OOShipGroup.m

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/*
OOShipGroup.m
 
IMPLEMENTATION NOTE:
This is implemented as a dynamic array rather than a hash table for the
following reasons:
 *  Ship groups are generally quite small, not motivating a more complex
    implementation.
 *  The code ship groups replace was all array-based and not a significant
    bottleneck.
 *  Ship groups are compacted (i.e., dead weak references removed) as a side
    effect of iteration.
 *  Many uses of ship groups involve iterating over the whole group anyway.
 
 
Oolite
Copyright (C) 2004-2013 Giles C Williams and contributors
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program 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 General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA.
 
*/
 
#import "ShipEntity.h"
#import "OOShipGroup.h"
#import "OOMaths.h"
 
 
enum
{
    kMinSize                = 4,
    kMaxFreeSpace           = 128
};
 
 
@interface OOShipGroupEnumerator: NSEnumerator
{
    // ivars are public so ShipGroupIterate() can peek at both these and OOShipGroup's. Naughty!
@public
    OOShipGroup             *_group;
    NSUInteger              _index, _updateCount;
    BOOL                    _considerCleanup, _cleanupNeeded;
}
 
- (id) initWithShipGroup:(OOShipGroup *)group;
 
- (NSUInteger) index;
- (void) setPerformCleanup:(BOOL)flag;
 
@end
 
 
@interface OOShipGroup (Private)
 
- (BOOL) resizeTo:(NSUInteger)newCapacity;
- (void) cleanUp;
 
- (NSUInteger) updateCount;
 
@end
 
 
static id ShipGroupIterate(OOShipGroupEnumerator *enumerator);
 
 
@implementation OOShipGroup
 
- (id) init
{
    return [self initWithName:nil];
}
 
 
- (id) initWithName:(NSString *)name
{
    if ((self = [super init]))
    {
        _capacity = kMinSize;
        _members = malloc(sizeof *_members * _capacity);
        if (_members == NULL)
        {
            [self release];
            return nil;
        }
        
        [self setName:name];
    }
    
    return self;
}
 
 
+ (instancetype) groupWithName:(NSString *)name
{
    return [[[self alloc] initWithName:name] autorelease];
}
 
 
+ (instancetype) groupWithName:(NSString *)name leader:(ShipEntity *)leader
{
    OOShipGroup *result = [self groupWithName:name];
    [result setLeader:leader];
    return result;
}
 
 
- (void) dealloc
{
    NSUInteger i;
    
    for (i = 0; i < _count; i++)
    {
        [_members[i] release];
    }
    free(_members);
    [_name release];
    
    [super dealloc];
}
 
 
- (NSString *) descriptionComponents
{
    NSString *desc = [NSString stringWithFormat:@"%llu ships", (unsigned long long)_count];
    if ([self name] != nil)
    {
        desc = [NSString stringWithFormat:@"\"%@\", %@", [self name], desc];
    }
    if ([self leader] != nil)
    {
        desc = [NSString stringWithFormat:@"%@, leader: %@", desc, [[self leader] shortDescription]];
    }
    return desc;
}
 
 
- (NSString *) name
{
    return _name;
}
 
 
- (void) setName:(NSString *)name
{
    _updateCount++;
    
    if (_name != name)
    {
        [_name release];
        _name = [name retain];
    }
}
 
 
- (ShipEntity *) leader
{
    ShipEntity *result = [_leader weakRefUnderlyingObject];
    
    // If reference is stale, delete weakref object.
    if (result == nil && _leader != nil)
    {
        [_leader release];
        _leader = nil;
    }
    
    return result;
}
 
 
- (void) setLeader:(ShipEntity *)leader
{
    _updateCount++;
    
    if (leader != [self leader])
    {
        [_leader release];
        [self addShip:leader];
        _leader = [leader weakRetain];
    }
}
 
 
- (NSEnumerator *) objectEnumerator
{
    return [[[OOShipGroupEnumerator alloc] initWithShipGroup:self] autorelease];
}
 
