feat: add identity multihash

Author: rvagg

README.md

@@ -141,6 +141,7 @@ import the ones you need yourself.
 | --- | --- | --- |
 | `sha2-256`, `sha2-512` | `multiformats/hashes/sha2` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/hashes) |
 | `sha3-224`, `sha3-256`, `sha3-384`,`sha3-512`, `shake-128`, `shake-256`, `keccak-224`, `keccak-256`, `keccak-384`, `keccak-512` | `@multiformats/sha3` | [multiformats/js-sha3](https://github.com/multiformats/js-sha3) |
+| `identity` | `multiformats/hashes/identity` | [multiformats/js-multiformats](https://github.com/multiformats/js-multiformats/tree/master/src/hashes/identity.js) |
 | `murmur3-128`, `murmur3-32` | `@multiformats/murmur3` | [multiformats/js-murmur3](https://github.com/multiformats/js-murmur3) |
 | `blake2b-*`, `blake2s-*` | `@multiformats/blake2` | [multiformats/js-blake2](https://github.com/multiformats/js-blake2) |
 

package.json

@@ -70,6 +70,9 @@
       "browser": "./src/hashes/sha2-browser.js",
       "import": "./src/hashes/sha2.js"
     },
+    "./hashes/identity": {
+      "import": "./src/hashes/identity.js"
+    },
     "./codecs/codec": {
       "import": "./src/codecs/codec.js"
     },

src/hashes/identity.js

@@ -0,0 +1,10 @@
+// @ts-check
+
+import { from } from './hasher.js'
+import { coerce } from '../bytes.js'
+
+export default from({
+  name: 'identity',
+  code: 0x0,
+  encode: (input) => coerce(input)
+})

test/test-multihash.js

@@ -5,6 +5,7 @@ import valid from './fixtures/valid-multihash.js'
 import invalid from './fixtures/invalid-multihash.js'
 import crypto from 'crypto'
 import { sha256, sha512, __browser } from 'multiformats/hashes/sha2'
+import identity from 'multiformats/hashes/identity'
 import { decode as decodeDigest, create as createDigest } from 'multiformats/hashes/digest'
 const test = it
 const encode = name => data => coerce(crypto.createHash(name).update(data).digest())
@@ -66,6 +67,16 @@ describe('multihash', () => {
       same(hash2.code, sha512.code)
       same(hash2.bytes, hash.bytes)
     })
+    test('hash identity', async () => {
+      const hash = await identity.digest(fromString('test'))
+      same(hash.code, identity.code)
+      same(identity.code, 0)
+      same(hash.digest, fromString('test'))
+
+      const hash2 = decodeDigest(hash.bytes)
+      same(hash2.code, identity.code)
+      same(hash2.bytes, hash.bytes)
+    })
   })
   describe('decode', () => {
     for (const { encoding, hex, size } of valid) {