From cc1307523283272594f9545836941ec0382a02b5 Mon Sep 17 00:00:00 2001
From: Jeromy <why@ipfs.io>
Date: Tue, 30 Aug 2016 10:04:50 -0700
Subject: [PATCH] add handling for V0 cids

---
 cid.go      | 49 ++++++++++++++++++++++++++++++++++-
 cid_test.go | 73 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 114 insertions(+), 8 deletions(-)

diff --git a/cid.go b/cid.go
index 785a74b..ff2cc21 100644
--- a/cid.go
+++ b/cid.go
@@ -2,10 +2,14 @@ package cid
 
 import (
 	"encoding/binary"
+	"fmt"
+
 	mh "github.com/jbenet/go-multihash"
 	mbase "github.com/multiformats/go-multibase"
 )
 
+const UnsupportedVersionString = "<unsupported cid version>"
+
 type Cid struct {
 	Version uint64
 	Type    uint64
@@ -13,6 +17,18 @@ type Cid struct {
 }
 
 func Decode(v string) (*Cid, error) {
+	if len(v) == 46 && v[:2] == "Qm" {
+		hash, err := mh.FromB58String(v)
+		if err != nil {
+			return nil, err
+		}
+
+		return &Cid{
+			Version: 0,
+			Hash:    hash,
+		}, nil
+	}
+
 	_, data, err := mbase.Decode(v)
 	if err != nil {
 		return nil, err
@@ -38,7 +54,38 @@ func Cast(data []byte) (*Cid, error) {
 	}, nil
 }
 
-func (c *Cid) Bytes() []byte {
+func (c *Cid) String() string {
+	switch c.Version {
+	case 0:
+		return c.Hash.B58String()
+	case 1:
+		mbstr, err := mbase.Encode(mbase.Base58BTC, c.bytesV1())
+		if err != nil {
+			panic("should not error with hardcoded mbase: " + err.Error())
+		}
+
+		return mbstr
+	default:
+		return "<unsupported cid version>"
+	}
+}
+
+func (c *Cid) Bytes() ([]byte, error) {
+	switch c.Version {
+	case 0:
+		return c.bytesV0(), nil
+	case 1:
+		return c.bytesV1(), nil
+	default:
+		return nil, fmt.Errorf("unsupported cid version")
+	}
+}
+
+func (c *Cid) bytesV0() []byte {
+	return []byte(c.Hash)
+}
+
+func (c *Cid) bytesV1() []byte {
 	buf := make([]byte, 8+len(c.Hash))
 	n := binary.PutUvarint(buf, c.Version)
 	n += binary.PutUvarint(buf[n:], c.Type)
diff --git a/cid_test.go b/cid_test.go
index 8d274e3..2a1890b 100644
--- a/cid_test.go
+++ b/cid_test.go
@@ -7,6 +7,20 @@ import (
 	mh "github.com/jbenet/go-multihash"
 )
 
+func assertEqual(t *testing.T, a, b *Cid) {
+	if a.Type != b.Type {
+		t.Fatal("mismatch on type")
+	}
+
+	if a.Version != b.Version {
+		t.Fatal("mismatch on version")
+	}
+
+	if !bytes.Equal(a.Hash, b.Hash) {
+		t.Fatal("multihash mismatch")
+	}
+}
+
 func TestBasicMarshaling(t *testing.T) {
 	h, err := mh.Sum([]byte("TEST"), mh.SHA3, 4)
 	if err != nil {
@@ -19,22 +33,67 @@ func TestBasicMarshaling(t *testing.T) {
 		Hash:    h,
 	}
 
-	data := cid.Bytes()
+	data, err := cid.Bytes()
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	out, err := Cast(data)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	if out.Type != cid.Type {
-		t.Fatal("mismatch on type")
+	assertEqual(t, cid, out)
+
+	s := cid.String()
+	out2, err := Decode(s)
+	if err != nil {
+		t.Fatal(err)
 	}
 
-	if out.Version != cid.Version {
-		t.Fatal("mismatch on version")
+	assertEqual(t, cid, out2)
+}
+
+func TestV0Handling(t *testing.T) {
+	old := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
+
+	cid, err := Decode(old)
+	if err != nil {
+		t.Fatal(err)
 	}
 
-	if !bytes.Equal(out.Hash, cid.Hash) {
-		t.Fatal("multihash mismatch")
+	if cid.Version != 0 {
+		t.Fatal("should have gotten version 0 cid")
+	}
+
+	if cid.Hash.B58String() != old {
+		t.Fatal("marshaling roundtrip failed")
+	}
+
+	if cid.String() != old {
+		t.Fatal("marshaling roundtrip failed")
+	}
+}
+
+func TestV0ErrorCases(t *testing.T) {
+	badb58 := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zIII"
+	_, err := Decode(badb58)
+	if err == nil {
+		t.Fatal("should have failed to decode that ref")
+	}
+}
+
+func TestBadVersion(t *testing.T) {
+	c := &Cid{
+		Version: 17,
+	}
+
+	if c.String() != UnsupportedVersionString {
+		t.Fatal("expected unsup string")
+	}
+
+	_, err := c.Bytes()
+	if err == nil {
+		t.Fatal("shouldnt have succeeded in calling bytes")
 	}
 }