rippled/modules/ripple_basics/json/json_internalmap.inl

//------------------------------------------------------------------------------
/*
    Copyright (c) 2011-2013, OpenCoin, Inc.
*/
//==============================================================================

// included by json_value.cpp
// everything is within Json namespace

// //////////////////////////////////////////////////////////////////
// //////////////////////////////////////////////////////////////////
// //////////////////////////////////////////////////////////////////
// class ValueInternalMap
// //////////////////////////////////////////////////////////////////
// //////////////////////////////////////////////////////////////////
// //////////////////////////////////////////////////////////////////

/** \internal MUST be safely initialized using memset( this, 0, sizeof(ValueInternalLink) );
   * This optimization is used by the fast allocator.
   */
ValueInternalLink::ValueInternalLink ()
    : previous_ ( 0 )
    , next_ ( 0 )
{
}

ValueInternalLink::~ValueInternalLink ()
{
    for ( int index = 0; index < itemPerLink; ++index )
    {
        if ( !items_[index].isItemAvailable () )
        {
            if ( !items_[index].isMemberNameStatic () )
                free ( keys_[index] );
        }
        else
            break;
    }
}



ValueMapAllocator::~ValueMapAllocator ()
{
}

#ifdef JSON_USE_SIMPLE_INTERNAL_ALLOCATOR
class DefaultValueMapAllocator : public ValueMapAllocator
{
public: // overridden from ValueMapAllocator
    virtual ValueInternalMap* newMap ()
    {
        return new ValueInternalMap ();
    }

    virtual ValueInternalMap* newMapCopy ( const ValueInternalMap& other )
    {
        return new ValueInternalMap ( other );
    }

    virtual void destructMap ( ValueInternalMap* map )
    {
        delete map;
    }

    virtual ValueInternalLink* allocateMapBuckets ( unsigned int size )
    {
        return new ValueInternalLink[size];
    }

    virtual void releaseMapBuckets ( ValueInternalLink* links )
    {
        delete [] links;
    }

    virtual ValueInternalLink* allocateMapLink ()
    {
        return new ValueInternalLink ();
    }

    virtual void releaseMapLink ( ValueInternalLink* link )
    {
        delete link;
    }
};
#else
/// @todo make this thread-safe (lock when accessign batch allocator)
class DefaultValueMapAllocator : public ValueMapAllocator
{
public: // overridden from ValueMapAllocator
    virtual ValueInternalMap* newMap ()
    {
        ValueInternalMap* map = mapsAllocator_.allocate ();
        new (map) ValueInternalMap (); // placement new
        return map;
    }

    virtual ValueInternalMap* newMapCopy ( const ValueInternalMap& other )
    {
        ValueInternalMap* map = mapsAllocator_.allocate ();
        new (map) ValueInternalMap ( other ); // placement new
        return map;
    }

    virtual void destructMap ( ValueInternalMap* map )
    {
        if ( map )
        {
            map->~ValueInternalMap ();
            mapsAllocator_.release ( map );
        }
    }

    virtual ValueInternalLink* allocateMapBuckets ( unsigned int size )
    {
        return new ValueInternalLink[size];
    }

    virtual void releaseMapBuckets ( ValueInternalLink* links )
    {
        delete [] links;
    }

    virtual ValueInternalLink* allocateMapLink ()
    {
        ValueInternalLink* link = linksAllocator_.allocate ();
        memset ( link, 0, sizeof (ValueInternalLink) );
        return link;
    }

    virtual void releaseMapLink ( ValueInternalLink* link )
    {
        link->~ValueInternalLink ();
        linksAllocator_.release ( link );
    }
private:
    BatchAllocator<ValueInternalMap, 1> mapsAllocator_;
    BatchAllocator<ValueInternalLink, 1> linksAllocator_;
};
#endif

static ValueMapAllocator*& mapAllocator ()
{
    static DefaultValueMapAllocator defaultAllocator;
    static ValueMapAllocator* mapAllocator = &defaultAllocator;
    return mapAllocator;
}

static struct DummyMapAllocatorInitializer
{
    DummyMapAllocatorInitializer ()
    {
        mapAllocator ();     // ensure mapAllocator() statics are initialized before main().
    }
} dummyMapAllocatorInitializer;



// h(K) = value * K >> w ; with w = 32 & K prime w.r.t. 2^32.

