1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/LibOVR/Src/Kernel/OVR_SharedMemory.cpp	Wed Jan 14 06:51:16 2015 +0200
     1.3 @@ -0,0 +1,691 @@
     1.4 +/************************************************************************************
     1.5 +
     1.6 +Filename    :   OVR_SharedMemory.cpp
     1.7 +Content     :   Inter-process shared memory subsystem
     1.8 +Created     :   June 1, 2014
     1.9 +Notes       : 
    1.10 +
    1.11 +Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.
    1.12 +
    1.13 +Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License"); 
    1.14 +you may not use the Oculus VR Rift SDK except in compliance with the License, 
    1.15 +which is provided at the time of installation or download, or which 
    1.16 +otherwise accompanies this software in either electronic or hard copy form.
    1.17 +
    1.18 +You may obtain a copy of the License at
    1.19 +
    1.20 +http://www.oculusvr.com/licenses/LICENSE-3.2 
    1.21 +
    1.22 +Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
    1.23 +distributed under the License is distributed on an "AS IS" BASIS,
    1.24 +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    1.25 +See the License for the specific language governing permissions and
    1.26 +limitations under the License.
    1.27 +
    1.28 +************************************************************************************/
    1.29 +
    1.30 +#include "OVR_SharedMemory.h"
    1.31 +#include "OVR_Atomic.h"
    1.32 +#include "OVR_Log.h"
    1.33 +#include "OVR_String.h"
    1.34 +#include "OVR_Array.h"
    1.35 +
    1.36 +#if defined(OVR_OS_WIN32) && !defined(OVR_FAKE_SHAREDMEMORY)
    1.37 +#include <Sddl.h> // ConvertStringSecurityDescriptorToSecurityDescriptor
    1.38 +#endif // OVR_OS_WIN32
    1.39 +
    1.40 +#if (defined(OVR_OS_LINUX) || defined(OVR_OS_MAC)) && !defined(OVR_FAKE_SHAREDMEMORY)
    1.41 +#include <sys/mman.h> // shm_open(), mmap()
    1.42 +#include <errno.h> // error results for mmap
    1.43 +#include <sys/stat.h> // mode constants
    1.44 +#include <fcntl.h> // O_ constants
    1.45 +#include <unistd.h> // close()
    1.46 +#endif // OVR_OS_LINUX
    1.47 +
    1.48 +OVR_DEFINE_SINGLETON(OVR::SharedMemoryFactory);
    1.49 +
    1.50 +namespace OVR {
    1.51 +
    1.52 +
    1.53 +    //// Fake version
    1.54 +
    1.55 +#if defined(OVR_FAKE_SHAREDMEMORY)
    1.56 +
    1.57 +    class FakeMemoryBlock : public RefCountBase<FakeMemoryBlock>
    1.58 +    {
    1.59 +        String Name;
    1.60 +        char*  Data;
    1.61 +        int    SizeBytes;
    1.62 +        int    References;
    1.63 +
    1.64 +    public:
    1.65 +        FakeMemoryBlock(const String& name, int size) :
    1.66 +            Name(name),
    1.67 +            Data(NULL),
    1.68 +            SizeBytes(size),
    1.69 +            References(1)
    1.70 +        {
    1.71 +            Data = new char[SizeBytes];
    1.72 +        }
    1.73 +        ~FakeMemoryBlock()
    1.74 +        {
    1.75 +            delete[] Data;
    1.76 +        }
    1.77 +
    1.78 +        bool IsNamed(const String& name)
    1.79 +        {
    1.80 +            return Name.CompareNoCase(name) == 0;
    1.81 +        }
    1.82 +        void* GetData()
    1.83 +        {
    1.84 +            return Data;
    1.85 +        }
    1.86 +        int GetSizeI()
