From aa319eb8b55356b97470dd0fb2261e431d1d2675 Mon Sep 17 00:00:00 2001
From: whyrusleeping <why@ipfs.io>
Date: Mon, 19 Aug 2019 17:13:12 -0700
Subject: [PATCH] Add fastpath cbor marshalers

---
 cid.go      | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 cid_test.go | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 go.mod      |  1 +
 go.sum      |  4 +++
 4 files changed, 148 insertions(+)

diff --git a/cid.go b/cid.go
index d88b661..3e79768 100644
--- a/cid.go
+++ b/cid.go
@@ -26,10 +26,13 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"strings"
 
 	mbase "github.com/multiformats/go-multibase"
 	mh "github.com/multiformats/go-multihash"
+
+	cbg "github.com/whyrusleeping/cbor-gen"
 )
 
 // UnsupportedVersionString just holds an error message
@@ -522,6 +525,74 @@ func (c Cid) Prefix() Prefix {
 	}
 }
 
+func (c Cid) MarshalCBOR(w io.Writer) error {
+	tag := cbg.CborEncodeMajorType(6, 42)
+	if _, err := w.Write(tag); err != nil {
+		return err
+	}
+
+	typ := cbg.CborEncodeMajorType(2, uint64(len(c.Bytes())+1))
+	if _, err := w.Write(typ); err != nil {
+		return err
+	}
+
+	// that binary multibase prefix...
+	if _, err := w.Write([]byte{0}); err != nil {
+		return err
+	}
+
+	if _, err := w.Write(c.Bytes()); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *Cid) UnmarshalCBOR(br cbg.ByteReader) error {
+	maj, low, err := cbg.CborReadHeader(br)
+	if err != nil {
+		return err
+	}
+
+	if maj != 6 || low != 42 {
+		return fmt.Errorf("CBOR serialized CIDs must have the tag 42")
+	}
+
+	maj, low, err = cbg.CborReadHeader(br)
+	if err != nil {
+		return err
+	}
+
+	if maj != 2 {
+		return fmt.Errorf("CBOR serialized CIDs must be tagged byte arrays")
+	}
+
+	if low > 256 {
+		return fmt.Errorf("CIDs cannot be longer than 256 bytes")
+	}
+	if low < 2 {
+		return fmt.Errorf("encoded CID body must be at least two bytes long")
+	}
+
+	buf := make([]byte, low)
+	if _, err := io.ReadFull(br, buf); err != nil {
+		return fmt.Errorf("failed to read CID body: %s", err)
+	}
+
+	if buf[0] != 0 {
+		return fmt.Errorf("encoded CID did not have binary multibase")
+	}
+
+	out, err := Cast(buf[1:])
+	if err != nil {
+		return err
+	}
+
+	*c = out
+
+	return nil
+}
+
 // Prefix represents all the metadata of a Cid,
 // that is, the Version, the Codec, the Multihash type
 // and the Multihash length. It does not contains
diff --git a/cid_test.go b/cid_test.go
index 1c181f9..566bd46 100644
--- a/cid_test.go
+++ b/cid_test.go
@@ -2,6 +2,7 @@ package cid
 
 import (
 	"bytes"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"math/rand"
@@ -499,6 +500,77 @@ func TestJsonRoundTrip(t *testing.T) {
 	}
 }
 
