gx publish 0.7.24

cid-fmt Enhancments

.gitignore

@@ -0,0 +1 @@
+cid-fuzz.zip

.gx/lastpubver

@@ -1 +1 @@
-0.0.0: QmWzxM6XsNv1GoLs4dpQBay2NdMSWXRTFKmZwSHcsxg8ys
+0.7.24: Qmdu2AYUV7yMoVBQPxXNfe7FJcdx16kYtsx6jAPKWQYF1y

.travis.yml

@@ -0,0 +1,24 @@
+sudo: false
+
+
+language: go
+go:
+  - 'tip'
+  
+install:
+  - go get github.com/whyrusleeping/gx
+  - go get github.com/whyrusleeping/gx-go
+  - gx install --global
+script:
+  - gx test -v -race -coverprofile=coverage.txt -covermode=atomic .
+  
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
+
+cache:
+  directories:
+    - $GOPATH/src/gx
+
+notifications:
+email: false
+  

LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2016 Protocol Labs, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

Makefile

@@ -0,0 +1,16 @@
+all: deps
+
+gx:
+	go get github.com/whyrusleeping/gx
+	go get github.com/whyrusleeping/gx-go
+
+covertools:
+	go get github.com/mattn/goveralls
+	go get golang.org/x/tools/cmd/cover
+
+deps: gx covertools
+	gx --verbose install --global
+	gx-go rewrite
+
+publish:
+	gx-go rewrite --undo

README.md

@@ -0,0 +1,125 @@
+go-cid
+==================
+
+[![](https://img.shields.io/badge/made%20by-Protocol%20Labs-blue.svg?style=flat-square)](http://ipn.io)
+[![](https://img.shields.io/badge/project-IPFS-blue.svg?style=flat-square)](http://ipfs.io/)
+[![](https://img.shields.io/badge/freenode-%23ipfs-blue.svg?style=flat-square)](http://webchat.freenode.net/?channels=%23ipfs)
+[![](https://img.shields.io/badge/readme%20style-standard-brightgreen.svg?style=flat-square)](https://github.com/RichardLitt/standard-readme)
+[![GoDoc](https://godoc.org/github.com/ipfs/go-cid?status.svg)](https://godoc.org/github.com/ipfs/go-cid)
+[![Coverage Status](https://coveralls.io/repos/github/ipfs/go-cid/badge.svg?branch=master)](https://coveralls.io/github/ipfs/go-cid?branch=master)
+[![Travis CI](https://travis-ci.org/ipfs/go-cid.svg?branch=master)](https://travis-ci.org/ipfs/go-cid)
+
+> A package to handle content IDs in Go.
+
+This is an implementation in Go of the [CID spec](https://github.com/ipld/cid).
+It is used in `go-ipfs` and related packages to refer to a typed hunk of data.
+
+
+## Table of Contents
+
+- [Install](#install)
+- [Usage](#usage)
+- [API](#api)
+- [Contribute](#contribute)
+- [License](#license)
+
+## Install
+
+`go-cid` is a standard Go module which can be installed with:
+
+```sh
+go get github.com/ipfs/go-cid
+```
+
+Note that `go-cid` is packaged with Gx, so it is recommended to use Gx to install and use it (see Usage section).
+
+## Usage
+
+### Using Gx and Gx-go
+
+This module is packaged with [Gx](https://github.com/whyrusleeping/gx). In order to use it in your own project it is recommended that you:
+
+```sh
+go get -u github.com/whyrusleeping/gx
+go get -u github.com/whyrusleeping/gx-go
+cd <your-project-repository>
+gx init
+gx import github.com/ipfs/go-cid
+gx install --global
+gx-go --rewrite
+```
+
+Please check [Gx](https://github.com/whyrusleeping/gx) and [Gx-go](https://github.com/whyrusleeping/gx-go) documentation for more information.
+
+### Running tests
+
+Before running tests, please run:
+
+```sh
+make deps
+```
+
+This will make sure that dependencies are rewritten to known working versions.
+
+### Examples
+
+#### Parsing string input from users
+
+```go
+// Create a cid from a marshaled string
+c, err := cid.Decode("zdvgqEMYmNeH5fKciougvQcfzMcNjF3Z1tPouJ8C7pc3pe63k")
+if err != nil {...}
+
+fmt.Println("Got CID: ", c)
+```
+
+#### Creating a CID from scratch
+
+```go
+// Create a cid manually by specifying the 'prefix' parameters
+pref := cid.Prefix{
+	Version: 1,
+	Codec: cid.Raw,
+	MhType: mh.SHA2_256,
+	MhLength: -1, // default length
+}
+
+// And then feed it some data
+c, err := pref.Sum([]byte("Hello World!"))
+if err != nil {...}
+
+fmt.Println("Created CID: ", c)
+```
+
+#### Check if two CIDs match
+
+```go
+// To test if two cid's are equivalent, be sure to use the 'Equals' method:
+if c1.Equals(c2) {
+	fmt.Println("These two refer to the same exact data!")
+}
+```
+
+#### Check if some data matches a given CID
+
+```go
+// To check if some data matches a given cid, 
+// Get your CIDs prefix, and use that to sum the data in question:
+other, err := c.Prefix().Sum(mydata)
+if err != nil {...}
+
+if !c.Equals(other) {
+	fmt.Println("This data is different.")
+}
+
+```
+
+## Contribute
+
+PRs are welcome!
+
+Small note: If editing the Readme, please conform to the [standard-readme](https://github.com/RichardLitt/standard-readme) specification.
+
+## License
+
+MIT © Jeromy Johnson

builder.go

@@ -0,0 +1,74 @@
+package cid
+
+import (
+	mh "github.com/multiformats/go-multihash"
+)
+
+type Builder interface {
+	Sum(data []byte) (*Cid, error)
+	GetCodec() uint64
+	WithCodec(uint64) Builder
+}
+
+type V0Builder struct{}
+
+type V1Builder struct {
+	Codec    uint64
+	MhType   uint64
+	MhLength int // MhLength <= 0 means the default length
+}
+
+func (p Prefix) GetCodec() uint64 {
+	return p.Codec
+}
+
+func (p Prefix) WithCodec(c uint64) Builder {
+	if c == p.Codec {
+		return p
+	}
+	p.Codec = c
+	if c != DagProtobuf {
+		p.Version = 1
+	}
+	return p
+}
+
+func (p V0Builder) Sum(data []byte) (*Cid, error) {
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		return nil, err
+	}
+	return NewCidV0(hash), nil
+}
+
+func (p V0Builder) GetCodec() uint64 {
+	return DagProtobuf
+}
+
+func (p V0Builder) WithCodec(c uint64) Builder {
+	if c == DagProtobuf {
+		return p
+	}
+	return V1Builder{Codec: c, MhType: mh.SHA2_256}
+}
+
+func (p V1Builder) Sum(data []byte) (*Cid, error) {
+	mhLen := p.MhLength
+	if mhLen <= 0 {
+		mhLen = -1
+	}
+	hash, err := mh.Sum(data, p.MhType, mhLen)
+	if err != nil {
+		return nil, err
+	}
+	return NewCidV1(p.Codec, hash), nil
+}
+
+func (p V1Builder) GetCodec() uint64 {
+	return p.Codec
+}
+
+func (p V1Builder) WithCodec(c uint64) Builder {
+	p.Codec = c
+	return p
+}