    1.87 +        {
    1.88 +            return SizeBytes;
    1.89 +        }
    1.90 +        void IncrementReferences()
    1.91 +        {
    1.92 +            ++References;
    1.93 +        }
    1.94 +        bool DecrementReferences()
    1.95 +        {
    1.96 +            return --References <= 0;
    1.97 +        }
    1.98 +    };
    1.99 +
   1.100 +    class SharedMemoryInternal : public NewOverrideBase
   1.101 +    {
   1.102 +    public:
   1.103 +        void* FileView;
   1.104 +        Ptr<FakeMemoryBlock> Block;
   1.105 +
   1.106 +        void Close();
   1.107 +
   1.108 +        SharedMemoryInternal(FakeMemoryBlock* block) :
   1.109 +            Block(block)
   1.110 +        {
   1.111 +            FileView = Block->GetData();
   1.112 +        }
   1.113 +        ~SharedMemoryInternal()
   1.114 +        {
   1.115 +            Close();
   1.116 +        }
   1.117 +
   1.118 +        static SharedMemoryInternal* CreateSharedMemory(const SharedMemory::OpenParameters& params);
   1.119 +    };
   1.120 +
   1.121 +
   1.122 +    //// FakeMemoryManager
   1.123 +
   1.124 +    class FakeMemoryManager : public NewOverrideBase, public SystemSingletonBase<FakeMemoryManager>
   1.125 +    {
   1.126 +        OVR_DECLARE_SINGLETON(FakeMemoryManager);
   1.127 +
   1.128 +        Lock FakeLock;
   1.129 +        Array< Ptr<FakeMemoryBlock> > FakeArray;
   1.130 +
   1.131 +    public:
   1.132 +        SharedMemoryInternal* Open(const char *name, int bytes, bool openOnly)
   1.133 +        {
   1.134 +            Lock::Locker locker(&FakeLock);
   1.135 +
   1.136 +            const int count = FakeArray.GetSizeI();
   1.137 +            for (int ii = 0; ii < count; ++ii)
   1.138 +            {
   1.139 +                if (FakeArray[ii]->IsNamed(name))
   1.140 +                {
   1.141 +                    FakeArray[ii]->IncrementReferences();
   1.142 +                    return new SharedMemoryInternal(FakeArray[ii]);
   1.143 +                }
   1.144 +            }
   1.145 +
   1.146 +            if (openOnly)
   1.147 +            {
   1.148 +                return NULL;
   1.149 +            }
   1.150 +
   1.151 +            Ptr<FakeMemoryBlock> data = *new FakeMemoryBlock(name, bytes);
   1.152 +            FakeArray.PushBack(data);
   1.153 +            return new SharedMemoryInternal(data);
   1.154 +        }
   1.155 +
   1.156 +        void Free(FakeMemoryBlock* block)
   1.157 +        {
   1.158 +            Lock::Locker locker(&FakeLock);
   1.159 +
   1.160 +            const int count = FakeArray.GetSizeI();
   1.161 +            for (int ii = 0; ii < count; ++ii)
   1.162 +            {
   1.163 +                if (FakeArray[ii].GetPtr() == block)
   1.164 +                {
   1.165 +                    // If the reference count hit zero,
   1.166 +                    if (FakeArray[ii]->DecrementReferences())
   1.167 +                    {
   1.168 +                        // Toast
   1.169 +                        FakeArray.RemoveAtUnordered(ii);
   1.170 +                    }
   1.171 +                    break;
   1.172 +                }
   1.173 +            }
   1.174 +        }
   1.175 +    };
   1.176 +
   1.177 +    FakeMemoryManager::FakeMemoryManager()
   1.178 +    {
   1.179 +        PushDestroyCallbacks();
   1.180 +    }
   1.181 +
