add preload from electrum.org. check for blockchain corruption.

lib/bcoin/chain.js

@@ -6,6 +6,7 @@
 
 var inherits = require('inherits');
 var EventEmitter = require('events').EventEmitter;
+var request = require('request');
 
 var bcoin = require('../bcoin');
 var bn = require('bn.js');
@@ -95,42 +96,137 @@ Chain.prototype._init = function _init() {
 
   utils.debug('Chain is loading.');
 
-  utils.nextTick(function() {
-    var count = self.db.count();
-    var lastEntry;
-    var i = 1;
+  this.preload(function(start) {
+    utils.nextTick(function() {
+      var count = self.db.count();
+      var i = start || 1;
+      var lastEntry;
 
-    function done(height) {
-      if (height != null) {
-        utils.debug(
-          'Blockchain is corrupt after height %d. Resetting.',
-          height);
-        self.resetHeight(height);
-      } else {
-        utils.debug('Chain successfully loaded.');
+      function done(height) {
+        if (height != null) {
+          utils.debug(
+            'Blockchain is corrupt after height %d. Resetting.',
+            height);
+          self.resetHeight(height);
+        } else {
+          utils.debug('Chain successfully loaded.');
+        }
+        self.loading = false;
+        self.emit('load');
       }
-      self.loading = false;
-      self.emit('load');
+
+      (function next() {
+        if (i >= count)
+          return done();
+
+        self.db.getAsync(i, function(err, entry) {
+          if (err)
+            throw err;
+
+          // Do some paranoid checks.
+          if (lastEntry && entry.prevBlock !== lastEntry.hash)
+            return done(Math.max(0, i - 2));
+
+          lastEntry = entry;
+          self._saveEntry(entry);
+          i += 1;
+          next();
+        });
+      })();
+    });
+  });
+};
+
+Chain.prototype.preload = function preload(callback) {
+  var self = this;
+  var url = 'https://headers.electrum.org/blockchain_headers';
+  var chainHeight, buf, height, stream;
+
+  if (this.options.preload === false)
+    return callback();
+
+  utils.debug('Loading %s', url);
+
+  stream = request.get(url);
+  chainHeight = this.db.count() - 1;
+  height = 0;
+  buf = {
+    data: [],
+    size: 0
+  };
+
+  stream.on('response', function(res) {
+    if (res.statusCode >= 400) {
+      utils.debug('Could not load electrum headers');
+      utils.debug('Status: %d', res.statusCode);
+      stream.destroy();
+      return callback();
+    }
+  });
+
+  stream.on('error', function(err) {
+    utils.debug('Could not load electrum headers');
+    utils.debug(err.stack + '');
+    self.resetHeight(Math.max(0, height - 2));
+    return callback(Math.max(0, height - 2));
+  });
+
+  stream.on('data', function(data) {
+    var blocks = [];
+    var need = 80 - buf.size;
+    var i, lastEntry;
+
+    while (data.length >= need) {
+      buf.data.push(data.slice(0, need));
+      blocks.push(Buffer.concat(buf.data));
+      buf.data.length = 0;
+      buf.size = 0;
+      data = data.slice(need);
+      need = 80 - buf.size;
     }
 
-    (function next() {
-      if (i >= count)
-        return done();
+    if (data.length > 0) {
+      assert(data.length < 80);
+      buf.data.push(data);
+      buf.size += data.length;
+    }
 
-      self.db.getAsync(i, function(err, entry) {
-        if (err)
-          throw err;
+    if (blocks.length === 0)
+      return;
 
-        // Do some paranoid checks.
-        if (lastEntry && entry.prevBlock !== lastEntry.hash)
-          return done(Math.max(0, i - 2));
+    blocks.forEach(function(data) {
+      var entry = bcoin.chainblock.fromRaw(self, height, data);
 
-        self._saveEntry(entry);
-        lastEntry = entry;
-        i += 1;
-        next();
-      });
-    })();
+      // Do some paranoid checks.
+      if (lastEntry && entry.prevBlock !== lastEntry.hash) {
+        utils.debug('Electrum headers are corrupt. Resetting.');
+        stream.destroy();
+        self.resetHeight(Math.max(0, height - 2));
+        return callback(Math.max(0, height - 2));
+      }
+
+      lastEntry = entry;
+
+      delete entry.chainwork;
+      entry.chainwork = entry.getChainwork();
+
+      // Skip the genesis block in case it ends up being corrupt
+      if (height === 0) {
+        height++;
+        return;
+      }
+
+      self._saveEntry(entry, height > chainHeight);
+
+      height++;
+
+      if ((height + 1) % 50000 === 0)
+        utils.debug('Received %d headers from electrum.org.', height + 1);
+    });
+  });
+
+  stream.on('end', function() {
+    return callback(null, height + 1);
   });
 };