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80 lines
2.7 KiB
C++
80 lines
2.7 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_MAC_BIND_OBJC_BLOCK_H_
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#define BASE_MAC_BIND_OBJC_BLOCK_H_
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#include <Block.h>
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#include "base/bind.h"
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#include "base/callback_forward.h"
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#include "base/compiler_specific.h"
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#include "base/mac/scoped_block.h"
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// BindBlock builds a callback from an Objective-C block. Example usages:
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//
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// Closure closure = BindBlock(^{DoSomething();});
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//
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// Callback<int(void)> callback = BindBlock(^{return 42;});
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//
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// Callback<void(const std::string&, const std::string&)> callback =
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// BindBlock(^(const std::string& arg0, const std::string& arg1) {
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// ...
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// });
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//
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// These variadic templates will accommodate any number of arguments, however
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// the underlying templates in bind_internal.h and callback.h are limited to
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// seven total arguments, and the bound block itself is used as one of these
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// arguments, so functionally the templates are limited to binding blocks with
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// zero through six arguments.
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//
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// For code compiled with ARC (automatic reference counting), use BindBlockArc.
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// This is because the method has a different implementation (to avoid over-
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// retaining the block) and need to have a different name not to break the ODR
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// (one definition rule). Another subtle difference is that the implementation
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// will call a different version of ScopedBlock constructor thus the linker must
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// not merge both functions.
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namespace base {
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namespace internal {
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// Helper function to run the block contained in the parameter.
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template<typename R, typename... Args>
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R RunBlock(base::mac::ScopedBlock<R(^)(Args...)> block, Args... args) {
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R(^extracted_block)(Args...) = block.get();
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return extracted_block(args...);
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}
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} // namespace internal
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#if !defined(__has_feature) || !__has_feature(objc_arc)
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// Construct a callback from an objective-C block with up to six arguments (see
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// note above).
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template<typename R, typename... Args>
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base::Callback<R(Args...)> BindBlock(R(^block)(Args...)) {
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return base::Bind(
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&base::internal::RunBlock<R, Args...>,
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base::mac::ScopedBlock<R (^)(Args...)>(
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base::mac::internal::ScopedBlockTraits<R (^)(Args...)>::Retain(
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block)));
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}
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#else
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// Construct a callback from an objective-C block with up to six arguments (see
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// note above).
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template <typename R, typename... Args>
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base::Callback<R(Args...)> BindBlockArc(R (^block)(Args...)) {
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return base::Bind(&base::internal::RunBlock<R, Args...>,
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base::mac::ScopedBlock<R (^)(Args...)>(block));
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}
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#endif
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} // namespace base
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#endif // BASE_MAC_BIND_OBJC_BLOCK_H_
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