From f6a35d081029d9d347e086896eb7bf61f0050bc7 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Wed, 20 Jan 2016 18:18:27 -0800
Subject: [PATCH] more chain db work.

---
 lib/bcoin/chain.js | 263 +++++++++++++++++++++++++--------------------
 1 file changed, 148 insertions(+), 115 deletions(-)

diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index 73f66f9a..545fb537 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -721,27 +721,36 @@ var BLOCK_SIZE = 80;
 // var BLOCK_SIZE = 144;
 
 function ChainDB(chain) {
+  var exists;
+
+  this.chain = chain;
   this.file = process.env.HOME + '/bcoin-' + network.type + '.blockchain';
+
+  this._queue = [];
+  this._cache = {};
+  this._bufferPool = {};
+  this._nullBlock = new Buffer(BLOCK_SIZE);
+  this._nullBlock.fill(0);
+
   try {
     fs.unlinkSync(this.file);
   } catch (e) {
+    ;
   }
-  var exists = false;
+
   try {
     fs.accessSync(file);
     exists = true;
   } catch (e) {
     exists = false;
   }
-  if (!exists)
+
+  if (!exists) {
     fs.writeFileSync(this.file, new Buffer(0));
+    fs.truncateSync(this.file, 0);
+  }
+
   this.fd = fs.openSync(this.file, 'r+');
-  this.chain = chain;
-  this._buffer = [];
-  this._cache = {};
-  this._bufferPool = {};
-  this._nullBlock = new Buffer(BLOCK_SIZE);
-  this._nullBlock.fill(0);
 }
 
 ChainDB.prototype.getBuffer = function(size) {
@@ -750,66 +759,162 @@ ChainDB.prototype.getBuffer = function(size) {
   return this._bufferPool[size];
 };
 
-ChainDB.prototype.save = function save(entry) {
+ChainDB.prototype.size = function size() {
+  try {
+    return fs.statSync(this.file).size;
+  } catch (e) {
+    return 0;
+  }
+};
+
+ChainDB.prototype.count = function count() {
+  return this.size() / BLOCK_SIZE | 0;
+};
+
+ChainDB.prototype.get = function get(height) {
+  var data;
+
+  if (this._cache[height])
+    return this._cache[height];
+
+  if (this._queue[height])
+    return this._queue[height];
+
+  data = this._read(BLOCK_SIZE, height * BLOCK_SIZE);
+
+  if (!data)
+    return;
+
+  if (utils.read32(data, 0) === 0)
+    return;
+
+  return ChainBlock.fromRaw(this.chain, height, data);
+};
+
+ChainDB.prototype.save = function save(entry, callback) {
+  var self = this;
+  var raw, offset;
+
   // Cache the past 2016 blocks in memory
   this._cache[entry.height] = entry;
   delete this._cache[entry.height - network.powDiffInterval];
   assert(Object.keys(this._cache).length < network.powDiffInterval + 1);
-  return this._write(new Buffer(entry.toRaw()), entry.height * BLOCK_SIZE);
-};
-
-ChainDB.prototype._write = function _write(data, offset) {
-  var size, bytes, index, hash;
-  var self = this;
-
-  if (offset < 0 || offset == null)
-    return false;
-
-  hash = offset;
-  size = data.length;
-  bytes = 0;
-  index = 0;
 
   // Something is already writing. Cancel it
   // and synchronously write the data after
   // it cancels.
-  if (this._buffer[hash]) {
-    assert(this._buffer[hash].data.length === data.length);
-    this._buffer[hash].data = data;
-    this._buffer[hash].queue.push([data, offset]);
+  if (this._queue[entry.height]) {
+    this._queue[entry.height] = entry;
     return;
   }
 
