refactor code

pscat/psargs.c

@@ -0,0 +1,56 @@
+#include <stddef.h>
+
+#include "psargs.h"
+
+/* Test string containing { c, '\0' } without iteration.
+ * Theoretically saves a little bit of time compared to strcmp(3). */
+#define SCMPFLAT(a, b) (*(a) != '\0' && *((a)+1) == '\0' && *(a) == (b))
+
+int
+check_arg(char **args, char l, char r){
+	enum {
+		UNINITIALIZED = 0,
+		NORMAL = 1,
+		INLPAREN = 2
+	} s;
+	int terms;
+
+	for(s = UNINITIALIZED, terms = 0; *args != NULL; ++args)
+		switch(s){
+		case UNINITIALIZED: case NORMAL:
+			if(SCMPFLAT(*args, l))
+				s = INLPAREN;
+			else
+				return 0; /* syntax error */
+			break;
+		default: /* >= INLPAREN */
+			/* decrement s if on an rparen, increment if on lparen
+			 * increment terms if on an rparen */
+			if(args[0][1] == '\0'){
+				s += (args[0][0] == l) - (args[0][0] == r);
+				terms += (args[0][0] == r && s == NORMAL);
+			}
+			break;
+		}
+
+	/* make sure nothing's open */
+	return terms * (s == NORMAL);
+}
+
+char **
+corresponding_arg(char **arg, char l, char r){
+	size_t p;
+
+	for(p = 1; p > 0;){
+		++arg;
+		/* branching here potentially saves a comparison.
+		 * this seems like the most optimal way to do this,
+		 * maybe it isn't, i don't care too much */
+		if(SCMPFLAT(*arg, l))
+			++p;
+		else if(SCMPFLAT(*arg, r))
+			--p;
+	}
+
+	return arg;
+}