feat: add defaultHashAlg (#17)

See ipld/interface-ipld-format#37

src/resolver.js

@@ -133,6 +133,7 @@ const resolveField = (dagNode, field) => {
 
 module.exports = {
   multicodec: 'bitcoin-block',
+  defaultHashAlg: 'dbl-sha2-256',
   resolve: resolve,
   tree: tree
 }

src/util.js

@@ -87,7 +87,9 @@ const cid = (dagNode, callback) => {
 
 // Convert a Bitcoin hash (as Buffer) to a CID
 const hashToCid = (hash) => {
-  const multihash = multihashes.encode(hash, 'dbl-sha2-256')
+  // avoid deadly embrace between resolver and util
+  const defaultHashAlg = require('./resolver').defaultHashAlg
+  const multihash = multihashes.encode(hash, defaultHashAlg)
   const cidVersion = 1
   const cid = new CID(cidVersion, 'bitcoin-block', multihash)
   return cid

test/resolver.spec.js

@@ -139,6 +139,11 @@ describe('IPLD format resolver API properties', () => {
     expect(IpldBitcoin.resolver.multicodec).to.equal('bitcoin-block')
     done()
   })
+
+  it('should have `defaultHashAlg` defined correctly', (done) => {
+    expect(IpldBitcoin.resolver.defaultHashAlg).to.equal('dbl-sha2-256')
+    done()
+  })
 })
 
 const verifyPath = (block, path, expected, done) => {