 
- (NSEnumerator *) mutationSafeEnumerator
{
    return [[self memberArray] objectEnumerator];
}
 
 
- (NSSet *) members
{
    return [NSSet setWithArray:[self memberArray]];
}
 
 
- (NSSet *) membersExcludingLeader
{
    return [NSSet setWithArray:[self memberArrayExcludingLeader]];
}
 
 
- (NSArray *) memberArray
{
    id                      *objects = NULL;
    NSUInteger              count = 0;
    NSArray                 *result = nil;
    
    if (_count == 0)  return [NSArray array];
    
    objects = malloc(sizeof *objects * _count);
    for (id ship in self)
    {
        objects[count++] = ship;
    }
    
    result = [NSArray arrayWithObjects:objects count:count];
    free(objects);
    
    return result;
}
 
 
- (NSArray *) memberArrayExcludingLeader
{
    id                      *objects = NULL;
    NSUInteger              count = 0;
    NSArray                 *result = nil;
    ShipEntity              *leader = nil;
    
    if (_count == 0)  return [NSArray array];
    leader = self.leader;
    
    objects = malloc(sizeof *objects * _count);
    for (id ship in self)
    {
        if (ship != leader)
        {
            objects[count++] = ship;
        }
    }
    
    result = [NSArray arrayWithObjects:objects count:count];
    free(objects);
    
    return result;
}
 
 
- (BOOL) containsShip:(ShipEntity *)ship
{
    ShipEntity              *containedShip = nil;
    
    for (containedShip in self)
    {
        if ([ship isEqual:containedShip])
        {
            return YES;
        }
    }
    
    return NO;
}
 
- (BOOL) addShip:(ShipEntity *)ship
{
    _updateCount++;
    
    if ([self containsShip:ship])  return YES;  // it's in the group already, result!
    
    // Ensure there's space.
    if (_count == _capacity)
    {
        if (![self resizeTo:(_capacity > kMaxFreeSpace) ? (_capacity + kMaxFreeSpace) : (_capacity * 2)])
        {
            if (![self resizeTo:_capacity + 1])
            {
                // Out of memory?
                return NO;
            }
        }
    }
    
    _members[_count++] = [ship weakRetain];
    return YES;
}
 
 
- (BOOL) removeShip:(ShipEntity *)ship
{
    OOShipGroupEnumerator   *shipEnum = nil;
    ShipEntity              *containedShip = nil;
    NSUInteger              index;
    BOOL                    foundIt = NO;
    
    _updateCount++;
    
    if (ship == [self leader])  [self setLeader:nil];
    
    shipEnum = (OOShipGroupEnumerator *)[self objectEnumerator];
    [shipEnum setPerformCleanup:NO];
    while ((containedShip = [shipEnum nextObject]))
    {
        if ([ship isEqual:containedShip])
        {
            index = [shipEnum index] - 1;
            _members[index] = _members[--_count];
            foundIt = YES;
            
            // Clean up
            [ship setGroup:nil];
            [ship setOwner:ship];
            [self cleanUp];
            break;
        }
    }
    return foundIt;
}
 
/* TODO post-1.78: profiling indicates this is a noticeable
 * contributor to ShipEntity::update time. Consider optimisation: may
 * be possible to return _count if invalidation of weakref and group
 * removal in ShipEntity::dealloc keeps the data consistent anyway -
 * CIM */
 
- (NSUInteger) count
{
    NSEnumerator        *memberEnum = nil;
    NSUInteger          result = 0;
    
    if (_count != 0)
    {
        memberEnum = [self objectEnumerator];
        while ([memberEnum nextObject] != nil)  result++;
    }
    
    assert(result == _count);
    
    return result;
}
 
 
- (BOOL) isEmpty
{
    if (_count == 0)  return YES;
    
    return [[self objectEnumerator] nextObject] == nil;
}
 
 
- (BOOL) resizeTo:(NSUInteger)newCapacity
{
    OOWeakReference         **temp = NULL;
    
    if (newCapacity < _count)  return NO;
    
    temp = realloc(_members, newCapacity * sizeof *_members);
    if (temp == NULL)  return NO;
    
