1 files changed, 101 insertions, 0 deletions
diff --git a/qpid/cpp/include/qpid/InlineAllocator.h b/qpid/cpp/include/qpid/InlineAllocator.h
new file mode 100644
index 0000000000..2502545dcb
--- /dev/null
+++ b/qpid/cpp/include/qpid/InlineAllocator.h
@@ -0,0 +1,101 @@
+#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>
+#include <assert.h>
+#include <boost/type_traits/type_with_alignment.hpp>
+#include <boost/type_traits/alignment_of.hpp>
+
+namespace qpid {
+
+template <typename RequestedType, typename InlineType, typename BaseAllocator, size_t Max>
+struct InlineRebind;
+
+
+/**
+ * An allocator that has inline storage for up to Max objects
+ * of type BaseAllocator::value_type.
+ */
+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) {}
+    InlineAllocator(const InlineAllocator& x) : BaseAllocator(x), allocated(false) {}
+
+    pointer allocate(size_type n) {
+        if (n <= Max && !allocated) {
+            allocated=true;
+            return reinterpret_cast<value_type*>(address());
+        }
+        else
+            return BaseAllocator::allocate(n, 0);
+    }
+
+    void deallocate(pointer p, size_type n) {
+        if (p == address()) {
+            assert(allocated);
+            allocated=false;
+        }
+        else
+            BaseAllocator::deallocate(p, n);
+    }
+
+    template<typename T1>
+    struct rebind {
+        typedef typename InlineRebind<T1, value_type, BaseAllocator, Max>::other other;
+    };
+
+  private:
+    // POD object with alignment and size to hold Max value_types.
+    static const size_t ALIGNMENT=boost::alignment_of<value_type>::value;
+    typedef typename boost::type_with_alignment<ALIGNMENT>::type Aligner;
+    union Store {
+      Aligner aligner_;
+      char sizer_[sizeof(value_type)*Max];
+    } store;
+    value_type* address() { return reinterpret_cast<value_type*>(&store); }
+    bool allocated;
+};
+
+
+// Rebind: if RequestedType == InlineType, use the InlineAllocator,
+// otherwise, use the BaseAllocator without any inlining.
+
+template <typename RequestedType, typename InlineType, typename BaseAllocator, size_t Max>
+struct InlineRebind {
+    typedef typename BaseAllocator::template rebind<RequestedType>::other other;
+};
+
+template <typename T, typename BaseAllocator, size_t Max>
+struct InlineRebind<T, T, BaseAllocator, Max> {
+    typedef typename qpid::InlineAllocator<BaseAllocator, Max> other;
+};
+
+} // namespace qpid
+
+#endif  /*!QPID_INLINEALLOCATOR_H*/