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/*

 *  linux/zBoot/xtract.c

 *

 *  Copyright (C) 1993  Hannu Savolainen

 *

 *      Extracts the system image and writes it to the stdout.

 *      based on tools/build.c by Linus Torvalds

 */

#include <stdio.h>      /* fprintf */

#include <string.h>

#include <stdlib.h>     /* contains exit */

#include <sys/types.h>  /* unistd.h needs this */

#include <sys/stat.h>

#include <sys/sysmacros.h>

#include <unistd.h>     /* contains read/write */

#include <fcntl.h>

#include <a.out.h>

#define N_MAGIC_OFFSET 1024

static int GCC_HEADER = sizeof(struct exec);

#define STRINGIFY(x) #x

void die(char * str)

{

        fprintf(stderr,"%s\n",str);

        exit(1);

}

void usage(void)

{

        die("Usage: xtract system [ | gzip | piggyback > piggy.s]");

}

int main(int argc, char ** argv)

{

        int id, sz;

        char buf[1024];

        struct exec *ex = ((struct exec *)buf) + 1;

        if (argc  != 2)

                usage();

        if ((id=open(argv[1],O_RDONLY,0))<0)

                die("Unable to open 'system'");

        if (read(id,ex,GCC_HEADER) != GCC_HEADER)

                die("Unable to read header of 'system'");

        switch (N_MAGIC(*ex)) {

        case ZMAGIC:

                GCC_HEADER = N_MAGIC_OFFSET;

                lseek(id, GCC_HEADER, SEEK_SET);

                break;

        case QMAGIC:

                memset (buf, 0, GCC_HEADER);

                buf[0x14] = 0x20;

                write (1, buf, GCC_HEADER);

                break;

        default:

                die("Non-GCC header of 'system'");

        }

        sz = N_SYMOFF(*ex) - GCC_HEADER + 4;    /* +4 to get the same result than tools/build */

        fprintf(stderr, "System size is %d\n", sz);

        while (sz) {

                int l, n;

                l = sz;

                if (l > sizeof(buf)) l = sizeof(buf);

                if ((n=read(id, buf, l)) !=l)

                {

                        if (n == -1)

                           perror(argv[1]);

                        else

                           fprintf(stderr, "Unexpected EOF\n");

                        die("Can't read system");

                }

                write(1, buf, l);

                sz -= l;

        }

        close(id);

        return(0);

}