zstream->next_in   = NULL;
    zstream->next_out  = NULL;
    zstream->avail_in  = 0;
    zstream->avail_out = 0;

    zip->memory = NULL;
    zip->source = NULL;
    zip->stream = NULL;
  }


  static FT_Error
  ft_gzip_file_reset( FT_GZipFile  zip )
  {
    FT_Stream  stream = zip->source;
    FT_Error   error;


    if ( !FT_STREAM_SEEK( zip->start ) )
    {
      z_stream*  zstream = &zip->zstream;


      inflateReset( zstream );

      zstream->avail_in  = 0;
      zstream->next_in   = zip->input;
      zstream->avail_out = 0;
      zstream->next_out  = zip->buffer;

      zip->limit  = zip->buffer + FT_GZIP_BUFFER_SIZE;
      zip->cursor = zip->limit;
      zip->pos    = 0;
    }

    return error;
  }


  static FT_Error
  ft_gzip_file_fill_input( FT_GZipFile  zip )
  {
    z_stream*  zstream = &zip->zstream;
    FT_Stream  stream  = zip->source;
    FT_ULong   size;


    if ( stream->read )
    {
      size = stream->read( stream, stream->pos, zip->input,
                           FT_GZIP_BUFFER_SIZE );
      if ( size == 0 )
        return Gzip_Err_Invalid_Stream_Operation;
    }
    else
    {
      size = stream->size - stream->pos;
      if ( size > FT_GZIP_BUFFER_SIZE )
        size = FT_GZIP_BUFFER_SIZE;

      if ( size == 0 )
        return Gzip_Err_Invalid_Stream_Operation;

      FT_MEM_COPY( zip->input, stream->base + stream->pos, size );
    }
    stream->pos += size;

    zstream->next_in  = zip->input;
    zstream->avail_in = size;

    return Gzip_Err_Ok;
  }


  static FT_Error
  ft_gzip_file_fill_output( FT_GZipFile  zip )
  {
    z_stream*  zstream = &zip->zstream;
    FT_Error   error   = 0;


    zip->cursor        = zip->buffer;
    zstream->next_out  = zip->cursor;
    zstream->avail_out = FT_GZIP_BUFFER_SIZE;

    while ( zstream->avail_out > 0 )
    {
      int  err;


      if ( zstream->avail_in == 0 )
      {
        error = ft_gzip_file_fill_input( zip );
        if ( error )
          break;
      }

      err = inflate( zstream, Z_NO_FLUSH );

      if ( err == Z_STREAM_END )
      {
        zip->limit = zstream->next_out;
        if ( zip->limit == zip->cursor )
          error = Gzip_Err_Invalid_Stream_Operation;
        break;
      }
      else if ( err != Z_OK )
      {
        error = Gzip_Err_Invalid_Stream_Operation;
        break;
      }
    }

    return error;
  }


  /* fill output buffer; `count' must be <= FT_GZIP_BUFFER_SIZE */
  static FT_Error
  ft_gzip_file_skip_output( FT_GZipFile  zip,
                            FT_ULong     count )
  {
    FT_Error  error = Gzip_Err_Ok;
    FT_ULong  delta;


    for (;;)
    {
      delta = (FT_ULong)( zip->limit - zip->cursor );
      if ( delta >= count )
        delta = count;

      zip->cursor += delta;
      zip->pos    += delta;

      count -= delta;
      if ( count == 0 )
        break;

      error = ft_gzip_file_fill_output( zip );
      if ( error )
        break;
    }

    return error;
  }


  static FT_ULong
  ft_gzip_file_io( FT_GZipFile  zip,
                   FT_ULong     pos,
                   FT_Byte*     buffer,
                   FT_ULong     count )
  {
    FT_ULong  result = 0;
    FT_Error  error;


    /* Reset inflate stream if we're seeking backwards.        */
    /* Yes, that is not too efficient, but it saves memory :-) */
    if ( pos < zip->pos )
    {
      error = ft_gzip_file_reset( zip );
      if ( error )
        goto Exit;
    }

    /* skip unwanted bytes */
    if ( pos > zip->pos )
    {
      error = ft_gzip_file_skip_output( zip, (FT_ULong)( pos - zip->pos ) );
      if ( error )
        goto Exit;
    }

    if ( count == 0 )
      goto Exit;

    /* now read the data */
    for (;;)
    {
      FT_ULong  delta;


      delta = (FT_ULong)( zip->limit - zip->cursor );
      if ( delta >= count )
        delta = count;

      FT_MEM_COPY( buffer, zip->cursor, delta );
      buffer      += delta;
      result      += delta;
      zip->cursor += delta;
      zip->pos    += delta;

      count -= delta;
      if ( count == 0 )
        break;

      error = ft_gzip_file_fill_output( zip );
      if ( error )
        break;
    }

  Exit:
    return result;
  }


/***************************************************************************/
/***************************************************************************/
/*****                                                                 *****/
/*****               G Z   E M B E D D I N G   S T R E A M             *****/
/*****                                                                 *****/
/***************************************************************************/
/***************************************************************************/

  static void
  ft_gzip_stream_close( FT_Stream  stream )
  {
    FT_GZipFile  zip    = (FT_GZipFile)stream->descriptor.pointer;
    FT_Memory    memory = stream->memory;


    if ( zip )
    {
      /* finalize gzip file descriptor */
      ft_gzip_file_done( zip );

      FT_FREE( zip );

      stream->descriptor.pointer = NULL;
    }
  }


  static FT_ULong
  ft_gzip_stream_io( FT_Stream  stream,
                     FT_ULong   pos,
                     FT_Byte*   buffer,
                     FT_ULong   count )
  {
    FT_GZipFile  zip = (FT_GZipFile)stream->descriptor.pointer;


    return ft_gzip_file_io( zip, pos, buffer, count );
  }


  FT_EXPORT_DEF( FT_Error )
  FT_Stream_OpenGzip( FT_Stream  stream,
                      FT_Stream  source )
  {
    FT_Error     error;
    FT_Memory    memory = source->memory;
    FT_GZipFile  zip;


    /*
     *  check the header right now; this prevents allocating un-necessary
     *  objects when we don't need them
     */
    error = ft_gzip_check_header( source );
    if ( error )
      goto Exit;

    FT_ZERO( stream );
    stream->memory = memory;

    if ( !FT_QNEW( zip ) )
    {
      error = ft_gzip_file_init( zip, stream, source );
      if ( error )
      {
        FT_FREE( zip );
        goto Exit;
      }

      stream->descriptor.pointer = zip;
    }

    stream->size  = 0x7FFFFFFFL;  /* don't know the real size! */
    stream->pos   = 0;
    stream->base  = 0;
    stream->read  = ft_gzip_stream_io;
    stream->close = ft_gzip_stream_close;

  Exit:
    return error;
  }

#else  /* !FT_CONFIG_OPTION_USE_ZLIB */

  FT_EXPORT_DEF( FT_Error )
  FT_Stream_OpenGzip( FT_Stream  stream,
                      FT_Stream  source )
  {
    FT_UNUSED( stream );
    FT_UNUSED( source );

    return Gzip_Err_Unimplemented_Feature;
  }

#endif /* !FT_CONFIG_OPTION_USE_ZLIB */


/* END */