/****************************************************************************

**

** Copyright (C) 2008-2010 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (developer.feedback@nokia.com)

**

** This file is part of the HbCore module of the UI Extensions for Mobile.

**

** GNU Lesser General Public License Usage

** This file may be used under the terms of the GNU Lesser General Public

** License version 2.1 as published by the Free Software Foundation and

** appearing in the file LICENSE.LGPL included in the packaging of this file.

** Please review the following information to ensure the GNU Lesser General

** Public License version 2.1 requirements will be met:

** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at developer.feedback@nokia.com.

**

****************************************************************************/

#include "hbsharedmemoryallocators_p.h"

#include <QDebug>

#include <QSharedMemory>

// this identifier is used to check, if the multisegment allocator is already

// initialized in given shared chunk

static const unsigned int INITIALIZED_MULTISEGMENTALLOCATOR_IDENTIFIER = 0x4D554C54; //'MULT'

// chunk sizes

// every size is aligned to 8

static const int ChunkSizes[AMOUNT_OF_DIFFERENT_CHUNK_SIZES] = {8, 16, 24, 32, 48, 64, 120, 224};

static const int CHUNKS_IN_ONE_LIST = 512;

/* 

* HbMultiSegmentAlgo implementation

*

* Since this function is crucial to the working of HbSharedMemory manager, it's required

* that it's initialize function is successfully completed. In the OOM condition,

* the exception is thrown.

*

* All chunk sizes should be multiples of 8 (so that the memory is automatically aligned).

* Based on actual data, following ranges are used:

*

* Range of sizes      Number of allocations for several applications

* between 0-8         926

* between 9-16        7715

* between 17-24       5814

* between 25-32       364

* between 33-48       409

* between 49-64       587

* between 65-120      430

* between 121-224     2322

*

*/

/**

 * HbMultiSegmentAllocator::initialize

 *

 * Initializes multisegment allocator.

 * This allocates memory from main allocator and won't block main allocator's

 * OOM exception.

  */

void HbMultiSegmentAllocator::initialize(QSharedMemory *sharedChunk,

                                         const unsigned int offset,

                                         HbSharedMemoryAllocator *mainAllocator)

{

    chunk = sharedChunk;

    this->offset = offset;

    this->mainAllocator = mainAllocator;

    // initialize fast index-getter table

    int index = 0;

    for (int i = 0; i < AMOUNT_OF_DIFFERENT_CHUNK_SIZES; i++) {

        int limit = ChunkSizes[i];

        do {

            indexTable[index++] = i;

        } while (index <= limit);

    }

    header = (MultiAllocatorHeader*)((unsigned char*)(chunk->data()) + offset);

    if (header->identifier == INITIALIZED_MULTISEGMENTALLOCATOR_IDENTIFIER) {

        return; // already initialized

    }

    // every chunk list have space for 512 chunks

    ChunkListHeader *listHeader;

    for (int i = 0; i < AMOUNT_OF_DIFFERENT_CHUNK_SIZES; i++) {

        header->offsetsToChunkLists[i] = mainAllocator->alloc(sizeof(ChunkListHeader) + (sizeof(int)+ChunkSizes[i])*CHUNKS_IN_ONE_LIST);

        header->offsetsToFreeChunkLists[i] = header->offsetsToChunkLists[i];

        listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + header->offsetsToChunkLists[i]);

        listHeader->chunkListIndex = i;

        listHeader->freedChunkCursor = -1;

        listHeader->allocCursor = header->offsetsToChunkLists[i]+sizeof(ChunkListHeader);

        listHeader->previousListOffset = -1;

        listHeader->nextListOffset = -1;

        listHeader->allocatedChunks = 0;

    }

    header->identifier = INITIALIZED_MULTISEGMENTALLOCATOR_IDENTIFIER;

}

/*

* Constructor

*/

HbMultiSegmentAllocator::HbMultiSegmentAllocator():

    chunk(0),

    offset(0),

    mainAllocator(0),

    header(0)

{

}

/*

* Destructor

*/

HbMultiSegmentAllocator::~HbMultiSegmentAllocator()

{

}

/*

* alloc function

* Will throw OOM (from main allocator) in case we run out of memory.

*/

int HbMultiSegmentAllocator::alloc(int size)

{

    // size should already be between 1...max. chunk size - no need to check

    // first find out correct list of chunks

    int i = indexTable[size];

    // qDebug() << "HbMultiSegmentAllocator::alloc, with size " << size << " chunkList " << i << " used\n";

    int dataOffset = -1;

    int *metaData = 0;

    // this should always point to list with free chunks

    ChunkListHeader *listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + header->offsetsToFreeChunkLists[i]);

    if (listHeader->freedChunkCursor >= 0) { // freedChunkCursor points to freed chunk

        dataOffset = listHeader->freedChunkCursor + sizeof(int);

        metaData = (int*)((unsigned char*)(chunk->data())+listHeader->freedChunkCursor);

        listHeader->freedChunkCursor = *metaData; // point to next freed chunk

    } else { // no chunks freed -> allocate in order

        dataOffset = listHeader->allocCursor + sizeof(int);

        metaData = (int*)((unsigned char*)(chunk->data())+listHeader->allocCursor);

