util.strbitop: Create buffer in the correct size (optimization) This avoids dynamically growing the buffer as Lua does when luaL_addchar is used, thus saving on realloc calls.

author: Kim Alvefur <zash@zash.se>
date: Thu, 15 Oct 2020 16:43:30 +0200
parent: 11167:ba32b9a6d75b
child: 11171:2c1583bb0e0f
--- a/util-src/strbitop.c	Thu Oct 15 16:41:51 2020 +0200
+++ b/util-src/strbitop.c	Thu Oct 15 16:43:30 2020 +0200
@@ -2,7 +2,7 @@
  * This project is MIT licensed. Please see the
  * COPYING file in the source package for more information.
  *
- * Copyright (C) 2016 Kim Alvefur
+ * Copyright (C) 2016-2020 Kim Alvefur
  */
 
 #include <lua.h>
@@ -27,10 +27,13 @@
 		return 1;
 	}
 
+	char *cbuf = luaL_buffinitsize(L, &buf, a);
+
 	for(i = 0; i < a; i++) {
-		luaL_addchar(&buf, str_a[i] & str_b[i % b]);
+		cbuf[i] = str_a[i] & str_b[i % b];
 	}
 
+	luaL_addsize(&buf, a);
 	luaL_pushresult(&buf);
 	return 1;
 }
@@ -48,10 +51,13 @@
 		return 1;
 	}
 
+	char *cbuf = luaL_buffinitsize(L, &buf, a);
+
 	for(i = 0; i < a; i++) {
-		luaL_addchar(&buf, str_a[i] | str_b[i % b]);
+		cbuf[i] = str_a[i] | str_b[i % b];
 	}
 
+	luaL_addsize(&buf, a);
 	luaL_pushresult(&buf);
 	return 1;
 }
@@ -62,17 +68,18 @@
 	const char *str_a = luaL_checklstring(L, 1, &a);
 	const char *str_b = luaL_checklstring(L, 2, &b);
 
-	luaL_buffinit(L, &buf);
-
 	if(a == 0 || b == 0) {
 		lua_settop(L, 1);
 		return 1;
 	}
 
+	char *cbuf = luaL_buffinitsize(L, &buf, a);
+
 	for(i = 0; i < a; i++) {
-		luaL_addchar(&buf, str_a[i] ^ str_b[i % b]);
+		cbuf[i] = str_a[i] ^ str_b[i % b];
 	}
 
+	luaL_addsize(&buf, a);
 	luaL_pushresult(&buf);
 	return 1;
 }