Create a CID encoder that optionally upgrads a CIDv0 to CIDv1

cidenc/encoder.go

@@ -0,0 +1,59 @@
+package cidenc
+
+import (
+	cid "github.com/ipfs/go-cid"
+	mbase "github.com/multiformats/go-multibase"
+)
+
+// Encoder is a basic Encoder that will encode Cid's using a specifed
+// base and optionally upgrade a CIDv0 to CIDv1
+type Encoder struct {
+	Base    mbase.Encoder // The multibase to use
+	Upgrade bool          // If true upgrade CIDv0 to CIDv1 when encoding
+}
+
+// Default return a new default encoder
+func Default() Encoder {
+	return Encoder{Base: mbase.MustNewEncoder(mbase.Base58BTC)}
+}
+
+// Encode encoded the cid using the parameters of the Encoder
+func (enc Encoder) Encode(c cid.Cid) string {
+	if enc.Upgrade && c.Version() == 0 {
+		c = cid.NewCidV1(c.Type(), c.Hash())
+	}
+	return c.Encode(enc.Base)
+}
+
+// Recode reencodes the cid string to match the parameters of the
+// encoder
+func (enc Encoder) Recode(v string) (string, error) {
+	skip, err := enc.noopRecode(v)
+	if skip || err != nil {
+		return v, err
+	}
+
+	c, err := cid.Decode(v)
+	if err != nil {
+		return v, err
+	}
+
+	return enc.Encode(c), nil
+}
+
+func (enc Encoder) noopRecode(v string) (bool, error) {
+	if len(v) < 2 {
+		return false, cid.ErrCidTooShort
+	}
+	ver := cidVer(v)
+	skip := ver == 0 && !enc.Upgrade || ver == 1 && v[0] == byte(enc.Base.Encoding())
+	return skip, nil
+}
+
+func cidVer(v string) int {
+	if len(v) == 46 && v[:2] == "Qm" {
+		return 0
+	} else {
+		return 1
+	}
+}