vegeta: Helper decoder function

file.go

@@ -1,7 +1,13 @@
 package main
 
 import (
+	"errors"
+	"fmt"
+	"io"
 	"os"
+	"strings"
+
+	vegeta "github.com/tsenart/vegeta/lib"
 )
 
 func file(name string, create bool) (*os.File, error) {
@@ -17,3 +23,40 @@ func file(name string, create bool) (*os.File, error) {
 		return os.Open(name)
 	}
 }
+
+func decoder(files []string) (vegeta.Decoder, io.Closer, error) {
+	closer := make(multiCloser, 0, len(files))
+	decs := make([]vegeta.Decoder, 0, len(files))
+	for _, f := range files {
+		rc, err := file(f, false)
+		if err != nil {
+			return nil, closer, err
+		}
+
+		dec := vegeta.DecoderFor(rc)
+		if dec == nil {
+			return nil, closer, fmt.Errorf("encode: can't detect encoding of %q", f)
+		}
+
+		decs = append(decs, dec)
+		closer = append(closer, rc)
+	}
+	return vegeta.NewRoundRobinDecoder(decs...), closer, nil
+}
+
+type multiCloser []io.Closer
+
+func (mc multiCloser) Close() error {
+	var errs []string
+	for _, c := range mc {
+		if err := c.Close(); err != nil {
+			errs = append(errs, err.Error())
+		}
+	}
+
+	if len(errs) > 0 {
+		return errors.New(strings.Join(errs, "; "))
+	}
+
+	return nil
+}