Implementation of IoBufferExtendedCore() using mmap()

1 files changed, 36 insertions, 6 deletions

diff --git a/zencore/iobuffer.cpp b/zencore/iobuffer.cpp
index 4a74b9a60..2473e0530 100644
--- a/zencore/iobuffer.cpp
+++ b/zencore/iobuffer.cpp
@@ -12,7 +12,12 @@
 #include <zencore/thread.h>
 #include <system_error>
 
-#include <atlfile.h>
+#if ZEN_PLATFORM_WINDOWS
+#	include <atlfile.h>
+#else
+#	include <sys/mman.h>
+#endif
+
 #include <gsl/gsl-lite.hpp>
 
 namespace zen {
@@ -156,17 +161,29 @@ IoBufferExtendedCore::~IoBufferExtendedCore()
 {
 	if (m_MappedPointer)
 	{
+#if ZEN_PLATFORM_WINDOWS
 		UnmapViewOfFile(m_MappedPointer);
+#else
+		uint64_t MapSize = ~uint64_t(uintptr_t(m_MmapHandle));
+		munmap(m_MappedPointer, MapSize);
+#endif
 	}
 
+#if ZEN_PLATFORM_WINDOWS
 	if (m_Flags & kOwnsMmap)
 	{
 		CloseHandle(m_MmapHandle);
 	}
+#endif
 
 	if (m_Flags & kOwnsFile)
 	{
+#if ZEN_PLATFORM_WINDOWS
 		BOOL Success = CloseHandle(m_FileHandle);
+#else
+		int Fd = int(uintptr_t(m_FileHandle));
+		bool Success = (close(Fd) == 0);
+#endif
 
 		if (!Success)
 		{
@@ -196,6 +213,11 @@ IoBufferExtendedCore::Materialize() const
 	if (m_MmapHandle)
 		return;
 
+	const uint64_t MapOffset				= m_FileOffset & ~0xffffull;
+	const uint64_t MappedOffsetDisplacement = m_FileOffset - MapOffset;
+	const uint64_t MapSize					= m_DataBytes + MappedOffsetDisplacement;
+
+#if ZEN_PLATFORM_WINDOWS
 	m_MmapHandle = CreateFileMapping(m_FileHandle,
 									 /* lpFileMappingAttributes */ nullptr,
 									 /* flProtect */ PAGE_READONLY,
@@ -211,20 +233,28 @@ IoBufferExtendedCore::Materialize() const
 
 	m_Flags |= kOwnsMmap;
 
-	const uint64_t MapOffset				= m_FileOffset & ~0xffffull;
-	const uint64_t MappedOffsetDisplacement = m_FileOffset - MapOffset;
-	const uint64_t MapSize					= m_DataBytes + MappedOffsetDisplacement;
-
 	void* MappedBase = MapViewOfFile(m_MmapHandle,
 									 /* dwDesiredAccess */ FILE_MAP_READ,
 									 /* FileOffsetHigh */ uint32_t(MapOffset >> 32),
 									 /* FileOffsetLow */ uint32_t(MapOffset & 0xffFFffFFu),
 									 /* dwNumberOfBytesToMap */ MapSize);
+#else
+	m_MmapHandle = (void*)uintptr_t(~MapSize); // ~ so it's never null (assuming MapSize >= 0)
+	m_Flags |= kOwnsMmap;
+
+	void* MappedBase = mmap(
+		/* addr */ nullptr,
+		/* length */ MapSize,
+		/* prot */ PROT_READ,
+		/* flags */ MAP_SHARED|MAP_NORESERVE,
+		/* fd */ int(uintptr_t(m_FileHandle)),
+		/* offset */ MapOffset);
+#endif // ZEN_PLATFORM_WINDOWS
 
 	if (MappedBase == nullptr)
 	{
 		throw std::system_error(
-			std::error_code(::GetLastError(), std::system_category()),
+			std::error_code(zen::GetLastError(), std::system_category()),
 			"MapViewOfFile failed (offset {:#x}, size {:#x}) file: '{}'"_format(MapOffset, MapSize, zen::PathFromHandle(m_FileHandle)));
 	}