From f9b2f9565cb87efd16cb40a998a50f7c6780c6e8 Mon Sep 17 00:00:00 2001
From: Archs <sun@archs.tk>
Date: Sun, 1 Mar 2015 00:33:40 +0800
Subject: [PATCH] streams.ssWriteData: calling setLen only when new data truely
 increases the underlying string buffer

---
 lib/pure/streams.nim | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lib/pure/streams.nim b/lib/pure/streams.nim
index 67c80e5926..1ba0fb9aaf 100644
--- a/lib/pure/streams.nim
+++ b/lib/pure/streams.nim
@@ -224,10 +224,12 @@ proc ssReadData(s: Stream, buffer: pointer, bufLen: int): int =
 
 proc ssWriteData(s: Stream, buffer: pointer, bufLen: int) = 
   var s = StringStream(s)
-  if bufLen > 0: 
+  if bufLen <= 0:
+    return
+  if s.pos + bufLen > s.data.len():
     setLen(s.data, s.data.len + bufLen)
-    copyMem(addr(s.data[s.pos]), buffer, bufLen)
-    inc(s.pos, bufLen)
+  copyMem(addr(s.data[s.pos]), buffer, bufLen)
+  inc(s.pos, bufLen)
 
 proc ssClose(s: Stream) =
   var s = StringStream(s)