JavaScriptCore/kjs/list.cpp

/*
 *  Copyright (C) 2003, 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 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
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include "list.h"

#include "internal.h"
#include <algorithm>

#define DUMP_STATISTICS 0

using std::min;

namespace KJS {

// tunable parameters
const int poolSize = 512;
const int inlineValuesSize = 5;

enum ListImpState { unusedInPool = 0, usedInPool, usedOnHeap, immortal };

struct ListImp : ListImpBase
{
    ListImpState state;
    int capacity;
    JSValue** overflow;

    union {
        JSValue *values[inlineValuesSize];
        ListImp *nextInFreeList;
    };

#if DUMP_STATISTICS
    int sizeHighWaterMark;
#endif

    void markValues();
};

struct HeapListImp : ListImp
{
    HeapListImp *nextInHeapList;
    HeapListImp *prevInHeapList;
};

static ListImp pool[poolSize];
static ListImp *poolFreeList;
static HeapListImp *heapList;
static int poolUsed;

#if DUMP_STATISTICS

static int numLists;
static int numListsHighWaterMark;

static int listSizeHighWaterMark;

static int numListsDestroyed;
static int numListsBiggerThan[17];

struct ListStatisticsExitLogger { ~ListStatisticsExitLogger(); };

static ListStatisticsExitLogger logger;

ListStatisticsExitLogger::~ListStatisticsExitLogger()
{
    printf("\nKJS::List statistics:\n\n");
    printf("%d lists were allocated\n", numLists);
    printf("%d lists was the high water mark\n", numListsHighWaterMark);
    printf("largest list had %d elements\n", listSizeHighWaterMark);
    if (numListsDestroyed) {
        putc('\n', stdout);
        for (int i = 0; i < 17; i++) {
            printf("%.1f%% of the lists (%d) had more than %d element%s\n",
                100.0 * numListsBiggerThan[i] / numListsDestroyed,
                numListsBiggerThan[i],
                i, i == 1 ? "" : "s");
        }
        putc('\n', stdout);
    }
}

#endif

inline void ListImp::markValues()
{
    int inlineSize = min(size, inlineValuesSize);
    for (int i = 0; i != inlineSize; ++i) {
        if (!values[i]->marked()) {
            values[i]->mark();
        }
    }

    int overflowSize = size - inlineSize;
    for (int i = 0; i != overflowSize; ++i) {
        if (!overflow[i]->marked()) {
            overflow[i]->mark();
        }
    }
}

void List::markProtectedLists()
{
    int seen = 0;
    int used = poolUsed;

    for (int i = 0; i < poolSize && seen < used; i++) {
        if (pool[i].state == usedInPool) {
            seen++;
            if (pool[i].valueRefCount > 0) {
                pool[i].markValues();
            }
        }
    }

    for (HeapListImp *l = heapList; l; l = l->nextInHeapList) {
        if (l->valueRefCount > 0) {
            l->markValues();
        }
    }
}


static inline ListImp *allocateListImp()
{
    ASSERT(JSLock::lockCount() > 0);
    
    // Find a free one in the pool.
    if (poolUsed < poolSize) {
        ListImp *imp = poolFreeList ? poolFreeList : &pool[0];
        poolFreeList = imp->nextInFreeList ? imp->nextInFreeList : imp + 1;
        imp->state = usedInPool;
        poolUsed++;
        return imp;
    }
    
    HeapListImp *imp = new HeapListImp;
    imp->state = usedOnHeap;
    // link into heap list
    if (heapList) {
        heapList->prevInHeapList = imp;
    }
    imp->nextInHeapList = heapList;
    imp->prevInHeapList = NULL;
    heapList = imp;

    return imp;
}

List::List() : _impBase(allocateListImp())
{
    ListImp *imp = static_cast<ListImp *>(_impBase);
    imp->size = 0;
    imp->refCount = 1;
    imp->valueRefCount = 1;
    imp->capacity = 0;
    imp->overflow = 0;

