Support for writing MBR in the system area, to make hybrid boot images.

With the specified isolinux option, a MBR is written to the system area, and this 
allows the image to boot from either CD/DVD or USB sticks.

This is also supported on overwriteable media (note that system area is always
overwritten), but it should not work on multisession media.

libisofs/system_area.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2008 Vreixo Formoso
+ *
+ * This file is part of the libisofs project; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation. See COPYING file for details.
+ */
+
+/*
+ * Functions for dealing with the system area, this is, the first 16 blocks
+ * of the image.
+ *
+ * At this time, this is only used for hybrid boot images with isolinux.
+ */
+
+#ifndef SYSTEM_AREA_H_
+#define SYSTEM_AREA_H_
+
+#include "ecma119.h"
+
+/*
+ * Create a MBR for an isohybrid enabled ISOLINUX boot image.
+ *
+ * It is assumed that the caller has verified the readiness of the boot image
+ * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin.
+ *
+ * @param bin_lba    The predicted LBA of isolinux.bin within the emerging ISO.
+ * @param img_blocks The predicted number of 2048 byte blocks in the ISO.
+ *                   It will get rounded up to full MBs and that many blocks
+ *                   must really be written as ISO 9660 image.
+ * @param mbr        A buffer of at least 512 bytes to take the result which is
+ *                   to be written as the very beginning of the ISO.
+ * @param flag    unused yet, submit 0
+ * @return  <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning
+ */
+int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
+
+/**
+ * Write the system area for the given image to the given buffer.
+ *
+ * @param buf
+ *      A buffer with at least 32 K allocated
+ * @return
+ *      1 if success, < 0 on error
+ */
+int iso_write_system_area(Ecma119Image *t, uint8_t *buf);
+
+#endif /* SYSTEM_AREA_H_ */