+#ifdef PNG_READ_APNG_SUPPORTED
+void /* PRIVATE */
+png_handle_acTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+ png_byte data[8];
+ png_uint_32 num_frames;
+ png_uint_32 num_plays;
+ png_uint_32 didSet;
+
+ png_debug(1, "in png_handle_acTL");
+
+ if (!(png_ptr->mode & PNG_HAVE_IHDR))
+ {
+ png_error(png_ptr, "Missing IHDR before acTL");
+ }
+ else if (png_ptr->mode & PNG_HAVE_IDAT)
+ {
+ png_warning(png_ptr, "Invalid acTL after IDAT skipped");
+ png_crc_finish(png_ptr, length);
+ return;
+ }
+ else if (png_ptr->mode & PNG_HAVE_acTL)
+ {
+ png_warning(png_ptr, "Duplicate acTL skipped");
+ png_crc_finish(png_ptr, length);
+ return;
+ }
+ else if (length != 8)
+ {
+ png_warning(png_ptr, "acTL with invalid length skipped");
+ png_crc_finish(png_ptr, length);
+ return;
+ }
+
+ png_crc_read(png_ptr, data, 8);
+ png_crc_finish(png_ptr, 0);
+
+ num_frames = png_get_uint_31(png_ptr, data);
+ num_plays = png_get_uint_31(png_ptr, data + 4);
+
+ /* the set function will do error checking on num_frames */
+ didSet = png_set_acTL(png_ptr, info_ptr, num_frames, num_plays);
+ if(didSet)
+ png_ptr->mode |= PNG_HAVE_acTL;
+}
+
+void /* PRIVATE */
+png_handle_fcTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+ png_byte data[22];
+ png_uint_32 width;
+ png_uint_32 height;
+ png_uint_32 x_offset;
+ png_uint_32 y_offset;
+ png_uint_16 delay_num;
+ png_uint_16 delay_den;
+ png_byte dispose_op;
+ png_byte blend_op;
+
+ png_debug(1, "in png_handle_fcTL");
+
+ png_ensure_sequence_number(png_ptr, length);
+
+ if (!(png_ptr->mode & PNG_HAVE_IHDR))
+ {
+ png_error(png_ptr, "Missing IHDR before fcTL");
+ }
+ else if (png_ptr->mode & PNG_HAVE_IDAT)
+ {
+ /* for any frames other then the first this message may be misleading,
+ * but correct. PNG_HAVE_IDAT is unset before the frame head is read
+ * i can't think of a better message */
+ png_warning(png_ptr, "Invalid fcTL after IDAT skipped");
+ png_crc_finish(png_ptr, length-4);
+ return;
+ }
+ else if (png_ptr->mode & PNG_HAVE_fcTL)
+ {
+ png_warning(png_ptr, "Duplicate fcTL within one frame skipped");
+ png_crc_finish(png_ptr, length-4);
+ return;
+ }
+ else if (length != 26)
+ {
+ png_warning(png_ptr, "fcTL with invalid length skipped");
+ png_crc_finish(png_ptr, length-4);
+ return;
+ }
+
+ png_crc_read(png_ptr, data, 22);
+ png_crc_finish(png_ptr, 0);
+
+ width = png_get_uint_31(png_ptr, data);
+ height = png_get_uint_31(png_ptr, data + 4);
+ x_offset = png_get_uint_31(png_ptr, data + 8);
+ y_offset = png_get_uint_31(png_ptr, data + 12);
+ delay_num = png_get_uint_16(data + 16);
+ delay_den = png_get_uint_16(data + 18);
+ dispose_op = data[20];
+ blend_op = data[21];
+
+ if (png_ptr->num_frames_read == 0 && (x_offset != 0 || y_offset != 0))
+ {
+ png_warning(png_ptr, "fcTL for the first frame must have zero offset");
+ return;
+ }
+
+ if (info_ptr != NULL)
+ {
+ if (png_ptr->num_frames_read == 0 &&
+ (width != info_ptr->width || height != info_ptr->height))
+ {
+ png_warning(png_ptr, "size in first frame's fcTL must match "
+ "the size in IHDR");
+ return;
+ }
+
+ /* The set function will do more error checking */
+ png_set_next_frame_fcTL(png_ptr, info_ptr, width, height,
+ x_offset, y_offset, delay_num, delay_den,
+ dispose_op, blend_op);
+
+ png_read_reinit(png_ptr, info_ptr);
+
+ png_ptr->mode |= PNG_HAVE_fcTL;
+ }
+}
+
+void /* PRIVATE */
+png_have_info(png_structp png_ptr, png_infop info_ptr)
+{
+ if((info_ptr->valid & PNG_INFO_acTL) && !(info_ptr->valid & PNG_INFO_fcTL))
+ {
+ png_ptr->apng_flags |= PNG_FIRST_FRAME_HIDDEN;
+ info_ptr->num_frames++;
+ }
+}
+
+void /* PRIVATE */
+png_handle_fdAT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+ png_ensure_sequence_number(png_ptr, length);
+
+ /* This function is only called from png_read_end(), png_read_info(),
+ * and png_push_read_chunk() which means that:
+ * - the user doesn't want to read this frame
+ * - or this is an out-of-place fdAT
+ * in either case it is safe to ignore the chunk with a warning */
+ png_warning(png_ptr, "ignoring fdAT chunk");
+ png_crc_finish(png_ptr, length - 4);
+ PNG_UNUSED(info_ptr)
+}
+
+void /* PRIVATE */
+png_ensure_sequence_number(png_structp png_ptr, png_uint_32 length)
+{
+ png_byte data[4];
+ png_uint_32 sequence_number;
+
+ if (length < 4)
+ png_error(png_ptr, "invalid fcTL or fdAT chunk found");
+
+ png_crc_read(png_ptr, data, 4);
+ sequence_number = png_get_uint_31(png_ptr, data);
+
+ if (sequence_number != png_ptr->next_seq_num)
+ png_error(png_ptr, "fcTL or fdAT chunk with out-of-order sequence "
+ "number found");
+
+ png_ptr->next_seq_num++;
+}
+#endif /* PNG_READ_APNG_SUPPORTED */
+