add some checks

lib/block.js

@@ -9,6 +9,7 @@ var BufferWriter = require('./encoding/bufferwriter');
 var Hash = require('./crypto/hash');
 var JSUtil = require('./util/js');
 var Transaction = require('./transaction');
+var $ = require('./util/preconditions');
 
 /**
  * Instantiate a Block from a Buffer, JSON object, or Object with
@@ -96,6 +97,7 @@ Block.fromJSON = function fromJSON(json) {
  */
 Block._fromBufferReader = function _fromBufferReader(br) {
   var info = {};
+  $.checkState(!br.finished(), 'No block data received');
   info.header = BlockHeader.fromBufferReader(br);
   var transactions = br.readVarintNum();
   info.transactions = [];

lib/encoding/bufferreader.js

@@ -28,6 +28,8 @@ BufferReader.prototype.eof = function() {
   return this.pos >= this.buf.length;
 };
 
+BufferReader.prototype.finished = BufferReader.prototype.eof;
+
 BufferReader.prototype.read = function(len) {
   $.checkArgument(!_.isUndefined(len), 'Must specify a length');
   var buf = this.buf.slice(this.pos, this.pos + len);

lib/transaction/transaction.js

@@ -189,6 +189,7 @@ Transaction.prototype.fromBuffer = function(buffer) {
 };
 
 Transaction.prototype.fromBufferReader = function(reader) {
+  $.checkArgument(!reader.finished(), 'No transaction data received');
   var i, sizeTxIns, sizeTxOuts;
 
   this.version = reader.readUInt32LE();