/* Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and /or associated documentation files

 * (the "Materials "), to deal in the Materials without restriction,

 * including without limitation the rights to use, copy, modify, merge,

 * publish, distribute, sublicense, and/or sell copies of the Materials,

 * and to permit persons to whom the Materials are furnished to do so,

 * subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included

 * in all copies or substantial portions of the Materials.

 *

 * THE MATERIALS ARE PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.

 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,

 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR

 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE MATERIALS OR

 * THE USE OR OTHER DEALINGS IN THE MATERIALS.

 */

#ifndef __SFFUNCTIONCACHE_H

#define __SFFUNCTIONCACHE_H

// (LRU) Cache for compiled pixelpipe functions. Never takes ownership of

// any of the objects.

// \todo LRU might not be the best strategy or the best strategy might

// depend on the use-case -> create more of these.

#include "riArray.h"

#if defined(__unix__)

#   include <pthread.h>

#else

#   include <windows.h>

#endif

#include "llvm/ExecutionEngine/ExecutionEngine.h"

#include "llvm/Module.h"

namespace llvm {

    class Function;

}

namespace OpenVGRI {

template<class HashClass> class FunctionCache 

{

private:

    enum { IMPLEMENTATION_MAX_CACHE_ENTRIES = 1024 };

    //enum { MAX_GLOBAL_TIME = 10000};

    enum { MAX_GLOBAL_TIME = RI_UINT32_MAX };

    struct CacheEntry 

    {

        CacheEntry() : refCount(1) {}

        CacheEntry(HashClass aHash, ::llvm::Function* aFunc, ::llvm::GlobalVariable* aConst, RIuint32 theUT) : refCount(1) {hash = aHash; llvmFunction = aFunc; llvmConstant = aConst; ut = theUT;}

        bool operator==(const CacheEntry& rhs) const { return hash == rhs.hash; }

        bool operator<(const CacheEntry& rhs) const { return ut < rhs.ut; } // Sort by time of usage.

        HashClass           hash;

        ::llvm::Function*   llvmFunction;

        ::llvm::GlobalVariable*   llvmConstant;

        RIuint32            ut;

        RIint32             refCount;

    };

public:

    typedef CacheEntry* EntryHandle;

public:

    FunctionCache(int nMaxEntries) :

        m_time(0)

    {

        // Limit so that if the cache is too large, you must optimize the implementation.

        // Also note that the optimized pixel pipes are most likely small, so it would 

        // be better to have a fast cache and a lot of entries!

        // \note A simple optimization is to sort the usage time sort order and remove the last

        // item in the array (instead of the first).

        RI_ASSERT(nMaxEntries > 0 && nMaxEntries < IMPLEMENTATION_MAX_CACHE_ENTRIES); 

        m_nMaxEntries = nMaxEntries;

        m_entries.reserve(nMaxEntries);

    }

    ~FunctionCache() 

    {

        for (int i = 0; i < m_entries.size(); i++)

        {

            clearEntry(m_entries[i]);

        }

    }

    // This info is needed for the module to remove functions and deallocate executable

    // functions:

    void setLLVMInterface(::llvm::ExecutionEngine* ee, ::llvm::Module* module)

    {

        m_executionEngine = ee;

        m_module = module;

    }

    // \todo If we never need the entry index, the locking can be

    // simplified a lot.

    // Must lock the cache during this operation!

    EntryHandle findCachedItemByHash(const HashClass& hash)

    {

        acquireMutex();

        int i = findCachedItemIndexByHash(hash, true);

        if (i == -1)

        {

            releaseMutex();

            return NULL;

        }

        EntryHandle handle = &m_entries[i];

        releaseMutex();

        return handle;

    }

    /**

     * \brief   Caches a function. Sets the reference count to 1

     * \return  EntryHandle != NULL on success.

     * \todo    The cache must be locked during the operation.