    _members = temp;
    _capacity = newCapacity;
    return YES;
}
 
 
- (void) cleanUp
{
    NSUInteger              newCapacity = _capacity;
    
    if (_count >= kMaxFreeSpace)
    {
        if (_capacity > _count + kMaxFreeSpace)
        {
            newCapacity = _count + 1;   // +1 keeps us at powers of two + multiples of kMaxFreespace.
        }
    }
    else
    {
        if (_capacity > _count * 2)
        {
            newCapacity = OORoundUpToPowerOf2_NS(_count);
            if (newCapacity < kMinSize) newCapacity = kMinSize;
        }
    }
    
    if (newCapacity != _capacity)  [self resizeTo:newCapacity];
}
 
 
- (NSUInteger) updateCount
{
    return _updateCount;
}
 
 
static id ShipGroupIterate(OOShipGroupEnumerator *enumerator)
{
    // The work is done here so that we can have access to both OOShipGroup's and OOShipGroupEnumerator's ivars.
    
    OOShipGroup             *group = enumerator->_group;
    ShipEntity              *result = nil;
    BOOL                    cleanupNeeded = NO;
    
    if (enumerator->_updateCount != group->_updateCount)
    {
        [NSException raise:NSGenericException format:@"Collection <OOShipGroup: %p> was mutated while being enumerated.", group];
    }
    
    while (enumerator->_index < group->_count)
    {
        result = [group->_members[enumerator->_index] weakRefUnderlyingObject];
        if (result != nil)
        {
            enumerator->_index++;
            break;
        }
        
        // If we got here, the group contains a stale reference to a dead ship.
        group->_members[enumerator->_index] = group->_members[--group->_count];
        cleanupNeeded = YES;
    }
    
    // Clean-up handling. Only perform actual clean-up at end of iteration.
    if (enumerator->_considerCleanup)
    {
        enumerator->_cleanupNeeded = enumerator->_cleanupNeeded && cleanupNeeded;
        if (enumerator->_cleanupNeeded && result == nil)
        {
            [group cleanUp];
        }
    }
    
    return result;
}
 
 
- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id *)stackbuf count:(NSUInteger)len
{
    NSUInteger              srcIndex, dstIndex = 0;
    ShipEntity              *item = nil;
    BOOL                    cleanupNeeded = NO;
    
    srcIndex = state->state;
    while (srcIndex < _count && dstIndex < len)
    {
        item = [_members[srcIndex] weakRefUnderlyingObject];
        if (item != nil)
        {
            stackbuf[dstIndex++] = item;
            srcIndex++;
        }
        else
        {
            _members[srcIndex] = _members[--_count];
            cleanupNeeded = YES;
        }
    }
    
    if (cleanupNeeded)  [self cleanUp];
    
    state->state = srcIndex;
    state->itemsPtr = stackbuf;
    state->mutationsPtr = &_updateCount;
    
    return dstIndex;
}
 
 
/*  This method exists purely to suppress Clang static analyzer warnings that
    this ivar is unused (but may be used by categories, which they are).
    FIXME: there must be a feature macro we can use to avoid actually building
    this into the app, but I can't find it in docs.
*/
- (BOOL) suppressClangStuff
{
    return !_jsSelf;
}
 
@end
 
 
@implementation OOShipGroupEnumerator
 
- (id) initWithShipGroup:(OOShipGroup *)group
{
    assert(group != nil);
    
    if ((self = [super init]))
    {
        _group = [group retain];
        _considerCleanup = YES;
        _updateCount = [_group updateCount];
    }
    
    return self;
}
 
 
- (void) dealloc
{
    DESTROY(_group);
    
    [super dealloc];
}
 
 
- (id) nextObject
{
    return ShipGroupIterate(self);
}
 
 
- (NSUInteger) index
{
    return _index;
}
 
 
- (void) setPerformCleanup:(BOOL)flag
{
    _considerCleanup = flag;
}
 
@end