Add arguments and now yemu is modular so other systems can be added easier

src/.gitignore

@@ -0,0 +1,2 @@
+*~
+yemu

src/Makefile

@@ -3,7 +3,7 @@ CFLAGS= -O2 -Wall -Wextra
 LFLAGS=
 
 SRCFILES= main.c 6502/6502.c
-OBJFILES= yemu-6502
+OBJFILES= yemu
 
 .PHONY: all clean 
 

src/main.c

@@ -1,18 +1,70 @@
 #include "6502/6502.h"
 #include <stdio.h>
 #include <stddef.h>
+#include <string.h>
+
+void usage() {
+  printf("%s - Yet another EMUlator\n", "yemu");
+  printf("Usage: %s [OPTIONS] [--] filename\n", "yemu");
+  printf("       %s --help\n", "yemu");
+  printf("Options:\n");
+  printf("\n");
+  printf("       --help                 display this message\n");
+  printf("       --system system_name   choose one of supported systems\n");
+}
 
 int main(int argc, char *argv[]) {
-  if (argc < 2) {
-    printf("%s: No input file specified\n", "yemu");
+  char *infilename = NULL;
+  char *system_name = NULL;
+  
+  if (argc == 1) {
+    usage();
+    return 0;
+  } else if (argc >= 2) {
+    for (int i = 1; i <= argc-1; i++) {
+      if (argv[i][0] == '-') {
+	argv[i]++;
+	if(argv[i][0] == '-')
+	  argv[i]++;
+	if (!strcmp(argv[i], "system")) {
+	  system_name = argv[i+1];
+	  i+=2;
+	} else if (!strcmp(argv[i], "help")) {
+	  usage();
+	  return 0;
+	} else {
+	  printf("Unknown argument: %s\n", argv[i]);
+	  return 1;
+	}
+      } else {
+	infilename = argv[i];
+      }
+    }
+  }
+  
+  if (infilename == NULL) {
+    printf("%s: no input file specified\n", "yemu");
     return 1;
   }
-	
-  FILE *infile = fopen(argv[1], "rb");
+  
+  FILE *infile = fopen(infilename, "rb");
+  
   if (infile == NULL) {
     perror("yemu");
     return 1;
-  }        
-  init6502(infile);
+  }
+
+  if (system_name == NULL) {
+    printf("%s: no system specified\n", "yemu");
+    return 1;
+  } else if (!strcmp(system_name, "6502")) {
+    init6502(infile);
+  } else {
+    printf("%s: not supported system\n", "yemu");
+    return 1;
+  }
+  
+  fclose(infile);
+  
   return 0;
 }