     */

    EntryHandle cacheFunction(HashClass hash, ::llvm::Function* function, ::llvm::GlobalVariable* constant)

    {

        acquireMutex();

        RI_ASSERT(findCachedItemIndexByHash(hash) == -1);

        if (m_entries.size() == m_nMaxEntries)

        {

            if (!removeLRU())

            {

                releaseMutex();

                return NULL;

            }

        }

        m_entries.push_back(CacheEntry(hash, function, constant, m_time));

        RI_ASSERT(m_entries.size() > 0);

        EntryHandle ret = &m_entries[m_entries.size()-1];

        incrementGlobalTime();

        releaseMutex();

        return ret;

    }

    ::llvm::Function* getFunction(EntryHandle handle)

    {

        return handle->llvmFunction;

    }

    // \note Does not remove the function from cache!

    void releaseEntry(EntryHandle handle)

    {

        RI_ASSERT(handle->refCount > 0);

        handle->refCount--;

    }

private:

    void incrementGlobalTime()

    {

        m_time++;

        if (m_time == MAX_GLOBAL_TIME)

            rebaseUsageTime();

    }

    void incrementAccessTime(CacheEntry &entry)

    {

        entry.ut = m_time;

        incrementGlobalTime();

    }

    int findCachedItemIndexByHash(const HashClass& hash, bool reserve = false)

    {

        // \note Could just overload operator== from entry and use the Array.find function.

        for (int i = 0; i < m_entries.size(); i++)

        {

            if (m_entries[i].hash == hash)

            {

                if (reserve)

                {

                    incrementAccessTime(m_entries[i]);

                    m_entries[i].refCount++;

                }

                return i;

            }

        }

        return -1;

    }

    void clearEntry(CacheEntry& entry)

    {

        m_executionEngine->freeMachineCodeForFunction(entry.llvmFunction);

        entry.llvmFunction->eraseFromParent();

        //entry.llvmConstant->eraseFromParent();

    }

    /**

     * \return  true if LRU item was successfully removed, false otherwise.

     * \note    Could try other pipes, but it is unlikely that the cache gets filled

     *          so soon that the blit for the least recently used blit has not been

     *          released.

     * \todo    Implement drop of other cache-entries?

     */

    bool removeLRU() 

    {

        // \note This is pretty inefficient for many cache size:

        // After first LRU removal, the cache is almost sorted anyway, so

        // more efficient solution should be implemented.

        //

        m_entries.sort();

        if (m_entries[0].refCount > 0)

            return false;

        clearEntry(m_entries[0]);

        m_entries.remove(m_entries[0]);

        return true;

    }

    void rebaseUsageTime()

    {

        RIuint32 i;

        m_entries.sort();

        RI_ASSERT(m_entries.size() > 0);

        for(i = 0; i < (RIuint32)m_entries.size(); i++)

        {

            m_entries[i].ut = i;

        };

        m_time = i;

    }

    static void acquireMutex();

    static void releaseMutex();

private:

    ::llvm::Module              *m_module;

    ::llvm::ExecutionEngine     *m_executionEngine;

    RIuint32            m_time;

    Array <CacheEntry>  m_entries;

    int                 m_nMaxEntries;

    static bool             s_mutexInitialized;

#if defined(__unix__)

    static pthread_mutex_t  s_mutex;

#else

    static CRITICAL_SECTION s_mutex;

#endif

};

template<class HashClass>

bool FunctionCache<HashClass>::s_mutexInitialized = false;

#if defined(__unix__)

template<class HashClass>

pthread_mutex_t FunctionCache<HashClass>::s_mutex;

#else

template<class HashClass>

CRITICAL_SECTION FunctionCache<HashClass>::s_mutex;

#endif

template<class HashClass>

void FunctionCache<HashClass>::acquireMutex()

{

    if (!s_mutexInitialized)

    {

#if defined(__unix__)

        int ret;

        pthread_mutexattr_t attr;

        ret = pthread_mutexattr_init(&attr);	//initially not locked

        RI_ASSERT(!ret);	//check that there aren't any errors

        ret = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);	//count the number of recursive locks

        RI_ASSERT(!ret);	//check that there aren't any errors

        ret = pthread_mutex_init(&s_mutex, &attr);

        pthread_mutexattr_destroy(&attr);

        RI_ASSERT(!ret);	//check that there aren't more errors

#else

        ::InitializeCriticalSection(&s_mutex);

#endif

        s_mutexInitialized = true;

    }

#if defined(__unix__)

    int ret = pthread_mutex_lock(&s_mutex);

    RI_ASSERT(!ret);

#else

    ::EnterCriticalSection(&s_mutex);

#endif

}

template<class HashClass>

void FunctionCache<HashClass>::releaseMutex()

{

    RI_ASSERT(s_mutexInitialized);

#if defined(__unix__)

    int ret = pthread_mutex_unlock(&s_mutex);

    RI_ASSERT(!ret);

#else

    ::LeaveCriticalSection(&s_mutex);

#endif

}

}

#endif