builder_test.go

@@ -0,0 +1,92 @@
+package cid
+
+import (
+	"testing"
+
+	mh "github.com/multiformats/go-multihash"
+)
+
+func TestV0Builder(t *testing.T) {
+	data := []byte("this is some test content")
+
+	// Construct c1
+	format := V0Builder{}
+	c1, err := format.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Construct c2
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := NewCidV0(hash)
+
+	if !c1.Equals(c2) {
+		t.Fatal("cids mismatch")
+	}
+	if c1.Prefix() != c2.Prefix() {
+		t.Fatal("prefixes mismatch")
+	}
+}
+
+func TestV1Builder(t *testing.T) {
+	data := []byte("this is some test content")
+
+	// Construct c1
+	format := V1Builder{Codec: DagCBOR, MhType: mh.SHA2_256}
+	c1, err := format.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Construct c2
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := NewCidV1(DagCBOR, hash)
+
+	if !c1.Equals(c2) {
+		t.Fatal("cids mismatch")
+	}
+	if c1.Prefix() != c2.Prefix() {
+		t.Fatal("prefixes mismatch")
+	}
+}
+
+func TestCodecChange(t *testing.T) {
+	t.Run("Prefix-CidV0", func(t *testing.T) {
+		p := Prefix{Version: 0, Codec: DagProtobuf, MhType: mh.SHA2_256, MhLength: mh.DefaultLengths[mh.SHA2_256]}
+		testCodecChange(t, p)
+	})
+	t.Run("Prefix-CidV1", func(t *testing.T) {
+		p := Prefix{Version: 1, Codec: DagProtobuf, MhType: mh.SHA2_256, MhLength: mh.DefaultLengths[mh.SHA2_256]}
+		testCodecChange(t, p)
+	})
+	t.Run("V0Builder", func(t *testing.T) {
+		testCodecChange(t, V0Builder{})
+	})
+	t.Run("V1Builder", func(t *testing.T) {
+		testCodecChange(t, V1Builder{Codec: DagProtobuf, MhType: mh.SHA2_256})
+	})
+}
+
+func testCodecChange(t *testing.T, b Builder) {
+	data := []byte("this is some test content")
+
+	if b.GetCodec() != DagProtobuf {
+		t.Fatal("original builder not using Protobuf codec")
+	}
+
+	b = b.WithCodec(Raw)
+	c, err := b.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c.Type() != Raw {
+		t.Fatal("new cid codec did not change to Raw")
+	}
+}

cid-fmt/main.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	c "github.com/ipfs/go-cid"
+
+	mb "github.com/multiformats/go-multibase"
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: %s [-b multibase-code] [-v cid-version] <fmt-str> <cid> ...\n\n", os.Args[0])
+	fmt.Fprintf(os.Stderr, "<fmt-str> is either 'prefix' or a printf style format string:\n%s", c.FormatRef)
+	os.Exit(2)
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		usage()
+	}
+	newBase := mb.Encoding(-1)
+	var verConv func(cid *c.Cid) (*c.Cid, error)
+	args := os.Args[1:]
+outer:
+	for {
+		switch args[0] {
+		case "-b":
+			if len(args) < 2 {
+				usage()
+			}
+			encoder, err := mb.EncoderByName(args[1])
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %s\n", err.Error())
+				os.Exit(2)
+			}
+			newBase = encoder.Encoding()
+			args = args[2:]
+		case "-v":
+			if len(args) < 2 {
+				usage()
+			}
+			switch args[1] {
+			case "0":
+				verConv = toCidV0
+			case "1":
+				verConv = toCidV1
+			default:
+				fmt.Fprintf(os.Stderr, "Error: Invalid cid version: %s\n", args[1])
+				os.Exit(2)
+			}
+			args = args[2:]
+		default:
+			break outer
+		}
+	}
+	if len(args) < 2 {
+		usage()
+	}
+	fmtStr := args[0]
+	switch fmtStr {
+	case "prefix":
+		fmtStr = "%P"
+	default:
+		if strings.IndexByte(fmtStr, '%') == -1 {
+			fmt.Fprintf(os.Stderr, "Error: Invalid format string: %s\n", fmtStr)
+			os.Exit(2)
+		}
+	}
+	for _, cidStr := range args[1:] {
+		cid, err := c.Decode(cidStr)
+		if err != nil {
+			fmt.Fprintf(os.Stdout, "!INVALID_CID!\n")
+			errorMsg("%s: %v", cidStr, err)
+			// Don't abort on a bad cid
+			continue
+		}
+		base := newBase
+		if newBase == -1 {
+			base, _ = c.ExtractEncoding(cidStr)
+		}
+		if verConv != nil {
+			cid, err = verConv(cid)
+			if err != nil {
+				fmt.Fprintf(os.Stdout, "!ERROR!\n")
+				errorMsg("%s: %v", cidStr, err)
+				// Don't abort on a bad conversion
+				continue
+			}
+		}
+		str, err := c.Format(fmtStr, base, cid)
+		switch err.(type) {
+		case c.FormatStringError:
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(2)
+		default:
+			fmt.Fprintf(os.Stdout, "!ERROR!\n")
+			errorMsg("%s: %v", cidStr, err)
+			// Don't abort on cid specific errors
+			continue
+		case nil:
+			// no error
+		}
+		fmt.Fprintf(os.Stdout, "%s\n", str)
+	}
+	os.Exit(exitCode)
+}
+
+var exitCode = 0
+
+func errorMsg(fmtStr string, a ...interface{}) {
+	fmt.Fprintf(os.Stderr, "Error: ")
+	fmt.Fprintf(os.Stderr, fmtStr, a...)
+	fmt.Fprintf(os.Stderr, "\n")
+	exitCode = 1
+}
+
+func toCidV0(cid *c.Cid) (*c.Cid, error) {
+	if cid.Type() != c.DagProtobuf {
+		return nil, fmt.Errorf("can't convert non-protobuf nodes to cidv0")
+	}
+	return c.NewCidV0(cid.Hash()), nil
+}
+
+func toCidV1(cid *c.Cid) (*c.Cid, error) {
+	return c.NewCidV1(cid.Type(), cid.Hash()), nil
+}

cid-fmt/main_test.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	c "github.com/ipfs/go-cid"
+)
+
+func TestCidConv(t *testing.T) {
+	cidv0 := "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"
+	cidv1 := "zdj7WbTaiJT1fgatdet9Ei9iDB5hdCxkbVyhyh8YTUnXMiwYi"
+	cid, err := c.Decode(cidv0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cid, err = toCidV1(cid)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if cid.String() != cidv1 {
+		t.Fatal("conversion failure")
+	}
+	cid, err = toCidV0(cid)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cidStr := cid.String()
+	if cidStr != cidv0 {
+		t.Error(fmt.Sprintf("conversion failure, expected: %s; but got: %s", cidv0, cidStr))
+	}
+}
+
+func TestBadCidConv(t *testing.T) {
+	// this cid is a raw leaf and should not be able to convert to cidv0
+	cidv1 := "zb2rhhzX7uSKrtQ2ZZXFAabKiKFYZrJqKY2KE1cJ8yre2GSWZ"
+	cid, err := c.Decode(cidv1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cid, err = toCidV0(cid)
+	if err == nil {
+		t.Fatal("expected failure")
+	}
+}