   1.182 +    FakeMemoryManager::~FakeMemoryManager()
   1.183 +    {
   1.184 +        OVR_ASSERT(FakeArray.GetSizeI() == 0);
   1.185 +    }
   1.186 +
   1.187 +    void FakeMemoryManager::OnSystemDestroy()
   1.188 +    {
   1.189 +        delete this;
   1.190 +    }
   1.191 +
   1.192 +
   1.193 +} // namespace OVR
   1.194 +
   1.195 +OVR_DEFINE_SINGLETON(FakeMemoryManager);
   1.196 +
   1.197 +namespace OVR {
   1.198 +
   1.199 +
   1.200 +void SharedMemoryInternal::Close()
   1.201 +{
   1.202 +	FakeMemoryManager::GetInstance()->Free(Block);
   1.203 +	Block.Clear();
   1.204 +}
   1.205 +
   1.206 +SharedMemoryInternal* SharedMemoryInternal::CreateSharedMemory(const SharedMemory::OpenParameters& params)
   1.207 +{
   1.208 +	return FakeMemoryManager::GetInstance()->Open(params.globalName, params.minSizeBytes, params.openMode == SharedMemory::OpenMode_OpenOnly);
   1.209 +}
   1.210 +
   1.211 +#endif
   1.212 +
   1.213 +
   1.214 +//// Windows version
   1.215 +
   1.216 +#if defined(OVR_OS_WIN32) && !defined(OVR_FAKE_SHAREDMEMORY)
   1.217 +
   1.218 +#pragma comment(lib, "advapi32.lib")
   1.219 +
   1.220 +// Hidden implementation class for OS-specific behavior
   1.221 +class SharedMemoryInternal : public NewOverrideBase
   1.222 +{
   1.223 +public:
   1.224 +	HANDLE FileMapping;
   1.225 +	void* FileView;
   1.226 +
   1.227 +	SharedMemoryInternal(HANDLE fileMapping, void* fileView) :
   1.228 +		FileMapping(fileMapping),
   1.229 +		FileView(fileView)
   1.230 +	{
   1.231 +	}
   1.232 +
   1.233 +	~SharedMemoryInternal()
   1.234 +	{
   1.235 +		// If file view is set,
   1.236 +		if (FileView)
   1.237 +		{
   1.238 +			UnmapViewOfFile(FileView);
   1.239 +			FileView = NULL;
   1.240 +		}
   1.241 +
   1.242 +		// If file mapping is set,
   1.243 +		if (FileMapping != NULL)
   1.244 +		{
   1.245 +			CloseHandle(FileMapping);
   1.246 +			FileMapping = NULL;
   1.247 +		}
   1.248 +	}
   1.249 +
   1.250 +	static SharedMemoryInternal* DoFileMap(HANDLE hFileMapping, const char* fileName, bool openReadOnly, int minSize);
   1.251 +	static SharedMemoryInternal* AttemptOpenSharedMemory(const char* fileName, int minSize, bool openReadOnly);
   1.252 +	static SharedMemoryInternal* AttemptCreateSharedMemory(const char* fileName, int minSize, bool openReadOnly, bool allowRemoteWrite);
   1.253 +	static SharedMemoryInternal* CreateSharedMemory(const SharedMemory::OpenParameters& params);
   1.254 +};
   1.255 +
   1.256 +SharedMemoryInternal* SharedMemoryInternal::DoFileMap(HANDLE hFileMapping, const char* fileName, bool openReadOnly, int minSize)
   1.257 +{
   1.258 +	// Interpret the access mode as a map desired access code
   1.259 +	DWORD mapDesiredAccess = openReadOnly ? FILE_MAP_READ : FILE_MAP_WRITE;
   1.260 +
   1.261 +	// Map view of the file to this process
   1.262 +	void* pFileView = MapViewOfFile(hFileMapping, mapDesiredAccess, 0, 0, minSize);
   1.263 +
   1.264 +	// If mapping could not be created,
   1.265 +	if (!pFileView)
   1.266 +	{
   1.267 +		CloseHandle(hFileMapping);
   1.268 +
   1.269 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to map view of file for %s error code = %d", fileName, GetLastError()));
   1.270 +        OVR_UNUSED(fileName);
   1.271 +		return NULL;
   1.272 +	}
   1.273 +
   1.274 +	// Create internal representation
   1.275 +	SharedMemoryInternal* pimple = new SharedMemoryInternal(hFileMapping, pFileView);
