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https://github.com/XRPLF/rippled.git
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34ef577604
This change replaces all include guards in the `src/` and `include/` directories by `#pragma once`.
90 lines
2.1 KiB
C++
90 lines
2.1 KiB
C++
/**
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*
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* TODO: Remove xrpl::basic_semaphore (and this file) and use
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* std::counting_semaphore.
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*
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* Background:
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* - PR: https://github.com/XRPLF/rippled/pull/5512/files
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* - std::counting_semaphore had a bug fixed in both GCC and Clang:
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* * GCC PR 104928: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104928
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* * LLVM PR 79265: https://github.com/llvm/llvm-project/pull/79265
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*
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* GCC:
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* According to GCC Bugzilla PR104928
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* (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104928#c15), the fix is
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* scheduled for inclusion in GCC 16.0 (see comment #15, Target
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* Milestone: 16.0). It is not included in GCC 14.x or earlier, and there is no
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* indication that it will be backported to GCC 13.x or 14.x branches.
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*
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* Clang:
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* The fix for is included in Clang 19.1.0+
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*
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* Once the minimum compiler version is updated to > GCC 16.0 or Clang 19.1.0,
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* we can remove this file.
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*
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* WARNING: Avoid using std::counting_semaphore until the minimum compiler
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* version is updated.
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*/
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#pragma once
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#include <condition_variable>
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#include <mutex>
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namespace xrpl {
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template <class Mutex, class CondVar>
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class basic_semaphore
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{
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private:
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Mutex m_mutex;
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CondVar m_cond;
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std::size_t m_count;
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public:
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using size_type = std::size_t;
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/** Create the semaphore, with an optional initial count.
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If unspecified, the initial count is zero.
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*/
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explicit basic_semaphore(size_type count = 0) : m_count(count)
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{
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}
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/** Increment the count and unblock one waiting thread. */
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void
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notify()
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{
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std::lock_guard lock{m_mutex};
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++m_count;
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m_cond.notify_one();
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}
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/** Block until notify is called. */
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void
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wait()
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{
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std::unique_lock lock{m_mutex};
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while (m_count == 0)
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m_cond.wait(lock);
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--m_count;
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}
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/** Perform a non-blocking wait.
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@return `true` If the wait would be satisfied.
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*/
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bool
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try_wait()
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{
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std::lock_guard lock{m_mutex};
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if (m_count == 0)
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return false;
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--m_count;
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return true;
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}
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};
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using semaphore = basic_semaphore<std::mutex, std::condition_variable>;
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} // namespace xrpl
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