basic arg parser with verbose flag

Author: mikeryan

ems.c

@@ -1,4 +1,5 @@
 #include <errno.h>
+#include <getopt.h>
 #include <signal.h>
 #include <string.h>
 #include <stdio.h>
@@ -9,6 +10,18 @@
 
 #include <libusb.h>
 
+/* options */
+typedef struct _options_t {
+    int verbose;
+    char *file;
+} options_t;
+
+// defaults
+options_t opts = {
+    .verbose            = 0,
+    .file               = NULL,
+};
+
 #define EMS_EP_SEND (2 | LIBUSB_ENDPOINT_OUT)
 #define EMS_EP_RECV (1 | LIBUSB_ENDPOINT_IN)
 
@@ -21,6 +34,7 @@ static struct libusb_device_handle *devh = NULL;
 
 static int find_ems_device(void) {
 	devh = libusb_open_device_with_vid_pid(NULL, 0x4670, 0x9394);
+
 	return devh ? 0 : -EIO;
 }
 
@@ -84,64 +98,107 @@ static int ems_write(uint32_t offset, unsigned char *buf, size_t count) {
     return r;
 }
 
+void get_options(int argc, char **argv) {
+    int c;
+
+    while (1) {
+        int this_option_optind = optind ? optind : 1;
+        int option_index = 0;
+        static struct option long_options[] = {
+            {"verbose", 0, 0, 'v'},
+            {0, 0, 0, 0}
+        };
+
+        c = getopt_long(
+            argc, argv, "v",
+            long_options, &option_index
+        );
+        if (c == -1)
+            break;
+
+        switch (c) {
+            case 'v':
+                opts.verbose = 1;
+                break;
+            default:
+                break;
+        }
+    }
+
+    // extra argument: ROM file
+    if (optind < argc)
+        opts.file = argv[optind];
+}
+
 int main(int argc, char **argv) {
     int r = 1;
     int i;
 
+    get_options(argc, argv);
+
     r = libusb_init(NULL);
     if (r < 0) {
-            fprintf(stderr, "failed to initialise libusb\n");
-            exit(1);
+        fprintf(stderr, "failed to initialise libusb\n");
+        exit(1);
     }
 
     r = find_ems_device();
     if (r < 0) {
-            fprintf(stderr, "Could not find/open device\n");
-            goto out;
+        fprintf(stderr, "Could not find/open device\n");
+        goto out;
     }
 
     r = libusb_claim_interface(devh, 0);
     if (r < 0) {
-            fprintf(stderr, "usb_claim_interface error %d\n", r);
-            goto out;
+        fprintf(stderr, "usb_claim_interface error %d\n", r);
+        goto out;
     }
-    printf("claimed interface\n");
 
-    if (argc > 1) {
-        FILE *write_file = fopen(argv[1], "r");
-        if (write_file == NULL)
-            err(1, "fopen");
+    if (opts.verbose)
+        printf("claimed interface\n");
+
+    // file provided: write the file
+    if (opts.file != NULL) {
+        FILE *write_file = fopen(opts.file, "r");
+        if (write_file == NULL) {
+            warn("Can't open ROM file %s", opts.file);
+            goto out_release;
+        }
 
         char buf[32];
         uint32_t offset = 0;
 
         while (fread(buf, sizeof(buf), 1, write_file) == 1) {
             r = ems_write(offset, buf, sizeof(buf));
-            if (r < 0)
-                errx(1, "can't write %d", r);
+            if (r < 0) {
+                warn("can't write %d", r);
+                goto out_release;
+            }
 
             offset += sizeof(buf);
         }
     }
 
+    // print the first 0x200 bytes in hex and ASCII
+    if (opts.verbose) {
+        unsigned char data[0x200];
+        r = ems_read(0x0, data, sizeof(data));
 
-    unsigned char data[0x200];
-    r = ems_read(0x0, data, sizeof(data));
+        printf("received %d\n", r);
 
-    printf("received %d\n", r);
-
-    for (i = 0; i < r; ++i) {
-        printf("%02x ", data[i]);
-        if ((i & 0xf) == 0xf)
-            printf("\n");
-    }
+        for (i = 0; i < r; ++i) {
+            printf("%02x ", data[i]);
+            if ((i & 0xf) == 0xf)
+                printf("\n");
+        }
 
-    for (i = 0; i < r; ++i) {
-        char pr = isprint(data[i]) ? data[i] : '.';
-        printf("%c", pr);
+        for (i = 0; i < r; ++i) {
+            char pr = isprint(data[i]) ? data[i] : '.';
+            printf("%c", pr);
 
-        if ((i & 0xf) == 0xf)
-            printf("\n");
+            if ((i & 0xf) == 0xf)
+                printf("\n");
+        }
     }
 
 out_release: