nixd: add basic "Auto" classes

nixd/tools/nixd/meson.build

@@ -1,4 +1,6 @@
 nixd_next = executable('nixd',
+    'src/AutoCloseFD.cpp',
+    'src/AutoRemoveShm.cpp',
     'src/CodeAction.cpp',
     'src/Convert.cpp',
     'src/Diagnostics.cpp',

nixd/tools/nixd/src/AutoCloseFD.cpp

@@ -0,0 +1,26 @@
+#include "AutoCloseFD.h"
+
+#include <unistd.h>
+
+namespace nixd {
+
+AutoCloseFD::~AutoCloseFD() {
+  if (FD != ReleasedFD) [[likely]]
+    close(FD);
+}
+
+AutoCloseFD::AutoCloseFD(AutoCloseFD &&That) noexcept : FD(That.get()) {
+  That.release();
+}
+
+AutoCloseFD::FDTy AutoCloseFD::get() const { return FD; }
+
+void AutoCloseFD::release() { FD = ReleasedFD; }
+
+bool AutoCloseFD::isReleased(FDTy FD) { return FD == ReleasedFD; }
+
+bool AutoCloseFD::isReleased() const { return isReleased(FD); }
+
+AutoCloseFD::AutoCloseFD(FDTy FD) : FD(FD) {}
+
+} // namespace nixd

nixd/tools/nixd/src/AutoCloseFD.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cerrno>
+#include <optional>
+
+namespace nixd {
+
+/// \brief File Descriptor RAII wrapper
+class AutoCloseFD {
+public:
+  using FDTy = int;
+
+private:
+  static constexpr FDTy ReleasedFD = -EBADF;
+  FDTy FD;
+
+public:
+  AutoCloseFD(FDTy FD);
+  AutoCloseFD(const AutoCloseFD &) = delete;
+  AutoCloseFD(AutoCloseFD &&That) noexcept;
+
+  [[nodiscard]] bool isReleased() const;
+  static bool isReleased(FDTy FD);
+
+  ~AutoCloseFD();
+
+  [[nodiscard]] FDTy get() const;
+  void release();
+};
+
+} // namespace nixd

nixd/tools/nixd/src/AutoRemoveShm.cpp

@@ -0,0 +1,14 @@
+#include "AutoRemoveShm.h"
+
+namespace nixd {
+
+AutoRemoveShm::AutoRemoveShm(std::string ShmName,
+                             boost::interprocess::offset_t Size)
+    : ShmName(std::move(ShmName)) {
+  Shm = boost::interprocess::shared_memory_object(
+      boost::interprocess::open_or_create, this->ShmName.c_str(),
+      boost::interprocess::read_write);
+  Shm.truncate(Size);
+}
+
+} // namespace nixd

nixd/tools/nixd/src/AutoRemoveShm.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <boost/interprocess/shared_memory_object.hpp>
+
+namespace nixd {
+
+/// Shared memory object, the object will be removed in dtor.
+class AutoRemoveShm {
+  boost::interprocess::shared_memory_object Shm;
+  std::string ShmName;
+
+public:
+  AutoRemoveShm(std::string ShmName, boost::interprocess::offset_t Size);
+
+  ~AutoRemoveShm() { Shm.remove(ShmName.c_str()); }
+
+  [[nodiscard]] const std::string &shmName() const { return ShmName; }
+
+  boost::interprocess::shared_memory_object &get() { return Shm; }
+};
+
+} // namespace nixd