chaindb: add allocator.

lib/bcoin/chain.js

@@ -720,7 +720,7 @@ function ChainDB(chain, options) {
 
   this._queue = [];
   this._cache = {};
-  this._bufferPool = {};
+  this._bufferPool = { used: {} };
   this._nullBlock = new Buffer(BLOCK_SIZE);
   this._nullBlock.fill(0);
   this.tip = -1;
@@ -764,16 +764,25 @@ ChainDB.prototype._init = function _init() {
   this.fd = fs.openSync(this.file, 'r+');
 };
 
-ChainDB.prototype.getBuffer = function(size) {
+ChainDB.prototype._malloc = function(size) {
   if (!this._bufferPool[size])
     this._bufferPool[size] = new Buffer(size);
 
-  // if (this._bufferPool[size].__used)
-  //   return new Buffer(size);
+  if (this._bufferPool.used[size] === this._bufferPool[size])
+    return new Buffer(size);
+
+  this._bufferPool.used[size] = this._bufferPool[size];
 
   return this._bufferPool[size];
 };
 
+ChainDB.prototype._free = function(buf) {
+  if (this._bufferPool.used[buf.length] === buf) {
+    assert(this._bufferPool[buf.length] === buf);
+    delete this._bufferPool.used[buf.length];
+  }
+};
+
 ChainDB.prototype.exists = function exists() {
   try {
     fs.statSync(this.file);
@@ -982,46 +991,56 @@ ChainDB.prototype.isNull = function isNull(height) {
 };
 
 ChainDB.prototype._read = function _read(size, offset) {
-  var data = this.getBuffer(size);
   var index = 0;
-  var bytes;
+  var data, bytes;
 
   if (offset < 0 || offset == null)
     return;
 
+  data = this._malloc(size);
+
   try {
     while (bytes = fs.readSync(this.fd, data, index, size, offset)) {
       index += bytes;
       size -= bytes;
       offset += bytes;
-      if (index === data.length)
+      if (index === data.length) {
+        this._free(data);
         return data;
+      }
     }
   } catch (e) {
-    return;
+    ;
   }
+
+  this._free(data);
 };
 
 ChainDB.prototype._readAsync = function _read(size, offset, callback) {
   var self = this;
-  var data = new Buffer(size);
   var index = 0;
-  var bytes;
+  var data, bytes;
 
   if (offset < 0 || offset == null)
     return false;
 
+  data = this._malloc(size);
+
   (function callee() {
     fs.read(self.fd, data, index, size, offset, function(err, bytes) {
-      if (err)
+      if (err) {
+        self._free(data);
         return callback(err);
+      }
 
       index += bytes;
       size -= bytes;
       offset += bytes;
 
-      if (index === data.length)
+      if (index === data.length) {
+        self._free(data);
         return callback(null, data);
+      }
 
       callee();
     });