Migrate to boost::asio::io_context

The code previously used the deprecated (and with bost 1.87.0 removed)
`boost::asio::io_service`, which used to be an alias to `io_context`.
The new version heavily changes the `io_context` API and therefore is no
the old interface was removed.

Fixes #208

Signed-off-by: Christian Heusel <[email protected]>

Author: christian-heusel

include/lucene++/ThreadPool.h

@@ -14,7 +14,9 @@
 
 namespace Lucene {
 
-typedef boost::shared_ptr<boost::asio::io_service::work> workPtr;
+
+typedef boost::asio::io_context io_context_t;
+typedef boost::asio::executor_work_guard<io_context_t::executor_type> work_t;
 
 /// A Future represents the result of an asynchronous computation. Methods are provided to check if the computation
 /// is complete, to wait for its completion, and to retrieve the result of the computation. The result can only be
@@ -51,8 +53,8 @@ class ThreadPool : public LuceneObject {
     LUCENE_CLASS(ThreadPool);
 
 protected:
-    boost::asio::io_service io_service;
-    workPtr work;
+    io_context_t io_context;
+    work_t work;
     boost::thread_group threadGroup;
 
     static const int32_t THREADPOOL_SIZE;
@@ -64,7 +66,7 @@ class ThreadPool : public LuceneObject {
     template <typename FUNC>
     FuturePtr scheduleTask(FUNC func) {
         FuturePtr future(newInstance<Future>());
-        io_service.post(boost::bind(&ThreadPool::execute<FUNC>, this, func, future));
+        boost::asio::post(io_context, boost::bind(&ThreadPool::execute<FUNC>, this, func, future));
         return future;
     }
 

src/core/util/ThreadPool.cpp

@@ -14,15 +14,16 @@ Future::~Future() {
 
 const int32_t ThreadPool::THREADPOOL_SIZE = 5;
 
-ThreadPool::ThreadPool() {
-    work.reset(new boost::asio::io_service::work(io_service));
+ThreadPool::ThreadPool()
+    :
+        work(boost::asio::make_work_guard(io_context))
+{
     for (int32_t i = 0; i < THREADPOOL_SIZE; ++i) {
-        threadGroup.create_thread(boost::bind(&boost::asio::io_service::run, &io_service));
+        threadGroup.create_thread(boost::bind(&boost::asio::io_context::run, &io_context));
     }
 }
 
 ThreadPool::~ThreadPool() {
-    work.reset(); // stop all threads
     threadGroup.join_all(); // wait for all competition
 }