qgcache.cpp

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/****************************************************************************
** 
**
** Implementation of QGCache and QGCacheIterator classes
**
** Created : 950208
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of the tools module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
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** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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#include "qgcache.h"
#include "qinternallist.h"
#include "qdict.h"
#include "qstring.h"


// NOT REVISED
/*!
  \class QGCache qgcache.h

  \brief The QGCache class is an internal class for implementing QCache template classes.

  QGCache is a strictly internal class that acts as a base class for the
  \link collection.html collection classes\endlink QCache and QIntCache.
*/


/*****************************************************************************
  QGCacheItem class (internal cache item)
 *****************************************************************************/

struct QCacheItem
{
    QCacheItem( void *k, QCollection::Item d, int c, short p )
        : priority(p), skipPriority(p), cost(c), key(k), data(d), node(0) {}
    short       priority;
    short       skipPriority;
    int         cost;
    void       *key;
    QCollection::Item data;
    QLNode     *node;
};


/*****************************************************************************
  QCList class (internal list of cache items)
 *****************************************************************************/

class QCList : private QInternalList<QCacheItem>
{
friend class QGCacheIterator;
friend class QCListIt;
public:
    QCList()    {}
   ~QCList();

    void        insert( QCacheItem * );         // insert according to priority
    void        insert( int, QCacheItem * );
    void        take( QCacheItem * );
    void        reference( QCacheItem * );

    void        setAutoDelete( bool del ) { QCollection::setAutoDelete(del); }

    bool        removeFirst()   { return QInternalList<QCacheItem>::removeFirst(); }
    bool        removeLast()    { return QInternalList<QCacheItem>::removeLast(); }

    QCacheItem *first()         { return QInternalList<QCacheItem>::first(); }
    QCacheItem *last()          { return QInternalList<QCacheItem>::last(); }
    QCacheItem *prev()          { return QInternalList<QCacheItem>::prev(); }
    QCacheItem *next()          { return QInternalList<QCacheItem>::next(); }

#if defined(DEBUG)
    int         inserts;                        // variables for statistics
    int         insertCosts;
    int         insertMisses;
    int         finds;
    int         hits;
    int         hitCosts;
    int         dumps;
    int         dumpCosts;
#endif
};


QCList::~QCList()
{
#if defined(DEBUG)
    ASSERT( count() == 0 );
#endif
}


void QCList::insert( QCacheItem *ci )
{
    QCacheItem *item = first();
    while( item && item->skipPriority > ci->priority ) {
        item->skipPriority--;
        item = next();
    }
    if ( item )
        QInternalList<QCacheItem>::insert( at(), ci );
    else
        append( ci );
#if defined(DEBUG)
    ASSERT( ci->node == 0 );
#endif
    ci->node = currentNode();
}

inline void QCList::insert( int i, QCacheItem *ci )
{
    QInternalList<QCacheItem>::insert( i, ci );
#if defined(DEBUG)
    ASSERT( ci->node == 0 );
#endif
    ci->node = currentNode();
}


void QCList::take( QCacheItem *ci )
{
    if ( ci ) {
#if defined(DEBUG)
        ASSERT( ci->node != 0 );
#endif
        takeNode( ci->node );
        ci->node = 0;
    }
}


inline void QCList::reference( QCacheItem *ci )
{
#if defined(DEBUG)
    ASSERT( ci != 0 && ci->node != 0 );
#endif
    ci->skipPriority = ci->priority;
    relinkNode( ci->node );                     // relink as first item
}


class QCListIt: public QInternalListIterator<QCacheItem>
{
public:
    QCListIt( const QCList *p ): QInternalListIterator<QCacheItem>( *p ) {}
    QCListIt( const QCListIt *p ): QInternalListIterator<QCacheItem>( *p ) {}
};


/*****************************************************************************
  QCDict class (internal dictionary of cache items)
 *****************************************************************************/

//
// Since we need to decide if the dictionary should use an int or const
// char * key (the "bool trivial" argument in the constructor below)
// we cannot use the macro/template dict, but inherit directly from QGDict.
//

class QCDict : public QGDict
{
public:
    QCDict( uint size, uint kt, bool caseSensitive, bool copyKeys )
        : QGDict( size, (KeyType)kt, caseSensitive, copyKeys ) {}