   1.276 +
   1.277 +	// If memory allocation fails,
   1.278 +	if (!pimple)
   1.279 +	{
   1.280 +		UnmapViewOfFile(pFileView);
   1.281 +		CloseHandle(hFileMapping);
   1.282 +
   1.283 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Out of memory"));
   1.284 +		return NULL;
   1.285 +	}
   1.286 +
   1.287 +	return pimple;
   1.288 +}
   1.289 +
   1.290 +SharedMemoryInternal* SharedMemoryInternal::AttemptOpenSharedMemory(const char* fileName, int minSize, bool openReadOnly)
   1.291 +{
   1.292 +	// Interpret the access mode as a map desired access code
   1.293 +	DWORD mapDesiredAccess = openReadOnly ? FILE_MAP_READ : FILE_MAP_WRITE;
   1.294 +
   1.295 +	// Open file mapping
   1.296 +	HANDLE hFileMapping = OpenFileMappingA(mapDesiredAccess, TRUE, fileName);
   1.297 +
   1.298 +	// If file was mapped unsuccessfully,
   1.299 +	if (NULL == hFileMapping)
   1.300 +	{
   1.301 +		OVR_DEBUG_LOG(("[SharedMemory] WARNING: Unable to open file mapping for %s error code = %d (not necessarily bad)", fileName, GetLastError()));
   1.302 +		return NULL;
   1.303 +	}
   1.304 +
   1.305 +	// Map the file
   1.306 +	return DoFileMap(hFileMapping, fileName, openReadOnly, minSize);
   1.307 +}
   1.308 +
   1.309 +SharedMemoryInternal* SharedMemoryInternal::AttemptCreateSharedMemory(const char* fileName, int minSize, bool openReadOnly, bool allowRemoteWrite)
   1.310 +{
   1.311 +	// Prepare a SECURITY_ATTRIBUTES object
   1.312 +	SECURITY_ATTRIBUTES security;
   1.313 +	ZeroMemory(&security, sizeof(security));
   1.314 +	security.nLength = sizeof(security);
   1.315 +
   1.316 +	// Security descriptor by DACL strings:
   1.317 +	// ACE strings grant Allow(A), Object/Contains Inheritance (OICI) of:
   1.318 +	// + Grant All (GA) to System (SY)
   1.319 +	// + Grant All (GA) to Built-in Administrators (BA)
   1.320 +	// + Grant Read-Only (GR) or Read-Write (GWGR) to Interactive Users (IU) - ie. games
   1.321 +	static const char* DACLString_ReadOnly = "D:P(A;OICI;GA;;;SY)(A;OICI;GA;;;BA)(A;OICI;GR;;;IU)";
   1.322 +	static const char* DACLString_ReadWrite = "D:P(A;OICI;GA;;;SY)(A;OICI;GA;;;BA)(A;OICI;GWGR;;;IU)";
   1.323 +
   1.324 +	// Select the remote process access mode
   1.325 +	const char* remoteAccessString =
   1.326 +		allowRemoteWrite ? DACLString_ReadWrite : DACLString_ReadOnly;
   1.327 +
   1.328 +	// Attempt to convert access string to security attributes
   1.329 +	// Note: This will allocate the security descriptor with LocalAlloc() and must be freed later
   1.330 +	BOOL bConvertOkay = ConvertStringSecurityDescriptorToSecurityDescriptorA(
   1.331 +		remoteAccessString, SDDL_REVISION_1, &security.lpSecurityDescriptor, NULL);
   1.332 +
   1.333 +	// If conversion fails,
   1.334 +	if (!bConvertOkay)
   1.335 +	{
   1.336 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to convert access string, error code = %d", GetLastError()));
   1.337 +		return NULL;
   1.338 +	}
   1.339 +
   1.340 +	// Interpret the access mode as a page protection code
   1.341 +	int pageProtectCode = openReadOnly ? PAGE_READONLY : PAGE_READWRITE;
   1.342 +
   1.343 +	// Attempt to create a file mapping
   1.344 +	HANDLE hFileMapping = CreateFileMappingA(INVALID_HANDLE_VALUE,	// From page file
   1.345 +											 &security,				// Security attributes
   1.346 +											 pageProtectCode,		// Read-only?
