buffer: optimize append()

Avoid repeatedly dereferencing list tail.

diff --git a/src/include/buffer.h b/src/include/buffer.h
index 57d2d6cc3ec44ef8f86af1fbebd0ec44872bb7c2..494c5b792f73f62fd6f90aeb9057b7380ab94d93 100644 (file)
--- a/src/include/buffer.h
+++ b/src/include/buffer.h
@@ -814,17 +814,19 @@ public:
     }
     void append(const ptr& bp, unsigned off, unsigned len) {
       assert(len+off <= bp.length());
-      if (!_buffers.empty() &&
-         _buffers.back().get_raw() == bp.get_raw() &&
-         _buffers.back().end() == bp.start() + off) {
-       // yay contiguous with tail bp!
-       _buffers.back().set_length(_buffers.back().length()+len);
-       _len += len;
-      } else {
-       // add new item to list
-       ptr tempbp(bp, off, len);
-       push_back(tempbp);
+      if (!_buffers.empty()) {
+       ptr &l = _buffers.back();
+       if (l.get_raw() == bp.get_raw() &&
+           l.end() == bp.start() + off) {
+         // yay contiguous with tail bp!
+         l.set_length(l.length()+len);
+         _len += len;
+         return;
+       }
       }
+      // add new item to list
+      ptr tempbp(bp, off, len);
+      push_back(tempbp);
     }
     void append(const list& bl) {
       _len += bl._len;