feat: expose codec code and allow construction by code

Ref: #117 (comment)

README.md

@@ -28,6 +28,7 @@
   - [new CID(baseEncodedString)](#new-cidbaseencodedstring)
   - [new CID(Uint8Array)](#new-ciduint8array)
     - [cid.codec](#cidcodec)
+    - [cid.code](#cidcode)
     - [cid.version](#cidversion)
     - [cid.multihash](#cidmultihash)
     - [cid.multibaseName](#cidmultibasename)
@@ -78,6 +79,7 @@ const cid = new CID('bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu
 
 cid.version       // 1
 cid.codec         // 'dag-pb'
+cid.code          // 112
 cid.multibaseName // 'base32'
 cid.toString()
 // 'bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu'
@@ -96,6 +98,14 @@ console.log(cid.toString())
 // bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu
 ```
 
+The multicodec integer code can also be used to create a new CID:
+
+```js
+const cid = new CID(1, 112, hash)
+console.log(cid.toString())
+// bafybeig6xv5nwphfmvcnektpnojts33jqcuam7bmye2pb54adnrtccjlsu
+```
+
 The string form of v1 CIDs defaults to `base32` encoding (v0 CIDs are always `base58btc` encoded). When creating a new instance you can optionally specify the default multibase to use when calling `toBaseEncodedString()` or `toString()`
 
 
@@ -150,7 +160,11 @@ Additionally, you can instantiate an instance from a `Uint8Array`.
 
 #### cid.codec
 
-Property containing the codec string.
+Property containing the string identifier of the codec.
+
+#### cid.code
+
+Property containing the integer identifier of the codec.
 
 #### cid.version
 

src/index.d.ts

@@ -30,7 +30,7 @@ declare class CID {
    */
   constructor(
     version: 0 | 1,
-    codec: string,
+    codec: string | number,
     multhash: Uint8Array,
     multibaseName?: string
   );
@@ -48,6 +48,11 @@ declare class CID {
    */
   codec: string;
 
+  /**
+   * The codec of the CID in its number form.
+   */
+  code: number;
+
   /**
    * The multihash of the CID.
    */

src/index.js

@@ -10,6 +10,11 @@ const uint8ArrayConcat = require('uint8arrays/concat')
 const uint8ArrayToString = require('uint8arrays/to-string')
 const uint8ArrayEquals = require('uint8arrays/equals')
 
+const codecInts = Object.keys(codecs).reduce((p, name) => {
+  p[codecs[name]] = name
+  return p
+}, {})
+
 /**
  * @typedef {Object} SerializedCID
  * @param {string} codec
@@ -50,7 +55,7 @@ class CID {
    * ```
    *
    * @param {string|Uint8Array|CID} version
-   * @param {string} [codec]
+   * @param {string|number} [codec]
    * @param {Uint8Array} [multihash]
    * @param {string} [multibaseName]
    *
@@ -124,6 +129,10 @@ class CID {
      */
     this.version = version
 
+    if (typeof codec === 'number') {
+      codec = codecInts[codec]
+    }
+
     /**
      * @type {string}
      */
@@ -188,6 +197,10 @@ class CID {
     return prefix
   }
 
+  get code () {
+    return codecs[this.codec]
+  }
+
   /**
    * Convert to a CID of version `0`.
    *

src/index.js.flow

@@ -2,16 +2,19 @@
 
 export type Version = 0 | 1
 export type Codec = string
+export type CodecCode = number
 export type Multihash = Uint8Array
 export type BaseEncodedString = string
 export type MultibaseName = string
 
 declare class CID<a> {
   constructor(Version, Codec, Multihash, multibaseName?:MultibaseName): void;
+  constructor(Version, CodecCode, Multihash, multibaseName?:MultibaseName): void;
   constructor(BaseEncodedString): void;
   constructor(Uint8Array): void;
 
   +codec: Codec;
+  +code: CodecCode;
   +multihash: Multihash;
   +bytes: Uint8Array;
   +prefix: Uint8Array;

test/index.spec.js

@@ -22,6 +22,7 @@ describe('CID', () => {
       const cid = new CID(mhStr)
 
       expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
       expect(cid).to.have.property('version', 0)
       expect(cid).to.have.property('multihash').that.eql(multihash.fromB58String(mhStr))
       expect(cid).to.have.property('multibaseName', 'base58btc')