cid.go

@@ -1,46 +1,201 @@
+// Package cid implements the Content-IDentifiers specification
+// (https://github.com/ipld/cid) in Go. CIDs are
+// self-describing content-addressed identifiers useful for
+// distributed information systems. CIDs are used in the IPFS
+// (https://ipfs.io) project ecosystem.
+//
+// CIDs have two major versions. A CIDv0 corresponds to a multihash of type
+// DagProtobuf, is deprecated and exists for compatibility reasons. Usually,
+// CIDv1 should be used.
+//
+// A CIDv1 has four parts:
+//
+//     <cidv1> ::= <multibase-prefix><cid-version><multicodec-packed-content-type><multihash-content-address>
+//
+// As shown above, the CID implementation relies heavily on Multiformats,
+// particularly Multibase
+// (https://github.com/multiformats/go-multibase), Multicodec
+// (https://github.com/multiformats/multicodec) and Multihash
+// implementations (https://github.com/multiformats/go-multihash).
 package cid
 
 import (
 	"bytes"
 	"encoding/binary"
+	"encoding/json"
+	"errors"
 	"fmt"
+	"strings"
 
-	mh "github.com/jbenet/go-multihash"
 	mbase "github.com/multiformats/go-multibase"
+	mh "github.com/multiformats/go-multihash"
 )
 
+// UnsupportedVersionString just holds an error message
 const UnsupportedVersionString = "<unsupported cid version>"
 
-const (
-	Protobuf = iota
-	Raw
-	JSON
-	CBOR
+var (
+	// ErrVarintBuffSmall means that a buffer passed to the cid parser was not
+	// long enough, or did not contain an invalid cid
+	ErrVarintBuffSmall = errors.New("reading varint: buffer too small")
+
+	// ErrVarintTooBig means that the varint in the given cid was above the
+	// limit of 2^64
+	ErrVarintTooBig = errors.New("reading varint: varint bigger than 64bits" +
+		" and not supported")
+
+	// ErrCidTooShort means that the cid passed to decode was not long
+	// enough to be a valid Cid
+	ErrCidTooShort = errors.New("cid too short")
+
+	// ErrInvalidEncoding means that selected encoding is not supported
+	// by this Cid version
+	ErrInvalidEncoding = errors.New("invalid base encoding")
 )
 
-func NewCidV0(h mh.Multihash) *Cid {
+// These are multicodec-packed content types. The should match
+// the codes described in the authoritative document:
+// https://github.com/multiformats/multicodec/blob/master/table.csv
+const (
+	Raw = 0x55
+
+	DagProtobuf = 0x70
+	DagCBOR     = 0x71
+
+	GitRaw = 0x78
+
+	EthBlock           = 0x90
+	EthBlockList       = 0x91
+	EthTxTrie          = 0x92
+	EthTx              = 0x93
+	EthTxReceiptTrie   = 0x94
+	EthTxReceipt       = 0x95
+	EthStateTrie       = 0x96
+	EthAccountSnapshot = 0x97
+	EthStorageTrie     = 0x98
+	BitcoinBlock       = 0xb0
+	BitcoinTx          = 0xb1
+	ZcashBlock         = 0xc0
+	ZcashTx            = 0xc1
+	DecredBlock        = 0xe0
+	DecredTx           = 0xe1
+)
+
+// Codecs maps the name of a codec to its type
+var Codecs = map[string]uint64{
+	"v0":                   DagProtobuf,
+	"raw":                  Raw,
+	"protobuf":             DagProtobuf,
+	"cbor":                 DagCBOR,
+	"git-raw":              GitRaw,
+	"eth-block":            EthBlock,
+	"eth-block-list":       EthBlockList,
+	"eth-tx-trie":          EthTxTrie,
+	"eth-tx":               EthTx,
+	"eth-tx-receipt-trie":  EthTxReceiptTrie,
+	"eth-tx-receipt":       EthTxReceipt,
+	"eth-state-trie":       EthStateTrie,
+	"eth-account-snapshot": EthAccountSnapshot,
+	"eth-storage-trie":     EthStorageTrie,
+	"bitcoin-block":        BitcoinBlock,
+	"bitcoin-tx":           BitcoinTx,
+	"zcash-block":          ZcashBlock,
+	"zcash-tx":             ZcashTx,
+	"decred-block":         DecredBlock,
+	"decred-tx":            DecredTx,
+}
+
+// CodecToStr maps the numeric codec to its name
+var CodecToStr = map[uint64]string{
+	Raw:                "raw",
+	DagProtobuf:        "protobuf",
+	DagCBOR:            "cbor",
+	GitRaw:             "git-raw",
+	EthBlock:           "eth-block",
+	EthBlockList:       "eth-block-list",
+	EthTxTrie:          "eth-tx-trie",
+	EthTx:              "eth-tx",
+	EthTxReceiptTrie:   "eth-tx-receipt-trie",
+	EthTxReceipt:       "eth-tx-receipt",
+	EthStateTrie:       "eth-state-trie",
+	EthAccountSnapshot: "eth-account-snapshot",
+	EthStorageTrie:     "eth-storage-trie",
+	BitcoinBlock:       "bitcoin-block",
+	BitcoinTx:          "bitcoin-tx",
+	ZcashBlock:         "zcash-block",
+	ZcashTx:            "zcash-tx",
+	DecredBlock:        "decred-block",
+	DecredTx:           "decred-tx",
+}
+
+// NewCidV0 returns a Cid-wrapped multihash.
+// They exist to allow IPFS to work with Cids while keeping
+// compatibility with the plain-multihash format used used in IPFS.
+// NewCidV1 should be used preferentially.
+func NewCidV0(mhash mh.Multihash) *Cid {
 	return &Cid{
 		version: 0,
-		codec:   Protobuf,
-		hash:    h,
+		codec:   DagProtobuf,
+		hash:    mhash,
 	}
 }
 
-func NewCidV1(c uint64, h mh.Multihash) *Cid {
+// NewCidV1 returns a new Cid using the given multicodec-packed
+// content type.
+func NewCidV1(codecType uint64, mhash mh.Multihash) *Cid {
 	return &Cid{
 		version: 1,
-		codec:   c,
-		hash:    h,
+		codec:   codecType,
+		hash:    mhash,
 	}
 }
 
+// Cid represents a self-describing content adressed
+// identifier. It is formed by a Version, a Codec (which indicates
+// a multicodec-packed content type) and a Multihash.
 type Cid struct {
 	version uint64
 	codec   uint64
 	hash    mh.Multihash
 }
 
+// Parse is a short-hand function to perform Decode, Cast etc... on
+// a generic interface{} type.
+func Parse(v interface{}) (*Cid, error) {
+	switch v2 := v.(type) {
+	case string:
+		if strings.Contains(v2, "/ipfs/") {
+			return Decode(strings.Split(v2, "/ipfs/")[1])
+		}
+		return Decode(v2)
+	case []byte:
+		return Cast(v2)
+	case mh.Multihash:
+		return NewCidV0(v2), nil
+	case *Cid:
+		return v2, nil
+	default:
+		return nil, fmt.Errorf("can't parse %+v as Cid", v2)
+	}
+}
+
+// Decode parses a Cid-encoded string and returns a Cid object.
+// For CidV1, a Cid-encoded string is primarily a multibase string:
+//
+//     <multibase-type-code><base-encoded-string>
+//
+// The base-encoded string represents a:
+//
+// <version><codec-type><multihash>
+//
+// Decode will also detect and parse CidV0 strings. Strings
+// starting with "Qm" are considered CidV0 and treated directly
+// as B58-encoded multihashes.
 func Decode(v string) (*Cid, error) {
+	if len(v) < 2 {
+		return nil, ErrCidTooShort
+	}
+
 	if len(v) == 46 && v[:2] == "Qm" {
 		hash, err := mh.FromB58String(v)
 		if err != nil {
@@ -58,6 +213,50 @@ func Decode(v string) (*Cid, error) {
 	return Cast(data)
 }
 
