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104 lines
2.9 KiB
Plaintext
104 lines
2.9 KiB
Plaintext
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#include "swift/Runtime/Config.h"
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#if SWIFT_OBJC_INTEROP
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#include "swift/Basic/Lazy.h"
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#include "swift/Basic/LLVM.h"
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#include "swift/Runtime/Metadata.h"
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#include "swift/Runtime/Mutex.h"
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#include "swift/Runtime/ObjCBridge.h"
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#include <vector>
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#import <Foundation/Foundation.h>
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#import <CoreFoundation/CoreFoundation.h>
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using namespace swift;
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/// Class of sentinel objects used to represent the `nil` value of nested
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/// optionals.
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@interface _SwiftNull : NSObject {
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@public
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unsigned depth;
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}
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@end
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@implementation _SwiftNull : NSObject
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- (NSString*)description {
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return [NSString stringWithFormat:@"<%@ %p depth = %u>", [self class],
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(void*)self,
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self->depth];
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}
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@end
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namespace {
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struct SwiftNullSentinelCache {
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std::vector<id> Cache;
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StaticReadWriteLock Lock;
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};
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static Lazy<SwiftNullSentinelCache> Sentinels;
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static id getSentinelForDepth(unsigned depth) {
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// For unnested optionals, use NSNull.
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if (depth == 1)
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return id_const_cast(kCFNull);
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// Otherwise, make up our own sentinel.
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// See if we created one for this depth.
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auto &theSentinels = Sentinels.get();
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unsigned depthIndex = depth - 2;
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{
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StaticScopedReadLock lock(theSentinels.Lock);
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const auto &cache = theSentinels.Cache;
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if (depthIndex < cache.size()) {
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id cached = cache[depthIndex];
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if (cached)
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return cached;
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}
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}
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// Make one if we need to.
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{
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StaticScopedWriteLock lock(theSentinels.Lock);
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if (depthIndex >= theSentinels.Cache.size())
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theSentinels.Cache.resize(depthIndex + 1);
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auto &cached = theSentinels.Cache[depthIndex];
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// Make sure another writer didn't sneak in.
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if (!cached) {
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auto sentinel = [[_SwiftNull alloc] init];
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sentinel->depth = depth;
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cached = sentinel;
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}
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return cached;
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}
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}
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}
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/// Return the sentinel object to use to represent `nil` for a given Optional
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/// type.
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SWIFT_RUNTIME_STDLIB_INTERFACE SWIFT_CC(swift)
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id _swift_Foundation_getOptionalNilSentinelObject(const Metadata *Wrapped) {
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// Figure out the depth of optionality we're working with.
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unsigned depth = 1;
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while (Wrapped->getKind() == MetadataKind::Optional) {
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++depth;
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Wrapped = cast<EnumMetadata>(Wrapped)->getGenericArgs()[0];
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}
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return objc_retain(getSentinelForDepth(depth));
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}
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#endif
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