Initial Commit

include/asio/detail/impl/strand_executor_service.ipp

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+//
+// detail/impl/strand_executor_service.ipp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef ASIO_DETAIL_IMPL_STRAND_EXECUTOR_SERVICE_IPP
+#define ASIO_DETAIL_IMPL_STRAND_EXECUTOR_SERVICE_IPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include "asio/detail/strand_executor_service.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+strand_executor_service::strand_executor_service(execution_context& ctx)
+  : execution_context_service_base<strand_executor_service>(ctx),
+    mutex_(),
+    salt_(0),
+    impl_list_(0)
+{
+}
+
+void strand_executor_service::shutdown()
+{
+  op_queue<scheduler_operation> ops;
+
+  asio::detail::mutex::scoped_lock lock(mutex_);
+
+  strand_impl* impl = impl_list_;
+  while (impl)
+  {
+    impl->mutex_->lock();
+    impl->shutdown_ = true;
+    ops.push(impl->waiting_queue_);
+    ops.push(impl->ready_queue_);
+    impl->mutex_->unlock();
+    impl = impl->next_;
+  }
+}
+
+strand_executor_service::implementation_type
+strand_executor_service::create_implementation()
+{
+  execution_context::allocator<void> alloc(context());
+  implementation_type new_impl = allocate_shared<strand_impl>(alloc);
+  new_impl->locked_ = false;
+  new_impl->shutdown_ = false;
+
+  asio::detail::mutex::scoped_lock lock(mutex_);
+
+  // Select a mutex from the pool of shared mutexes.
+  std::size_t salt = salt_++;
+  std::size_t mutex_index = reinterpret_cast<std::size_t>(new_impl.get());
+  mutex_index += (reinterpret_cast<std::size_t>(new_impl.get()) >> 3);
+  mutex_index ^= salt + 0x9e3779b9 + (mutex_index << 6) + (mutex_index >> 2);
+  mutex_index = mutex_index % num_mutexes;
+  if (!mutexes_[mutex_index])
+    mutexes_[mutex_index] = allocate_shared<mutex>(alloc);
+  new_impl->mutex_ = mutexes_[mutex_index].get();
+
+  // Insert implementation into linked list of all implementations.
+  new_impl->next_ = impl_list_;
+  new_impl->prev_ = 0;
+  if (impl_list_)
+    impl_list_->prev_ = new_impl.get();
+  impl_list_ = new_impl.get();
+  new_impl->service_ = this;
+
+  return new_impl;
+}
+
+strand_executor_service::strand_impl::~strand_impl()
+{
+  asio::detail::mutex::scoped_lock lock(service_->mutex_);
+
+  // Remove implementation from linked list of all implementations.
+  if (service_->impl_list_ == this)
+    service_->impl_list_ = next_;
+  if (prev_)
+    prev_->next_ = next_;
+  if (next_)
+    next_->prev_= prev_;
+}
+
+bool strand_executor_service::enqueue(const implementation_type& impl,
+    scheduler_operation* op)
+{
+  impl->mutex_->lock();
+  if (impl->shutdown_)
+  {
+    impl->mutex_->unlock();
+    op->destroy();
+    return false;
+  }
+  else if (impl->locked_)
+  {
+    // Some other function already holds the strand lock. Enqueue for later.
+    impl->waiting_queue_.push(op);
+    impl->mutex_->unlock();
+    return false;
+  }
+  else
+  {
+    // The function is acquiring the strand lock and so is responsible for
+    // scheduling the strand.
+    impl->locked_ = true;
+    impl->mutex_->unlock();
+    impl->ready_queue_.push(op);
+    return true;
+  }
+}
+
+bool strand_executor_service::running_in_this_thread(
+    const implementation_type& impl)
+{
+  return !!call_stack<strand_impl>::contains(impl.get());
+}
+
+bool strand_executor_service::push_waiting_to_ready(implementation_type& impl)
+{
+  impl->mutex_->lock();
+  impl->ready_queue_.push(impl->waiting_queue_);
+  bool more_handlers = impl->locked_ = !impl->ready_queue_.empty();
+  impl->mutex_->unlock();
+  return more_handlers;
+}
+
+void strand_executor_service::run_ready_handlers(implementation_type& impl)
+{
+  // Indicate that this strand is executing on the current thread.
+  call_stack<strand_impl>::context ctx(impl.get());
+
+  // Run all ready handlers. No lock is required since the ready queue is
+  // accessed only within the strand.
+  asio::error_code ec;
+  while (scheduler_operation* o = impl->ready_queue_.front())
+  {
+    impl->ready_queue_.pop();
+    o->complete(impl.get(), ec, 0);
+  }
+}
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_IMPL_STRAND_EXECUTOR_SERVICE_IPP