3 files changed, 33 insertions, 1 deletions
diff --git a/include/cru/common/Exception.h b/include/cru/common/Exception.h
index 6f458d35..d7e32a5a 100644
--- a/include/cru/common/Exception.h
+++ b/include/cru/common/Exception.h
@@ -20,6 +20,9 @@ class CRU_BASE_API Exception : public std::exception {
 
   const char* what() const noexcept override;
 
+ protected:
+  void SetMessage(String message) { message_ = std::move(message); }
+
  private:
   String message_;
   mutable std::string utf8_message_;
diff --git a/include/cru/common/io/FileNotExistException.h b/include/cru/common/io/FileNotExistException.h
new file mode 100644
index 00000000..f49271b1
--- /dev/null
+++ b/include/cru/common/io/FileNotExistException.h
@@ -0,0 +1,19 @@
+#pragma once
+
+#include "../Base.h"
+#include "../Exception.h"
+
+namespace cru::io {
+  class CRU_BASE_API FileNotExistException : public Exception {
+    public:
+      FileNotExistException(String path);
+
+      CRU_DEFAULT_COPY(FileNotExistException)
+      CRU_DEFAULT_MOVE(FileNotExistException)
+
+      ~FileNotExistException() override = default;
+
+    private:
+      String path_;
+  };
+}
diff --git a/include/cru/common/io/OpenFileFlag.h b/include/cru/common/io/OpenFileFlag.h
index fd8b6e2c..4a5789fb 100644
--- a/include/cru/common/io/OpenFileFlag.h
+++ b/include/cru/common/io/OpenFileFlag.h
@@ -11,11 +11,14 @@ using OpenFileFlag = Bitmask<details::OpenFileFlagTag>;
 struct OpenFileFlags {
   /**
    * \brief for reading
+   * If the file does not exist, FileNotExistException should be thrown.
    */
   static constexpr OpenFileFlag Read{0x1};
 
   /**
    * \brief for writing
+   * If the file does not exist and Create is not specified,
+   * FileNotExistException should be thrown.
    */
   static constexpr OpenFileFlag Write{0x2};
 
@@ -34,7 +37,8 @@ struct OpenFileFlags {
 
   /**
    * \brief when writing, if the file does not exist, create one
-   * Only effective for writing.
+   * Only effective for writing. When file does not exist, FileNotExistException
+   * will NOT be thrown and a new file will be created.
    */
   static constexpr OpenFileFlag Create{0x10};
 
@@ -43,4 +47,10 @@ struct OpenFileFlags {
    */
   static constexpr OpenFileFlag Exclusive{0x20};
 };
+
+/**
+ * Append, Truncate, Create must be used with Write.
+ * Append and Truncate must not be used together.
+ */
+bool CheckOpenFileFlag(OpenFileFlag flags);
 }  // namespace cru::io