fexc: prepare for multitool support and validate input and output format options

Makefile

@@ -1,5 +1,6 @@
 CC = gcc
-CFLAGS = -g -O2 -Wall -Wextra -std=c99
+CFLAGS = -g -O2 -Wall -Wextra
+CFLAGS += -std=c99 -D_POSIX_C_SOURCE=200112L
 
 TOOLS = fexc bin2fex fex2bin
 

fexc.c

@@ -17,7 +17,83 @@
 
 #include "fexc.h"
 
-int main(int UNUSED(argc), char *UNUSED(argv[]))
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+/*
+ */
+static inline void app_usage(const char *arg0, int mode)
 {
+	errf("Usage: %s [-vq]%s[<input> [<output>]]\n", arg0,
+	     mode ? " " : " [-I <infmt>] [-O <outfmt>] ");
+
+	if (mode == 0)
+		fputs("\ninfmt:  fex, bin  (default:fex)"
+		      "\noutfmt: fex, bin  (default:bin)\n",
+		      stderr);
+}
+
+static inline int app_choose_mode(char *arg0)
+{
+	const char *name = basename(arg0);
+	if (strcmp(name, "fex2bin") == 0)
+		return 1;
+	else if (strcmp(name, "bin2fex") == 0)
+		return 2;
+	else
+		return 0;
+}
+
+/*
+ */
+int main(int argc, char *argv[])
+{
+	static const char *formats[] = { "fex", "bin", NULL };
+	int infmt=0, outfmt=1;
+
+	int app_mode = app_choose_mode(argv[0]);
+
+	const char *opt_string = "I:O:vq?"+ ((app_mode == 0)? 0: 4);
+	int opt;
+	int verbose = 0;
+
+	while ((opt = getopt(argc, argv, opt_string)) != -1) {
+		switch (opt) {
+		case 'I':
+			infmt=0;
+			for (const char **f = formats; *f; f++, infmt++) {
+				if (strcmp(*f, optarg) == 0)
+					break;
+			}
+			if (!formats[infmt]) {
+				errf("%s: invalid format -- \"%s\"\n",
+				     argv[0], optarg);
+				goto show_usage;
+			}
+			break;
+		case 'O':
+			outfmt=0;
+			for (const char **f = formats; *f; f++, outfmt++) {
+				if (strcmp(*f, optarg) == 0)
+					break;
+			}
+			if (!formats[outfmt]) {
+				errf("%s: invalid format -- \"%s\"\n",
+				     argv[0], optarg);
+				goto show_usage;
+			}
+			break;
+		case 'v':
+			verbose++;
+			break;
+		default:
+show_usage:
+			app_usage(argv[0], app_mode);
+			exit(1);
+		}
+	}
 	return 1;
 }