Merge pull request ipld/go-car#350 from ipld/feat/cmd-create-external…

…-index

feat(cmd): add index create subcommand to create an external carv2 index

This commit was moved from ipld/go-car@31cce71

ipld/car/cmd/car/car.go

@@ -153,6 +153,11 @@ func main1() int {
 						Usage: "Write output as a v1 or v2 format car",
 					},
 				},
+				Subcommands: []*cli.Command{{
+					Name:   "create",
+					Usage:  "Write out a detached index",
+					Action: CreateIndex,
+				}},
 			},
 			{
 				Name:   "inspect",

ipld/car/cmd/car/index.go

@@ -166,3 +166,45 @@ func IndexCar(c *cli.Context) error {
 	_, err = index.WriteTo(idx, outStream)
 	return err
 }
+
+// CreateIndex is a command to write out an index of the CAR file
+func CreateIndex(c *cli.Context) error {
+	r, err := carv2.OpenReader(c.Args().Get(0))
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	outStream := os.Stdout
+	if c.Args().Len() >= 2 {
+		outStream, err = os.Create(c.Args().Get(1))
+		if err != nil {
+			return err
+		}
+	}
+	defer outStream.Close()
+
+	var mc multicodec.Code
+	if err := mc.Set(c.String("codec")); err != nil {
+		return err
+	}
+	idx, err := index.New(mc)
+	if err != nil {
+		return err
+	}
+
+	dr, err := r.DataReader()
+	if err != nil {
+		return err
+	}
+
+	if err := carv2.LoadIndex(idx, dr); err != nil {
+		return err
+	}
+
+	if _, err := index.WriteTo(idx, outStream); err != nil {
+		return err
+	}
+
+	return nil
+}

ipld/car/cmd/car/testdata/script/index-create.txt

@@ -0,0 +1,3 @@
+car index create ${INPUTS}/sample-v1.car sample-v1.car.idx
+car detach-index ${INPUTS}/sample-wrapped-v2.car sample-wrapped-v2.car.idx
+cmp sample-v1.car.idx sample-wrapped-v2.car.idx