Minor optimizations

cmd/micro/util.go

@@ -37,6 +37,40 @@ func toRunes(b []byte) []rune {
 	return runes
 }
 
+func sliceStart(slc []byte, index int) []byte {
+	len := len(slc)
+	i := 0
+	totalSize := 0
+	for totalSize < len {
+		if i >= index {
+			return slc[totalSize:]
+		}
+
+		_, size := utf8.DecodeRune(slc[totalSize:])
+		totalSize += size
+		i++
+	}
+
+	return slc[totalSize:]
+}
+
+func sliceEnd(slc []byte, index int) []byte {
+	len := len(slc)
+	i := 0
+	totalSize := 0
+	for totalSize < len {
+		if i >= index {
+			return slc[:totalSize]
+		}
+
+		_, size := utf8.DecodeRune(slc[totalSize:])
+		totalSize += size
+		i++
+	}
+
+	return slc[:totalSize]
+}
+
 // NumOccurrences counts the number of occurrences of a byte in a string
 func NumOccurrences(s string, c byte) int {
 	var n int
@@ -144,7 +178,7 @@ func GetLeadingWhitespace(str string) string {
 }
 
 // IsSpaces checks if a given string is only spaces
-func IsSpaces(str string) bool {
+func IsSpaces(str []byte) bool {
 	for _, c := range str {
 		if c != ' ' {
 			return false