From a4e456ef7a9ff6fc37b0bd4ec0dfc25a282cafb3 Mon Sep 17 00:00:00 2001
From: Martin Ridgers <martin.ridgers@epicgames.com>
Date: Fri, 29 Oct 2021 14:31:23 +0200
Subject: Implemented ZenServerState's shared memory layer for POSIX

---
 zenutil/zenserverprocess.cpp | 95 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 71 insertions(+), 24 deletions(-)

(limited to 'zenutil/zenserverprocess.cpp')

diff --git a/zenutil/zenserverprocess.cpp b/zenutil/zenserverprocess.cpp
index ab547b98c..1974772d2 100644
--- a/zenutil/zenserverprocess.cpp
+++ b/zenutil/zenserverprocess.cpp
@@ -8,13 +8,17 @@
 #include <zencore/logging.h>
 #include <zencore/session.h>
 #include <zencore/string.h>
+#include <zencore/thread.h>
 
+#include <atomic>
 #include <source_location>
 
 #if ZEN_PLATFORM_WINDOWS
 #	include <atlbase.h>
 #	include <shellapi.h>
 #	include <zencore/windows.h>
+#else
+#	include <sys/mman.h>
 #endif
 
 //////////////////////////////////////////////////////////////////////////
@@ -22,6 +26,7 @@
 namespace zen {
 
 namespace zenutil {
+#if ZEN_PLATFORM_WINDOWS
 	class SecurityAttributes
 	{
 	public:
@@ -55,6 +60,7 @@ namespace zenutil {
 			}
 		}
 	};
+#endif // ZEN_PLATFORM_WINDOWS
 
 }  // namespace zenutil
 
@@ -74,59 +80,85 @@ ZenServerState::~ZenServerState()
 		m_OurEntry = nullptr;
 	}
 
+#if ZEN_PLATFORM_WINDOWS
 	if (m_Data)
 	{
 		UnmapViewOfFile(m_Data);
-		m_Data = nullptr;
 	}
 
 	if (m_hMapFile)
 	{
 		CloseHandle(m_hMapFile);
 	}
+#else
+	if (m_Data != nullptr)
+	{
+		munmap(m_Data, m_MaxEntryCount * sizeof(ZenServerEntry));
+	}
+
+	int Fd = int(intptr_t(m_hMapFile));
+	close(Fd);
+#endif
+
+	m_Data = nullptr;
 }
 
 void
 ZenServerState::Initialize()
 {
+	size_t MapSize = m_MaxEntryCount * sizeof(ZenServerEntry);
+
+#if ZEN_PLATFORM_WINDOWS
 	// TODO: there's a small chance of a race here, this logic could be tightened up with a mutex to
 	//		 ensure only a single process at a time creates the mapping
 
-	if (HANDLE hMap = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, L"Global\\ZenMap"))
-	{
-		m_hMapFile = hMap;
-	}
-	else
+	HANDLE hMap = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, L"Global\\ZenMap");
+	if (hMap == NULL)
 	{
 		// Security attributes to enable any user to access state
 		zenutil::AnyUserSecurityAttributes Attrs;
 
-		hMap = CreateFileMapping(INVALID_HANDLE_VALUE,						// use paging file
-								 Attrs.Attributes(),						// allow anyone to access
-								 PAGE_READWRITE,							// read/write access
-								 0,											// maximum object size (high-order DWORD)
-								 m_MaxEntryCount * sizeof(ZenServerEntry),	// maximum object size (low-order DWORD)
-								 L"Global\\ZenMap");						// name of mapping object
+		hMap = CreateFileMapping(INVALID_HANDLE_VALUE,	// use paging file
+								 Attrs.Attributes(),	// allow anyone to access
+								 PAGE_READWRITE,		// read/write access
+								 0,						// maximum object size (high-order DWORD)
+								 MapSize,				// maximum object size (low-order DWORD)
+								 L"Global\\ZenMap");	// name of mapping object
 
 		if (hMap == NULL)
 		{
 			ThrowLastError("Could not open or create file mapping object for Zen server state");
 		}
-
-		m_hMapFile = hMap;
 	}
 
-	void* pBuf = MapViewOfFile(m_hMapFile,			 // handle to map object
+	void* pBuf = MapViewOfFile(hMap,				 // handle to map object
 							   FILE_MAP_ALL_ACCESS,	 // read/write permission
 							   0,					 // offset high
 							   0,					 // offset low
-							   m_MaxEntryCount * sizeof(ZenServerEntry));
+							   MapSize);
 
 	if (pBuf == NULL)
 	{
 		ThrowLastError("Could not map view of Zen server state");
 	}
+#else
+	int Fd = shm_open("UnrealEngineZen", O_RDWR|O_CREAT, 0666);
+	if (Fd < 0)
+	{
+		ThrowLastError("Could not open a shared memory object");
+	}
+	void* hMap = (void*)intptr_t(Fd);
 
+	ftruncate(Fd, MapSize);
+
+	void* pBuf = mmap(nullptr, MapSize, PROT_READ|PROT_WRITE, MAP_SHARED, Fd, 0);
+	if (pBuf == MAP_FAILED)
+	{
+		ThrowLastError("Could not map view of Zen server state");
+	}
+#endif
+
+	m_hMapFile	 = hMap;
 	m_Data		 = reinterpret_cast<ZenServerEntry*>(pBuf);
 	m_IsReadOnly = false;
 }
@@ -134,27 +166,42 @@ ZenServerState::Initialize()
 bool
 ZenServerState::InitializeReadOnly()
 {
-	if (HANDLE hMap = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, L"Global\\ZenMap"))
-	{
-		m_hMapFile = hMap;
-	}
-	else
+	size_t MapSize = m_MaxEntryCount * sizeof(ZenServerEntry);
+
+#if ZEN_PLATFORM_WINDOWS
+	HANDLE hMap = OpenFileMapping(FILE_MAP_ALL_ACCESS, FALSE, L"Global\\ZenMap");
+	if (hMap == NULL)
 	{
 		return false;
 	}
 
-	void* pBuf = MapViewOfFile(m_hMapFile,	   // handle to map object
+	void* pBuf = MapViewOfFile(hMap,		   // handle to map object
 							   FILE_MAP_READ,  // read permission
 							   0,			   // offset high
 							   0,			   // offset low
-							   m_MaxEntryCount * sizeof(ZenServerEntry));
+							   MapSize);
 
 	if (pBuf == NULL)
 	{
 		ThrowLastError("Could not map view of Zen server state");
 	}
+#else
+	int Fd = shm_open("UnrealEngineZen", O_RDONLY, 0666);
+	if (Fd < 0)
+	{
+		return false;
+	}
+	void* hMap = (void*)intptr_t(Fd);
+
+	void* pBuf = mmap(nullptr, MapSize, PROT_READ, MAP_PRIVATE, Fd, 0);
+	if (pBuf == MAP_FAILED)
+	{
+		ThrowLastError("Could not map read-only view of Zen server state");
+	}
+#endif
 
-	m_Data = reinterpret_cast<ZenServerEntry*>(pBuf);
+	m_hMapFile	= hMap;
+	m_Data		= reinterpret_cast<ZenServerEntry*>(pBuf);
 
 	return true;
 }
-- 
cgit v1.2.3