   1.347 +											 0,						// High word for size = 0
   1.348 +											 minSize,				// Low word for size
   1.349 +											 fileName);				// Name of global shared memory file
   1.350 +
   1.351 +	// Free the security descriptor buffer
   1.352 +	LocalFree(security.lpSecurityDescriptor);
   1.353 +
   1.354 +	// If mapping could not be created,
   1.355 +	if (NULL == hFileMapping)
   1.356 +	{
   1.357 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to create file mapping for %s error code = %d", fileName, GetLastError()));
   1.358 +		return NULL;
   1.359 +	}
   1.360 +
   1.361 +#ifndef OVR_ALLOW_CREATE_FILE_MAPPING_IF_EXISTS
   1.362 +	// If the file mapping already exists,
   1.363 +	if (GetLastError() == ERROR_ALREADY_EXISTS)
   1.364 +	{
   1.365 +		CloseHandle(hFileMapping);
   1.366 +
   1.367 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: File mapping at %s already exists", fileName));
   1.368 +		return NULL;
   1.369 +	}
   1.370 +#endif
   1.371 +
   1.372 +	// Map the file
   1.373 +	return DoFileMap(hFileMapping, fileName, openReadOnly, minSize);
   1.374 +}
   1.375 +
   1.376 +SharedMemoryInternal* SharedMemoryInternal::CreateSharedMemory(const SharedMemory::OpenParameters& params)
   1.377 +{
   1.378 +	SharedMemoryInternal* retval = NULL;
   1.379 +
   1.380 +	// Construct the file mapping name in a Windows-specific way
   1.381 +	OVR::String fileMappingName = params.globalName;
   1.382 +	const char *fileName = fileMappingName.ToCStr();
   1.383 +
   1.384 +	// Is being opened read-only?
   1.385 +	const bool openReadOnly = (params.accessMode == SharedMemory::AccessMode_ReadOnly);
   1.386 +
   1.387 +	// Try up to 3 times to reduce low-probability failures:
   1.388 +	static const int ATTEMPTS_MAX = 3;
   1.389 +	for (int attempts = 0; attempts < ATTEMPTS_MAX; ++attempts)
   1.390 +	{
   1.391 +		// If opening should be attempted first,
   1.392 +		if (params.openMode != SharedMemory::OpenMode_CreateOnly)
   1.393 +		{
   1.394 +			// Attempt to open a shared memory map
   1.395 +			retval = AttemptOpenSharedMemory(fileName, params.minSizeBytes, openReadOnly);
   1.396 +
   1.397 +			// If successful,
   1.398 +			if (retval)
   1.399 +			{
   1.400 +				// Done!
   1.401 +				break;
   1.402 +			}
   1.403 +		}
   1.404 +
   1.405 +		// If creating the shared memory is also acceptable,
   1.406 +		if (params.openMode != SharedMemory::OpenMode_OpenOnly)
   1.407 +		{
   1.408 +			// Interpret create mode
   1.409 +			const bool allowRemoteWrite = (params.remoteMode == SharedMemory::RemoteMode_ReadWrite);
   1.410 +
   1.411 +			// Attempt to create a shared memory map
   1.412 +			retval = AttemptCreateSharedMemory(fileName, params.minSizeBytes, openReadOnly, allowRemoteWrite);
   1.413 +
   1.414 +			// If successful,
   1.415 +			if (retval)
   1.416 +			{
   1.417 +				// Done!
   1.418 +				break;
   1.419 +			}
   1.420 +		}
   1.421 +	} // Re-attempt create/open
   1.422 +
   1.423 +	// Note: On Windows the initial contents of the region are guaranteed to be zero.
