my solution to lab5

lab/lib/args.c

@@ -0,0 +1,73 @@
+#include <inc/args.h>
+#include <inc/string.h>
+
+void
+argstart(int *argc, char **argv, struct Argstate *args)
+{
+	args->argc = argc;
+	args->argv = (const char **) argv;
+	args->curarg = (*argc > 1 && argv ? "" : 0);
+	args->argvalue = 0;
+}
+
+int
+argnext(struct Argstate *args)
+{
+	int arg;
+
+	args->argvalue = 0;
+
+	// Done processing arguments if args->curarg == 0
+	if (args->curarg == 0)
+		return -1;
+
+	if (!*args->curarg) {
+		// Need to process the next argument
+		// Check for end of argument list
+		if (*args->argc == 1
+		    || args->argv[1][0] != '-'
+		    || args->argv[1][1] == '\0')
+			goto endofargs;
+		// Shift arguments down one
+		args->curarg = args->argv[1] + 1;
+		memmove(args->argv + 1, args->argv + 2, sizeof(const char *) * (*args->argc - 1));
+		(*args->argc)--;
+		// Check for "--": end of argument list
+		if (args->curarg[0] == '-' && args->curarg[1] == '\0')
+			goto endofargs;
+	}
+
+	arg = (unsigned char) *args->curarg;
+	args->curarg++;
+	return arg;
+
+    endofargs:
+	args->curarg = 0;
+	return -1;
+}
+
+char *
+argvalue(struct Argstate *args)
+{
+	return (char*) (args->argvalue ? args->argvalue : argnextvalue(args));
+}
+
+char *
+argnextvalue(struct Argstate *args)
+{
+	if (!args->curarg)
+		return 0;
+	if (*args->curarg) {
+		args->argvalue = args->curarg;
+		args->curarg = "";
+	} else if (*args->argc > 1) {
+		args->argvalue = args->argv[1];
+		memmove(args->argv + 1, args->argv + 2, sizeof(const char *) * (*args->argc - 1));
+		(*args->argc)--;
+	} else {
+		args->argvalue = 0;
+		args->curarg = 0;
+	}
+	return (char*) args->argvalue;
+}
+