/*
use linked list hash map.
buckets array is a container.
linked list element contains 6 key/values. (memory = (16+4) * 6 + 4 = 124)
value have extra state: valid, available, deleted
*/


ValueInternalMap::ValueInternalMap ()
    : buckets_ ( 0 )
    , tailLink_ ( 0 )
    , bucketsSize_ ( 0 )
    , itemCount_ ( 0 )
{
}


ValueInternalMap::ValueInternalMap ( const ValueInternalMap& other )
    : buckets_ ( 0 )
    , tailLink_ ( 0 )
    , bucketsSize_ ( 0 )
    , itemCount_ ( 0 )
{
    reserve ( other.itemCount_ );
    IteratorState it;
    IteratorState itEnd;
    other.makeBeginIterator ( it );
    other.makeEndIterator ( itEnd );

    for ( ; !equals (it, itEnd); increment (it) )
    {
        bool isStatic;
        const char* memberName = key ( it, isStatic );
        const Value& aValue = value ( it );
        resolveReference (memberName, isStatic) = aValue;
    }
}


ValueInternalMap&
ValueInternalMap::operator = ( const ValueInternalMap& other )
{
    ValueInternalMap dummy ( other );
    swap ( dummy );
    return *this;
}


ValueInternalMap::~ValueInternalMap ()
{
    if ( buckets_ )
    {
        for ( BucketIndex bucketIndex = 0; bucketIndex < bucketsSize_; ++bucketIndex )
        {
            ValueInternalLink* link = buckets_[bucketIndex].next_;

            while ( link )
            {
                ValueInternalLink* linkToRelease = link;
                link = link->next_;
                mapAllocator ()->releaseMapLink ( linkToRelease );
            }
        }

        mapAllocator ()->releaseMapBuckets ( buckets_ );
    }
}


void
ValueInternalMap::swap ( ValueInternalMap& other )
{
    ValueInternalLink* tempBuckets = buckets_;
    buckets_ = other.buckets_;
    other.buckets_ = tempBuckets;
    ValueInternalLink* tempTailLink = tailLink_;
    tailLink_ = other.tailLink_;
    other.tailLink_ = tempTailLink;
    BucketIndex tempBucketsSize = bucketsSize_;
    bucketsSize_ = other.bucketsSize_;
    other.bucketsSize_ = tempBucketsSize;
    BucketIndex tempItemCount = itemCount_;
    itemCount_ = other.itemCount_;
    other.itemCount_ = tempItemCount;
}


void
ValueInternalMap::clear ()
{
    ValueInternalMap dummy;
    swap ( dummy );
}


ValueInternalMap::BucketIndex
ValueInternalMap::size () const
{
    return itemCount_;
}

bool
ValueInternalMap::reserveDelta ( BucketIndex growth )
{
    return reserve ( itemCount_ + growth );
}

bool
ValueInternalMap::reserve ( BucketIndex newItemCount )
{
    if ( !buckets_  &&  newItemCount > 0 )
    {
        buckets_ = mapAllocator ()->allocateMapBuckets ( 1 );
        bucketsSize_ = 1;
        tailLink_ = &buckets_[0];
    }

    //   BucketIndex idealBucketCount = (newItemCount + ValueInternalLink::itemPerLink) / ValueInternalLink::itemPerLink;
    return true;
}


const Value*
ValueInternalMap::find ( const char* key ) const
{
    if ( !bucketsSize_ )
        return 0;

    HashKey hashedKey = hash ( key );
    BucketIndex bucketIndex = hashedKey % bucketsSize_;

    for ( const ValueInternalLink* current = &buckets_[bucketIndex];
            current != 0;
            current = current->next_ )
    {
        for ( BucketIndex index = 0; index < ValueInternalLink::itemPerLink; ++index )
        {
            if ( current->items_[index].isItemAvailable () )
                return 0;

            if ( strcmp ( key, current->keys_[index] ) == 0 )
                return &current->items_[index];
        }
    }

    return 0;
}


Value*
ValueInternalMap::find ( const char* key )
{
    const ValueInternalMap* constThis = this;
    return const_cast<Value*> ( constThis->find ( key ) );
}


Value&
ValueInternalMap::resolveReference ( const char* key,
                                     bool isStatic )
{
    HashKey hashedKey = hash ( key );

    if ( bucketsSize_ )
    {
        BucketIndex bucketIndex = hashedKey % bucketsSize_;
        ValueInternalLink** previous = 0;
        BucketIndex index;

        for ( ValueInternalLink* current = &buckets_[bucketIndex];
                current != 0;
                previous = &current->next_, current = current->next_ )
        {
            for ( index = 0; index < ValueInternalLink::itemPerLink; ++index )
            {
                if ( current->items_[index].isItemAvailable () )
                    return setNewItem ( key, isStatic, current, index );

                if ( strcmp ( key, current->keys_[index] ) == 0 )
                    return current->items_[index];
            }
        }
    }

    reserveDelta ( 1 );
    return unsafeAdd ( key, isStatic, hashedKey );
}


void
ValueInternalMap::remove ( const char* key )
{
    HashKey hashedKey = hash ( key );

    if ( !bucketsSize_ )
        return;

