skip memory alloc on regex parsing

storage/execout/filename.go

@@ -45,13 +45,15 @@ func parseIndexFileName(filename string) (*FileInfo, error) {
 }
 
 func fileNameToRange(filename string, regex *regexp.Regexp) (*block.Range, error) {
-	res := regex.FindAllStringSubmatch(filename, 1)
+	regex.FindAllSubmatchIndex([]byte(filename), 1)
+
+	res := regex.FindAllSubmatchIndex([]byte(filename), 1)
 	if len(res) != 1 {
 		return nil, fmt.Errorf("invalid output cache filename, %q", filename)
 	}
 
-	start := uint64(mustAtoi(res[0][1]))
-	end := uint64(mustAtoi(res[0][2]))
+	start := uint64(mustAtoi(filename[res[0][2]:res[0][3]]))
+	end := uint64(mustAtoi(filename[res[0][4]:res[0][5]]))
 
 	return &block.Range{
 		StartBlock:        start,

storage/execout/filename_test.go

@@ -0,0 +1,59 @@
+package execout
+
+import (
+	"reflect"
+	"regexp"
+	"testing"
+
+	"github.com/streamingfast/substreams/block"
+)
+
+func Test_fileNameToRange(t *testing.T) {
+	type args struct {
+		filename string
+		regex    *regexp.Regexp
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    *block.Range
+		wantErr bool
+	}{
+		{
+			name: "cache filename",
+			args: args{
+				filename: "0013368000-0013369000.output",
+				regex:    cacheFilenameRegex,
+			},
+			want: &block.Range{
+				StartBlock:        13368000,
+				ExclusiveEndBlock: 13369000,
+			},
+			wantErr: false,
+		},
+		{
+			name: "index filename",
+			args: args{
+				filename: "0000122000-0000123000.index",
+				regex:    indexFilenameRegex,
+			},
+			want: &block.Range{
+				StartBlock:        122000,
+				ExclusiveEndBlock: 123000,
+			},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := fileNameToRange(tt.args.filename, tt.args.regex)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("fileNameToRange() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("fileNameToRange() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}