WIP: fix slow parsing of large messages (#229)

* fix slow parsing of large messages

* Fix names

* Define length to avoid internal loop

Author: porsager

lib/connection.js

@@ -33,6 +33,8 @@ function Connection(options = {}) {
   let next = false
   let statements = {}
   let connect_timer
+  let buffers = null
+  let remaining = 0
 
   const queries = Queue()
       , id = count++
@@ -285,17 +287,31 @@ function Connection(options = {}) {
   }
 
   function data(x) {
-    buffer = buffer.length === 0
-      ? x
-      : Buffer.concat([buffer, x], buffer.length + x.length)
+    if (buffers) {
+      buffers.push(x)
+      remaining -= x.length
+      if (remaining >= 0)
+        return
+    }
+
+    buffer = buffers
+      ? Buffer.concat(buffers, length - remaining)
+      : buffer.length === 0
+        ? x
+        : Buffer.concat([buffer, x], buffer.length + x.length)
 
     while (buffer.length > 4) {
       length = buffer.readInt32BE(1)
-      if (length >= buffer.length)
+      if (length >= buffer.length) {
+        remaining = length - buffer.length
+        buffers = [buffer]
         break
+      }
 
       backend[buffer[0]](buffer.slice(0, length + 1))
       buffer = buffer.slice(length + 1)
+      remaining = 0
+      buffers = null
     }
   }