   1.424 +	return retval;
   1.425 +}
   1.426 +
   1.427 +#endif // OVR_OS_WIN32
   1.428 +
   1.429 +
   1.430 +#if (defined(OVR_OS_LINUX) || defined(OVR_OS_MAC)) && !defined(OVR_FAKE_SHAREDMEMORY)
   1.431 +
   1.432 +// Hidden implementation class for OS-specific behavior
   1.433 +class SharedMemoryInternal
   1.434 +{
   1.435 +public:
   1.436 +	int   FileMapping;
   1.437 +	void* FileView;
   1.438 +    int   FileSize;
   1.439 +
   1.440 +	SharedMemoryInternal(int fileMapping, void* fileView, int fileSize) :
   1.441 +		FileMapping(fileMapping),
   1.442 +		FileView(fileView),
   1.443 +        FileSize(fileSize)
   1.444 +	{
   1.445 +	}
   1.446 +
   1.447 +	~SharedMemoryInternal()
   1.448 +	{
   1.449 +		// If file view is set,
   1.450 +		if (FileView)
   1.451 +		{
   1.452 +            munmap(FileView, FileSize);
   1.453 +			FileView = MAP_FAILED;
   1.454 +		}
   1.455 +
   1.456 +		// If file mapping is set,
   1.457 +		if (FileMapping >= 0)
   1.458 +		{
   1.459 +            close(FileMapping);
   1.460 +			FileMapping = -1;
   1.461 +		}
   1.462 +	}
   1.463 +
   1.464 +	static SharedMemoryInternal* DoFileMap(int hFileMapping, const char* fileName, bool openReadOnly, int minSize);
   1.465 +	static SharedMemoryInternal* AttemptOpenSharedMemory(const char* fileName, int minSize, bool openReadOnly);
   1.466 +	static SharedMemoryInternal* AttemptCreateSharedMemory(const char* fileName, int minSize, bool openReadOnly, bool allowRemoteWrite);
   1.467 +	static SharedMemoryInternal* CreateSharedMemory(const SharedMemory::OpenParameters& params);
   1.468 +};
   1.469 +
   1.470 +SharedMemoryInternal* SharedMemoryInternal::DoFileMap(int hFileMapping, const char* fileName, bool openReadOnly, int minSize)
   1.471 +{
   1.472 +    // Calculate the required flags based on read/write mode
   1.473 +    int prot = openReadOnly ? PROT_READ : (PROT_READ|PROT_WRITE);
   1.474 +
   1.475 +    // Map the file view
   1.476 +    void* pFileView = mmap(NULL, minSize, prot, MAP_SHARED, hFileMapping, 0);
   1.477 +
   1.478 +    if (pFileView == MAP_FAILED)
   1.479 +    {
   1.480 +        close(hFileMapping);
   1.481 +
   1.482 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to map view of file for %s error code = %d", fileName, errno));
   1.483 +        OVR_UNUSED(fileName);
   1.484 +		return NULL;
   1.485 +    }
   1.486 +
   1.487 +	// Create internal representation
   1.488 +	SharedMemoryInternal* pimple = new SharedMemoryInternal(hFileMapping, pFileView, minSize);
   1.489 +
   1.490 +	// If memory allocation fails,
   1.491 +	if (!pimple)
   1.492 +	{
   1.493 +        munmap(pFileView, minSize);
   1.494 +        close(hFileMapping);
   1.495 +
   1.496 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Out of memory"));
   1.497 +		return NULL;
   1.498 +	}
   1.499 +
   1.500 +	return pimple;
   1.501 +}
   1.502 +
   1.503 +SharedMemoryInternal* SharedMemoryInternal::AttemptOpenSharedMemory(const char* fileName, int minSize, bool openReadOnly)
   1.504 +{
   1.505 +    // Calculate permissions and flags based on read/write mode
   1.506 +    int flags = openReadOnly ? O_RDONLY : O_RDWR;
   1.507 +    int perms = openReadOnly ? S_IRUSR : (S_IRUSR | S_IWUSR);
   1.508 +
   1.509 +    // Attempt to open the shared memory file
   1.510 +    int hFileMapping = shm_open(fileName, flags, perms);
   1.511 +
   1.512 +    // If file was not opened successfully,
   1.513 +    if (hFileMapping < 0)
   1.514 +    {
   1.515 +		OVR_DEBUG_LOG(("[SharedMemory] WARNING: Unable to open file mapping for %s error code = %d (not necessarily bad)", fileName, errno));
   1.516 +		return NULL;
   1.517 +    }
   1.518 +
   1.519 +	// Map the file
   1.520 +	return DoFileMap(hFileMapping, fileName, openReadOnly, minSize);
   1.521 +}
   1.522 +
   1.523 +SharedMemoryInternal* SharedMemoryInternal::AttemptCreateSharedMemory(const char* fileName, int minSize, bool openReadOnly, bool allowRemoteWrite)
   1.524 +{
   1.525 +    // Create mode
   1.526 +    // Note: Cannot create the shared memory file read-only because then ftruncate() will fail.
