From 76bead9fd862f6b8f8294075526eaf617d5e92f0 Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Fri, 8 Mar 2024 17:26:57 +0800
Subject: [PATCH] nixd: add basic "Auto" classes

---
 nixd/tools/nixd/meson.build           |  2 ++
 nixd/tools/nixd/src/AutoCloseFD.cpp   | 26 ++++++++++++++++++++++
 nixd/tools/nixd/src/AutoCloseFD.h     | 31 +++++++++++++++++++++++++++
 nixd/tools/nixd/src/AutoRemoveShm.cpp | 14 ++++++++++++
 nixd/tools/nixd/src/AutoRemoveShm.h   | 22 +++++++++++++++++++
 5 files changed, 95 insertions(+)
 create mode 100644 nixd/tools/nixd/src/AutoCloseFD.cpp
 create mode 100644 nixd/tools/nixd/src/AutoCloseFD.h
 create mode 100644 nixd/tools/nixd/src/AutoRemoveShm.cpp
 create mode 100644 nixd/tools/nixd/src/AutoRemoveShm.h

diff --git a/nixd/tools/nixd/meson.build b/nixd/tools/nixd/meson.build
index 1d35c1a98..e6d964ced 100644
--- a/nixd/tools/nixd/meson.build
+++ b/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',
diff --git a/nixd/tools/nixd/src/AutoCloseFD.cpp b/nixd/tools/nixd/src/AutoCloseFD.cpp
new file mode 100644
index 000000000..930d6bd4a
--- /dev/null
+++ b/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
diff --git a/nixd/tools/nixd/src/AutoCloseFD.h b/nixd/tools/nixd/src/AutoCloseFD.h
new file mode 100644
index 000000000..ad340d4f5
--- /dev/null
+++ b/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
diff --git a/nixd/tools/nixd/src/AutoRemoveShm.cpp b/nixd/tools/nixd/src/AutoRemoveShm.cpp
new file mode 100644
index 000000000..3d239c42e
--- /dev/null
+++ b/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
diff --git a/nixd/tools/nixd/src/AutoRemoveShm.h b/nixd/tools/nixd/src/AutoRemoveShm.h
new file mode 100644
index 000000000..90001bda6
--- /dev/null
+++ b/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