copy the other repo and make packages install.

detached_timestamp.go

@@ -0,0 +1,100 @@
+package opentimestamps
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+)
+
+var fileHeaderMagic = []byte(
+	"\x00OpenTimestamps\x00\x00Proof\x00\xbf\x89\xe2\xe8\x84\xe8\x92\x94",
+)
+
+const (
+	minFileDigestLength = 20
+	maxFileDigestLength = 32
+	fileMajorVersion    = 1
+)
+
+type DetachedTimestamp struct {
+	HashOp    cryptOp
+	FileHash  []byte
+	Timestamp *Timestamp
+}
+
+func (d *DetachedTimestamp) Dump() string {
+	w := &bytes.Buffer{}
+	fmt.Fprintf(
+		w, "File %s hash: %x\n", d.HashOp.name, d.Timestamp.Message,
+	)
+	fmt.Fprint(w, d.Timestamp.Dump())
+	return w.String()
+}
+
+func (d *DetachedTimestamp) encode(ctx *serializationContext) error {
+	if err := ctx.writeBytes(fileHeaderMagic); err != nil {
+		return err
+	}
+	if err := ctx.writeVarUint(fileMajorVersion); err != nil {
+		return err
+	}
+	if err := d.HashOp.encode(ctx); err != nil {
+		return err
+	}
+	if err := ctx.writeBytes(d.FileHash); err != nil {
+		return err
+	}
+	return d.Timestamp.encode(ctx)
+}
+
+func (d *DetachedTimestamp) WriteToStream(w io.Writer) error {
+	return d.encode(&serializationContext{w})
+}
+
+func NewDetachedTimestamp(
+	hashOp cryptOp, fileHash []byte, ts *Timestamp,
+) (*DetachedTimestamp, error) {
+	if len(fileHash) != hashOp.digestLength {
+		return nil, fmt.Errorf(
+			"op %v expects %d byte digest, got %d",
+			hashOp, hashOp.digestLength, len(fileHash),
+		)
+	}
+	return &DetachedTimestamp{hashOp, fileHash, ts}, nil
+}
+
+func NewDetachedTimestampFromReader(r io.Reader) (*DetachedTimestamp, error) {
+	ctx := newDeserializationContext(r)
+	if err := ctx.assertMagic([]byte(fileHeaderMagic)); err != nil {
+		return nil, err
+	}
+	major, err := ctx.readVarUint()
+	if err != nil {
+		return nil, err
+	}
+	if major != uint64(fileMajorVersion) {
+		return nil, fmt.Errorf("unexpected major version %d", major)
+	}
+	fileHashOp, err := parseCryptOp(ctx)
+	if err != nil {
+		return nil, err
+	}
+	fileHash, err := ctx.readBytes(fileHashOp.digestLength)
+	if err != nil {
+		return nil, err
+	}
+	ts, err := newTimestampFromContext(ctx, fileHash)
+	if err != nil {
+		return nil, err
+	}
+	return &DetachedTimestamp{*fileHashOp, fileHash, ts}, nil
+}
+
+func NewDetachedTimestampFromPath(p string) (*DetachedTimestamp, error) {
+	f, err := os.Open(p)
+	if err != nil {
+		return nil, err
+	}
+	return NewDetachedTimestampFromReader(f)
+}