        // we will never allocate from full list, so allocCursor is always valid

        listHeader->allocCursor += ChunkSizes[listHeader->chunkListIndex]+sizeof(int);

    }

    // for allocated chunks metadata is:

    // 00xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx,

    // where xx... = offset to this list's header (max. 1 GB)

    *metaData = header->offsetsToFreeChunkLists[i] /* & 0x3FFFFFFF */;

    listHeader->allocatedChunks++;

    if (listHeader->allocatedChunks == CHUNKS_IN_ONE_LIST) { // list full

        if (!setFreeList(listHeader->chunkListIndex)) {

            // there is no list(s) with free chunks, so add new list

            addList(listHeader->chunkListIndex,

                mainAllocator->alloc((sizeof(ChunkListHeader)+sizeof(int)+ChunkSizes[listHeader->chunkListIndex])*CHUNKS_IN_ONE_LIST));

        }

    }

    return dataOffset;

}

/*

* free the offset

*/

void HbMultiSegmentAllocator::free(int offset)

{

    // metadata has offset to list's header

    int *metaData = (int*)((unsigned char*)(chunk->data())+offset-sizeof(int));

    int listHeaderOffset = *metaData;

    ChunkListHeader *listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + listHeaderOffset);

    listHeader->allocatedChunks--;

    if (listHeader->allocatedChunks == 0) {

        // if there are multiple lists, this list could be released

        ChunkListHeader *previous = 0;

        if (listHeader->previousListOffset > -1) {

            previous = (ChunkListHeader*)((unsigned char*)(chunk->data()) + listHeader->previousListOffset);

        }

        ChunkListHeader *next = 0;

        if (listHeader->nextListOffset > -1) {

            next = (ChunkListHeader*)((unsigned char*)(chunk->data()) + listHeader->nextListOffset);

        }

        if (previous || next) {

            if (previous) {

                previous->nextListOffset = listHeader->nextListOffset;

            } else {

                // with no previous list, we are removing first list

                // and because if we don't have previous, next will be valid list

                header->offsetsToChunkLists[listHeader->chunkListIndex] = listHeader->nextListOffset;

            }

            if (next) {

                next->previousListOffset = listHeader->previousListOffset;

            }

            if (setFreeList(listHeader->chunkListIndex)) {

                // there is space in other list(s), so this list can be removed

                mainAllocator->free(listHeaderOffset);

            } else {

                // all the other lists are full, so just add this list back

                addList(listHeader->chunkListIndex, listHeaderOffset);

            }

        } else {

            // only list can't be freed

            *metaData = listHeader->freedChunkCursor;

            listHeader->freedChunkCursor = offset-sizeof(int);

        }

    } else {

        // this list is not yet empty

        *metaData = listHeader->freedChunkCursor;

        listHeader->freedChunkCursor = offset-sizeof(int);

    }

}

/**

 * HbMultiSegmentAllocator::allocatedSize

 *

 * Used for reallocation.

 * Returns actual allocated size for given offset.

 */

int HbMultiSegmentAllocator::allocatedSize(int offset)

{

    int *metaData = (int*)((unsigned char*)(chunk->data())+offset-sizeof(int));

    ChunkListHeader *listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + *metaData);

    // not actual size in alloc(), but the size of chunk, where this data is stored

    return ChunkSizes[listHeader->chunkListIndex];

}

/*

* Helper method for adding new list of chunks.

* Won't fail, because memory for the list is already allocated (offset).

*/

void HbMultiSegmentAllocator::addList(int index, int offset)

{

    ChunkListHeader *newListHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + offset);

    ChunkListHeader *oldListHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + header->offsetsToChunkLists[index]);

    // when this method is called, there will be at least one list,

    // so oldListHeader is valid and also all the lists are full

    newListHeader->allocatedChunks = 0;

    newListHeader->allocCursor = offset+sizeof(ChunkListHeader);

    newListHeader->chunkListIndex = index;

    newListHeader->freedChunkCursor = -1;

    newListHeader->previousListOffset = -1;

    newListHeader->nextListOffset = header->offsetsToChunkLists[index];

    oldListHeader->previousListOffset = offset;

    header->offsetsToChunkLists[index] = offset;

    setFreeList(index); // won't fail, because we just added free list

}

/*

* Try to set (new) free list to given index. If no such list exists (all are full),

* return false. Otherwise sets free list and returns true.

*/

bool HbMultiSegmentAllocator::setFreeList(int index)

{

    ChunkListHeader *listHeader;

    listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + header->offsetsToChunkLists[index]);

    bool retVal = false;

    for (;;) {

        if (listHeader->allocatedChunks < CHUNKS_IN_ONE_LIST) {

            int offset = (int)((char*)(listHeader)-(char*)(chunk->data()));

            header->offsetsToFreeChunkLists[index] = offset;

            retVal = true;

            break;

        }

        if (listHeader->nextListOffset == -1) {

            break;

        }

        listHeader = (ChunkListHeader*)((unsigned char*)(chunk->data()) + listHeader->nextListOffset);

    }

    return retVal;

}