stream: add file::exists and file::readonly

We are targeting C++14, while C++17 already has std::filesystem::exists. 😢

Signed-off-by: Simon Rozman <simon@rozman.si>

UnitTests/main.cpp

@@ -1,4 +1,4 @@
-/*
+/*
 	SPDX-License-Identifier: MIT
 	Copyright © 2023 Amebis
 */
@@ -26,6 +26,7 @@ int main(int argc, const char * argv[])
 		UnitTests::stream::async();
 		UnitTests::stream::replicator();
 		UnitTests::stream::open_close();
+		UnitTests::stream::file_stat();
 		UnitTests::unicode::str2wstr();
 		UnitTests::unicode::wstr2str();
 		UnitTests::unicode::charset_encoder();

UnitTests/stream.cpp

@@ -139,6 +139,13 @@ namespace UnitTests
 				std::filesystem::remove(filename[i]);
 		}
 
+		TEST_METHOD(file_stat)
+		{
+			sstring path(temp_path());
+			Assert::IsTrue(stdex::stream::file::exists(path));
+			Assert::IsFalse(stdex::stream::file::readonly(path));
+		}
+
 	protected:
 		static sstring temp_path()
 		{

include/stdex/stream.hpp

@@ -2777,6 +2777,61 @@ namespace stdex
 #endif
 				throw std::runtime_error("failed to set file mtime");
 			}
+
+			///
+			/// Checks if file/folder/symlink likely exists
+			///
+			/// \param[in] filename  Filename
+			///
+			static bool exists(_In_z_ const stdex::schar_t* filename)
+			{
+#ifdef _WIN32
+				return GetFileAttributes(filename) != INVALID_FILE_ATTRIBUTES;
+#else
+				struct stat s;
+				return stat(filename, &s) == 0;
+#endif
+			}
+
+			///
+			/// Checks if file/folder/symlink likely exists
+			///
+			/// \param[in] filename  Filename
+			///
+			static inline bool exists(_In_ const stdex::sstring& filename)
+			{
+				return exists(filename.c_str());
+			}
+
+			///
+			/// Checks if file/folder/symlink is read-only
+			///
+			/// For inexisting or inaccessible paths, writeability is assumed.
+			///
+			/// \param[in] filename  Filename
+			///
+			static bool readonly(_In_z_ const stdex::schar_t* filename)
+			{
+#ifdef _WIN32
+				DWORD dwAttr = GetFileAttributes(filename);
+				return dwAttr != INVALID_FILE_ATTRIBUTES && (dwAttr & FILE_ATTRIBUTE_READONLY) != 0;
+#else
+				struct stat s;
+				return stat(filename, &s) == 0 && (s.st_mode & (S_IWUSR|S_IWGRP|S_IWOTH)) == 0;
+#endif
+			}
+
+			///
+			/// Checks if file/folder/symlink is read-only
+			///
+			/// For inexisting or inaccessible paths, writeability is assumed.
+			///
+			/// \param[in] filename  Filename
+			///
+			static inline bool readonly(_In_ const stdex::sstring& filename)
+			{
+				return readonly(filename.c_str());
+			}
 		};
 #pragma warning(pop)