implement ObjectDBFile. Not finished yet.
diff --git a/include/object-db-file.h b/include/object-db-file.h
new file mode 100644
index 0000000..fb9ca91
--- /dev/null
+++ b/include/object-db-file.h
@@ -0,0 +1,143 @@
+#ifndef OBJECT_DB_FILE_H
+#define OBJECT_DB_FILE_H
+
+#include "object-db.h"
+#include <stdio.h>
+#include <fstream>
+#include <ifstream>
+#include <ofstream>
+#include <sstream>
+#include <boost/thread/locks.hpp>
+#include <boost/thread/recursive_mutex.hpp>
+#include <boost/lexical_cast.hpp>
+
+#define _OVERRIDE
+#ifdef __GNUC__
+#if __GNUC_MAJOR >= 4 && __GNUC_MINOR__ >= 7
+ #undef _OVERRIDE
+ #define _OVERRIDE override
+#endif // __GNUC__ version
+#endif // __GNUC__
+
+using namespace std;
+
+// This is a file based ObjectDB implementation
+// The assumption is, the Content Objects will be stored sequentially
+
+// To provide random access, we will have a table of "address" for each
+// ContentObject at the beginning of the file.
+// This also requires another assumption, that is the number of COs must
+// be know a priori. This requirement is reasonable for our dropbox-like
+// System, as the file we publish is static file and we can easily know
+// the number of COs before we store them into ObjectDB.
+
+/* How file looks like:
+ * |MAGIC_NUM|capacity|size|pos for each CO ...|1st CO|2nd CO| ... |
+ */
+
+class ObjectDBFile
+{
+public:
+ typedef boost::shared_mutex Lock;
+ typedef boost::unique_lock<Lock> WriteLock;
+ typedef boost::shared_lock<Lock> ReadLock;
+
+ ObjectDBFile(const string &filename);
+ virtual ~ObjectDBFile(){}
+
+ // reserve the "address" table for n COs; must reserve before
+ // write anything (unless reserved quota has not be consumed yet)
+ void
+ init(int capacity);
+
+ bool
+ initialized() const { return m_initialized; }
+
+ // assume sequential
+ virtual void
+ append(const Bytes &co) _OVERRIDE;
+
+ // get next CO
+ virtual Bytes
+ next() _OVERRIDE;
+
+ // get n COs; if the remaining number of COs < n, return all;
+ virtual void
+ read(vector<Bytes> &vco, int n) _OVERRIDE;
+
+ // size in terms of number of COs
+ // This is the lazy form of size, i.e. it returns the size cached in this object
+ // but that may not necessarily equal to the actual size kept in file
+ // This is enough if the caller knows for sure that no other thread is changing the
+ // file or the caller does not care about the new size.
+ virtual int
+ size() const _OVERRIDE;
+
+ // this returns the actual size (also update the size cache in this object), but it is more costly, and requires file IO
+ int
+ fSize();
+
+ // the index of the CO to be read
+ int
+ index();
+
+ // set the pos to be the desired CO
+ // return true if success
+ bool
+ seek(int index);
+
+ // reset pos to be zero
+ void
+ rewind();
+
+protected:
+ // write lock should have been grabbed already before the call
+ void
+ prepareWrite();
+
+ // read or write lock should have been grabbed already before the call
+ void
+ checkInit(const string &msg);
+
+ // read lock should have been grabbed already before the call
+ void
+ updateSize();
+
+ #define MAGIC_NUM 0xAAAAAAAA
+
+protected:
+ string m_filename;
+ ifstream m_istream;
+ ofstream m_ostream;
+ Lock m_lock;
+ bool m_writable;
+ bool m_initialized;
+ // capacity in terms of number of COs
+ int m_cap;
+ int m_size;
+ // the index (or seq) of the CO to be read
+ int m_index;
+};
+
+void inline
+writeInt(ostream &out, const int &x)
+{
+ out.write((const char *)&x, sizeof(int));
+}
+
+void inline
+readInt(istream &in, int &x)
+{
+ in.read((char *)&x, sizeof(int));
+}
+
+// write size and then the actual bytes
+// operator << overloading is not used to avoid confusion
+void
+writeBytes(ostream &out, const Bytes &bytes);
+
+// read size and then the actual bytes
+void
+readBytes(istream &in, Bytes &bytes);
+
+#endif