diff --git a/src/util/thread_pool_executor.cc b/src/util/thread_pool_executor.cc
index b496d2e9..231c3921 100644
--- a/src/util/thread_pool_executor.cc
+++ b/src/util/thread_pool_executor.cc
@@ -1,23 +1,93 @@
 /**
-* src/util/thread_pool_executor.cc
-*
-* Copyright (c) 2021-2022 Bartek Kryza <bkryza@gmail.com>
-*
-* Licensed under the Apache License, Version 2.0 (the "License");
-* you may not use this file except in compliance with the License.
-* You may obtain a copy of the License at
-*
-*     http://www.apache.org/licenses/LICENSE-2.0
-*
-* Unless required by applicable law or agreed to in writing, software
-* distributed under the License is distributed on an "AS IS" BASIS,
-* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-* See the License for the specific language governing permissions and
-* limitations under the License.
-*/
+ * src/util/thread_pool_executor.cc
+ *
+ * Copyright (c) 2021-2022 Bartek Kryza <bkryza@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
 #include "thread_pool_executor.h"
 
 namespace clanguml::util {
+thread_pool_executor::thread_pool_executor()
+    : thread_pool_executor{0}
+{
+}
+
+thread_pool_executor::thread_pool_executor(unsigned int pool_size)
+    : done_{false}
+{
+    if (pool_size == 0U)
+        pool_size = std::thread::hardware_concurrency();
+
+    for (auto i = 0U; i < pool_size; i++) {
+        threads_.push_back(std::thread{&thread_pool_executor::worker, this});
+    }
+}
+
+~thread_pool_executor::thread_pool_executor() { stop(); }
+
+std::future<void> thread_pool_executor::add(std::function<void()> &&task)
+{
+    std::unique_lock<std::mutex> l(tasks_mutex_);
+
+    std::packaged_task<void()> ptask{std::move(task)};
+    auto res = ptask.get_future();
+
+    tasks_.emplace_back(std::move(ptask));
+
+    l.unlock();
+    tasks_cond_.notify_one();
+
+    return res;
+}
+
+void thread_pool_executor::stop()
+{
+    done_ = true;
+    for (auto &thread : threads_) {
+        if (thread.joinable())
+            thread.join();
+    }
+}
+
+void thread_pool_executor::worker()
+{
+    try {
+        while (!done_) {
+            auto task = get();
+
+            task();
+        }
+    }
+    catch (std::runtime_error &e) {
+    }
+}
+
+std::packaged_task<void()> thread_pool_executor::get()
+{
+    std::unique_lock<std::mutex> l(tasks_mutex_);
+
+    while (tasks_.empty()) {
+        if (done_)
+            throw std::runtime_error("Thread pool closing...");
+
+        tasks_cond_.wait_for(l, std::chrono::seconds(1));
+    }
+
+    auto res = std::move(tasks_.front());
+    tasks_.pop_front();
+    return res;
+}
 
 }
diff --git a/src/util/thread_pool_executor.h b/src/util/thread_pool_executor.h
index 4a570c72..52e19fdf 100644
--- a/src/util/thread_pool_executor.h
+++ b/src/util/thread_pool_executor.h
@@ -25,78 +25,20 @@
 namespace clanguml::util {
 class thread_pool_executor {
 public:
-    thread_pool_executor()
-        : thread_pool_executor{0}
-    {
-    }
+    thread_pool_executor();
 
-    thread_pool_executor(unsigned int pool_size)
-        : done_{false}
-    {
-        if (pool_size == 0U)
-            pool_size = std::thread::hardware_concurrency();
+    thread_pool_executor(unsigned int pool_size);
 
-        for (auto i = 0U; i < pool_size; i++) {
-            threads_.push_back(
-                std::thread{&thread_pool_executor::worker, this});
-        }
-    }
+    ~thread_pool_executor();
 
-    ~thread_pool_executor() { stop(); }
+    std::future<void> add(std::function<void()> &&task);
 
-    std::future<void> add(std::function<void()> &&task)
-    {
-        std::unique_lock<std::mutex> l(tasks_mutex_);
-
-        std::packaged_task<void()> ptask{std::move(task)};
-        auto res = ptask.get_future();
-
-        tasks_.emplace_back(std::move(ptask));
-
-        l.unlock();
-        tasks_cond_.notify_one();
-
-        return res;
-    }
-
-    void stop()
-    {
-        done_ = true;
-        for (auto &thread : threads_) {
-            if (thread.joinable())
-                thread.join();
-        }
-    }
+    void stop();
 
 private:
-    void worker()
-    {
-        try {
-            while (!done_) {
-                auto task = get();
+    void worker();
 
-                task();
-            }
-        }
-        catch (std::runtime_error &e) {
-        }
-    }
-
-    std::packaged_task<void()> get()
-    {
-        std::unique_lock<std::mutex> l(tasks_mutex_);
-
-        while (tasks_.empty()) {
-            if (done_)
-                throw std::runtime_error("Thread pool closing...");
-
-            tasks_cond_.wait_for(l, std::chrono::seconds(1));
-        }
-
-        auto res = std::move(tasks_.front());
-        tasks_.pop_front();
-        return res;
-    }
+    std::packaged_task<void()> get();
 
     std::atomic_bool done_;