METHODDEF(void)
init_source (j_decompress_ptr cinfo)
{
}

METHODDEF(boolean)
fill_input_buffer(j_decompress_ptr cinfo)
{
  return TRUE;
}

METHODDEF(void)
skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
  if (num_bytes >  0 )
  {
    cinfo->src->next_input_byte += (size_t) num_bytes;
    cinfo->src->bytes_in_buffer -= (size_t) num_bytes;
  }
}
METHODDEF(void)
term_source (j_decompress_ptr cinfo)
{
}

...

 cinfo.src->init_source = init_source;
 cinfo.src->fill_input_buffer = fill_input_buffer;
 cinfo.src->skip_input_data = skip_input_data;
 cinfo.src->resync_to_restart = jpeg_resync_to_restart; /* use default method */
 cinfo.src->term_source = term_source;
 cinfo.src->bytes_in_buffer = files[cfc].second;
 cinfo.src->next_input_byte = files[cfc].first;

...