add a read lock for walletdb.

lib/bcoin/input.js

@@ -442,7 +442,6 @@ Input.prototype.inspect = function inspect() {
     type: this.getType(),
     subtype: this.getSubtype(),
     address: this.getAddress(),
-    value: utils.btc(coin.value),
     script: this.script,
     witness: this.witness,
     redeem: this.getRedeem(),

lib/bcoin/locker.js

@@ -21,7 +21,9 @@ var assert = utils.assert;
 
 function Locker(parent, add) {
   if (!(this instanceof Locker))
-    return Locker(parent, add);
+    return new Locker(parent, add);
+
+  EventEmitter.call(this);
 
   this.parent = parent;
   this.jobs = [];

lib/bcoin/walletdb.js

@@ -50,6 +50,10 @@ function WalletDB(options) {
   this.options = options;
   this.network = bcoin.network.get(options.network);
 
+  // We need one read lock for `get` and `create`.
+  // It will hold locks specific to wallet ids.
+  this.readLock = new ReadLock(this);
+
   this.db = bcoin.ldb({
     network: this.network,
     name: this.options.name || 'wallet',
@@ -156,6 +160,15 @@ WalletDB.prototype._close = function close(callback) {
   });
 };
 
+/**
+ * Invoke mutex lock.
+ * @returns {Function} unlock
+ */
+
+WalletDB.prototype._lock = function lock(id, func, args, force) {
+  return this.readLock.lock(id, func, args, force);
+};
+
 /**
  * Emit balance events after a tx is saved.
  * @private
@@ -398,7 +411,14 @@ WalletDB.prototype.hasListener = function hasListener(id, event) {
 
 WalletDB.prototype.get = function get(id, callback) {
   var self = this;
-  var watcher, wallet;
+  var unlock, watcher, wallet;
+
+  unlock = this._lock(id, get, [id, callback]);
+
+  if (!unlock)
+    return;
+
+  callback = utils.wrap(callback, unlock);
 
   if (!id)
     return callback();
@@ -459,13 +479,20 @@ WalletDB.prototype.save = function save(wallet, callback) {
 
 WalletDB.prototype.create = function create(options, callback) {
   var self = this;
-  var wallet;
+  var wallet, unlock;
 
   if (typeof options === 'function') {
     callback = options;
     options = {};
   }
 
+  unlock = this._lock(options.id, create, [options, callback]);
+
+  if (!unlock)
+    return;
+
+  callback = utils.wrap(callback, unlock);
+
   this.has(options.id, function(err, exists) {
     if (err)
       return callback(err);
@@ -1049,9 +1076,6 @@ WalletDB.prototype._getKey = function _getKey(id, account, errback, callback) {
 
 WalletDB.prototype.removeBlockSPV = function removeBlockSPV(block, callback) {
   var self = this;
-
-  callback = utils.ensure(callback);
-
   this.tx.getHeightHashes(block.height, function(err, hashes) {
     if (err)
       return callback(err);
@@ -1071,9 +1095,6 @@ WalletDB.prototype.removeBlockSPV = function removeBlockSPV(block, callback) {
 
 WalletDB.prototype.removeBlock = function removeBlock(block, callback) {
   var self = this;
-
-  callback = utils.ensure(callback);
-
   utils.forEachSerial(block.txs, function(tx, next) {
     self.tx.unconfirm(tx.hash('hex'), next);
   }, callback);
@@ -1438,6 +1459,51 @@ function isAlpha(key) {
   return /^[\u0030-\u007d]+$/.test(key);
 }
 
+function ReadLock(parent) {
+  if (!(this instanceof ReadLock))
+    return new ReadLock(parent);
+
+  this.parent = parent;
+  this.jobs = [];
+  this.busy = {};
+}
+
+ReadLock.prototype.lock = function lock(id, func, args, force) {
+  var self = this;
+  var called;
+
+  if (force || !id) {
+    assert(!id || this.busy[id]);
+    return function unlock() {
+      assert(!called);
+      called = true;
+    };
+  }
+
+  if (this.busy[id]) {
+    this.jobs.push([func, args]);
+    return;
+  }
+
+  this.busy[id] = true;
+
+  return function unlock() {
+    var item;
+
+    assert(!called);
+    called = true;
+
+    delete self.busy[id];
+
+    if (self.jobs.length === 0)
+      return;
+
+    item = self.jobs.shift();
+
+    item[0].apply(self.parent, item[1]);
+  };
+};
+
 /*
  * Expose
  */