make this O(1)

Author: braindigitalis

include/basic/tokenizer.h

@@ -179,21 +179,18 @@ typedef void (*keyword_handler_t)(struct basic_ctx*);
 
 GENERATE_ENUM_LIST(TOKEN, token_t)
 
-/* Pair of token id and its dispatcher (can be NULL) */
-struct keyword_dispatch_t {
-	enum token_t token;
-	keyword_handler_t handler;
-};
+/* Uniform handler type */
+typedef void (*keyword_handler_t)(struct basic_ctx *);
 
-/* Expand one TOKEN() entry into a { token, handler } initializer */
-#define GENERATE_DISPATCH_ENTRY(NAME, FLAG, DISPATCHER) { NAME, (keyword_handler_t)(DISPATCHER) },
+/* Build a flat handler table indexed by token id */
+#define GENERATE_HANDLER_ENTRY(NAME, FLAG, DISPATCHER) (keyword_handler_t)(DISPATCHER),
 
-/* Emit a const array named ARRAY_NAME with one element per TOKEN() entry */
-#define GENERATE_DISPATCH_TABLE(ARRAY_NAME) \
-    const struct keyword_dispatch_t ARRAY_NAME[] = { \
-        TOKEN(GENERATE_DISPATCH_ENTRY) \
+#define GENERATE_HANDLER_TABLE(ARRAY_NAME) \
+    static const keyword_handler_t ARRAY_NAME[] = { \
+        TOKEN(GENERATE_HANDLER_ENTRY) \
     };
 
+/* Size helper */
 #define DISPATCH_TABLE_COUNT(ARRAY_NAME) (sizeof(ARRAY_NAME) / sizeof((ARRAY_NAME)[0]))
 
 /**

src/basic/statement.c

@@ -8,19 +8,17 @@ void statement(struct basic_ctx* ctx)
 
 	basic_debug("line %ld statement(%d)\n", ctx->current_linenum, token);
 
-	GENERATE_DISPATCH_TABLE(keyword_dispatch);
-	for (size_t t = 0; t < DISPATCH_TABLE_COUNT(keyword_dispatch); ++t) {
-		if (token == keyword_dispatch[t].token) {
-			if (keyword_dispatch[t].handler != NULL) {
-				keyword_dispatch[t].handler(ctx);
-				return;
-			}
+	GENERATE_HANDLER_TABLE(dispatch_by_token)
+	if (token < DISPATCH_TABLE_COUNT(dispatch_by_token)) {
+		if (dispatch_by_token[token] != NULL) {
+			dispatch_by_token[token](ctx);
+			return;
 		}
 	}
 
-	/* If we got here, token wasn’t found in the table at all */
 	dprintf("Unknown keyword: %d\n", token);
-	return tokenizer_error_print(ctx, "Unknown keyword");
+	tokenizer_error_print(ctx, "Unknown keyword");
+
 }
 
 void line_statement(struct basic_ctx* ctx)