mkfs: first working version

It can create a basic filesystem of arbitrary size.

Signed-off-by: Sean Cross <sean@xobs.io>

tests/mkfs-simple.c

@@ -0,0 +1,37 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <string.h>
+
+#include "fat12.h"
+
+static int make_image(const char *name, uint32_t size) {
+
+    int fd = open(name, O_WRONLY | O_CREAT, 0777);
+    if (-1 == fd) {
+        fprintf(stderr, "couldn't open %s: %s\n", name, strerror(errno));
+        return 1;
+    }
+
+    if (-1 == fat12_mkfs(fd, size)) {
+        fprintf(stderr, "couldn't make fat12 on %s: %s\n", name, strerror(errno));
+        close(fd);
+        return 1;
+    }
+    close(fd);
+    return 0;
+}
+
+int main(int argc, char **argv) {
+    int ret = 0;
+
+    ret += make_image("fat12-1300k.img", 1300 * 1024);
+    // ret += make_image("fat12-1800k.img", 1800 * 1024);
+    // ret += make_image("fat12-128k.img", 128 * 1024);
+    ret += make_image("fat12-16M.img", 16 * 1024 * 1024);
+
+    return ret;
+}