//cut macBinary
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

#define uchar unsigned char
#define ulong unsigned long
#define FILENAMELEN 256

void errexit(char *s){
    fprintf(stderr, "err: %s\n", s);
    exit(1);
}

// network order(Big Endian) to host order(Big/Little Endian); unsigned long
ulong ntohl(ulong ul){
    static int endian = 0;

    // initialize
    if(endian==0){
	long n = 0x12345678;
	if(*(char *)(&n) == 0x12)
	    endian = 1; //big endian, MSBfirst
	else
	    endian = 2; //little endian, LSBfirst
	//printf("endian=%s\n", (endian==1)?"BigEndian":"LittleEndian");
    }

    if(endian == 1){
	// Big to Big
	return ul;
    }else{
	// Big to Little
	uchar c[4];
	int i;
	for(i=0; i<4; i++){
	    uchar *p = (uchar *)&ul;
	    *(c+3-i) = *(p+i);
	}
	return *(ulong*)c;
    }
}


int main(int argc, char *argv[]){
    FILE *fin, *fout;
    struct stat info;
    uchar *p;
    ulong headlen, newflen;
    char newfname[FILENAMELEN];
    int i;

    if(argc != 2)
	errexit("macbincut filename");

    /*
     * file open & read all
     */
    if((fin=fopen(argv[1],"rb")) == NULL)
	errexit("fopen");
    if(stat(argv[1], &info) != 0)
	errexit("stat");
    if((p=malloc(info.st_size)) == NULL)
	errexit("malloc");
    if(fread(p, 1, info.st_size, fin) != info.st_size)
	errexit("fread");
    fclose(fin);    

    /*
     * is mac header?
     */
    if(*p!=0 || *(p+74)!=0 || *(p+82)!=0)
	errexit("This file don't have mac header. 1");	
    for(i=108; i<=115; i++){
	if(*(p+i)!=0)
	    errexit("This file don't have mac header. 2");
    }

    headlen = 128 + ntohl(*(ulong*)(p+83));
    //headlen = 128 + (*p<<24 | *(p+1)<<16 | *(p+2)<<8 | *(p+3)); //big endian

    p += headlen;
    newflen = info.st_size - headlen;

    /*
     * cut mac binary & save
     */
    //new filename
    memset(newfname, 0x00, FILENAMELEN);
    sprintf(newfname, "new_%s", argv[1]);

    //file write
    if((fout=fopen(newfname,"wb")) == NULL)
	errexit("fopen 2");
    if(fwrite(p, 1, newflen, fout) != newflen)
	errexit("fwrite");
    fclose(fout);

    printf("saved '%s' cut %ld bytes\n", newfname, headlen);

    return 0;
}
//end of file