    BucketIndex bucketIndex = hashedKey % bucketsSize_;

    for ( ValueInternalLink* link = &buckets_[bucketIndex];
            link != 0;
            link = link->next_ )
    {
        BucketIndex index;

        for ( index = 0; index < ValueInternalLink::itemPerLink; ++index )
        {
            if ( link->items_[index].isItemAvailable () )
                return;

            if ( strcmp ( key, link->keys_[index] ) == 0 )
            {
                doActualRemove ( link, index, bucketIndex );
                return;
            }
        }
    }
}

void
ValueInternalMap::doActualRemove ( ValueInternalLink* link,
                                   BucketIndex index,
                                   BucketIndex bucketIndex )
{
    // find last item of the bucket and swap it with the 'removed' one.
    // set removed items flags to 'available'.
    // if last page only contains 'available' items, then desallocate it (it's empty)
    ValueInternalLink*& lastLink = getLastLinkInBucket ( index );
    BucketIndex lastItemIndex = 1; // a link can never be empty, so start at 1

    for ( ;
            lastItemIndex < ValueInternalLink::itemPerLink;
            ++lastItemIndex ) // may be optimized with dicotomic search
    {
        if ( lastLink->items_[lastItemIndex].isItemAvailable () )
            break;
    }

    BucketIndex lastUsedIndex = lastItemIndex - 1;
    Value* valueToDelete = &link->items_[index];
    Value* valueToPreserve = &lastLink->items_[lastUsedIndex];

    if ( valueToDelete != valueToPreserve )
        valueToDelete->swap ( *valueToPreserve );

    if ( lastUsedIndex == 0 )  // page is now empty
    {
        // remove it from bucket linked list and delete it.
        ValueInternalLink* linkPreviousToLast = lastLink->previous_;

        if ( linkPreviousToLast != 0 )   // can not deleted bucket link.
        {
            mapAllocator ()->releaseMapLink ( lastLink );
            linkPreviousToLast->next_ = 0;
            lastLink = linkPreviousToLast;
        }
    }
    else
    {
        Value dummy;
        valueToPreserve->swap ( dummy ); // restore deleted to default Value.
        valueToPreserve->setItemUsed ( false );
    }

    --itemCount_;
}


ValueInternalLink*&
ValueInternalMap::getLastLinkInBucket ( BucketIndex bucketIndex )
{
    if ( bucketIndex == bucketsSize_ - 1 )
        return tailLink_;

    ValueInternalLink*& previous = buckets_[bucketIndex + 1].previous_;

    if ( !previous )
        previous = &buckets_[bucketIndex];

    return previous;
}


Value&
ValueInternalMap::setNewItem ( const char* key,
                               bool isStatic,
                               ValueInternalLink* link,
                               BucketIndex index )
{
    char* duplicatedKey = valueAllocator ()->makeMemberName ( key );
    ++itemCount_;
    link->keys_[index] = duplicatedKey;
    link->items_[index].setItemUsed ();
    link->items_[index].setMemberNameIsStatic ( isStatic );
    return link->items_[index]; // items already default constructed.
}


Value&
ValueInternalMap::unsafeAdd ( const char* key,
                              bool isStatic,
                              HashKey hashedKey )
{
    JSON_ASSERT_MESSAGE ( bucketsSize_ > 0, "ValueInternalMap::unsafeAdd(): internal logic error." );
    BucketIndex bucketIndex = hashedKey % bucketsSize_;
    ValueInternalLink*& previousLink = getLastLinkInBucket ( bucketIndex );
    ValueInternalLink* link = previousLink;
    BucketIndex index;

    for ( index = 0; index < ValueInternalLink::itemPerLink; ++index )
    {
        if ( link->items_[index].isItemAvailable () )
            break;
    }

    if ( index == ValueInternalLink::itemPerLink ) // need to add a new page
    {
        ValueInternalLink* newLink = mapAllocator ()->allocateMapLink ();
        index = 0;
        link->next_ = newLink;
        previousLink = newLink;
        link = newLink;
    }

    return setNewItem ( key, isStatic, link, index );
}


ValueInternalMap::HashKey
ValueInternalMap::hash ( const char* key ) const
{
    HashKey hash = 0;

    while ( *key )
        hash += *key++ * 37;

    return hash;
}


int
ValueInternalMap::compare ( const ValueInternalMap& other ) const
{
    int sizeDiff ( itemCount_ - other.itemCount_ );

    if ( sizeDiff != 0 )
        return sizeDiff;

