revised lockfile implementation

source/util/LockFile.cpp

@@ -0,0 +1,25 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+#include <stdexcept>
+#include "LockFile.h"
+
+using namespace Aws::Iot::DeviceClient::Util;
+
+LockFile::LockFile(const std::string& filename)
+    : filename(filename)
+      , file(fopen(filename.c_str(), "wx"))
+{
+    if (!file)
+    {
+        throw std::runtime_error{"unable to open lockfile"};
+    }
+    flockfile(file);
+}
+
+LockFile::~LockFile()
+{
+    funlockfile(file);
+    fclose(file);
+    remove(filename.c_str());
+}

source/util/LockFile.h

@@ -0,0 +1,37 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef AWS_IOT_DEVICE_CLIENT_LOCKFILE_H
+#define AWS_IOT_DEVICE_CLIENT_LOCKFILE_H
+
+#include <string>
+
+namespace Aws
+{
+    namespace Iot
+    {
+        namespace DeviceClient
+        {
+            namespace Util
+            {
+                struct LockFile
+                {
+                  private:
+                    static constexpr char TAG[] = "LockFile.cpp";
+                    std::string filename;
+                    FILE *file{nullptr};
+
+                  public:
+                    LockFile(const std::string& filename);
+                    ~LockFile();
+
+                    // Non-copyable.
+                    LockFile(const LockFile &) = delete;
+                    LockFile &operator=(const LockFile &) = delete;
+                };
+            } // namespace Util
+        }     // namespace DeviceClient
+    }         // namespace Iot
+} // namespace Aws
+
+#endif // AWS_IOT_DEVICE_CLIENT_LOCKFILE_H