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/** Key-Value Coding Safe Caching Support
Copyright (C) 2024 Free Software Foundation, Inc.
Written by: Hugo Melder <hugo@algoriddim.com>
Created: August 2024
This file is part of the GNUstep Base Library.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free
Software Foundation, Inc., 31 Milk Street #960789 Boston, MA 02196 USA.
*/
/**
* It turns out that valueForKey: is a very expensive operation, and a major
* bottleneck for Key-Value Observing and other operations such as sorting
* an array by key.
*
* The accessor search patterns for Key-Value observing are discussed in the
* Apple Key-Value Coding Programming Guide. The return value may be
* encapuslated into an NSNumber or NSValue object, depending on the Objective-C
* type encoding of the return value. This means that once valueForKey: found an
* existing accessor, the Objective-C type encoding of the accessor is
* retrieved. We then go through a huge switch case to determine the right way
* to invoke the IMP and potentially encapsulate the return type. The resulting
* object is then returned.
* The algorithm for setValue:ForKey: is similar.
*
* We can speed this up by caching the IMP of the accessor in a hash table.
* However, without proper versioning, this quickly becomes very dangerous.
* The user might exchange implementations, or add new ones expecting the
* search pattern invariant to still hold. If we clamp onto an IMP, this
* invariant no longer holds.
*
* We will make use of libobjc2's safe caching to avoid this.
*
* Note that the caching is opaque. You will only need to redirect all
* valueForKey: calls to the function below.
*/
#import "Foundation/NSString.h"
#import "GSPrivate.h"
id
valueForKeyWithCaching(id obj, NSString *aKey) GS_ATTRIB_PRIVATE;
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