    QCacheItem *find_string(const QString &key) const
        { return (QCacheItem*)((QCDict*)this)->look_string(key, 0, 0); }
    QCacheItem *find_ascii(const char *key) const
        { return (QCacheItem*)((QCDict*)this)->look_ascii(key, 0, 0); }
    QCacheItem *find_int(long key) const
        { return (QCacheItem*)((QCDict*)this)->look_int(key, 0, 0); }

    QCacheItem *take_string(const QString &key)
        { return (QCacheItem*)QGDict::take_string(key); }
    QCacheItem *take_ascii(const char *key)
        { return (QCacheItem*)QGDict::take_ascii(key); }
    QCacheItem *take_int(long key)
        { return (QCacheItem*)QGDict::take_int(key); }

    bool  insert_string( const QString &key, const QCacheItem *ci )
        { return QGDict::look_string(key,(Item)ci,1)!=0;}
    bool  insert_ascii( const char *key, const QCacheItem *ci )
        { return QGDict::look_ascii(key,(Item)ci,1)!=0;}
    bool  insert_int( long key, const QCacheItem *ci )
        { return QGDict::look_int(key,(Item)ci,1)!=0;}

    bool  remove_string( QCacheItem *item )
        { return QGDict::remove_string(*((QString*)(item->key)),item); }
    bool  remove_ascii( QCacheItem *item )
        { return QGDict::remove_ascii((const char *)item->key,item); }
    bool  remove_int( QCacheItem *item )
        { return QGDict::remove_int((intptr_t)item->key,item);}

    void  statistics()                  { QGDict::statistics(); }
};


/*****************************************************************************
  QGDict member functions
 *****************************************************************************/

/*!
  \internal
  Constructs a cache.
*/

QGCache::QGCache( int maxCost, uint size, KeyType kt, bool caseSensitive,
                  bool copyKeys )
{
    keytype = kt;
    lruList = new QCList;
    CHECK_PTR( lruList );
    lruList->setAutoDelete( TRUE );
    copyk   = ((keytype == AsciiKey) && copyKeys);
    dict    = new QCDict( size, kt, caseSensitive, FALSE );
    CHECK_PTR( dict );
    mCost   = maxCost;
    tCost   = 0;
#if defined(DEBUG)
    lruList->inserts      = 0;
    lruList->insertCosts  = 0;
    lruList->insertMisses = 0;
    lruList->finds        = 0;
    lruList->hits         = 0;
    lruList->hitCosts     = 0;
    lruList->dumps        = 0;
    lruList->dumpCosts    = 0;
#endif
}

/*!
  \internal
  Cannot copy a cache.
*/

QGCache::QGCache( const QGCache & )
    : QCollection()
{
#if defined(CHECK_NULL)
    qFatal( "QGCache::QGCache(QGCache &): Cannot copy a cache" );
#endif
}

/*!
  \internal
  Removes all items from the cache and destroys it.
*/

QGCache::~QGCache()
{
    clear();                                    // delete everything first
    delete dict;
    delete lruList;
}

/*!
  \internal
  Cannot assign a cache.
*/

QGCache &QGCache::operator=( const QGCache & )
{
#if defined(CHECK_NULL)
    qFatal( "QGCache::operator=: Cannot copy a cache" );
#endif
    return *this;                               // satisfy the compiler
}


/*!
  \fn uint QGCache::count() const
  \internal
  Returns the number of items in the cache.
*/

/*!
  \fn uint QGCache::size() const
  \internal
  Returns the size of the hash array.
*/

/*!
  \fn int QGCache::maxCost() const
  \internal
  Returns the maximum cache cost.
*/

/*!
  \fn int QGCache::totalCost() const
  \internal
  Returns the total cache cost.
*/

/*!
  \internal
  Sets the maximum cache cost.
*/

void QGCache::setMaxCost( int maxCost )
{
    if ( maxCost < tCost ) {
        if ( !makeRoomFor(tCost - maxCost) )    // remove excess cost
            return;
    }
    mCost = maxCost;
}


/*!
  \internal
  Inserts an item into the cache.

