QPID-4339: simple paged queue implementation

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@1477236 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 74 insertions, 0 deletions

diff --git a/cpp/src/qpid/sys/MemoryMappedFile.h b/cpp/src/qpid/sys/MemoryMappedFile.h
new file mode 100644
index 0000000000..3dabada06b
--- /dev/null
+++ b/cpp/src/qpid/sys/MemoryMappedFile.h
@@ -0,0 +1,74 @@
+#ifndef QPID_SYS_MEMORYMAPPEDFILE_H
+#define QPID_SYS_MEMORYMAPPEDFILE_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 <string>
+
+namespace qpid {
+namespace sys {
+
+class MemoryMappedFilePrivate;
+/**
+ * Abstraction of memory mapping functionality
+ */
+class MemoryMappedFile {
+  public:
+    MemoryMappedFile();
+    /**
+     * Opens a file that can be mapped by region into memory
+     */
+    std::string open(const std::string& name, const std::string& directory);
+    /**
+     * Returns the page size
+     */
+    size_t getPageSize();
+    /**
+     * Load a portion of the file into memory
+     */
+    char* map(size_t offset, size_t size);
+    /**
+     * Evict a portion of the file from memory
+     */
+    void unmap(char* region, size_t size);
+    /**
+     * Flush any changes to a previously mapped region of the file
+     * back to disk
+     */
+    void flush(char* region, size_t size);
+    /**
+     * Expand the capacity of the file
+     */
+    void expand(size_t offset);
+    /**
+     * Returns true if memory mapping is supported, false otherwise
+     */
+    static bool isSupported();
+  private:
+    std::auto_ptr<MemoryMappedFilePrivate> state;
+
+    MemoryMappedFile(const MemoryMappedFile&);
+    MemoryMappedFile& operator=(const MemoryMappedFile&);
+};
+}} // namespace qpid::sys
+
+#endif  /*!QPID_SYS_MEMORYMAPPEDFILE_H*/