/usr/include/hphp/util/default-ptr.h is in hhvm-dev 3.21.0+dfsg-2ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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+----------------------------------------------------------------------+
| HipHop for PHP |
+----------------------------------------------------------------------+
| Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com) |
+----------------------------------------------------------------------+
| This source file is subject to version 3.01 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_01.txt |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
*/
#ifndef incl_HPHP_DEFAULT_PTR_H_
#define incl_HPHP_DEFAULT_PTR_H_
#include <cstddef>
#include <utility>
namespace HPHP {
///////////////////////////////////////////////////////////////////////////////
/*
* Pointer which can be safely const-dereferenced when null to yield a
* default-constructed value.
*/
template <class T>
struct default_ptr {
/*
* Constructors.
*/
default_ptr() : m_p{fallback()} {}
/* implicit */ default_ptr(std::nullptr_t) {}
/* implicit */ default_ptr(T* p) : m_p{p ? p : fallback()} {}
/*
* Thread-safe allocation.
*/
T* ensureAllocated() {
if (auto p = raw()) return p;
auto ptr = new T();
T* expected = fallback();
if (!m_p.compare_exchange_strong(
expected, ptr, std::memory_order_relaxed)) {
// Already set by someone else, use theirs.
delete ptr;
return expected;
} else {
return ptr;
}
}
/*
* Assignments.
*/
default_ptr& operator=(std::nullptr_t p) {
m_p.store(fallback(), std::memory_order_relaxed);
return *this;
}
default_ptr& operator=(T* p) {
m_p.store(p ? p : fallback(), std::memory_order_relaxed);
return *this;
}
/*
* Observers.
*/
const T* get() const {
return m_p.load(std::memory_order_relaxed);
}
const T& operator*() const {
return *get();
}
const T* operator->() const {
return get();
}
T* raw() const {
auto p = m_p.load(std::memory_order_relaxed);
return p == &s_default ? nullptr : p;
}
explicit operator bool() const {
return raw();
}
/*
* Modifiers.
*/
void reset(T* p = nullptr) {
operator=(p);
}
private:
/*
* Internals.
*/
static T* fallback() {
return const_cast<T*>(&s_default);
}
private:
std::atomic<T*> m_p{const_cast<T*>(&s_default)};
static const T s_default;
};
template <class T>
const T default_ptr<T>::s_default;
///////////////////////////////////////////////////////////////////////////////
}
#endif // incl_HPHP_DEFAULT_PTR_H_
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