@@ -36,6 +37,7 @@ describe('CID', () => {
       const cid = new CID(mh)
 
       expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
       expect(cid).to.have.property('version', 0)
       expect(cid).to.have.property('multihash').that.eql(mh)
       expect(cid).to.have.property('multibaseName', 'base58btc')
@@ -47,6 +49,17 @@ describe('CID', () => {
       const cid = new CID(0, 'dag-pb', hash)
 
       expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
+      expect(cid).to.have.property('version', 0)
+      expect(cid).to.have.property('multihash')
+      expect(cid).to.have.property('multibaseName', 'base58btc')
+    })
+
+    it('create by parts (int codec)', () => {
+      const cid = new CID(0, 112, hash)
+
+      expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
       expect(cid).to.have.property('version', 0)
       expect(cid).to.have.property('multihash')
       expect(cid).to.have.property('multibaseName', 'base58btc')
@@ -110,6 +123,7 @@ describe('CID', () => {
       const cid = new CID(cidStr)
 
       expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
       expect(cid).to.have.property('version', 1)
       expect(cid).to.have.property('multihash')
       expect(cid).to.have.property('multibaseName', 'base58btc')
@@ -124,6 +138,7 @@ describe('CID', () => {
       const cid = new CID(cidBuf)
 
       expect(cid).to.have.property('codec', 'dag-pb')
+      expect(cid).to.have.property('code', 112)
       expect(cid).to.have.property('version', 1)
       expect(cid).to.have.property('multihash')
       expect(cid).to.have.property('multibaseName', 'base32')
@@ -137,6 +152,7 @@ describe('CID', () => {
       const cid = new CID(peerIdStr)
 
       expect(cid).to.have.property('codec', 'libp2p-key')
+      expect(cid).to.have.property('code', 114)
       expect(cid).to.have.property('version', 1)
       expect(cid).to.have.property('multihash')
       expect(cid).to.have.property('multibaseName', 'base36')
@@ -148,6 +164,7 @@ describe('CID', () => {
       const cid = new CID(1, 'dag-cbor', hash)
 
       expect(cid).to.have.property('codec', 'dag-cbor')
+      expect(cid).to.have.property('code', 113)
       expect(cid).to.have.property('version', 1)
       expect(cid).to.have.property('multihash')
       expect(cid).to.have.property('multibaseName', 'base32')
@@ -158,6 +175,7 @@ describe('CID', () => {
       const cid2 = new CID(cid1.toBaseEncodedString())
 
       expect(cid1).to.have.property('codec').that.eql(cid2.codec)
+      expect(cid1).to.have.property('code').that.eql(cid2.code)
       expect(cid1).to.have.property('version').that.eql(cid2.version)
       expect(cid1).to.have.property('multihash').that.eql(cid2.multihash)
       expect(cid1).to.have.property('multibaseName').that.eql(cid2.multibaseName)
@@ -170,6 +188,7 @@ describe('CID', () => {
       const cid2 = new CID(cid1.toBaseEncodedString())
 
       expect(cid1).to.have.property('codec', 'eth-block')
+      expect(cid1).to.have.property('code', 144)
       expect(cid1).to.have.property('version', 1)
       expect(cid1).to.have.property('multihash').that.eql(mh)
       expect(cid1).to.have.property('multibaseName', 'base32')
@@ -189,13 +208,15 @@ describe('CID', () => {
       const cid0 = new CID(0, 'dag-pb', mh)
 
       expect(cid0).to.have.property('codec', 'dag-pb')
+      expect(cid0).to.have.property('code', 112)
       expect(cid0).to.have.property('version', 0)
       expect(cid0).to.have.property('multihash').that.eql(mh)
       expect(cid0.toBaseEncodedString()).to.eql('161g3c')
 
       const cid1 = new CID(1, 'dag-cbor', mh)
 
       expect(cid1).to.have.property('codec', 'dag-cbor')
+      expect(cid1).to.have.property('code', 113)
       expect(cid1).to.have.property('version', 1)
       expect(cid1).to.have.property('multihash').that.eql(mh)
       expect(cid1.toBaseEncodedString()).to.eql('bafyqaa3bmjrq')