varfmt/fmt.go

@@ -17,17 +17,18 @@ func Sprintf(format string, args ...any) string {
 	// init output strings.Builder and num rune buffer
 	// cant use strings.Builder for storing num since
 	// builder can't clear its contents without reallocating
-	output, num := strings.Builder{}, make([]rune, 0, 1)
+	output, num := strings.Builder{}, make([]rune, 0, 2) // first alloc here
 	// convert args slice to strArgs string slice
-	strArgs, maxLen := make([]string, len(args), cap(args)), 0
+	strArgs, maxLen := make([]string, len(args), cap(args)), 0 // second alloc here
 	for i, arg := range args {
-		strArgs[i] = fmt.Sprint(arg)
+		strArgs[i] = fmt.Sprint(arg) // third and other allocs happen here
+		// could be further optimized
 		if len(strArgs[i]) > maxLen {
 			maxLen = len(strArgs[i])
 		}
 	}
 	// allocate maximum possible length of the resulting string
-	output.Grow(len(format) + len(args)*maxLen)
+	output.Grow(len(format) + len(args)*maxLen) // third alloc here
 	start, argIndex := 0, 0
 	// decode runes one by one
 	for start < len(format) {
@@ -46,7 +47,7 @@ func Sprintf(format string, args ...any) string {
 				// append new rune if the number is bigger
 				// than the current buffer
 				if numLength >= len(num) {
-					num = append(num, r)
+					num = append(num, r) // further allocs happen here
 				} else {
 					num[numLength] = r
 				}