+// Extract the encoding from a Cid.  If Decode on the same string did
+// not return an error neither will this function.
+func ExtractEncoding(v string) (mbase.Encoding, error) {
+	if len(v) < 2 {
+		return -1, ErrCidTooShort
+	}
+
+	if len(v) == 46 && v[:2] == "Qm" {
+		return mbase.Base58BTC, nil
+	}
+
+	encoding := mbase.Encoding(v[0])
+
+	// check encoding is valid
+	_, err := mbase.NewEncoder(encoding)
+	if err != nil {
+		return -1, err
+	}
+
+	return encoding, nil
+}
+
+func uvError(read int) error {
+	switch {
+	case read == 0:
+		return ErrVarintBuffSmall
+	case read < 0:
+		return ErrVarintTooBig
+	default:
+		return nil
+	}
+}
+
+// Cast takes a Cid data slice, parses it and returns a Cid.
+// For CidV1, the data buffer is in the form:
+//
+//     <version><codec-type><multihash>
+//
+// CidV0 are also supported. In particular, data buffers starting
+// with length 34 bytes, which starts with bytes [18,32...] are considered
+// binary multihashes.
+//
+// Please use decode when parsing a regular Cid string, as Cast does not
+// expect multibase-encoded data. Cast accepts the output of Cid.Bytes().
 func Cast(data []byte) (*Cid, error) {
 	if len(data) == 34 && data[0] == 18 && data[1] == 32 {
 		h, err := mh.Cast(data)
@@ -66,18 +265,25 @@ func Cast(data []byte) (*Cid, error) {
 		}
 
 		return &Cid{
-			codec:   Protobuf,
+			codec:   DagProtobuf,
 			version: 0,
 			hash:    h,
 		}, nil
 	}
 
 	vers, n := binary.Uvarint(data)
+	if err := uvError(n); err != nil {
+		return nil, err
+	}
+
 	if vers != 0 && vers != 1 {
 		return nil, fmt.Errorf("invalid cid version number: %d", vers)
 	}
 
 	codec, cn := binary.Uvarint(data[n:])
+	if err := uvError(cn); err != nil {
+		return nil, err
+	}
 
 	rest := data[n+cn:]
 	h, err := mh.Cast(rest)
@@ -92,10 +298,14 @@ func Cast(data []byte) (*Cid, error) {
 	}, nil
 }
 
+// Type returns the multicodec-packed content type of a Cid.
 func (c *Cid) Type() uint64 {
 	return c.codec
 }
 
+// String returns the default string representation of a
+// Cid. Currently, Base58 is used as the encoding for the
+// multibase string.
 func (c *Cid) String() string {
 	switch c.version {
 	case 0:
@@ -112,10 +322,30 @@ func (c *Cid) String() string {
 	}
 }
 
+// String returns the string representation of a Cid
+// encoded is selected base
+func (c *Cid) StringOfBase(base mbase.Encoding) (string, error) {
+	switch c.version {
+	case 0:
+		if base != mbase.Base58BTC {
+			return "", ErrInvalidEncoding
+		}
+		return c.hash.B58String(), nil
+	case 1:
+		return mbase.Encode(base, c.bytesV1())
+	default:
+		panic("not possible to reach this point")
+	}
+}
+
+// Hash returns the multihash contained by a Cid.
 func (c *Cid) Hash() mh.Multihash {
 	return c.hash
 }
 
+// Bytes returns the byte representation of a Cid.
+// The output of bytes can be parsed back into a Cid
+// with Cast().
 func (c *Cid) Bytes() []byte {
 	switch c.version {
 	case 0:
@@ -132,25 +362,45 @@ func (c *Cid) bytesV0() []byte {
 }
 
 func (c *Cid) bytesV1() []byte {
-	buf := make([]byte, 8+len(c.hash))
+	// two 8 bytes (max) numbers plus hash
+	buf := make([]byte, 2*binary.MaxVarintLen64+len(c.hash))
 	n := binary.PutUvarint(buf, c.version)
 	n += binary.PutUvarint(buf[n:], c.codec)
-	copy(buf[n:], c.hash)
+	cn := copy(buf[n:], c.hash)
+	if cn != len(c.hash) {
+		panic("copy hash length is inconsistent")
+	}
 
 	return buf[:n+len(c.hash)]
 }
 
+// Equals checks that two Cids are the same.
+// In order for two Cids to be considered equal, the
+// Version, the Codec and the Multihash must match.
 func (c *Cid) Equals(o *Cid) bool {
 	return c.codec == o.codec &&
 		c.version == o.version &&
 		bytes.Equal(c.hash, o.hash)
 }
 
