Swiftgram/Source/Private/ASWeakMap.h
appleguy 465abb1ded [License] Simplify the Texture license to be pure Apache 2 (removing ASDK-Licenses). (#1077)
* [License] Simplify the Texture license to be pure Apache 2 (removing ASDK-Licenses)

With permission of the Facebook Open Source team, we are simplifying the Texture
license so that clients can rely on the Apache 2 terms that most of Texture is
already covered by. This means that code originally forked from AsyncDisplayKit
will be re-licensed from "BSD 3-clause + PATENTS v2" to Apache 2 without a
PATENTS file.

After getting confirmation that the updates to these core files look good, we'll
propagate this new license header to all files (in this same PR) and get sign-off
from all parties before landing.

* [License] Update all Texture source files to be pure Apache 2.

* Changelog entry for Apache 2 license update.

* Revert "[License] Update all Texture source files to be pure Apache 2."

This reverts commit ffa0fbbba9717d871dd16c4b07539f2f8208fc2b.

* [License] Update all Texture source files to be pure Apache 2, maintaining copyrights.

* [License] Update CONTRIBUTING, README, Podspec & Dangerfile.
2018-08-28 07:39:18 -07:00

60 lines
2.1 KiB
Objective-C

//
// ASWeakMap.h
// Texture
//
// Copyright (c) Facebook, Inc. and its affiliates. All rights reserved.
// Changes after 4/13/2017 are: Copyright (c) Pinterest, Inc. All rights reserved.
// Licensed under Apache 2.0: http://www.apache.org/licenses/LICENSE-2.0
//
#import <Foundation/Foundation.h>
#import <AsyncDisplayKit/ASBaseDefines.h>
NS_ASSUME_NONNULL_BEGIN
/**
* This class is used in conjunction with ASWeakMap. Instances of this type are returned by an ASWeakMap,
* must retain this value for as long as they want the entry to exist in the map.
*/
AS_SUBCLASSING_RESTRICTED
@interface ASWeakMapEntry<Value> : NSObject
@property (readonly) Value value;
@end
/**
* This is not a full-featured map. It does not support features like `count` and FastEnumeration because there
* is not currently a need.
*
* This is a map that does not retain keys or values added to it. When both getting and setting, the caller is
* returned a ASWeakMapEntry and must retain it for as long as it wishes the key/value to remain in the map.
* We return a single Entry value to the caller to avoid two potential problems:
*
* 1) It's easier for callers to retain one value (the Entry) and not two (a key and a value).
* 2) Key values are tested for `isEqual` equality. If if a caller asks for a key "A" that is equal to a key "B"
* already in the map, then we need the caller to retain key "B" and not key "A". Returning an Entry simplifies
* the semantics.
*
* The underlying storage is a hash table and the Key type should implement `hash` and `isEqual:`.
*/
AS_SUBCLASSING_RESTRICTED
@interface ASWeakMap<__covariant Key, Value> : NSObject
/**
* Read from the cache. The Value object is accessible from the returned ASWeakMapEntry.
*/
- (nullable ASWeakMapEntry<Value> *)entryForKey:(Key)key AS_WARN_UNUSED_RESULT;
/**
* Put a value into the cache. If an entry with an equal key already exists, then the value is updated on the existing entry.
*/
- (ASWeakMapEntry<Value> *)setObject:(Value)value forKey:(Key)key AS_WARN_UNUSED_RESULT;
@end
NS_ASSUME_NONNULL_END