  \warning If this function returns FALSE, you must delete \a data
  yourself.  Additionally, be very careful about using \a data after
  calling this function, as any other insertions into the cache, from
  anywhere in the application, or within Qt itself, could cause the
  data to be discarded from the cache, and the pointer to become
  invalid.
*/

bool QGCache::insert_string( const QString &key, QCollection::Item data,
                             int cost, int priority)
{
    if ( tCost + cost > mCost ) {
        if ( !makeRoomFor(tCost + cost - mCost, priority) ) {
#if defined(DEBUG)
            lruList->insertMisses++;
#endif
            return FALSE;
        }
    }
#if defined(DEBUG)
    ASSERT( keytype == StringKey );
    lruList->inserts++;
    lruList->insertCosts += cost;
#endif
    if ( priority < -32768 )
        priority = -32768;
    else if ( priority > 32767 )
        priority = 32677;
    QCacheItem *ci = new QCacheItem( new QString(key), newItem(data),
                                     cost, (short)priority );
    CHECK_PTR( ci );
    lruList->insert( 0, ci );
    dict->insert_string( key, ci );
    tCost += cost;
    return TRUE;
}


/*! \internal */

bool QGCache::insert_other( const char *key, QCollection::Item data,
                            int cost, int priority)
{
    if ( tCost + cost > mCost ) {
        if ( !makeRoomFor(tCost + cost - mCost, priority) ) {
#if defined(DEBUG)
            lruList->insertMisses++;
#endif
            return FALSE;
        }
    }
#if defined(DEBUG)
    ASSERT( keytype != StringKey );
    lruList->inserts++;
    lruList->insertCosts += cost;
#endif
    if ( keytype == AsciiKey && copyk )
        key = qstrdup( key );
    if ( priority < -32768 )
        priority = -32768;
    else if ( priority > 32767 )
        priority = 32677;
    QCacheItem *ci = new QCacheItem( (void*)key, newItem(data), cost,
                                     (short)priority );
    CHECK_PTR( ci );
    lruList->insert( 0, ci );
    if ( keytype == AsciiKey )
        dict->insert_ascii( key, ci );
    else
        dict->insert_int( (intptr_t)key, ci );
    tCost += cost;
    return TRUE;
}


/*!
  \internal
  Removes an item from the cache.
*/

bool QGCache::remove_string( const QString &key )
{
    Item d = take_string( key );
    if ( d )
        deleteItem( d );
    return d != 0;
}


/*! \internal */

bool QGCache::remove_other( const char *key )
{
    Item d = take_other( key );
    if ( d )
        deleteItem( d );
    return d != 0;
}


/*!
  \internal
  Takes an item out of the cache (no delete).
*/

QCollection::Item QGCache::take_string( const QString &key )
{
    QCacheItem *ci = dict->take_string( key );  // take from dict
    Item d;
    if ( ci ) {
        d = ci->data;
        tCost -= ci->cost;
        lruList->take( ci );                    // take from list
        delete (QString*)ci->key;
        delete ci;
    } else {
        d = 0;
    }
    return d;
}

/*!
  \internal
  Takes an item out of the cache (no delete).
*/

QCollection::Item QGCache::take_other( const char *key )
{
    QCacheItem *ci;
    if ( keytype == AsciiKey )
        ci = dict->take_ascii( key );
    else
        ci = dict->take_int( (intptr_t)key );
    Item d;
    if ( ci ) {
        d = ci->data;
        tCost -= ci->cost;
        lruList->take( ci );                    // take from list
        if ( copyk )
            delete [] (char *)ci->key;
        delete ci;
    } else {
        d = 0;
    }
    return d;
}


/*!
  \internal
  Clears the cache.
*/

void QGCache::clear()
{
    QCacheItem *ci;
    while ( (ci = lruList->first()) ) {
        switch ( keytype ) {
            case StringKey:
                dict->remove_string( ci );
                delete (QString*)ci->key;
                break;
            case AsciiKey:
                dict->remove_ascii( ci );
                if ( copyk )
                    delete [] (char*)ci->key;
                break;
            case IntKey:
                dict->remove_int( ci );
                break;
            case PtrKey:                        // unused
                break;
        }
        deleteItem( ci->data );                 // delete data
        lruList->removeFirst();                 // remove from list
    }
    tCost = 0;
}