+// UnmarshalJSON parses the JSON representation of a Cid.
 func (c *Cid) UnmarshalJSON(b []byte) error {
 	if len(b) < 2 {
 		return fmt.Errorf("invalid cid json blob")
 	}
-	out, err := Decode(string(b[1 : len(b)-1]))
+	obj := struct {
+		CidTarget string `json:"/"`
+	}{}
+	err := json.Unmarshal(b, &obj)
+	if err != nil {
+		return err
+	}
+
+	if obj.CidTarget == "" {
+		return fmt.Errorf("cid was incorrectly formatted")
+	}
+
+	out, err := Decode(obj.CidTarget)
 	if err != nil {
 		return err
 	}
@@ -161,6 +411,111 @@ func (c *Cid) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func (c *Cid) MarshalJSON() ([]byte, error) {
-	return []byte(fmt.Sprintf("\"%s\"", c.String())), nil
+// MarshalJSON procudes a JSON representation of a Cid, which looks as follows:
+//
+//    { "/": "<cid-string>" }
+//
+// Note that this formatting comes from the IPLD specification
+// (https://github.com/ipld/specs/tree/master/ipld)
+func (c Cid) MarshalJSON() ([]byte, error) {
+	return []byte(fmt.Sprintf("{\"/\":\"%s\"}", c.String())), nil
+}
+
+// KeyString casts the result of cid.Bytes() as a string, and returns it.
+func (c *Cid) KeyString() string {
+	return string(c.Bytes())
+}
+
+// Loggable returns a Loggable (as defined by
+// https://godoc.org/github.com/ipfs/go-log).
+func (c *Cid) Loggable() map[string]interface{} {
+	return map[string]interface{}{
+		"cid": c,
+	}
+}
+
+// Prefix builds and returns a Prefix out of a Cid.
+func (c *Cid) Prefix() Prefix {
+	dec, _ := mh.Decode(c.hash) // assuming we got a valid multiaddr, this will not error
+	return Prefix{
+		MhType:   dec.Code,
+		MhLength: dec.Length,
+		Version:  c.version,
+		Codec:    c.codec,
+	}
+}
+
+// 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
+// any actual content information.
+// NOTE: The use -1 in MhLength to mean default length is deprecated,
+//   use the V0Builder or V1Builder structures instead
+type Prefix struct {
+	Version  uint64
+	Codec    uint64
+	MhType   uint64
+	MhLength int
+}
+
+// Sum uses the information in a prefix to perform a multihash.Sum()
+// and return a newly constructed Cid with the resulting multihash.
+func (p Prefix) Sum(data []byte) (*Cid, error) {
+	hash, err := mh.Sum(data, p.MhType, p.MhLength)
+	if err != nil {
+		return nil, err
+	}
+
+	switch p.Version {
+	case 0:
+		return NewCidV0(hash), nil
+	case 1:
+		return NewCidV1(p.Codec, hash), nil
+	default:
+		return nil, fmt.Errorf("invalid cid version")
+	}
+}
+
+// Bytes returns a byte representation of a Prefix. It looks like:
+//
+//     <version><codec><mh-type><mh-length>
+func (p Prefix) Bytes() []byte {
+	buf := make([]byte, 4*binary.MaxVarintLen64)
+	n := binary.PutUvarint(buf, p.Version)
+	n += binary.PutUvarint(buf[n:], p.Codec)
+	n += binary.PutUvarint(buf[n:], uint64(p.MhType))
+	n += binary.PutUvarint(buf[n:], uint64(p.MhLength))
+	return buf[:n]
+}
+
+// PrefixFromBytes parses a Prefix-byte representation onto a
+// Prefix.
+func PrefixFromBytes(buf []byte) (Prefix, error) {
+	r := bytes.NewReader(buf)
+	vers, err := binary.ReadUvarint(r)
+	if err != nil {
+		return Prefix{}, err
+	}
+
+	codec, err := binary.ReadUvarint(r)
+	if err != nil {
+		return Prefix{}, err
+	}
+
+	mhtype, err := binary.ReadUvarint(r)
+	if err != nil {
+		return Prefix{}, err
+	}
+
+	mhlen, err := binary.ReadUvarint(r)
+	if err != nil {
+		return Prefix{}, err
+	}
+
+	return Prefix{
+		Version:  vers,
+		Codec:    codec,
+		MhType:   mhtype,
+		MhLength: int(mhlen),
+	}, nil
 }

cid_fuzz.go

@@ -0,0 +1,37 @@
+// +build gofuzz
+
+package cid
+
+func Fuzz(data []byte) int {
+	cid, err := Cast(data)
+
+	if err != nil {
+		return 0
+	}
+
+	_ = cid.Bytes()
+	_ = cid.String()
+	p := cid.Prefix()
+	_ = p.Bytes()
+
+	if !cid.Equals(cid) {
+		panic("inequality")
+	}
+
+	// json loop
+	json, err := cid.MarshalJSON()
+	if err != nil {
+		panic(err.Error())
+	}
+	cid2 := &Cid{}
+	err = cid2.UnmarshalJSON(json)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	if !cid.Equals(cid2) {
+		panic("json loop not equal")
+	}
+
+	return 1
+}

cid_test.go

@@ -2,11 +2,41 @@ package cid
 
 import (
 	"bytes"
+	"encoding/json"
+	"fmt"
+	"math/rand"
+	"strings"
 	"testing"
 
-	mh "github.com/jbenet/go-multihash"
+	mbase "github.com/multiformats/go-multibase"
+	mh "github.com/multiformats/go-multihash"
 )
 
+// Copying the "silly test" idea from
+// https://github.com/multiformats/go-multihash/blob/7aa9f26a231c6f34f4e9fad52bf580fd36627285/multihash_test.go#L13
+// Makes it so changing the table accidentally has to happen twice.
+var tCodecs = map[uint64]string{
+	Raw:                "raw",
+	DagProtobuf:        "protobuf",
+	DagCBOR:            "cbor",
+	GitRaw:             "git-raw",
+	EthBlock:           "eth-block",
+	EthBlockList:       "eth-block-list",
+	EthTxTrie:          "eth-tx-trie",
+	EthTx:              "eth-tx",
+	EthTxReceiptTrie:   "eth-tx-receipt-trie",
+	EthTxReceipt:       "eth-tx-receipt",
+	EthStateTrie:       "eth-state-trie",
+	EthAccountSnapshot: "eth-account-snapshot",
+	EthStorageTrie:     "eth-storage-trie",
+	BitcoinBlock:       "bitcoin-block",
+	BitcoinTx:          "bitcoin-tx",
+	ZcashBlock:         "zcash-block",
+	ZcashTx:            "zcash-tx",
+	DecredBlock:        "decred-block",
+	DecredTx:           "decred-tx",
+}
+
 func assertEqual(t *testing.T, a, b *Cid) {
 	if a.codec != b.codec {
 		t.Fatal("mismatch on type")
@@ -21,6 +51,26 @@ func assertEqual(t *testing.T, a, b *Cid) {
 	}
 }
 
+func TestTable(t *testing.T) {
+	if len(tCodecs) != len(Codecs)-1 {
+		t.Errorf("Item count mismatch in the Table of Codec. Should be %d, got %d", len(tCodecs)+1, len(Codecs))
+	}
+
+	for k, v := range tCodecs {
+		if Codecs[v] != k {
+			t.Errorf("Table mismatch: 0x%x %s", k, v)
+		}
+	}
+}
+
+// The table returns cid.DagProtobuf for "v0"
+// so we test it apart
+func TestTableForV0(t *testing.T) {
+	if Codecs["v0"] != DagProtobuf {
+		t.Error("Table mismatch: Codecs[\"v0\"] should resolve to DagProtobuf (0x70)")
+	}
+}
+
 func TestBasicMarshaling(t *testing.T) {
 	h, err := mh.Sum([]byte("TEST"), mh.SHA3, 4)
 	if err != nil {
@@ -51,6 +101,67 @@ func TestBasicMarshaling(t *testing.T) {
 	assertEqual(t, cid, out2)
 }
 
+func TestBasesMarshaling(t *testing.T) {
+	h, err := mh.Sum([]byte("TEST"), mh.SHA3, 4)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cid := &Cid{
+		codec:   7,
+		version: 1,
+		hash:    h,
+	}
+
+	data := cid.Bytes()
+
+	out, err := Cast(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertEqual(t, cid, out)
+
+	testBases := []mbase.Encoding{
+		mbase.Base16,
+		mbase.Base32,
+		mbase.Base32hex,
+		mbase.Base32pad,
+		mbase.Base32hexPad,
+		mbase.Base58BTC,
+		mbase.Base58Flickr,
+		mbase.Base64pad,
+		mbase.Base64urlPad,
+		mbase.Base64url,
+		mbase.Base64,
+	}
+
+	for _, b := range testBases {
+		s, err := cid.StringOfBase(b)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if s[0] != byte(b) {
+			t.Fatal("Invalid multibase header")
+		}
+
+		out2, err := Decode(s)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		assertEqual(t, cid, out2)
+	}
+}
+
+func TestEmptyString(t *testing.T) {
+	_, err := Decode("")
+	if err == nil {
+		t.Fatal("shouldnt be able to parse an empty cid")
+	}
+}
+
 func TestV0Handling(t *testing.T) {
 	old := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
 