   1.527 +    int flags = O_CREAT | O_RDWR;
   1.528 +
   1.529 +#ifndef OVR_ALLOW_CREATE_FILE_MAPPING_IF_EXISTS
   1.530 +    // Require exclusive access when creating (seems like a good idea without trying it yet..)
   1.531 +    if (shm_unlink(fileName) < 0)
   1.532 +    {
   1.533 +		OVR_DEBUG_LOG(("[SharedMemory] WARNING: Unable to unlink shared memory file %s error code = %d", fileName, errno));
   1.534 +    }
   1.535 +    flags |= O_EXCL;
   1.536 +#endif
   1.537 +
   1.538 +    // Set own read/write permissions
   1.539 +    int perms = openReadOnly ? S_IRUSR : (S_IRUSR|S_IWUSR);
   1.540 +
   1.541 +    // Allow other users to read/write the shared memory file
   1.542 +    perms |= allowRemoteWrite ? (S_IWGRP|S_IWOTH|S_IRGRP|S_IROTH) : (S_IRGRP|S_IROTH);
   1.543 +
   1.544 +    // Attempt to open the shared memory file
   1.545 +    int hFileMapping = shm_open(fileName, flags, perms);
   1.546 +
   1.547 +    // If file was not opened successfully,
   1.548 +    if (hFileMapping < 0)
   1.549 +    {
   1.550 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to create file mapping for %s error code = %d", fileName, errno));
   1.551 +		return NULL;
   1.552 +    }
   1.553 +
   1.554 +    int truncRes = ftruncate(hFileMapping, minSize);
   1.555 +
   1.556 +    // If file was not opened successfully,
   1.557 +    if (truncRes < 0)
   1.558 +    {
   1.559 +        close(hFileMapping);
   1.560 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Unable to truncate file for %s to %d error code = %d", fileName, minSize, errno));
   1.561 +		return NULL;
   1.562 +    }
   1.563 +
   1.564 +	// Map the file
   1.565 +	return DoFileMap(hFileMapping, fileName, openReadOnly, minSize);
   1.566 +}
   1.567 +
   1.568 +SharedMemoryInternal* SharedMemoryInternal::CreateSharedMemory(const SharedMemory::OpenParameters& params)
   1.569 +{
   1.570 +	SharedMemoryInternal* retval = NULL;
   1.571 +
   1.572 +	// Construct the file mapping name in a Linux-specific way
   1.573 +	OVR::String fileMappingName = "/";
   1.574 +	fileMappingName += params.globalName;
   1.575 +	const char *fileName = fileMappingName.ToCStr();
   1.576 +
   1.577 +	// Is being opened read-only?
   1.578 +	const bool openReadOnly = (params.accessMode == SharedMemory::AccessMode_ReadOnly);
   1.579 +
   1.580 +	// Try up to 3 times to reduce low-probability failures:
   1.581 +	static const int ATTEMPTS_MAX = 3;
   1.582 +	for (int attempts = 0; attempts < ATTEMPTS_MAX; ++attempts)
   1.583 +	{
   1.584 +		// If opening should be attempted first,
   1.585 +		if (params.openMode != SharedMemory::OpenMode_CreateOnly)
   1.586 +		{
   1.587 +			// Attempt to open a shared memory map
   1.588 +			retval = AttemptOpenSharedMemory(fileName, params.minSizeBytes, openReadOnly);
   1.589 +
   1.590 +			// If successful,
   1.591 +			if (retval)
   1.592 +			{
   1.593 +				// Done!