   // Speed up writes by doing them asynchronously
   // and keeping the data to be written in memory.
-  this._buffer[hash] = { queue: [], data: data };
+  this._queue[entry.height] = entry;
+
+  // Write asynchronously to the db.
+  raw = new Buffer(entry.toRaw());
+  offset = entry.height * BLOCK_SIZE;
+
+  return this._write(raw, offset, function(err, success) {
+    var item = self._queue[entry.height];
+
+    assert(item);
+
+    // Something tried to write here but couldn't.
+    // Synchronously write it and get it over with.
+    try {
+      if (item !== entry)
+        success = self._writeSync(new Buffer(item.toRaw()), offset);
+    } catch (e) {
+      err = e;
+    }
+
+    delete self._queue[entry.height];
+
+    if (err) {
+      if (callback)
+        return callback(err);
+      else
+        throw err;
+    }
+
+    if (callback)
+      return callback(null, success);
+  });
+};
+
+ChainDB.prototype.del = function del(height) {
+  assert(height >= 0);
+
+  this._writeSync(this._nullBlock, height * BLOCK_SIZE);
+
+  // If we deleted several blocks at the end, go back
+  // to the last non-null block and truncate the file
+  // beyond that point.
+  if (height * BLOCK_SIZE + BLOCK_SIZE === this.size()) {
+    while (this.isNull(height))
+      height--;
+    fs.ftruncateSync(this.fd, height * BLOCK_SIZE + BLOCK_SIZE);
+  }
+
+  return true;
+};
+
+ChainDB.prototype.isNull = function isNull(height) {
+  var data = this._read(1, height * BLOCK_SIZE);
+  if (!data)
+    return false;
+  return utils.read32(data, 0) === 0;
+};
+
+ChainDB.prototype._read = function _read(size, offset) {
+  var data = this.getBuffer(size);
+  var bytes = 0;
+  var index = 0;
+
+  if (offset < 0 || offset == null)
+    return;
+
+  try {
+    while (bytes = fs.readSync(this.fd, data, index, size, offset)) {
+      index += bytes;
+      size -= bytes;
+      offset += bytes;
+      if (index === data.length)
+        return data;
+    }
+  } catch (e) {
+    return;
+  }
+};
+
+ChainDB.prototype._write = function _write(data, offset, callback) {
+  var self = this;
+  var size, bytes, index;
+
+  if (offset < 0 || offset == null)
+    return false;
+
+  size = data.length;
+  bytes = 0;
+  index = 0;
 
   (function callee() {
     fs.write(self.fd, data, index, size, offset, function(err, bytes) {
-      // Something tried to write here but couldn't.
-      // Synchronously write it and get it over with.
-      if (self._buffer[hash].queue.length) {
-        self._buffer[hash].queue.forEach(function(chunk) {
-          self._writeSync(chunk[0], chunk[1]);
-        });
-        delete self._buffer[hash];
-        return;
-      }
+      if (err)
+        return callback(err);
 
       index += bytes;
       size -= bytes;
       offset += bytes;
 
-      if (index === data.length) {
-        delete self._buffer[hash];
-        return;
-      }
+      if (index === data.length)
+        return callback(null, true);
 
       callee();
     });
   })();
-
-  return false;
 };
 
 ChainDB.prototype._writeSync = function _writeSync(data, offset) {
@@ -833,78 +938,6 @@ ChainDB.prototype._writeSync = function _writeSync(data, offset) {
   return false;
 };
 
-ChainDB.prototype.del = function del(height) {
-  this._write(this._nullBlock, height * BLOCK_SIZE);
-  if (height * BLOCK_SIZE + BLOCK_SIZE === this.size()) {
-    while (this.isNull(height))
-      height--;
-    fs.ftruncateSync(this.fd, height * BLOCK_SIZE + BLOCK_SIZE);
-  }
-  return true;
-};
-
-ChainDB.prototype.isNull = function isNull(height) {
-  var data = this._read(1, height * BLOCK_SIZE);
-  if (!data)
-    return false;
-  return utils.read32(data, 0) === 0;
-};
-
-ChainDB.prototype._read = function _read(size, offset) {
-  var data = this.getBuffer(size);
-  var bytes = 0;
-  var index = 0;
-
-  if (offset < 0 || offset == null)
-    return;
-
-  if (this._buffer[offset]) {
-    assert(this._buffer[offset].data.length >= size);
-    return this._buffer[offset].data.slice(0, size);
-  }
-
-  try {
-    while (bytes = fs.readSync(this.fd, data, index, size, offset)) {
-      index += bytes;
-      size -= bytes;
-      offset += bytes;
-      if (index === data.length) {
-        if (utils.read32(data, 0) === 0)
-          return;
-        return data;
-      }
-    }
-  } catch (e) {
-    return;
-  }
-};
-
-ChainDB.prototype.size = function size() {
-  try {
-    return fs.statSync(this.file).size;
-  } catch (e) {
-    return 0;
-  }
-};
-
-ChainDB.prototype.count = function count() {
-  return this.size() / BLOCK_SIZE | 0;
-};
-
-ChainDB.prototype.get = function get(height) {
-  var data;
-
-  if (this._cache[height])
-    return this._cache[height];
-
-  data = this._read(BLOCK_SIZE, height * BLOCK_SIZE);
-
-  if (!data)
-    return;
-
-  return ChainBlock.fromRaw(this.chain, height, data);
-};
-
 /**
  * ChainBlock
  */