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, 74 insertions, 0 deletions

diff --git a/cpp/src/qpid/InlineAllocator.h b/cpp/src/qpid/InlineAllocator.h
new file mode 100644
index 0000000000..06f79c95e3
--- /dev/null
+++ b/cpp/src/qpid/InlineAllocator.h
@@ -0,0 +1,74 @@
+#ifndef QPID_INLINEALLOCATOR_H
+#define QPID_INLINEALLOCATOR_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 <memory>
+
+namespace qpid {
+
+/**
+ * An allocator that has inline storage for up to Max objects
+ * of type BaseAllocator::value_type.
+ * Store small requests inline, uses BaseAllocator::allocate otherwise.
+ */
+template <class BaseAllocator, size_t Max> 
+class InlineAllocator : public BaseAllocator {
+  public:
+    typedef typename BaseAllocator::pointer pointer;
+    typedef typename BaseAllocator::size_type size_type;
+    typedef typename BaseAllocator::value_type value_type;
+
+    InlineAllocator() : allocated(false) {}
+    
+    pointer allocate(size_type n) {
+        if (n <= Max && !allocated) {
+            allocated=true;
+            return data();
+        }
+        else 
+            return BaseAllocator::allocate(n, 0);
+    }
+
+    void deallocate(pointer p, size_type n) {
+        if (p == data()) allocated=false;
+        else BaseAllocator::deallocate(p, n);
+    }
+
+    template<typename T1>
+    struct rebind {
+        typedef typename BaseAllocator::template rebind<T1>::other BaseOther;
+        typedef InlineAllocator<BaseOther, Max> other;
+    };
+
+  private:
+    value_type* data() {
+        return reinterpret_cast<value_type*>(store);
+    }
+
+    char store[Max * sizeof(value_type)];
+    bool allocated;
+};
+
+} // namespace qpid
+
+#endif  /*!QPID_INLINEALLOCATOR_H*/