != dataLength) printf("didn't consume all the bytes\n");
#endif
        outUnicodeLen = written;
        // null terminate.
        (*unicodeData)[outUnicodeLen] = '\0';
      }
    }  // if valid length
  }
}

/*
 * get "charset" information from clipboard data
 * return value can be:
 *  1. "UTF-16":      mozilla or "text/html" with "charset=utf-16"
 *  2. "UNKNOWN":     mozilla can't detect what encode it use
 *  3. other:         "text/html" with other charset than utf-16
 */
void GetHTMLCharset(const char *data, int32_t dataLength, nsCString &str) {
  // if detect "FFFE" or "FEFF", assume UTF-16
  char16_t *beginChar = (char16_t *)data;
  if ((beginChar[0] == 0xFFFE) || (beginChar[0] == 0xFEFF)) {
    str.AssignLiteral("UTF-16");
    return;
  }
  // no "FFFE" and "FEFF", assume ASCII first to find "charset" info
  const nsDependentCString htmlStr(data, dataLength);
  nsACString::const_iterator start, end;
  htmlStr.BeginReading(start);
  htmlStr.EndReading(end);
  nsACString::const_iterator valueStart(start), valueEnd(start);

  if (CaseInsensitiveFindInReadable(NS_LITERAL_CSTRING("CONTENT=\"text/html;"),
                                    start, end)) {
    start = end;
    htmlStr.EndReading(end);

    if (CaseInsensitiveFindInReadable(NS_LITERAL_CSTRING("charset="), start,
                                      end)) {
      valueStart = end;
      start = end;
      htmlStr.EndReading(end);

      if (FindCharInReadable('"', start, end)) valueEnd = start;
    }
  }
  // find "charset" in HTML
  if (valueStart != valueEnd) {
    str = Substring(valueStart, valueEnd);
    ToUpperCase(str);
#ifdef DEBUG_CLIPBOARD
    printf("Charset of HTML = %s\n", charsetUpperStr.get());
#endif
    return;
  }
  str.AssignLiteral("UNKNOWN");
}