$NetBSD: patch-ac,v 1.1 2006/04/19 17:02:22 wiz Exp $

--- png_write_sig.c.orig	2006-04-19 15:45:16.000000000 +0200
+++ png_write_sig.c
@@ -0,0 +1,61 @@
+/* png_write_sig.c from libpng-1.2.9 */
+
+/* pngwutil.c - utilities to write a PNG file
+ *
+ * Last changed in libpng 1.2.9 April 14, 2006
+ * For conditions of distribution and use, see copyright notice in png.h
+ * Copyright (c) 1998-2006 Glenn Randers-Pehrson
+ * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+ * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ */
+
+#define PNG_INTERNAL
+#include "png.h"
+
+/* Simple function to write the signature.  If we have already written
+ * the magic bytes of the signature, or more likely, the PNG stream is
+ * being embedded into another stream and doesn't need its own signature,
+ * we should call png_set_sig_bytes() to tell libpng how many of the
+ * bytes have already been written.
+ */
+void /* PRIVATE */
+png_write_sig(png_structp png_ptr)
+{
+   png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
+   /* write the rest of the 8 byte signature */
+   png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
+      (png_size_t)8 - png_ptr->sig_bytes);
+   if(png_ptr->sig_bytes < 3)
+      png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
+}
+
+/* pngwio.c - functions for data output
+ *
+ * Last changed in libpng 1.2.3 - May 21, 2002
+ * For conditions of distribution and use, see copyright notice in png.h
+ * Copyright (c) 1998-2002 Glenn Randers-Pehrson
+ * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+ * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ *
+ * This file provides a location for all output.  Users who need
+ * special handling are expected to write functions that have the same
+ * arguments as these and perform similar functions, but that possibly
+ * use different output methods.  Note that you shouldn't change these
+ * functions, but rather write replacement functions and then change
+ * them at run time with png_set_write_fn(...).
+ */
+
+/* Write the data to whatever output you are using.  The default routine
+   writes to a file pointer.  Note that this routine sometimes gets called
+   with very small lengths, so you should implement some kind of simple
+   buffering if you are using unbuffered writes.  This should never be asked
+   to write more than 64K on a 16 bit machine.  */
+
+void /* PRIVATE */
+png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
+{
+   if (png_ptr->write_data_fn != NULL )
+      (*(png_ptr->write_data_fn))(png_ptr, data, length);
+   else
+      png_error(png_ptr, "Call to NULL write function");
+}