@@ -79,3 +190,227 @@ func TestV0ErrorCases(t *testing.T) {
 		t.Fatal("should have failed to decode that ref")
 	}
 }
+
+func TestNewPrefixV1(t *testing.T) {
+	data := []byte("this is some test content")
+
+	// Construct c1
+	prefix := NewPrefixV1(DagCBOR, mh.SHA2_256)
+	c1, err := prefix.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c1.Prefix() != prefix {
+		t.Fatal("prefix not preserved")
+	}
+
+	// Construct c2
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := NewCidV1(DagCBOR, hash)
+
+	if !c1.Equals(c2) {
+		t.Fatal("cids mismatch")
+	}
+	if c1.Prefix() != c2.Prefix() {
+		t.Fatal("prefixes mismatch")
+	}
+}
+
+func TestNewPrefixV0(t *testing.T) {
+	data := []byte("this is some test content")
+
+	// Construct c1
+	prefix := NewPrefixV0(mh.SHA2_256)
+	c1, err := prefix.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c1.Prefix() != prefix {
+		t.Fatal("prefix not preserved")
+	}
+
+	// Construct c2
+	hash, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := NewCidV0(hash)
+
+	if !c1.Equals(c2) {
+		t.Fatal("cids mismatch")
+	}
+	if c1.Prefix() != c2.Prefix() {
+		t.Fatal("prefixes mismatch")
+	}
+}
+
+func TestPrefixRoundtrip(t *testing.T) {
+	data := []byte("this is some test content")
+	hash, _ := mh.Sum(data, mh.SHA2_256, -1)
+	c := NewCidV1(DagCBOR, hash)
+
+	pref := c.Prefix()
+
+	c2, err := pref.Sum(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !c.Equals(c2) {
+		t.Fatal("output didnt match original")
+	}
+
+	pb := pref.Bytes()
+
+	pref2, err := PrefixFromBytes(pb)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if pref.Version != pref2.Version || pref.Codec != pref2.Codec ||
+		pref.MhType != pref2.MhType || pref.MhLength != pref2.MhLength {
+		t.Fatal("input prefix didnt match output")
+	}
+}
+
+func Test16BytesVarint(t *testing.T) {
+	data := []byte("this is some test content")
+	hash, _ := mh.Sum(data, mh.SHA2_256, -1)
+	c := NewCidV1(DagCBOR, hash)
+
+	c.codec = 1 << 63
+	_ = c.Bytes()
+}
+
+func TestFuzzCid(t *testing.T) {
+	buf := make([]byte, 128)
+	for i := 0; i < 200; i++ {
+		s := rand.Intn(128)
+		rand.Read(buf[:s])
+		_, _ = Cast(buf[:s])
+	}
+}
+
+func TestParse(t *testing.T) {
+	cid, err := Parse(123)
+	if err == nil {
+		t.Fatalf("expected error from Parse()")
+	}
+	if !strings.Contains(err.Error(), "can't parse 123 as Cid") {
+		t.Fatalf("expected int error, got %s", err.Error())
+	}
+
+	theHash := "QmdfTbBqBPQ7VNxZEYEj14VmRuZBkqFbiwReogJgS1zR1n"
+	h, err := mh.FromB58String(theHash)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertions := [][]interface{}{
+		[]interface{}{NewCidV0(h), theHash},
+		[]interface{}{NewCidV0(h).Bytes(), theHash},
+		[]interface{}{h, theHash},
+		[]interface{}{theHash, theHash},
+		[]interface{}{"/ipfs/" + theHash, theHash},
+		[]interface{}{"https://ipfs.io/ipfs/" + theHash, theHash},
+		[]interface{}{"http://localhost:8080/ipfs/" + theHash, theHash},
+	}
+
+	assert := func(arg interface{}, expected string) error {
+		cid, err = Parse(arg)
+		if err != nil {
+			return err
+		}
+		if cid.version != 0 {
+			return fmt.Errorf("expected version 0, got %s", string(cid.version))
+		}
+		actual := cid.Hash().B58String()
+		if actual != expected {
+			return fmt.Errorf("expected hash %s, got %s", expected, actual)
+		}
+		actual = cid.String()
+		if actual != expected {
+			return fmt.Errorf("expected string %s, got %s", expected, actual)
+		}
+		return nil
+	}
+
+	for _, args := range assertions {
+		err := assert(args[0], args[1].(string))
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestHexDecode(t *testing.T) {
+	hexcid := "f015512209d8453505bdc6f269678e16b3e56c2a2948a41f2c792617cc9611ed363c95b63"
+	c, err := Decode(hexcid)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c.String() != "zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG" {
+		t.Fatal("hash value failed to round trip decoding from hex")
+	}
+}
+
+func ExampleDecode() {
+	encoded := "zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG"
+	c, err := Decode(encoded)
+	if err != nil {
+		fmt.Printf("Error: %s", err)
+		return
+	}
+
+	fmt.Println(c)
+	// Output: zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG
+}
+
+func TestFromJson(t *testing.T) {
+	cval := "zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG"
+	jsoncid := []byte(`{"/":"` + cval + `"}`)
+	var c Cid
+	err := json.Unmarshal(jsoncid, &c)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c.String() != cval {
+		t.Fatal("json parsing failed")
+	}
+}
+
+func TestJsonRoundTrip(t *testing.T) {
+	exp, err := Decode("zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify it works for a *Cid.
+	enc, err := json.Marshal(exp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var actual Cid
+	err = json.Unmarshal(enc, &actual)
+	if !exp.Equals(&actual) {
+		t.Fatal("cids not equal for *Cid")
+	}
+
+	// Verify it works for a Cid.
+	enc, err = json.Marshal(*exp)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var actual2 Cid
+	err = json.Unmarshal(enc, &actual2)
+	if !exp.Equals(&actual2) {
+		t.Fatal("cids not equal for Cid")
+	}
+}

codecov.yml

@@ -0,0 +1,3 @@
+coverage:
+  range: "50...100"
+comment: off

deprecated.go

@@ -0,0 +1,28 @@
+package cid
+
+import (
+	mh "github.com/multiformats/go-multihash"
+)
+
+// NewPrefixV0 returns a CIDv0 prefix with the specified multihash type.
+// DEPRECATED: Use V0Builder
+func NewPrefixV0(mhType uint64) Prefix {
+	return Prefix{
+		MhType:   mhType,
+		MhLength: mh.DefaultLengths[mhType],
+		Version:  0,
+		Codec:    DagProtobuf,
+	}
+}
+
+// NewPrefixV1 returns a CIDv1 prefix with the specified codec and multihash
+// type.
+// DEPRECATED: Use V1Builder
+func NewPrefixV1(codecType uint64, mhType uint64) Prefix {
+	return Prefix{
+		MhType:   mhType,
+		MhLength: mh.DefaultLengths[mhType],
+		Version:  1,
+		Codec:    codecType,
+	}
+}

