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Name	Size	Permission	Date
api-constants.h	2.83 KB	-rw-r--r--	2024-04-10 12:29
atomic-entry-flag.h	1.72 KB	-rw-r--r--	2022-10-11 10:59
base-page-handle.h	1.44 KB	-rw-r--r--	2024-04-10 12:29
caged-heap-local-data.h	3.61 KB	-rw-r--r--	2024-04-10 12:29
caged-heap.h	2.21 KB	-rw-r--r--	2024-04-10 12:29
compiler-specific.h	1019 B	-rw-r--r--	2022-10-11 10:59
finalizer-trait.h	2.59 KB	-rw-r--r--	2022-10-11 10:59
gc-info.h	6.31 KB	-rw-r--r--	2024-04-10 12:29
logging.h	1.66 KB	-rw-r--r--	2022-10-11 10:59
member-storage.h	8.7 KB	-rw-r--r--	2024-04-10 12:29
name-trait.h	4.08 KB	-rw-r--r--	2024-04-10 12:29
persistent-node.h	5.89 KB	-rw-r--r--	2024-04-10 12:29
pointer-policies.h	8.34 KB	-rw-r--r--	2024-04-10 12:29
write-barrier.h	19.09 KB	-rw-r--r--	2024-04-10 12:29

Rename

// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_
#define INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_

#include <atomic>

namespace cppgc {
namespace internal {

// A flag which provides a fast check whether a scope may be entered on the
// current thread, without needing to access thread-local storage or mutex.  Can
// have false positives (i.e., spuriously report that it might be entered), so
// it is expected that this will be used in tandem with a precise check that the
// scope is in fact entered on that thread.
//
// Example:
//   g_frobnicating_flag.MightBeEntered() &&
//   ThreadLocalFrobnicator().IsFrobnicating()
//
// Relaxed atomic operations are sufficient, since:
// - all accesses remain atomic
// - each thread must observe its own operations in order
// - no thread ever exits the flag more times than it enters (if used correctly)
// And so if a thread observes zero, it must be because it has observed an equal
// number of exits as entries.
class AtomicEntryFlag final {
 public:
  void Enter() { entries_.fetch_add(1, std::memory_order_relaxed); }
  void Exit() { entries_.fetch_sub(1, std::memory_order_relaxed); }

// Returns false only if the current thread is not between a call to Enter
  // and a call to Exit. Returns true if this thread or another thread may
  // currently be in the scope guarded by this flag.
  bool MightBeEntered() const {
    return entries_.load(std::memory_order_relaxed) != 0;
  }

private:
  std::atomic_int entries_{0};
};

}  // namespace internal
}  // namespace cppgc

#endif  // INCLUDE_CPPGC_INTERNAL_ATOMIC_ENTRY_FLAG_H_