/*
 * bootpage.c is a modified version of:
 *   $Id: tpip.c,v 1.19 2004/01/12 03:12:34 millert Exp $
 *
 * Copyright (c) 2003-2004 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <fcntl.h>

#if BYTE_ORDER == BIG_ENDIAN
# define TIVO_BOOT_MAGIC	0x1492
# define MAC_PARTITION_MAGIC	0x504d
#elif BYTE_ORDER == LITTLE_ENDIAN
# define TIVO_BOOT_MAGIC	0x9214
# define MAC_PARTITION_MAGIC	0x4d50
#else
# error Unknown byte order!
#endif
#define	HOST_BYTE_ORDER		BYTE_ORDER

struct tcdbootpage {
	/*
	 * NOTE: values are stored in network byte order (little endian)
	 */
	u_int16_t signature;
	u_int8_t  primaryBootPartition;
	u_int8_t  alternateBootPartition;
	char	  bootParams[128];
	char	  padding[380];		/* we don't need the other bits */
};

int TIVO_BYTE_ORDER;

char *bootpage(const char *device) {
	int fd;
	struct tcdbootpage *bootpg, bpbuf[2];

	if ((fd = open(device, O_RDWR, 0644)) == -1)
		err(1, "error opening %s", device);

	/* read the TiVo boot page */
	bootpg = &bpbuf[0];
	switch (read(fd, bootpg, sizeof(struct tcdbootpage))) {
	case -1:
		fprintf(stderr, "error reading from %s", device);
		return NULL;
	case sizeof(struct tcdbootpage):
		/* OK */
		break;
	default:
		fprintf(stderr, "%s: short read", device);
		return NULL;
	}

	if (bootpg->signature == TIVO_BOOT_MAGIC) {
		TIVO_BYTE_ORDER = HOST_BYTE_ORDER;
	} else if (bootpg->signature == cpu_to_be16(TIVO_BOOT_MAGIC)) {
		// TiVo disk is byte-swapped
		#if HOST_BYTE_ORDER == BIG_ENDIAN
			TIVO_BYTE_ORDER = LITTLE_ENDIAN;
		#else
			TIVO_BYTE_ORDER = BIG_ENDIAN;
		#endif
		swab((char *)&bpbuf[0], (char *)&bpbuf[1],
		    sizeof(struct tcdbootpage));
		bootpg = &bpbuf[1];
	} else if (bootpg->signature != TIVO_BOOT_MAGIC) {
		fprintf(stderr, "unknown bootpage signature: 0x%x", bootpg->signature);
		return NULL;
	}

	fsync(fd);

	return bootpg->bootParams;
}