/*!
  \internal
  Finds an item in the cache.
*/

QCollection::Item QGCache::find_string( const QString &key, bool ref ) const
{
    QCacheItem *ci = dict->find_string( key );
#if defined(DEBUG)
    lruList->finds++;
#endif
    if ( ci ) {
#if defined(DEBUG)
        lruList->hits++;
        lruList->hitCosts += ci->cost;
#endif
        if ( ref )
            lruList->reference( ci );
        return ci->data;
    }
    return 0;
}


/*!
  \internal
  Finds an item in the cache.
*/

QCollection::Item QGCache::find_other( const char *key, bool ref ) const
{
    QCacheItem *ci = keytype == AsciiKey ? dict->find_ascii(key)
                                         : dict->find_int((intptr_t)key);
#if defined(DEBUG)
    lruList->finds++;
#endif
    if ( ci ) {
#if defined(DEBUG)
        lruList->hits++;
        lruList->hitCosts += ci->cost;
#endif
        if ( ref )
            lruList->reference( ci );
        return ci->data;
    }
    return 0;
}


/*!
  \internal
  Allocates cache space for one or more items.
*/

bool QGCache::makeRoomFor( int cost, int priority )
{
    if ( cost > mCost )                         // cannot make room for more
        return FALSE;                           //   than maximum cost
    if ( priority == -1 )
        priority = 32767;
    register QCacheItem *ci = lruList->last();
    int cntCost = 0;
    int dumps   = 0;                            // number of items to dump
    while ( cntCost < cost && ci && ci->skipPriority <= priority ) {
        cntCost += ci->cost;
        ci       = lruList->prev();
        dumps++;
    }
    if ( cntCost < cost )                       // can enough cost be dumped?
        return FALSE;                           // no
#if defined(DEBUG)
    ASSERT( dumps > 0 );
#endif
    while ( dumps-- ) {
        ci = lruList->last();
#if defined(DEBUG)
        lruList->dumps++;
        lruList->dumpCosts += ci->cost;
#endif
        switch ( keytype ) {
            case StringKey:
                dict->remove_string( ci );
                delete (QString*)ci->key;
                break;
            case AsciiKey:
                dict->remove_ascii( ci );
                if ( copyk )
                    delete [] (char *)ci->key;
                break;
            case IntKey:
                dict->remove_int( ci );
                break;
            case PtrKey:                        // unused
                break;
        }
        deleteItem( ci->data );                 // delete data
        lruList->removeLast();                  // remove from list
    }
    tCost -= cntCost;
    return TRUE;
}


/*!
  \internal
  Outputs debug statistics.
*/

void QGCache::statistics() const
{
#if defined(DEBUG)
    QString line;
    line.fill( '*', 80 );
    qDebug( "%s",line.ascii() );
    qDebug( "CACHE STATISTICS:" );
    qDebug( "cache contains %d item%s, with a total cost of %d",
           count(), count() != 1 ? "s" : "", tCost );
    qDebug( "maximum cost is %d, cache is %d%% full.",
           mCost, (200*tCost + mCost) / (mCost*2) );
    qDebug( "find() has been called %d time%s",
           lruList->finds, lruList->finds != 1 ? "s" : "" );
    qDebug( "%d of these were hits, items found had a total cost of %d.",
           lruList->hits,lruList->hitCosts );
    qDebug( "%d item%s %s been inserted with a total cost of %d.",
           lruList->inserts,lruList->inserts != 1 ? "s" : "",
           lruList->inserts != 1 ? "have" : "has", lruList->insertCosts );
    qDebug( "%d item%s %s too large or had too low priority to be inserted.",
           lruList->insertMisses, lruList->insertMisses != 1 ? "s" : "",
           lruList->insertMisses != 1 ? "were" : "was" );
    qDebug( "%d item%s %s been thrown away with a total cost of %d.",
           lruList->dumps, lruList->dumps != 1 ? "s" : "",
           lruList->dumps != 1 ? "have" : "has", lruList->dumpCosts );
    qDebug( "Statistics from internal dictionary class:" );
    dict->statistics();
    qDebug( "%s",line.ascii() );
#endif
}

int QGCache::hits() const
{
  return lruList->hits;
}

int QGCache::misses() const
{
  return lruList->finds - lruList->hits;
}


/*****************************************************************************
  QGCacheIterator member functions
 *****************************************************************************/

/*!
  \class QGCacheIterator qgcache.h

  \brief An internal class for implementing QCacheIterator and QIntCacheIterator.

