5 files changed, 65 insertions, 14 deletions
diff --git a/include/cru/common/Event.h b/include/cru/common/Event.h
index 564afc40..14d68833 100644
--- a/include/cru/common/Event.h
+++ b/include/cru/common/Event.h
@@ -5,7 +5,6 @@
 
 #include <algorithm>
 #include <functional>
-#include <initializer_list>
 #include <memory>
 #include <utility>
 #include <vector>
diff --git a/include/cru/common/Format.h b/include/cru/common/Format.h
index a15e7ce7..e6935343 100644
--- a/include/cru/common/Format.h
+++ b/include/cru/common/Format.h
@@ -1,9 +1,9 @@
 #pragma once
 
-#include <double-conversion/double-conversion.h>
 #include "Exception.h"
 #include "String.h"
 
+#include <double-conversion/double-conversion.h>
 #include <charconv>
 
 namespace cru {
diff --git a/include/cru/common/Range.h b/include/cru/common/Range.h
index e61d90ca..edc2ec55 100644
--- a/include/cru/common/Range.h
+++ b/include/cru/common/Range.h
@@ -3,23 +3,22 @@
 
 namespace cru {
 struct Range final {
-  constexpr static Range FromTwoSides(gsl::index start, gsl::index end) {
+  constexpr static Range FromTwoSides(Index start, Index end) {
     return Range(start, end - start);
   }
 
-  constexpr static Range FromTwoSides(gsl::index start, gsl::index end,
-                                      gsl::index offset) {
+  constexpr static Range FromTwoSides(Index start, Index end, Index offset) {
     return Range(start + offset, end - start);
   }
 
   constexpr Range() = default;
-  constexpr Range(const gsl::index position, const gsl::index count = 0)
+  constexpr Range(const Index position, const Index count = 0)
       : position(position), count(count) {}
 
-  gsl::index GetStart() const { return position; }
-  gsl::index GetEnd() const { return position + count; }
+  Index GetStart() const { return position; }
+  Index GetEnd() const { return position + count; }
 
-  void ChangeEnd(gsl::index new_end) { count = new_end - position; }
+  void ChangeEnd(Index new_end) { count = new_end - position; }
 
   Range Normalize() const {
     auto result = *this;
@@ -30,14 +29,14 @@ struct Range final {
     return result;
   }
 
-  Range CoerceInto(gsl::index min, gsl::index max) const {
-    auto coerce = [min, max](gsl::index index) {
+  Range CoerceInto(Index min, Index max) const {
+    auto coerce = [min, max](Index index) {
       return index > max ? max : (index < min ? min : index);
     };
     return Range::FromTwoSides(coerce(GetStart()), coerce(GetEnd()));
   }
 
-  gsl::index position = 0;
-  gsl::index count = 0;
+  Index position = 0;
+  Index count = 0;
 };
 }  // namespace cru
diff --git a/include/cru/common/SelfResolvable.h b/include/cru/common/SelfResolvable.h
index c8acd4b9..0cbb35fb 100644
--- a/include/cru/common/SelfResolvable.h
+++ b/include/cru/common/SelfResolvable.h
@@ -2,7 +2,6 @@
 #include "PreConfig.h"
 
 #include <memory>
-#include <type_traits>
 
 namespace cru {
 template <typename T>
diff --git a/include/cru/common/SubProcess.h b/include/cru/common/SubProcess.h
new file mode 100644
index 00000000..341afc5c
--- /dev/null
+++ b/include/cru/common/SubProcess.h
@@ -0,0 +1,54 @@
+#pragma once
+#include "Base.h"
+#include "String.h"
+
+#include <chrono>
+#include <optional>
+#include <vector>
+
+namespace cru {
+enum class PlatformSubProcessStatus {
+  /**
+   * @brief The process has not been created and started.
+   */
+  Prepare,
+  /**
+   * @brief The process is running now.
+   */
+  Running,
+  /**
+   * @brief The process has been exited.
+   */
+  Exited,
+};
+
+/**
+ * Interface of a platform process. It is one-time, which means it starts and
+ * exits and can't start again.
+ */
+struct IPlatformSubProcess : virtual Interface {
+  /**
+   * Create and start a real process.
+   */
+  void Start(String program, std::vector<String> arguments,
+             std::vector<String> environments);
+  void Wait(std::optional<std::chrono::milliseconds> wait_time);
+  void Reap();
+  PlatformSubProcessStatus GetStatus() const;
+  int GetExitCode() const;
+};
+
+class CRU_BASE_API SubProcess : public Object {
+ public:
+  SubProcess();
+
+  CRU_DELETE_COPY(SubProcess)
+
+  SubProcess(SubProcess&& other);
+  SubProcess& operator=(SubProcess&& other);
+
+  ~SubProcess();
+
+ private:
+};
+}  // namespace cru