Merge pull request #52 from vpulim/fix-head-saving

Add getLatestHeader() and getLatestBlock() methods, fix saveHeads() bug and update API docs

Author: holgerd77

README.md

@@ -38,6 +38,8 @@ new Blockchain({db: db}).iterator('i', (block, reorg, cb) => {
     - [`BlockChain` methods](#blockchain-methods)
         - [`blockchain.putGenesis(genesis, [cb])`](#blockchainputgenesisgenesis-cb)
         - [`blockchain.getHead(name, [cb])`](#blockchaingetheadname-cb)
+        - [`blockchain.getLatestHeader([cb])`](#blockchaingetlatestheadercb)
+        - [`blockchain.getLatestBlock([cb])`](#blockchaingetlatestblockcb)
         - [`blockchain.putBlocks(blocks, [cb])`](#blockchainputblocksblocks-cb)
         - [`blockchain.putBlock(block, [cb])`](#blockchainputblockblock-cb)
         - [`blockchain.getBlock(hash, [cb])`](#blockchaingetblockhash-cb)
@@ -50,7 +52,7 @@ new Blockchain({db: db}).iterator('i', (block, reorg, cb) => {
 Implements functions for retrieving, manipulating and storing Ethereum's blockchain
 
 ### `new Blockchain(opts)`
-Creates new Blockchain object 
+Creates new Blockchain object
 - `opts.db` - Database to store blocks and metadata. Should be a [levelup](https://github.com/rvagg/node-levelup) instance.
 - `opts.validate` - this the flag to validate blocks (e.g. Proof-of-Work).
 
@@ -69,12 +71,24 @@ Puts the genesis block in the database.
 --------------------------------------------------------
 
 #### `blockchain.getHead(name, cb)`
-Returns that head block.
+Returns the specified iterator head.
 - `name` - Optional name of the state root head (default: 'vm')
 - `cb` - the callback. It is given two parameters `err` and the returned `block`
 
 --------------------------------------------------------
 
+#### `blockchain.getLatestHeader(cb)`
+Returns the latest header in the canonical chain.
+- `cb` - the callback. It is given two parameters `err` and the returned `header`
+
+--------------------------------------------------------
+
+#### `blockchain.getLatestBlock(cb)`
+Returns the latest full block in the canonical chain.
+- `cb` - the callback. It is given two parameters `err` and the returned `block`
+
+--------------------------------------------------------
+
 #### `blockchain.putBlocks(blocks, cb)`
 Adds many blocks to the blockchain.
 - `blocks` - the blocks to be added to the blockchain
@@ -91,7 +105,7 @@ Adds a block to the blockchain.
 #### `blockchain.getBlock(blockTag, cb)`
 Gets a block by its blockTag.
 - `blockTag`  - the block's hash or number
-- `cb` - the callback. It is given two parameters `err` and the found `block` (an instance of https://github.com/ethereumjs/ethereumjs-block) if any. 
+- `cb` - the callback. It is given two parameters `err` and the found `block` (an instance of https://github.com/ethereumjs/ethereumjs-block) if any.
 
 --------------------------------------------------------
 
@@ -113,7 +127,7 @@ Looks up many blocks relative to blockId.
 #### `blockchain.selectNeededHashes(hashes, cb)`
 Given an ordered array, returns to the callback an array of hashes that are not in the blockchain yet.
 - `hashes`  - Ordered array of hashes
-- `cb` - the callback. It is given two parameters `err` and hashes found. 
+- `cb` - the callback. It is given two parameters `err` and hashes found.
 
 --------------------------------------------------------
 
@@ -135,4 +149,3 @@ Iterates through blocks starting at the specified verified state root head and c
 Tests can be found in the ``test`` directory and run with ``npm run test``.
 
 These can also be valuable as examples/inspiration on how to run the library and invoke different parts of the API.
-

index.js

@@ -1,10 +1,5 @@
 'use strict'
 
-/**
- * NOTES
- * meta.rawHead is the the head of the chain with the most POW
- * meta.head is the head of the chain that has had its state root verifed
- */
 const async = require('async')
 const Stoplight = require('flow-stoplight')
 const semaphore = require('semaphore')
@@ -86,8 +81,8 @@ Blockchain.prototype = {
 
 /**
  * Fetches the meta info about the blockchain from the db. Meta info contains
- * hashes of the headerchain head, blockchain head, genesis block and verified
- * state root heads.
+ * hashes of the headerchain head, blockchain head, genesis block and iterator
+ * heads.
  * @method _init
  */
 Blockchain.prototype._init = function (cb) {
@@ -113,8 +108,9 @@ Blockchain.prototype._init = function (cb) {
   function getHeads (genesisHash, cb) {
     self._genesis = genesisHash
     async.series([
-      // load verified state root heads
+      // load verified iterator heads
       (cb) => self.db.get('heads', {
+        keyEncoding: 'binary',
         valueEncoding: 'json'
       }, (err, heads) => {
         if (err) heads = {}
@@ -124,13 +120,15 @@ Blockchain.prototype._init = function (cb) {
       }),
       // load headerchain head
       (cb) => self.db.get(headHeaderKey, {
+        keyEncoding: 'binary',
         valueEncoding: 'binary'
       }, (err, hash) => {
         self._headHeader = err ? genesisHash : hash
         cb()
       }),
       // load blockchain head
       (cb) => self.db.get(headBlockKey, {
+        keyEncoding: 'binary',
         valueEncoding: 'binary'
       }, (err, hash) => {
         self._headBlock = err ? genesisHash : hash
@@ -161,8 +159,9 @@ Blockchain.prototype.putGenesis = function (genesis, cb) {
 }
 