  QGCacheIterator is a strictly internal class that does the heavy work for
  QCacheIterator and QIntCacheIterator.
*/

/*!
  \internal
  Constructs an iterator that operates on the cache \e c.
*/

QGCacheIterator::QGCacheIterator( const QGCache &c )
{
    it = new QCListIt( c.lruList );
#if defined(DEBUG)
    ASSERT( it != 0 );
#endif
}

/*!
  \internal
  Constructs an iterator that operates on the same cache as \e ci.
*/

QGCacheIterator::QGCacheIterator( const QGCacheIterator &ci )
{
    it = new QCListIt( ci.it );
#if defined(DEBUG)
    ASSERT( it != 0 );
#endif
}

/*!
  \internal
  Destroys the iterator.
*/

QGCacheIterator::~QGCacheIterator()
{
    delete it;
}

/*!
  \internal
  Assigns the iterator \e ci to this cache iterator.
*/

QGCacheIterator &QGCacheIterator::operator=( const QGCacheIterator &ci )
{
    *it = *ci.it;
    return *this;
}

/*!
  \internal
  Returns the number of items in the cache.
*/

uint QGCacheIterator::count() const
{
    return it->count();
}

/*!
  \internal
  Returns TRUE if the iterator points to the first item.
*/

bool  QGCacheIterator::atFirst() const
{
    return it->atFirst();
}

/*!
  \internal
  Returns TRUE if the iterator points to the last item.
*/

bool QGCacheIterator::atLast() const
{
    return it->atLast();
}

/*!
  \internal
  Sets the list iterator to point to the first item in the cache.
*/

QCollection::Item QGCacheIterator::toFirst()
{
    QCacheItem *item = it->toFirst();
    return item ? item->data : 0;
}

/*!
  \internal
  Sets the list iterator to point to the last item in the cache.
*/

QCollection::Item QGCacheIterator::toLast()
{
    QCacheItem *item = it->toLast();
    return item ? item->data : 0;
}

/*!
  \internal
  Returns the current item.
*/

QCollection::Item QGCacheIterator::get() const
{
    QCacheItem *item = it->current();
    return item ? item->data : 0;
}

/*!
  \internal
  Returns the key of the current item.
*/

QString QGCacheIterator::getKeyString() const
{
    QCacheItem *item = it->current();
    return item ? *((QString*)item->key) : QString::null;
}

/*!
  \internal
  Returns the key of the current item, as a \0-terminated C string.
*/

const char *QGCacheIterator::getKeyAscii() const
{
    QCacheItem *item = it->current();
    return item ? (const char *)item->key : 0;
}

/*!
  \internal
  Returns the key of the current item, as a long.
*/

intptr_t QGCacheIterator::getKeyInt() const
{
    QCacheItem *item = it->current();
    return item ? (intptr_t)item->key : 0;
}

/*!
  \internal
  Moves to the next item (postfix).
*/

QCollection::Item QGCacheIterator::operator()()
{
    QCacheItem *item = it->operator()();
    return item ? item->data : 0;
}

/*!
  \internal
  Moves to the next item (prefix).
*/

QCollection::Item QGCacheIterator::operator++()
{
    QCacheItem *item = it->operator++();
    return item ? item->data : 0;
}

/*!
  \internal
  Moves \e jumps positions forward.
*/

QCollection::Item QGCacheIterator::operator+=( uint jump )
{
    QCacheItem *item = it->operator+=(jump);
    return item ? item->data : 0;
}

/*!
  \internal
  Moves to the previous item (prefix).
*/

QCollection::Item QGCacheIterator::operator--()
{
    QCacheItem *item = it->operator--();
    return item ? item->data : 0;
}

/*!
  \internal
  Moves \e jumps positions backward.
*/

QCollection::Item QGCacheIterator::operator-=( uint jump )
{
    QCacheItem *item = it->operator-=(jump);
    return item ? item->data : 0;
}