8 files changed, 88 insertions, 5 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
diff --git a/src/common/Base.cpp b/src/common/Base.cpp
index b6d39fef..ba4077b4 100644
--- a/src/common/Base.cpp
+++ b/src/common/Base.cpp
@@ -1,6 +1,6 @@
 #include "cru/common/Base.h"
 
-#include <stdexcept>
+#include <exception>
 
 namespace cru {
 void UnreachableCode() { std::terminate(); }
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
index 2c7f28e0..6541f156 100644
--- a/src/common/CMakeLists.txt
+++ b/src/common/CMakeLists.txt
@@ -7,6 +7,7 @@ add_library(CruBase
 	StringToNumberConverter.cpp
 	StringUtil.cpp
 	io/CFileStream.cpp
+	io/FileNotExistException.cpp
 	io/Stream.cpp
 	io/Resource.cpp
 	io/MemoryStream.cpp
diff --git a/src/common/io/CFileStream.cpp b/src/common/io/CFileStream.cpp
index 68fb137d..133cd8f6 100644
--- a/src/common/io/CFileStream.cpp
+++ b/src/common/io/CFileStream.cpp
@@ -46,22 +46,41 @@ CFileStream::CFileStream(std::FILE* file, bool readable, bool writable,
 }
 
 namespace {
-std::string ConvertOpenFileFlagToCFileFlag(OpenFileFlag flags) {
+/**
+ *  Generally the fopen will return a NULL ptr if the file does not exist. Then
+ * we must throw FileNotExistException. However, there are cases we have to
+ * check existence explicitly before. The case is OpenFileFlags::Write is
+ * specified but OpenFileFlags::Create is not, in which fopen usually create a
+ * new file automatically but we want a FileNotExistException to be thrown.
+ */
+std::string ConvertOpenFileFlagToCFileFlag(OpenFileFlag flags,
+                                           bool* explicit_check_exist) {
+  *explicit_check_exist = false;
+
   std::string result;
+
   bool need_read = flags & OpenFileFlags::Read;
   bool need_write = flags & OpenFileFlags::Write;
-  bool append = flags & OpenFileFlags::Append;
 
   if (!need_write) {
     // No need to write? The simplest
+    // Note even OpenFileFlags::Create is set, we still have to check exist.
     return "r";
   }
 
   // Now we need writing.
-  if (!need_read) {
 
+  bool create = OpenFileFlags::Create;
+
+  if (!create) {
+    *explicit_check_exist = true;
   }
 
+  bool append = flags & OpenFileFlags::Append;
+
+  if (!need_read) {
+    return "w";
+  }
 }
 }  // namespace
 
diff --git a/src/common/io/FileNotExistException.cpp b/src/common/io/FileNotExistException.cpp
new file mode 100644
index 00000000..a2e1fdb1
--- /dev/null
+++ b/src/common/io/FileNotExistException.cpp
@@ -0,0 +1,12 @@
+#include "cru/common/io/FileNotExistException.h"
+
+#include "cru/common/Exception.h"
+#include "cru/common/Format.h"
+
+#include <utility>
+
+namespace cru::io {
+  FileNotExistException::FileNotExistException(String path): Exception(), path_(std::move(path)) {
+    SetMessage(Format(u"File {} does not exist.", path_));
+  }
+}
diff --git a/src/common/io/OpenFileFlag.cpp b/src/common/io/OpenFileFlag.cpp
new file mode 100644
index 00000000..6b9957fe
--- /dev/null
+++ b/src/common/io/OpenFileFlag.cpp
@@ -0,0 +1,19 @@
+#include "cru/common/io/OpenFileFlag.h"
+
+namespace cru::io {
+bool CheckOpenFileFlag(OpenFileFlag flags) {
+  auto has = [flags](OpenFileFlag flag) { return flags & flag; };
+
+  if ((has(OpenFileFlags::Append) || has(OpenFileFlags::Truncate) ||
+       has(OpenFileFlags::Create)) &&
+      !has(OpenFileFlags::Write)) {
+    return false;
+  }
+
+  if (has(OpenFileFlags::Truncate) && has(OpenFileFlags::Append)) {
+    return false;
+  }
+
+  return true;
+}
+}  // namespace cru::io