 /**
- * Returns that head block
+ * Returns the specified iterator head.
  * @method getHead
+ * @param name name of the head (default: 'vm')
  * @param cb Function the callback
  */
 Blockchain.prototype.getHead = function (name, cb) {
@@ -185,6 +184,37 @@ Blockchain.prototype.getHead = function (name, cb) {
   })
 }
 
+/**
+ * Returns the latest header in the canonical chain.
+ * @method getLatestHeader
+ * @param cb Function the callback
+ */
+Blockchain.prototype.getLatestHeader = function (cb) {
+  const self = this
+
+  // ensure init completed
+  self._initLock.await(function runGetLatestHeader () {
+    self.getBlock(self._headHeader, (err, block) => {
+      if (err) return cb(err)
+      cb(null, block.header)
+    })
+  })
+}
+
+/**
+ * Returns the latest full block in the canonical chain.
+ * @method getLatestBlock
+ * @param cb Function the callback
+ */
+Blockchain.prototype.getLatestBlock = function (cb) {
+  const self = this
+
+  // ensure init completed
+  self._initLock.await(function runGetLatestBlock () {
+    self.getBlock(self._headBlock, cb)
+  })
+}
+
 /**
  * Adds many blocks to the blockchain
  * @method putBlocks
@@ -518,9 +548,26 @@ Blockchain.prototype.selectNeededHashes = function (hashes, cb) {
 }
 
 Blockchain.prototype._saveHeads = function (cb) {
-  this.db.put('heads', this._heads, {
-    keyEncoding: 'json'
-  }, cb)
+  var dbOps = [{
+    type: 'put',
+    key: 'heads',
+    keyEncoding: 'binary',
+    valueEncoding: 'json',
+    value: this._heads
+  }, {
+    type: 'put',
+    key: headHeaderKey,
+    keyEncoding: 'binary',
+    valueEncoding: 'binary',
+    value: this._headHeader
+  }, {
+    type: 'put',
+    key: headBlockKey,
+    keyEncoding: 'binary',
+    valueEncoding: 'binary',
+    value: this._headBlock
+  }]
+  this._batchDbOps(dbOps, cb)
 }
 
 // delete canonical number assignments for specified number and above
@@ -537,7 +584,7 @@ Blockchain.prototype._deleteStaleAssignments = function (number, headHash, ops,
     })
     self._cache.numberToHash.del(key)
 
-    // reset stale verified state root heads to current canonical head
+    // reset stale iterator heads to current canonical head
     Object.keys(self._heads).forEach(function (name) {
       if (self._heads[name].equals(hash)) {
         self._heads[name] = headHash
@@ -751,10 +798,11 @@ Blockchain.prototype._delChild = function (hash, number, headHash, ops, cb) {
 }
 
 /**
- * Iterates through blocks starting at the specified verified state root head
- * and calls the onBlock function on each block
+ * Iterates through blocks starting at the specified iterator head and calls
+ * the onBlock function on each block. The current location of an iterator head
+ * can be retrieved using the `getHead()`` method
  * @method iterator
- * @param {String} name - the name of the verified state root head
+ * @param {String} name - the name of the iterator head
  * @param {function} onBlock - function called on each block with params (block, reorg, cb)
  * @param {function} cb - a callback function
  */

test/index.js

@@ -11,7 +11,7 @@ const testData = require('./testdata.json')
 const BN = require('bn.js')
 
 test('blockchain test', function (t) {
-  t.plan(57)
+  t.plan(59)
   var blockchain = new Blockchain()
   var genesisBlock
   var blocks = []
@@ -343,6 +343,27 @@ test('blockchain test', function (t) {
           })
         ], done)
       })
+    },
+    function saveHeads (done) {
+      var db = levelup('', { db: memdown })
+      var blockchain = new Blockchain({db: db, validate: false})
+
+      blockchain.putBlock(blocks[1], (err) => {
+        if (err) return done(err)
+        blockchain = new Blockchain({db: db, validate: false})
+        async.series([
+          (cb) => blockchain.getLatestHeader((err, header) => {
+            if (err) return done(err)
+            t.equals(header.hash().toString('hex'), blocks[1].hash().toString('hex'), 'should get latest header')
+            cb()
+          }),
+          (cb) => blockchain.getLatestBlock((err, headBlock) => {
+            if (err) return done(err)
+            t.equals(headBlock.hash().toString('hex'), blocks[1].hash().toString('hex'), 'should get latest block')
+            cb()
+          })
+        ], done)
+      })
     }
   ], function (err) {
     if (err) {