feat: validation. fixes #43 (#44)

Simple algorithm agnostic validation w/ tests.

Author: mikeal

src/index.js

@@ -139,3 +139,11 @@ Multihashing.functions = {
 
 // add blake functions
 crypto.addBlake(Multihashing.functions)
+
+Multihashing.validate = (data, hash, callback) => {
+  let algo = multihash.decode(hash).name
+  Multihashing(data, algo, (err, newHash) => {
+    if (err) return callback(err)
+    callback(err, Buffer.compare(hash, newHash) === 0)
+  })
+}

test/index.spec.js

@@ -76,3 +76,27 @@ describe('multihashing', () => {
     })
   })
 })
+
+describe('validate', () => {
+  it('true on pass', done => {
+    multihashing(Buffer.from('test'), 'sha2-256', (err, hash) => {
+      if (err) throw done(err)
+      multihashing.validate(Buffer.from('test'), hash, (err, bool) => {
+        if (err) throw done(err)
+        expect(bool).to.eql(true)
+        done()
+      })
+    })
+  })
+
+  it('false on fail', done => {
+    multihashing(Buffer.from('test'), 'sha2-256', (err, hash) => {
+      if (err) throw done(err)
+      multihashing.validate(Buffer.from('test-fail'), hash, (err, bool) => {
+        if (err) throw done(err)
+        expect(bool).to.eql(false)
+        done()
+      })
+    })
+  })
+})