+func TestCBORSerialization(t *testing.T) {
+	cases := map[string]string{
+		"bafybeibpzhw63c3vh7vushzvfzvkc2nbhr6nm3ui2o7kj33cx3xoovnzp4": "d82a582500017012202fc9eded8b753feb491f352e6aa169a13c7cd66e88d3bea4ef62beeee755b97f",
+		"QmRZCTZPygAnfagZKzjy48b4LMmqPNpJnNBEg5LtCCzHCA":              "d82a58230012202fc9eded8b753feb491f352e6aa169a13c7cd66e88d3bea4ef62beeee755b97f",
+	}
+
+	for cs, encs := range cases {
+		c, err := Decode(cs)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		buf := new(bytes.Buffer)
+		if err := c.MarshalCBOR(buf); err != nil {
+			t.Fatal(err)
+		}
+
+		exp, err := hex.DecodeString(encs)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !bytes.Equal(exp, buf.Bytes()) {
+			t.Fatalf("serialization incorrect: %x != %x", buf.Bytes(), exp)
+		}
+
+		var out Cid
+		if err := out.UnmarshalCBOR(bytes.NewReader(exp)); err != nil {
+			t.Fatalf("unmarshal case %s failed: %s", cs, err)
+		}
+
+		if out != c {
+			t.Fatal("unmarshal CBOR failed")
+		}
+	}
+}
+
+func BenchmarkCBORMarshal(b *testing.B) {
+	c, err := Decode("bafybeibpzhw63c3vh7vushzvfzvkc2nbhr6nm3ui2o7kj33cx3xoovnzp4")
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	b.ReportAllocs()
+
+	buf := new(bytes.Buffer)
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		if err := c.MarshalCBOR(buf); err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
+func BenchmarkCBORUnmarshal(b *testing.B) {
+	enc, err := hex.DecodeString("d82a582500017012202fc9eded8b753feb491f352e6aa169a13c7cd66e88d3bea4ef62beeee755b97f")
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	b.ReportAllocs()
+
+	var c Cid
+	for i := 0; i < b.N; i++ {
+		br := bytes.NewReader(enc)
+		if err := c.UnmarshalCBOR(br); err != nil {
+			b.Fatal(err)
+		}
+	}
+}
+
 func BenchmarkStringV1(b *testing.B) {
 	data := []byte("this is some test content")
 	hash, _ := mh.Sum(data, mh.SHA2_256, -1)
diff --git a/go.mod b/go.mod
index 8e1b5f4..9864e46 100644
--- a/go.mod
+++ b/go.mod
@@ -3,4 +3,5 @@ module github.com/ipfs/go-cid
 require (
 	github.com/multiformats/go-multibase v0.0.1
 	github.com/multiformats/go-multihash v0.0.1
+	github.com/whyrusleeping/cbor-gen v0.0.0-20190819235733-17c06ddc16cb
 )
diff --git a/go.sum b/go.sum
index d6043b8..e526e86 100644
--- a/go.sum
+++ b/go.sum
@@ -14,6 +14,10 @@ github.com/multiformats/go-multibase v0.0.1 h1:PN9/v21eLywrFWdFNsFKaU04kLJzuYzmr
 github.com/multiformats/go-multibase v0.0.1/go.mod h1:bja2MqRZ3ggyXtZSEDKpl0uO/gviWFaSteVbWT51qgs=
 github.com/multiformats/go-multihash v0.0.1 h1:HHwN1K12I+XllBCrqKnhX949Orn4oawPkegHMu2vDqQ=
 github.com/multiformats/go-multihash v0.0.1/go.mod h1:w/5tugSrLEbWqlcgJabL3oHFKTwfvkofsjW2Qa1ct4U=
+github.com/whyrusleeping/cbor-gen v0.0.0-20190818214716-81392149d1dd h1:Nj8P2Fg3mRVnBfkNnxZK+QhjwCxI3kLng2nfTTLIudk=
+github.com/whyrusleeping/cbor-gen v0.0.0-20190818214716-81392149d1dd/go.mod h1:ga0xb76iSIPvNNiuR+g3+c3Rnwy0oVuBGvqDwsEV6x4=
+github.com/whyrusleeping/cbor-gen v0.0.0-20190819235733-17c06ddc16cb h1:49o2mhJ/B2nsmSjV4fUsrFEoKGM9NLWQSnk+YrAKFLg=
+github.com/whyrusleeping/cbor-gen v0.0.0-20190819235733-17c06ddc16cb/go.mod h1:ga0xb76iSIPvNNiuR+g3+c3Rnwy0oVuBGvqDwsEV6x4=
 golang.org/x/crypto v0.0.0-20190211182817-74369b46fc67 h1:ng3VDlRp5/DHpSWl02R4rM9I+8M2rhmsuLwAMmkLQWE=
 golang.org/x/crypto v0.0.0-20190211182817-74369b46fc67/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/sys v0.0.0-20190219092855-153ac476189d h1:Z0Ahzd7HltpJtjAHHxX8QFP3j1yYgiuvjbjRzDj/KH0=