add context to MapViewOfFile errors (#282)

* added FileSizeFromHandle function
* added file size to error message when MapViewOfFile fails

3 files changed, 32 insertions, 3 deletions

diff --git a/src/zencore/filesystem.cpp b/src/zencore/filesystem.cpp
index a17773024..8a6a9869c 100644
--- a/src/zencore/filesystem.cpp
+++ b/src/zencore/filesystem.cpp
@@ -1022,6 +1022,27 @@ PathFromHandle(void* NativeHandle)
 #endif	// ZEN_PLATFORM_WINDOWS
 }
 
+uint64_t
+FileSizeFromHandle(void* NativeHandle)
+{
+	uint64_t FileSize = ~0ull;
+
+#if ZEN_PLATFORM_WINDOWS
+	BY_HANDLE_FILE_INFORMATION Bhfh = {};
+	if (GetFileInformationByHandle(NativeHandle, &Bhfh))
+	{
+		FileSize = uint64_t(Bhfh.nFileSizeHigh) << 32 | Bhfh.nFileSizeLow;
+	}
+#else
+	int			Fd = int(intptr_t(NativeHandle));
+	struct stat Stat;
+	fstat(Fd, &Stat);
+	FileSize = size_t(Stat.st_size);
+#endif
+
+	return FileSize;
+}
+
 std::filesystem::path
 GetRunningExecutablePath()
 {
diff --git a/src/zencore/include/zencore/filesystem.h b/src/zencore/include/zencore/filesystem.h
index fa5f94170..230d8d1c2 100644
--- a/src/zencore/include/zencore/filesystem.h
+++ b/src/zencore/include/zencore/filesystem.h
@@ -1,4 +1,5 @@
 // Copyright Epic Games, Inc. All Rights Reserved.
+// Copyright Epic Games, Inc. All Rights Reserved.
 
 #pragma once
 
@@ -32,6 +33,10 @@ ZENCORE_API bool CleanDirectory(const std::filesystem::path& dir);
  */
 ZENCORE_API std::filesystem::path PathFromHandle(void* NativeHandle);
 
+/** Query file size from native file handle
+ */
+ZENCORE_API uint64_t FileSizeFromHandle(void* NativeHandle);
+
 ZENCORE_API std::filesystem::path GetRunningExecutablePath();
 
 /** Set the max open file handle count to max allowed for the current process on Linux and MacOS
diff --git a/src/zencore/iobuffer.cpp b/src/zencore/iobuffer.cpp
index 1d7d47695..e28bf11b2 100644
--- a/src/zencore/iobuffer.cpp
+++ b/src/zencore/iobuffer.cpp
@@ -356,16 +356,19 @@ IoBufferExtendedCore::Materialize() const
 #if ZEN_PLATFORM_WINDOWS
 		CloseHandle(NewMmapHandle);
 #endif	// ZEN_PLATFORM_WINDOWS
-		ZEN_ERROR("MapViewOfFile failed (offset {:#x}, size {:#x}) file: '{}', {}",
+
+		ZEN_ERROR("MapViewOfFile failed (offset {:#x}, size {:#x}) file: '{}' (size {:#x}), {}",
 				  MapOffset,
 				  MapSize,
 				  zen::PathFromHandle(m_FileHandle),
+				  zen::FileSizeFromHandle(m_FileHandle),
 				  GetSystemErrorAsString(Error));
 		throw std::system_error(std::error_code(Error, std::system_category()),
-								fmt::format("MapViewOfFile failed (offset {:#x}, size {:#x}) file: '{}'",
+								fmt::format("MapViewOfFile failed (offset {:#x}, size {:#x}) file: '{}' (size {:#x})",
 											MapOffset,
 											MapSize,
-											zen::PathFromHandle(m_FileHandle)));
+											zen::PathFromHandle(m_FileHandle),
+											zen::FileSizeFromHandle(m_FileHandle)));
 	}
 
 	m_MappedPointer = MappedBase;