   1.594 +				break;
   1.595 +			}
   1.596 +		}
   1.597 +
   1.598 +		// If creating the shared memory is also acceptable,
   1.599 +		if (params.openMode != SharedMemory::OpenMode_OpenOnly)
   1.600 +		{
   1.601 +            // Interpret create mode
   1.602 +            const bool allowRemoteWrite = (params.remoteMode == SharedMemory::RemoteMode_ReadWrite);
   1.603 +
   1.604 +            // Attempt to create a shared memory map
   1.605 +            retval = AttemptCreateSharedMemory(fileName, params.minSizeBytes, openReadOnly, allowRemoteWrite);
   1.606 +
   1.607 +            // If successful,
   1.608 +            if (retval)
   1.609 +            {
   1.610 +                // Done!
   1.611 +                break;
   1.612 +            }
   1.613 +		}
   1.614 +	} // Re-attempt create/open
   1.615 +
   1.616 +	// Note: On Windows the initial contents of the region are guaranteed to be zero.
   1.617 +	return retval;
   1.618 +}
   1.619 +
   1.620 +#endif // OVR_OS_LINUX
   1.621 +
   1.622 +
   1.623 +//// SharedMemory
   1.624 +
   1.625 +SharedMemory::SharedMemory(int size, void* data, SharedMemoryInternal* pInternal) :
   1.626 +	Size(size),
   1.627 +	Data(data),
   1.628 +	Internal(pInternal)
   1.629 +{
   1.630 +}
   1.631 +// Call close when it goes out of scope
   1.632 +SharedMemory::~SharedMemory()
   1.633 +{
   1.634 +	Close();
   1.635 +    delete Internal;
   1.636 +}
   1.637 +
   1.638 +void SharedMemory::Close()
   1.639 +{
   1.640 +	if (Internal)
   1.641 +	{
   1.642 +		delete Internal;
   1.643 +		Internal = NULL;
   1.644 +	}
   1.645 +}
   1.646 +
   1.647 +
   1.648 +//// SharedMemoryFactory
   1.649 +
   1.650 +Ptr<SharedMemory> SharedMemoryFactory::Open(const SharedMemory::OpenParameters& params)
   1.651 +{
   1.652 +	Ptr<SharedMemory> retval;
   1.653 +
   1.654 +	// If no name specified or no size requested,
   1.655 +	if (!params.globalName || (params.minSizeBytes <= 0))
   1.656 +	{
   1.657 +		OVR_DEBUG_LOG(("[SharedMemory] FAILURE: Invalid parameters to Create()"));
   1.658 +		return NULL;
   1.659 +	}
   1.660 +
   1.661 +	OVR_DEBUG_LOG(("[SharedMemory] Creating shared memory region: %s > %d bytes",
   1.662 +		params.globalName, params.minSizeBytes));
   1.663 +
   1.664 +	// Attempt to create a shared memory region from the parameters
   1.665 +	SharedMemoryInternal* pInternal = SharedMemoryInternal::CreateSharedMemory(params);
   1.666 +
   1.667 +	if (pInternal)
   1.668 +	{
   1.669 +		// Create the wrapper object
   1.670 +		retval = *new SharedMemory(params.minSizeBytes, pInternal->FileView, pInternal);
   1.671 +	}
   1.672 +
   1.673 +	return retval;
   1.674 +}
   1.675 +
   1.676 +SharedMemoryFactory::SharedMemoryFactory()
   1.677 +{
   1.678 +	OVR_DEBUG_LOG(("[SharedMemory] Creating factory"));
   1.679 +
   1.680 +    PushDestroyCallbacks();
   1.681 +}
   1.682 +
   1.683 +SharedMemoryFactory::~SharedMemoryFactory()
   1.684 +{
   1.685 +	OVR_DEBUG_LOG(("[SharedMemory] Destroying factory"));
   1.686 +}
   1.687 +
   1.688 +void SharedMemoryFactory::OnSystemDestroy()
   1.689 +{
   1.690 +    delete this;
   1.691 +}
   1.692 +
   1.693 +
   1.694 +} // namespace OVR