XFA: Upgrade libpng to 1.6.20.

third_party/libpng/pngrio.c

+
 /* pngrio.c - functions for data input
  *
- * Last changed in libpng 1.6.0 [February 14, 2013]
- * Copyright (c) 1998-2013 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.17 [March 26, 2015]
+ * Copyright (c) 1998-2015 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 code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
  *
  * This file provides a location for all input.  Users who need
  * special handling are expected to write a function that has the same
  * arguments as this and performs a similar function, but that possibly
  * has a different input method.  Note that you shouldn't change this
  * function, but rather write a replacement function and then make
  * libpng use it at run time with png_set_read_fn(...).
  */
 
 #include "pngpriv.h"
 
 #ifdef PNG_READ_SUPPORTED
 
 /* Read the data from whatever input you are using.  The default routine
  * reads from 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 reads.  This should never be asked
- * to read more then 64K on a 16 bit machine.
+ * to read more than 64K on a 16-bit machine.
  */
 void /* PRIVATE */
 png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
 {
    png_debug1(4, "reading %d bytes", (int)length);
 
    if (png_ptr->read_data_fn != NULL)
       (*(png_ptr->read_data_fn))(png_ptr, data, length);
 
    else
@@ skipping 55 matching lines @@
 #ifdef PNG_STDIO_SUPPORTED
    if (read_data_fn != NULL)
       png_ptr->read_data_fn = read_data_fn;
 
    else
       png_ptr->read_data_fn = png_default_read_data;
 #else
    png_ptr->read_data_fn = read_data_fn;
 #endif
 
+#ifdef PNG_WRITE_SUPPORTED
    /* It is an error to write to a read device */
    if (png_ptr->write_data_fn != NULL)
    {
       png_ptr->write_data_fn = NULL;
       png_warning(png_ptr,
           "Can't set both read_data_fn and write_data_fn in the"
           " same structure");
    }
+#endif
 
 #ifdef PNG_WRITE_FLUSH_SUPPORTED
    png_ptr->output_flush_fn = NULL;
 #endif
 }
-#endif /* PNG_READ_SUPPORTED */
+#endif /* READ */