Add cmd/gots-stamp

Usage `gots-stamp FILENAME`

Creates a detached, upgradable timestamp FILENAME.ots

Author: OttoAllmendinger

cmd/gots-stamp/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+
+	"github.com/BlockchainSource/go-opentimestamps/opentimestamps"
+)
+
+const defaultCalendar = "https://alice.btc.calendar.opentimestamps.org"
+
+func main() {
+	flag.Parse()
+	path := flag.Arg(0)
+
+	cal, err := opentimestamps.NewRemoteCalendar(defaultCalendar)
+	if err != nil {
+		log.Fatalf("error creating remote calendar: %v", err)
+	}
+
+	outFile, err := os.Create(path + ".ots")
+	if err != nil {
+		log.Fatalf("error creating output file: %v", err)
+	}
+
+	dts, err := opentimestamps.CreateDetachedTimestampForFile(path, cal)
+	if err != nil {
+		log.Fatalf(
+			"error creating detached timestamp for %s: %v",
+			path, err,
+		)
+	}
+	if err := dts.WriteToStream(outFile); err != nil {
+		log.Fatalf("error writing detached timestamp: %v", err)
+	}
+}

opentimestamps/commands.go

@@ -0,0 +1,26 @@
+package opentimestamps
+
+import (
+	"crypto/sha256"
+	"io"
+	"os"
+)
+
+func CreateDetachedTimestampForFile(
+	path string, cal *RemoteCalendar,
+) (*DetachedTimestamp, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	hasher := sha256.New()
+	if _, err := io.Copy(hasher, f); err != nil {
+		return nil, err
+	}
+	digest := hasher.Sum([]byte{})
+	ts, err := cal.Submit(digest)
+	if err != nil {
+		return nil, err
+	}
+	return NewDetachedTimestamp(*opSHA256, digest, ts)
+}