    // Strict order guaranty is required. Compare all keys FIRST, then compare values.
    IteratorState it;
    IteratorState itEnd;
    makeBeginIterator ( it );
    makeEndIterator ( itEnd );

    for ( ; !equals (it, itEnd); increment (it) )
    {
        if ( !other.find ( key ( it ) ) )
            return 1;
    }

    // All keys are equals, let's compare values
    makeBeginIterator ( it );

    for ( ; !equals (it, itEnd); increment (it) )
    {
        const Value* otherValue = other.find ( key ( it ) );
        int valueDiff = value (it).compare ( *otherValue );

        if ( valueDiff != 0 )
            return valueDiff;
    }

    return 0;
}


void
ValueInternalMap::makeBeginIterator ( IteratorState& it ) const
{
    it.map_ = const_cast<ValueInternalMap*> ( this );
    it.bucketIndex_ = 0;
    it.itemIndex_ = 0;
    it.link_ = buckets_;
}


void
ValueInternalMap::makeEndIterator ( IteratorState& it ) const
{
    it.map_ = const_cast<ValueInternalMap*> ( this );
    it.bucketIndex_ = bucketsSize_;
    it.itemIndex_ = 0;
    it.link_ = 0;
}


bool
ValueInternalMap::equals ( const IteratorState& x, const IteratorState& other )
{
    return x.map_ == other.map_
           &&  x.bucketIndex_ == other.bucketIndex_
           &&  x.link_ == other.link_
           &&  x.itemIndex_ == other.itemIndex_;
}


void
ValueInternalMap::incrementBucket ( IteratorState& iterator )
{
    ++iterator.bucketIndex_;
    JSON_ASSERT_MESSAGE ( iterator.bucketIndex_ <= iterator.map_->bucketsSize_,
                          "ValueInternalMap::increment(): attempting to iterate beyond end." );

    if ( iterator.bucketIndex_ == iterator.map_->bucketsSize_ )
        iterator.link_ = 0;
    else
        iterator.link_ = & (iterator.map_->buckets_[iterator.bucketIndex_]);

    iterator.itemIndex_ = 0;
}


void
ValueInternalMap::increment ( IteratorState& iterator )
{
    JSON_ASSERT_MESSAGE ( iterator.map_, "Attempting to iterator using invalid iterator." );
    ++iterator.itemIndex_;

    if ( iterator.itemIndex_ == ValueInternalLink::itemPerLink )
    {
        JSON_ASSERT_MESSAGE ( iterator.link_ != 0,
                              "ValueInternalMap::increment(): attempting to iterate beyond end." );
        iterator.link_ = iterator.link_->next_;

        if ( iterator.link_ == 0 )
            incrementBucket ( iterator );
    }
    else if ( iterator.link_->items_[iterator.itemIndex_].isItemAvailable () )
    {
        incrementBucket ( iterator );
    }
}


void
ValueInternalMap::decrement ( IteratorState& iterator )
{
    if ( iterator.itemIndex_ == 0 )
    {
        JSON_ASSERT_MESSAGE ( iterator.map_, "Attempting to iterate using invalid iterator." );

        if ( iterator.link_ == &iterator.map_->buckets_[iterator.bucketIndex_] )
        {
            JSON_ASSERT_MESSAGE ( iterator.bucketIndex_ > 0, "Attempting to iterate beyond beginning." );
            -- (iterator.bucketIndex_);
        }

        iterator.link_ = iterator.link_->previous_;
        iterator.itemIndex_ = ValueInternalLink::itemPerLink - 1;
    }
}


const char*
ValueInternalMap::key ( const IteratorState& iterator )
{
    JSON_ASSERT_MESSAGE ( iterator.link_, "Attempting to iterate using invalid iterator." );
    return iterator.link_->keys_[iterator.itemIndex_];
}

const char*
ValueInternalMap::key ( const IteratorState& iterator, bool& isStatic )
{
    JSON_ASSERT_MESSAGE ( iterator.link_, "Attempting to iterate using invalid iterator." );
    isStatic = iterator.link_->items_[iterator.itemIndex_].isMemberNameStatic ();
    return iterator.link_->keys_[iterator.itemIndex_];
}


Value&
ValueInternalMap::value ( const IteratorState& iterator )
{
    JSON_ASSERT_MESSAGE ( iterator.link_, "Attempting to iterate using invalid iterator." );
    return iterator.link_->items_[iterator.itemIndex_];
}


int
ValueInternalMap::distance ( const IteratorState& x, const IteratorState& y )
{
    int offset = 0;
    IteratorState it = x;

    while ( !equals ( it, y ) )
        increment ( it );

    return offset;
}