/* mpcimg.c                                               vi: se ts=8 sw=8: */

/* Written by Peter Backes.
 *
 * Copyright abandoned.
 */

#include <stdio.h>
#include <string.h> /* strpcy(), strcmp() */
#include <stdlib.h> /* strtoul(), #EXIT_FAILURE, #EXIT_SUCCESS */


#define MPCIMG_MAGIC 0x7f309ac5UL   /* MPC image header magic. */

/* MPC image header structure.
 *
 * If you input the drive size in megabytes on creating the image,
 * then hdrsiz is initialized with 64, imgsiz with 
 * drive size in megabytes times 1024000, secsiz with 512,
 * nsecs with drive size in megabytes times 2000 and resvd all with
 * zero.
 */
struct mpchdr {
	unsigned long magic, /* MPCI_MAGIC */
		hdrsiz,      /* Size of the header in bytes, usually 64. */
		imgsiz,      /* Size of the image behind the header. */
		secsiz,      /* Sector size in bytes, usually 512. */
		nsecs,       /* Total sector count. */
		resvd[11];   /* Reserved. */
};

#if BUFSIZ < 64
#error BUFSIZ must be at least 64.
#endif
/* Intel pop */
#define popi32b(d, s) (d = *s++, d |= *s++ << 8, \
	d |= *s++ << 16, d |= *s++ << 24)
/* Intel push */
#define pushi32b(d, s) (*d++ = s & 0xFFUL, *d++ = (s & 0xFF00UL) >> 8, \
	*d++ = (s & 0xFF0000UL) >> 16, *d++ = (s & 0xFF000000UL) >> 24);

int fcopy(unsigned char *buf, FILE *is, FILE *os,
	unsigned long s, unsigned long n)
{
	while (n-- > 0)
		if (fread(buf, s, 1, is) != 1 || fwrite(buf, s, 1, os) != 1)
			return 1;
	return 0;
}

int extract(FILE *is, FILE *os, unsigned long s, unsigned long n)
{
	unsigned char buf[BUFSIZ], *t = buf;
	struct mpchdr h;

	if (fread(buf, 64, 1, is) != 1)
		return 1;

	popi32b(h.magic, t);
	popi32b(h.hdrsiz, t);
	popi32b(h.imgsiz, t);
	popi32b(h.secsiz, t);
	popi32b(h.nsecs, t);
	popi32b(h.resvd[0], t);
	popi32b(h.resvd[1], t);
	popi32b(h.resvd[2], t);
	popi32b(h.resvd[3], t);
	popi32b(h.resvd[4], t);
	popi32b(h.resvd[5], t);
	popi32b(h.resvd[6], t);
	popi32b(h.resvd[7], t);
	popi32b(h.resvd[8], t);
	popi32b(h.resvd[9], t);
	popi32b(h.resvd[10], t);

	if (h.magic != MPCIMG_MAGIC || h.hdrsiz != 64
	 || h.secsiz > BUFSIZ || !h.secsiz)
		return 1;

	return fcopy(buf, is, os, h.secsiz, h.nsecs);
}

int store(FILE *is, FILE *os, unsigned long s, unsigned long n)
{
	unsigned char buf[BUFSIZ], *t = buf;
	struct mpchdr h = {MPCIMG_MAGIC, 64UL, 0UL, 0UL, 0UL, {0UL}};
	if (s > BUFSIZ)
		return 0;
	if (!n) {
		long len;
		if (fseek(is, 0, SEEK_END) == -1 || (len = ftell(is)) == -1
		 || len % s)
			return 1;
		rewind(is);
		n = len / s;
	}
	h.secsiz = s;
	h.imgsiz = n * s;
	h.nsecs = n;

	pushi32b(t, h.magic);
	pushi32b(t, h.hdrsiz);
	pushi32b(t, h.imgsiz);
	pushi32b(t, h.secsiz);
	pushi32b(t, h.nsecs);
	pushi32b(t, h.resvd[0]);
	pushi32b(t, h.resvd[1]);
	pushi32b(t, h.resvd[2]);
	pushi32b(t, h.resvd[3]);
	pushi32b(t, h.resvd[4]);
	pushi32b(t, h.resvd[5]);
	pushi32b(t, h.resvd[6]);
	pushi32b(t, h.resvd[7]);
	pushi32b(t, h.resvd[8]);
	pushi32b(t, h.resvd[9]);
	pushi32b(t, h.resvd[10]);
	
	if (fwrite(buf, 64, 1, os) != 1)
		return 1;

	return fcopy(buf, is, os, s, n);
}

int main(int argc, char *argv[])
{
	unsigned long s = 512, n = 0;
	FILE *is, *os;
	int optind;
	for (optind = 1; optind < argc; optind++) {
		int (*f)(FILE *, FILE *, unsigned long, unsigned long);
		char *ep, *suf;
		int err;
		if (*argv[optind] == '-')
			switch (argv[optind][1]) {
				char *optarg;
			case 's': /* Set sector size */
				if (!(optarg = argv[++optind]))
					return EXIT_FAILURE;
				s = strtoul(optarg, NULL, 10);
				continue;
			case 'n': /* Set sector count */
				if (!(optarg = argv[++optind]))
					return EXIT_FAILURE;
				n = strtoul(optarg, NULL, 10);
				continue;
			default:
				return EXIT_FAILURE;
			}
		if (!(ep = strrchr(argv[optind], '.'))) {
			fprintf(stderr, "Unidentifiable suffix on %s.\n", 
				argv[optind]);
			return EXIT_FAILURE;
		}
		if (!strcmp(ep, ".img")) {
			suf = ".mpc";
			f = &store;
		} else if (!strcmp(ep, ".mpc")) {
			suf = ".img";
			f = &extract;
		} else {
			fprintf(stderr, "Unrecognized suffix on %s.\n",
				argv[optind]);
			return EXIT_FAILURE;
		}
		if (!(is = fopen(argv[optind], "rb"))) {
			fprintf(stderr, "Coudln't open %s.\n", argv[optind]);
			return EXIT_FAILURE;
		}
		strcpy(ep, suf);
		if (!(os = fopen(argv[optind], "wb"))) {
			fclose(is);
			fprintf(stderr, "Couldn't open %s.\n", argv[optind]);
			return EXIT_FAILURE;
		}
		err = f(is, os, s, n);
		fclose(os);
		fclose(is);
		if (err) {
			fprintf(stderr, "Processing error.\n");
			return EXIT_FAILURE;
		}
	}
	return EXIT_SUCCESS;
}