/* Copyright (c) 2007 Peter O'Gorman <peter@pogma.com> 
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <sys/types.h>
#include <inttypes.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <stdio.h>
#include <unistd.h>
#include <mach-o/fat.h>
#include <mach-o/loader.h>
#include <stdlib.h>
#include <sys/errno.h>


uint32_t cur_ver = 0;
uint32_t com_ver = 0;
int swap=0;
/* This function stolen from Apple's ld64 sources - licensed APSL */
uint32_t version_num(const char * string)
{
	unsigned long x = 0;
	unsigned long y = 0;
	unsigned long z = 0;
	char* end;
	x = strtoul(string, &end, 10);
	if ( *end == '.' ) {
		y = strtoul(&end[1], &end, 10);
		if ( *end == '.' ) {
			z = strtoul(&end[1], &end, 10);
		}
	}
	return (x << 16) | ( y << 8 ) | z;
}

void adjust_version(struct mach_header * in)
{
	char * pointer;
	int x = in->ncmds;
	if ((in->magic == MH_MAGIC) || (in->magic == MH_CIGAM))
		pointer = (char*)in + sizeof(struct mach_header);
	else if ((in->magic == MH_MAGIC_64) || (in->magic == MH_CIGAM_64))
		pointer = (char*)in + sizeof(struct mach_header_64);
	else {fprintf(stderr,"dead\n"); exit(1);}
	if ((in->magic == MH_CIGAM) || (in->magic == MH_CIGAM_64))
		 swap=1;
	else swap=0;
	if (swap) {
		x=OSSwapInt32(in->ncmds);
	}
	do {
		if (swap) {
			if (LC_ID_DYLIB == OSSwapInt32(((struct load_command *)pointer)->cmd)) {
				pointer += sizeof(struct load_command);
				((struct dylib *)pointer)->current_version = OSSwapInt32(cur_ver);
				((struct dylib *)pointer)->compatibility_version = OSSwapInt32(com_ver);
				x = 0;
			} else { 
				pointer += OSSwapInt32(((struct load_command *)pointer)->cmdsize);
				x--;
			}
		} else {
			if (LC_ID_DYLIB == ((struct load_command *)pointer)->cmd) {
				pointer += sizeof(struct load_command);
				((struct dylib *)pointer)->current_version = cur_ver;
				((struct dylib *)pointer)->compatibility_version = com_ver;
				x = 0;
			} else { 
				pointer += ((struct load_command *)pointer)->cmdsize;
				x--;
			}
		}
	} while (x);
}
void usage(void) {
	fprintf(stderr,"Usage:\n%s <filename> <compatibility_version> <current_version>\n",getprogname());
}
int main(int argc, const char * argv[])
{
	int fd = 0;
	ssize_t bytesread = 0;
	size_t bytes = 0;
	struct stat sbuf;
	void * buffer;
	if (argc != 4) {
		fprintf(stderr,"Incorrect number of arguments\n");
		usage();
		exit(1);
	}
	if (stat(argv[1],&sbuf)) {
		fprintf(stderr,"File does not exist\n");
		usage();
		exit(1);
	}

	com_ver = version_num(argv[2]);
	cur_ver = version_num(argv[3]);
		
	if (!(fd = open(argv[1],O_RDWR | O_EXCL ,sbuf.st_mode))) {
		fprintf(stderr,"OPen failed %s\n",strerror(errno));
		exit (1);
	}
	bytes = sbuf.st_size;
	buffer = malloc(bytes);
	if (!buffer) { 
		fprintf(stderr,"Failed to allocate %d bytes\n",bytes);
		exit(1);
	}
		
	do {
		bytesread = read(fd,buffer,bytes);
		if (bytesread == -1) {
			fprintf(stderr,"Error %s\n",strerror(errno));
			exit(1);
		}
		else if (bytesread == 0)
			bytes = 0;
		else
			bytes -= bytesread;
	} while (bytes);
	if (lseek(fd,0,SEEK_SET)) {
		fprintf(stderr,"Failed to seek to beginning of file\n");
		exit(1);
	}

	if ((((struct fat_header*)buffer)->magic == FAT_MAGIC) ||
		(((struct fat_header*)buffer)->magic == FAT_CIGAM)) {
		struct fat_header * fh = (struct fat_header*)buffer;
		uint32_t num_arches = fh->nfat_arch;
		struct fat_arch * arch= (struct fat_arch *)((char*)buffer + sizeof(struct fat_header));
#ifdef __LITTLE_ENDIAN__
		num_arches = OSSwapInt32(fh->nfat_arch);
#endif
		do {
#ifdef __LITTLE_ENDIAN__
			adjust_version((struct mach_header*)((char*)buffer + OSSwapInt32(arch->offset)));
#else
			adjust_version((struct mach_header*)((char*)buffer + arch->offset));
#endif
			arch++;
			num_arches--;
		} while(num_arches);
	 } else
		adjust_version(buffer);

		bytes = 0;

		do {
			bytes += write(fd,buffer,sbuf.st_size - bytes);
	} while (sbuf.st_size - bytes);

	if (fd) close(fd);
	fd = 0;
	return 0;
}