libcore/include/sirikata/core/transfer/CachePolicy.hpp

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/*  Sirikata Transfer -- Content Transfer management system
 *  CachePolicy.hpp
 *
 *  Copyright (c) 2008, Patrick Reiter Horn
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *  * Neither the name of Sirikata nor the names of its contributors may
 *    be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*  Created on: Jan 5, 2009 */

#ifndef SIRIKATA_CachePolicy_HPP__
#define SIRIKATA_CachePolicy_HPP__

#include <sirikata/core/transfer/Defs.hpp>

namespace Sirikata {
namespace Transfer {

static const cache_usize_type tebibyte = 0x10000000000LL, terabyte = 1000000000000LL;
static const cache_usize_type gibibyte = 0x40000000,      gigabyte = 1000000000;
static const cache_usize_type mebibyte = 0x100000,        megabyte = 1000000;
static const cache_usize_type kibibyte = 0x400,           kilobyte = 1000;
static const cache_usize_type byte     = 1;

class CachePolicy {

protected:
    cache_usize_type mTotalSize;
    float mMaxSizePct;
    cache_ssize_type mFreeSpace;

    inline void updateSpace(cache_usize_type oldsize, cache_usize_type newsize) {
        std::ostringstream oss;
        oss << "[CachePolicy] ";
        if (oldsize) {
            if (newsize) {
                oss << "Resizing cache data from " << oldsize << " to " << newsize;
            } else {
                oss << "Deallocating cache data of " << oldsize;
            }
        } else {
            oss << "Allocating cache data of " << newsize;
        }
        mFreeSpace += oldsize;
        mFreeSpace -= newsize;
        oss << "; free space is now " << mFreeSpace << ".";
        SILOG(cachepolicy,insane,oss.str());
    }

public:

    struct Data {
    };

    CachePolicy(cache_usize_type allocatedSpace, float maxSizePct)
            : mTotalSize(allocatedSpace),
            mMaxSizePct(maxSizePct),
            mFreeSpace((cache_ssize_type)allocatedSpace) {
        }

    virtual ~CachePolicy() {
    }

    virtual void use(const Fingerprint &id, Data* data, cache_usize_type size) = 0;

    virtual void useAndUpdate(const Fingerprint &id, Data* data, cache_usize_type oldsize, cache_usize_type newsize) = 0;

    virtual void destroy(const Fingerprint &id, Data* data, cache_usize_type size) = 0;

    virtual Data* create(const Fingerprint &id, cache_usize_type size) = 0;

    virtual bool cachable(cache_usize_type requiredSpace) {
        if (((cache_ssize_type)requiredSpace) < 0) {
            // overflows a ssize_t.
            return false;
        }
        if ((double)requiredSpace >= (double)mTotalSize * mMaxSizePct) {
            SILOG(cachepolicy,insane,"Rejecting allocation for " << requiredSpace << " bytes of " << mFreeSpace << " free");
            return false;
        }
        SILOG(cachepolicy,insane,"Need to allocate " << requiredSpace << " bytes of " << mFreeSpace << " free");
        return true;
    }

    virtual bool nextItem(cache_usize_type requiredSpace, Fingerprint &myprint) = 0;
};


}
}

#include "CacheLayer.hpp"

#endif /* SIRIKATA_CachePolicy_HPP__ */