Added qpid::InlineVector - std::vector with inline storage to avoid

heap allocation for small vectors.

Made SequenceNumberSet : public InlineVector<SequenceNumber, 2>

In 100k perftest reduces heap allocation in client by  40%, broker 9%.
.


git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@595808 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 68 insertions, 0 deletions

diff --git a/cpp/src/qpid/InlineVector.h b/cpp/src/qpid/InlineVector.h
new file mode 100644
index 0000000000..551b9912e7
--- /dev/null
+++ b/cpp/src/qpid/InlineVector.h
@@ -0,0 +1,68 @@
+#ifndef QPID_INLINEVECTOR_H
+#define QPID_INLINEVECTOR_H
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+
+#include "InlineAllocator.h"
+#include <vector>
+
+namespace qpid {
+
+/**
+ * A vector that stores up to Max elements in inline storage,
+ * otherwise uses normal vector allocation.
+ *
+ * NOTE: depends on some non-standard but highly probably assumptions
+ * about how std::vector uses its allocator, they are true for g++.
+ *  - default constructor does not allocate.
+ *  - reserve(N) does not allocate more than N elements.
+ *  - vector never re-allocates when size() < capacity()
+ */
+template <class T, size_t Max, class Alloc=std::allocator<T> >
+class InlineVector : public std::vector<T, InlineAllocator<Alloc, Max> >
+{
+    typedef std::vector<T, InlineAllocator<Alloc, Max> > Base;
+  public:
+    typedef typename Base::allocator_type allocator_type;
+    typedef typename Base::value_type value_type;
+    typedef typename Base::size_type size_type;
+    
+    explicit InlineVector(const allocator_type& a=allocator_type()) : Base(a) {
+        this->reserve(Max);
+    }
+
+    explicit InlineVector(size_type n, const value_type& x = value_type(),
+                          const allocator_type& a=allocator_type()) : Base(a)
+    {
+        this->reserve(std::max(n, Max));
+        this->insert(this->end(), n, x);
+    }
+
+    InlineVector(const InlineVector& x) : Base() {
+        this->reserve(std::max(x.size(), Max));
+        *this = x;
+    }
+};
+
+} // namespace qpid
+
+#endif  /*!QPID_INLINEVECTOR_H*/