mkfile.c

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/*      mkfile 1.0 - create a file under DOS for use as a Minix "disk".
 *                                                      Author: Kees J. Bot
 *                                                              9 May 1998
 */
#define nil 0
#include <sys/types.h>
#include <string.h>
#include <limits.h>

/* Stuff normally found in <unistd.h>, <errno.h>, etc. */
extern int errno;
int creat(const char *file, int mode);
int open(const char *file, int oflag);
off_t lseek(int fd, off_t offset, int whence);
ssize_t write(int fd, const char *buf, size_t len);
void exit(int status);
int printf(const char *fmt, ...);

#define O_WRONLY        1
#define SEEK_SET        0
#define SEEK_END        2

/* Kernel printf requires a putk() function. */
int putk(int c)
{
        char ch = c;

        if (c == 0) return;
        if (c == '\n') putk('\r');
        (void) write(2, &ch, 1);
}

static void usage(void)
{
        printf("Usage: mkfile <size>[gmk] <file>\n"
                "(Example sizes, all 50 meg: 52428800, 51200k, 50m)\n");
        exit(1);
}

char *strerror(int err)
/* Translate some DOS error numbers to text. */
{
        static struct errlist {
                int     err;
                char    *what;
        } errlist[] = {
                {  0, "No error" },
                {  1, "Function number invalid" },
                {  2, "File not found" },
                {  3, "Path not found" },
                {  4, "Too many open files" },
                {  5, "Access denied" },
                {  6, "Invalid handle" },
                { 12, "Access code invalid" },
                { 39, "Insufficient disk space" },
        };
        struct errlist *ep;
        static char unknown[]= "Error 65535";
        unsigned e;
        char *p;

        for (ep= errlist; ep < errlist + sizeof(errlist)/sizeof(errlist[0]);
                                                                        ep++) {
                if (ep->err == err) return ep->what;
        }
        p= unknown + sizeof(unknown) - 1;
        e= err;
        do *--p= '0' + (e % 10); while ((e /= 10) > 0);
        strcpy(unknown + 6, p);
        return unknown;
}

int main(int argc, char **argv)
{
        int i;
        static char buf[512];
        unsigned long size, mul;
        off_t offset;
        char *cp;
        int fd;
        char *file;

        if (argc != 3) usage();

        cp= argv[1];
        size= 0;
        while ((unsigned) (*cp - '0') < 10) {
                unsigned d= *cp++ - '0';
                if (size <= (ULONG_MAX-9) / 10) {
                        size= size * 10 + d;
                } else {
                        size= ULONG_MAX;
                }
        }
        if (cp == argv[1]) usage();
        while (*cp != 0) {
                mul = 1;
                switch (*cp++) {
                case 'G':
                case 'g':       mul *= 1024;
                case 'M':
                case 'm':       mul *= 1024;
                case 'K':
                case 'k':       mul *= 1024;
                case 'B':
                case 'b':       break;
                default:        usage();
                }
                if (size <= ULONG_MAX / mul) {
                        size *= mul;
                } else {
                        size= ULONG_MAX;
                }
        }

        if (size > 1024L*1024*1024) {
                printf("mkfile: A file size over 1G is a bit too much\n");
                exit(1);
        }

        /* Open existing file, or create a new file. */
        file= argv[2];
        if ((fd= open(file, O_WRONLY)) < 0) {
                if (errno == 2) {
                        fd= creat(file, 0666);
                }
        }
        if (fd < 0) {
                printf("mkfile: Can't open %s: %s\n", file, strerror(errno));
                exit(1);
        }

        /* How big is the file now? */
        if ((offset= lseek(fd, 0, SEEK_END)) == -1) {
                printf("mkfile: Can't seek in %s: %s\n", file, strerror(errno));
                exit(1);
        }

        if (offset == 0 && size == 0) exit(0);  /* Huh? */

        /* Write the first bit if the file is zero length.  This is necessary
         * to circumvent a DOS bug by extending a new file by lseek.  We also
         * want to make sure there are zeros in the first sector.
         */
        if (offset == 0) {
                if (write(fd, buf, sizeof(buf)) == -1) {
                        printf("mkfile: Can't write to %s: %s\n",
                                file, strerror(errno));
                        exit(1);
                }
        }

        /* Seek to the required size and write 0 bytes to extend/truncate the
         * file to that size.
         */
        if (lseek(fd, size, SEEK_SET) == -1) {
                printf("mkfile: Can't seek in %s: %s\n", file, strerror(errno));
                exit(1);
        }
        if (write(fd, buf, 0) == -1) {
                printf("mkfile: Can't write to %s: %s\n",
                        file, strerror(errno));
                exit(1);
        }

        /* Did the file become the required size? */
        if ((offset= lseek(fd, 0, SEEK_END)) == -1) {
                printf("mkfile: Can't seek in %s: %s\n", file, strerror(errno));
                exit(1);
        }
        if (offset != size) {
                printf("mkfile: Failed to extend %s.  Disk full?\n", file);
                exit(1);
        }
        return 0;
}

/*
 * $PchId: mkfile.c,v 1.4 2000/08/13 22:06:40 philip Exp $
 */

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