format.go

@@ -0,0 +1,151 @@
+package cid
+
+import (
+	"bytes"
+	"fmt"
+
+	mb "github.com/multiformats/go-multibase"
+	mh "github.com/multiformats/go-multihash"
+)
+
+// FormatRef is a string documenting the format string for the Format function
+const FormatRef = `
+   %% literal %
+   %b multibase name
+   %B multibase code
+   %v version string
+   %V version number
+   %c codec name
+   %C codec code
+   %h multihash name
+   %H multihash code
+   %L hash digest length
+   %m multihash encoded in base %b (with multibase prefix)
+   %M multihash encoded in base %b without multibase prefix
+   %d hash digest encoded in base %b (with multibase prefix)
+   %D hash digest encoded in base %b without multibase prefix
+   %s cid string encoded in base %b (1)
+   %S cid string encoded in base %b without multibase prefix
+   %P cid prefix: %v-%c-%h-%L
+
+(1) For CID version 0 the multibase must be base58btc and no prefix is
+used.  For Cid version 1 the multibase prefix is included.
+`
+
+// Format formats a cid according to the format specificer as
+// documented in the FormatRef constant
+func Format(fmtStr string, base mb.Encoding, cid *Cid) (string, error) {
+	p := cid.Prefix()
+	var out bytes.Buffer
+	var err error
+	encoder, err := mb.NewEncoder(base)
+	if err != nil {
+		return "", err
+	}
+	for i := 0; i < len(fmtStr); i++ {
+		if fmtStr[i] != '%' {
+			out.WriteByte(fmtStr[i])
+			continue
+		}
+		i++
+		if i >= len(fmtStr) {
+			return "", FormatStringError{"premature end of format string", ""}
+		}
+		switch fmtStr[i] {
+		case '%':
+			out.WriteByte('%')
+		case 'b': // base name
+			out.WriteString(baseToString(base))
+		case 'B': // base code
+			out.WriteByte(byte(base))
+		case 'v': // version string
+			fmt.Fprintf(&out, "cidv%d", p.Version)
+		case 'V': // version num
+			fmt.Fprintf(&out, "%d", p.Version)
+		case 'c': // codec name
+			out.WriteString(codecToString(p.Codec))
+		case 'C': // codec code
+			fmt.Fprintf(&out, "%d", p.Codec)
+		case 'h': // hash fun name
+			out.WriteString(hashToString(p.MhType))
+		case 'H': // hash fun code
+			fmt.Fprintf(&out, "%d", p.MhType)
+		case 'L': // hash length
+			fmt.Fprintf(&out, "%d", p.MhLength)
+		case 'm', 'M': // multihash encoded in base %b
+			out.WriteString(encode(encoder, cid.Hash(), fmtStr[i] == 'M'))
+		case 'd', 'D': // hash digest encoded in base %b
+			dec, err := mh.Decode(cid.Hash())
+			if err != nil {
+				return "", err
+			}
+			out.WriteString(encode(encoder, dec.Digest, fmtStr[i] == 'D'))
+		case 's': // cid string encoded in base %b
+			str, err := cid.StringOfBase(base)
+			if err != nil {
+				return "", err
+			}
+			out.WriteString(str)
+		case 'S': // cid string without base prefix
+			out.WriteString(encode(encoder, cid.Bytes(), true))
+		case 'P': // prefix
+			fmt.Fprintf(&out, "cidv%d-%s-%s-%d",
+				p.Version,
+				codecToString(p.Codec),
+				hashToString(p.MhType),
+				p.MhLength,
+			)
+		default:
+			return "", FormatStringError{"unrecognized specifier in format string", fmtStr[i-1 : i+1]}
+		}
+
+	}
+	return out.String(), err
+}
+
+// FormatStringError is the error return from Format when the format
+// string is ill formed
+type FormatStringError struct {
+	Message   string
+	Specifier string
+}
+
+func (e FormatStringError) Error() string {
+	if e.Specifier == "" {
+		return e.Message
+	} else {
+		return fmt.Sprintf("%s: %s", e.Message, e.Specifier)
+	}
+}
+
+func baseToString(base mb.Encoding) string {
+	baseStr, ok := mb.EncodingToStr[base]
+	if !ok {
+		return fmt.Sprintf("base?%c", base)
+	}
+	return baseStr
+}
+
+func codecToString(num uint64) string {
+	name, ok := CodecToStr[num]
+	if !ok {
+		return fmt.Sprintf("codec?%d", num)
+	}
+	return name
+}
+
+func hashToString(num uint64) string {
+	name, ok := mh.Codes[num]
+	if !ok {
+		return fmt.Sprintf("hash?%d", num)
+	}
+	return name
+}
+
+func encode(base mb.Encoder, data []byte, strip bool) string {
+	str := base.Encode(data)
+	if strip {
+		return str[1:]
+	}
+	return str
+}

format_test.go

@@ -0,0 +1,73 @@
+package cid
+
+import (
+	"fmt"
+	"testing"
+
+	mb "github.com/multiformats/go-multibase"
+)
+
+func TestFmt(t *testing.T) {
+	cids := map[string]string{
+		"cidv0": "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn",
+		"cidv1": "zdj7WfLr9DhLrb1hsoSi4fSdjjxuZmeqgEtBPWxMLtPbDNbFD",
+	}
+	tests := []struct {
+		cidId   string
+		newBase mb.Encoding
+		fmtStr  string
+		result  string
+	}{
+		{"cidv0", -1, "%P", "cidv0-protobuf-sha2-256-32"},
+		{"cidv0", -1, "%b-%v-%c-%h-%L", "base58btc-cidv0-protobuf-sha2-256-32"},
+		{"cidv0", -1, "%s", "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"},
+		{"cidv0", -1, "%S", "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"},
+		{"cidv0", -1, "ver#%V/#%C/#%H/%L", "ver#0/#112/#18/32"},
+		{"cidv0", -1, "%m", "zQmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"},
+		{"cidv0", -1, "%M", "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn"},
+		{"cidv0", -1, "%d", "z72gdmFAgRzYHkJzKiL8MgMMRW3BTSCGyDHroPxJbxMJn"},
+		{"cidv0", -1, "%D", "72gdmFAgRzYHkJzKiL8MgMMRW3BTSCGyDHroPxJbxMJn"},
+		{"cidv0", 'B', "%S", "CIQFTFEEHEDF6KLBT32BFAGLXEZL4UWFNWM4LFTLMXQBCERZ6CMLX3Y"},
+		{"cidv0", 'B', "%B%S", "BCIQFTFEEHEDF6KLBT32BFAGLXEZL4UWFNWM4LFTLMXQBCERZ6CMLX3Y"},
+		{"cidv1", -1, "%P", "cidv1-protobuf-sha2-256-32"},
+		{"cidv1", -1, "%b-%v-%c-%h-%L", "base58btc-cidv1-protobuf-sha2-256-32"},
+		{"cidv1", -1, "%s", "zdj7WfLr9DhLrb1hsoSi4fSdjjxuZmeqgEtBPWxMLtPbDNbFD"},
+		{"cidv1", -1, "%S", "dj7WfLr9DhLrb1hsoSi4fSdjjxuZmeqgEtBPWxMLtPbDNbFD"},
+		{"cidv1", -1, "ver#%V/#%C/#%H/%L", "ver#1/#112/#18/32"},
+		{"cidv1", -1, "%m", "zQmYFbmndVP7QqAVWyKhpmMuQHMaD88pkK57RgYVimmoh5H"},
+		{"cidv1", -1, "%M", "QmYFbmndVP7QqAVWyKhpmMuQHMaD88pkK57RgYVimmoh5H"},
+		{"cidv1", -1, "%d", "zAux4gVVsLRMXtsZ9fd3tFEZN4jGYB6kP37fgoZNTc11H"},
+		{"cidv1", -1, "%D", "Aux4gVVsLRMXtsZ9fd3tFEZN4jGYB6kP37fgoZNTc11H"},
+		{"cidv1", 'B', "%s", "BAFYBEIETJGSRL3EQPQPCABV3G6IUBYTSIFVQ24XRRHD3JUETSKLTGQ7DJA"},
+		{"cidv1", 'B', "%S", "AFYBEIETJGSRL3EQPQPCABV3G6IUBYTSIFVQ24XRRHD3JUETSKLTGQ7DJA"},
+		{"cidv1", 'B', "%B%S", "BAFYBEIETJGSRL3EQPQPCABV3G6IUBYTSIFVQ24XRRHD3JUETSKLTGQ7DJA"},
+	}
+	for _, tc := range tests {
+		name := fmt.Sprintf("%s/%s", tc.cidId, tc.fmtStr)
+		if tc.newBase != -1 {
+			name = fmt.Sprintf("%s/%c", name, tc.newBase)
+		}
+		cidStr := cids[tc.cidId]
+		t.Run(name, func(t *testing.T) {
+			testFmt(t, cidStr, tc.newBase, tc.fmtStr, tc.result)
+		})
+	}
+}
+
+func testFmt(t *testing.T, cidStr string, newBase mb.Encoding, fmtStr string, result string) {
+	cid, err := Decode(cidStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	base := newBase
+	if newBase == -1 {
+		base, _ = ExtractEncoding(cidStr)
+	}
+	str, err := Format(fmtStr, base, cid)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if str != result {
+		t.Error(fmt.Sprintf("expected: %s; but got: %s", result, str))
+	}
+}