#if DUMP_STATISTICS
    if (++numLists > numListsHighWaterMark)
        numListsHighWaterMark = numLists;
    imp->sizeHighWaterMark = 0;
#endif
}

void List::markValues()
{
    static_cast<ListImp *>(_impBase)->markValues();
}

void List::release()
{   
    ASSERT(JSLock::lockCount() > 0);
    
    ListImp *imp = static_cast<ListImp *>(_impBase);
    
#if DUMP_STATISTICS
    --numLists;
    ++numListsDestroyed;
    for (int i = 0; i < 17; i++)
        if (imp->sizeHighWaterMark > i)
            ++numListsBiggerThan[i];
#endif

    delete [] imp->overflow;
    imp->overflow = 0;

    if (imp->state == usedInPool) {
        imp->state = unusedInPool;
        imp->nextInFreeList = poolFreeList;
        poolFreeList = imp;
        poolUsed--;
    } else {
        ASSERT(imp->state == usedOnHeap);
        HeapListImp *list = static_cast<HeapListImp *>(imp);

        // unlink from heap list
        if (!list->prevInHeapList) {
            heapList = list->nextInHeapList;
            if (heapList) {
                heapList->prevInHeapList = NULL;
            }
        } else {
            list->prevInHeapList->nextInHeapList = list->nextInHeapList;
            if (list->nextInHeapList) {
                list->nextInHeapList->prevInHeapList = list->prevInHeapList;
            }
        }

        delete list;
    }
}

JSValue *List::at(int i) const
{
    ListImp *imp = static_cast<ListImp *>(_impBase);
    if ((unsigned)i >= (unsigned)imp->size)
        return jsUndefined();
    if (i < inlineValuesSize)
        return imp->values[i];
    return imp->overflow[i - inlineValuesSize];
}

void List::clear()
{
    _impBase->size = 0;
}

void List::append(JSValue *v)
{
    ASSERT(JSLock::lockCount() > 0);
    
    ListImp *imp = static_cast<ListImp *>(_impBase);

    int i = imp->size++;

#if DUMP_STATISTICS
    if (imp->size > listSizeHighWaterMark)
        listSizeHighWaterMark = imp->size;
#endif

    if (i < inlineValuesSize) {
        imp->values[i] = v;
        return;
    }
    
    if (i >= imp->capacity) {
        int newCapacity = i * 2;
        JSValue** newOverflow = new JSValue* [newCapacity - inlineValuesSize];
        JSValue** oldOverflow = imp->overflow;
        int oldOverflowSize = i - inlineValuesSize;
        for (int j = 0; j != oldOverflowSize; j++)
            newOverflow[j] = oldOverflow[j];
        delete [] oldOverflow;
        imp->overflow = newOverflow;
        imp->capacity = newCapacity;
    }
    
    imp->overflow[i - inlineValuesSize] = v;
}

List List::copy() const
{
    List copy;
    copy.copyFrom(*this);
    return copy;
}

void List::copyFrom(const List& other)
{
    ListImp *imp = static_cast<ListImp *>(other._impBase);

    int size = imp->size;

    int inlineSize = min(size, inlineValuesSize);
    for (int i = 0; i != inlineSize; ++i)
        append(imp->values[i]);

    JSValue** overflow = imp->overflow;
    int overflowSize = size - inlineSize;
    for (int i = 0; i != overflowSize; ++i)
        append(overflow[i]);
}


List List::copyTail() const
{
    List copy;

    ListImp *imp = static_cast<ListImp *>(_impBase);

    int size = imp->size;

    int inlineSize = min(size, inlineValuesSize);
    for (int i = 1; i < inlineSize; ++i)
        copy.append(imp->values[i]);

    JSValue** overflow = imp->overflow;
    int overflowSize = size - inlineSize;
    for (int i = 0; i < overflowSize; ++i)
        copy.append(overflow[i]);

    return copy;
}

const List& List::empty()
{
    static List* staticEmptyList = new List;
    return *staticEmptyList;
}

List &List::operator=(const List &b)
{
    ListImpBase *bImpBase = b._impBase;
    ++bImpBase->refCount;
    ++bImpBase->valueRefCount;
    deref();
    _impBase = bImpBase;
    return *this;
}

} // namespace KJS