#!/usr/bin/tcc -run

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <err.h>
#include <sysexits.h>

/* Remoe 0xff bytes from the end of argv[1] */

int main(int argc, char** argv)
{
	int fd;
	struct stat s;
	char *m;
	size_t i;

	argc >= 2                        || err(EX_USAGE, "usage: dstrim file");
	(fd = open(argv[1], O_RDWR)) > 0 || err(EX_NOINPUT, "open");
	fstat(fd, &s)               == 0 || err(EX_NOINPUT, "fstat");
	(m = mmap(NULL, s.st_size,
	          PROT_READ, MAP_SHARED,
	          fd, 0))  != MAP_FAILED || err(EX_NOINPUT, "mmap");
	for(i = s.st_size - 1; i > 0 && m[i] == '\xff'; --i);
	printf("File size:\t%9d\nData size:\t%9d\nJunk space:\t%9d\n",
	              s.st_size,             i+1, s.st_size - (i+1)   );
	munmap(m, s.st_size) == 0 || err(EX_OSERR, "munmap");
	ftruncate(fd, i+1)   == 0 || err(EX_OSERR, "truncate");
	close(fd)            == 0 || err(EX_OSERR, "close");
}