BESDapFunctionResponseCache.h

// -*- mode: c++; c-basic-offset:4 -*-
 
// This file is part of Hyrax, A C++ implementation of the OPeNDAP Data
// Access Protocol.
 
// Copyright (c) 2016 OPeNDAP, Inc.
// Author: Nathan David Potter <ndp@opendap.org>
//         James Gallagher <jgallagher@opendap.org>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
 
#ifndef _bes_dap_function_response_cache_h
#define _bes_dap_function_response_cache_h
 
#include <string>
 
#include "BESFileLockingCache.h"
 
class BESDapResponseBuilder;
 
namespace libdap {
class DDS;
class ConstraintEvaluator;
class BaseTypeFactory;
}

 
class BESDapFunctionResponseCache: public BESFileLockingCache {
private:
    static bool d_enabled;
    static BESDapFunctionResponseCache *d_instance;

    static void delete_instance() {
        delete d_instance;
        d_instance = 0;
    }

    BESDapFunctionResponseCache();
    BESDapFunctionResponseCache(const BESDapFunctionResponseCache &src);
 
    bool is_valid(const std::string &cache_file_name, const std::string &dataset);
 
    std::string get_resource_id(libdap::DDS *dds, const std::string &constraint);
    std::string get_hash_basename(const std::string &resource_id);
 
    libdap::DDS *read_cached_data(std::istream &cached_data);
 
    libdap::DDS *write_dataset_to_cache(libdap::DDS *dds, const std::string &resourceId, const std::string &constraint,
        const std::string &cache_file_name);
 
    libdap::DDS *load_from_cache(const std::string &resource_id, std::string &cache_file_name);
 
    friend class FunctionResponseCacheTest;
    friend class StoredResultTest;
 
protected:
    BESDapFunctionResponseCache(const std::string &cache_dir, const std::string &prefix, unsigned long long size) :
        BESFileLockingCache(cache_dir, prefix, size)
    {
    }
 
public:
    static const std::string PATH_KEY;
    static const std::string PREFIX_KEY;
    static const std::string SIZE_KEY;
 
    static BESDapFunctionResponseCache *get_instance(const std::string &cache_dir, const std::string &prefix,
                                                     unsigned long long size);
    static BESDapFunctionResponseCache *get_instance();
 
    virtual ~BESDapFunctionResponseCache()
    {
    }
 
    // If the DDS is in the cache and valid, return it otherwise, build the dds, cache it and return it.
    // TODO cache_dataset() was too confusing, but get_or_... is not that great either
    virtual libdap::DDS *get_or_cache_dataset(libdap::DDS *dds, const std::string &constraint);
 
    virtual bool can_be_cached(libdap::DDS *dds, const std::string &constraint);
 
    static string get_cache_dir_from_config();
    static string get_cache_prefix_from_config();
    static unsigned long get_cache_size_from_config();
};
 
#endif // _bes_dap_response_cache_h