attempt 11: convert byte slice to string directly

README.md

@@ -12,4 +12,5 @@
 |7|In the city <> temperatures map, replaced the value for each key (city) to preprocessed min, max, count and sum of all temperatures instead of storing all recorded temperatures for the city.|1:39.81|-71.79|[e5213a8](https://github.com/shraddhaag/1brc/commit/e5213a836b17bec0a858474a11f07c902e724bba)|
 |8|Use producer consumer pattern to read file in chunks and process the chunks in parallel.|1:43.82|+14.01|[067f2a4](https://github.com/shraddhaag/1brc/commit/067f2a44c0d6b3bb7cc073639364f733bce09e3e)|
 |9|Reduce memory allocation by processing each read chunk into a map. Result channel now can collate the smaller processed chunk maps.|0:28.544|-75.286|[d4153ac](https://github.com/shraddhaag/1brc/commit/d4153ac7a841170a5ceee47d930e97738b5a19f6)|
-|10|Avoid string concatenation overhead by not reading the decimal point when processing city temperature.|0:24.571|-3.973||
+|10|Avoid string concatenation overhead by not reading the decimal point when processing city temperature.|0:24.571|-3.973||
+|11|Convert byte slice to string directly instead of using a `strings.Builder`.|0:18.910|-5.761||

main.go

@@ -177,19 +177,20 @@ func readFileLineByLineIntoAMap(filepath string) (map[string]cityTemperatureInfo
 }
 
 func processReadChunk(buf []byte, resultStream chan<- map[string]cityTemperatureInfo) {
-	var stringsBuilder strings.Builder
 	toSend := make(map[string]cityTemperatureInfo)
-	var city string
+	var start int
+	var city, tempString string
 
-	for _, char := range buf {
+	stringBuf := string(buf)
+	for index, char := range stringBuf {
 		switch char {
 		case ';':
-			city = stringsBuilder.String()
-			stringsBuilder.Reset()
+			city = stringBuf[start:index]
+			start = index + 1
 		case '\n':
-			if stringsBuilder.Len() != 0 && len(city) != 0 {
-				temp, _ := strconv.ParseInt(stringsBuilder.String(), 10, 64)
-				stringsBuilder.Reset()
+			if (index-start) > 1 && len(city) != 0 {
+				temp, _ := strconv.ParseInt(tempString+string(stringBuf[index-1]), 10, 64)
+				start = index + 1
 
 				if val, ok := toSend[city]; ok {
 					val.count++
@@ -214,11 +215,9 @@ func processReadChunk(buf []byte, resultStream chan<- map[string]cityTemperature
 				city = ""
 			}
 		case '.':
-			if len(city) == 0 {
-				stringsBuilder.WriteByte(char)
+			if len(city) != 0 {
+				tempString = stringBuf[start:index]
 			}
-		default:
-			stringsBuilder.WriteByte(char)
 		}
 	}
 	resultStream <- toSend