fuzz-data/corpus/cid0

@@ -0,0 +1 @@
+ ëgáD1üüÊe<C38A>-D˜/¹q3ø~å(Ä7`8–<38>‡n

fuzz-data/corpus/cid1

@@ -0,0 +1 @@
+
q -[<5B>ï<EFBFBD>h<EFBFBD>[<5B><10><>

package.json

@@ -1,28 +1,30 @@
 {
   "author": "whyrusleeping",
   "bugs": {
-    "url": "https://github.com/multiformats/go-cid"
+    "url": "https://github.com/ipfs/go-cid"
   },
   "gx": {
-    "dvcsimport": "github.com/multiformats/go-cid"
+    "dvcsimport": "github.com/ipfs/go-cid"
   },
   "gxDependencies": [
     {
       "author": "whyrusleeping",
-      "hash": "QmYf7ng2hG5XBtJA3tN34DQ2GUN5HNksEw1rLDkmr6vGku",
+      "hash": "QmPnFwZ2JXKnXgMw8CdBPxn7FWh6LLdjUjxV1fKHuJnkr8",
       "name": "go-multihash",
-      "version": "0.0.0"
+      "version": "1.0.8"
     },
     {
       "author": "whyrusleeping",
-      "hash": "QmYiTi9mKBMjfiup7na7PhJK7QEZPdMTJenLdgFYVQ2NUv",
+      "hash": "QmSbvata2WqNkqGtZNg8MR3SKwnB8iQ7vTPJgWqB8bC5kR",
       "name": "go-multibase",
-      "version": "0.2.0"
+      "version": "0.2.7"
     }
   ],
   "gxVersion": "0.8.0",
   "language": "go",
-  "license": "",
+  "license": "MIT",
   "name": "go-cid",
-  "version": "0.0.0"
+  "releaseCmd": "git commit -a -m \"gx publish $VERSION\"",
+  "version": "0.7.24"
 }
+

set.go

@@ -1,39 +1,49 @@
 package cid
 
+// Set is a implementation of a set of Cids, that is, a structure
+// to which holds a single copy of every Cids that is added to it.
 type Set struct {
 	set map[string]struct{}
 }
 
+// NewSet initializes and returns a new Set.
 func NewSet() *Set {
 	return &Set{set: make(map[string]struct{})}
 }
 
+// Add puts a Cid in the Set.
 func (s *Set) Add(c *Cid) {
 	s.set[string(c.Bytes())] = struct{}{}
 }
 
+// Has returns if the Set contains a given Cid.
 func (s *Set) Has(c *Cid) bool {
 	_, ok := s.set[string(c.Bytes())]
 	return ok
 }
 
+// Remove deletes a Cid from the Set.
 func (s *Set) Remove(c *Cid) {
 	delete(s.set, string(c.Bytes()))
 }
 
+// Len returns how many elements the Set has.
 func (s *Set) Len() int {
 	return len(s.set)
 }
 
+// Keys returns the Cids in the set.
 func (s *Set) Keys() []*Cid {
-	var out []*Cid
-	for k, _ := range s.set {
+	out := make([]*Cid, 0, len(s.set))
+	for k := range s.set {
 		c, _ := Cast([]byte(k))
 		out = append(out, c)
 	}
 	return out
 }
 
+// Visit adds a Cid to the set only if it is
+// not in it already.
 func (s *Set) Visit(c *Cid) bool {
 	if !s.Has(c) {
 		s.Add(c)
@@ -42,3 +52,16 @@ func (s *Set) Visit(c *Cid) bool {
 
 	return false
 }
+
+// ForEach allows to run a custom function on each
+// Cid in the set.
+func (s *Set) ForEach(f func(c *Cid) error) error {
+	for cs := range s.set {
+		c, _ := Cast([]byte(cs))
+		err := f(c)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

set_test.go

@@ -0,0 +1,92 @@
+package cid
+
+import (
+	"crypto/rand"
+	"errors"
+	"testing"
+
+	mh "github.com/multiformats/go-multihash"
+)
+
+func makeRandomCid(t *testing.T) *Cid {
+	p := make([]byte, 256)
+	_, err := rand.Read(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	h, err := mh.Sum(p, mh.SHA3, 4)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cid := &Cid{
+		codec:   7,
+		version: 1,
+		hash:    h,
+	}
+
+	return cid
+}
+
+func TestSet(t *testing.T) {
+	cid := makeRandomCid(t)
+	cid2 := makeRandomCid(t)
+	s := NewSet()
+
+	s.Add(cid)
+
+	if !s.Has(cid) {
+		t.Error("should have the CID")
+	}
+
+	if s.Len() != 1 {
+		t.Error("should report 1 element")
+	}
+
+	keys := s.Keys()
+
+	if len(keys) != 1 || !keys[0].Equals(cid) {
+		t.Error("key should correspond to Cid")
+	}
+
+	if s.Visit(cid) {
+		t.Error("visit should return false")
+	}
+
+	foreach := []*Cid{}
+	foreachF := func(c *Cid) error {
+		foreach = append(foreach, c)
+		return nil
+	}
+
+	if err := s.ForEach(foreachF); err != nil {
+		t.Error(err)
+	}
+
+	if len(foreach) != 1 {
+		t.Error("ForEach should have visited 1 element")
+	}
+
+	foreachErr := func(c *Cid) error {
+		return errors.New("test")
+	}
+
+	if err := s.ForEach(foreachErr); err == nil {
+		t.Error("Should have returned an error")
+	}
+
+	if !s.Visit(cid2) {
+		t.Error("should have visited a new Cid")
+	}
+
+	if s.Len() != 2 {
+		t.Error("len should be 2 now")
+	}
+
+	s.Remove(cid2)
+
+	if s.Len() != 1 {
+		t.Error("len should be 1 now")
+	}
+}