private static FileStream CreateSharedBackingObject(
Interop.libc.MemoryMappedProtections protections, long capacity,
out string mapName, out SafeMemoryMappedFileHandle.FileStreamSource fileHandleSource)
{
mapName = MemoryMapObjectFilePrefix + Guid.NewGuid().ToString("N") + ".tmp";
fileHandleSource = SafeMemoryMappedFileHandle.FileStreamSource.ManufacturedFile;
FileAccess access =
(protections & (Interop.libc.MemoryMappedProtections.PROT_READ | Interop.libc.MemoryMappedProtections.PROT_WRITE)) != 0 ? FileAccess.ReadWrite :
(protections & (Interop.libc.MemoryMappedProtections.PROT_WRITE)) != 0 ? FileAccess.Write :
FileAccess.Read;
const int DefaultBufferSize = 0x1000;
var fs = new FileStream(Path.Combine(Path.GetTempPath(), mapName),
FileMode.CreateNew, TranslateProtectionsToFileAccess(protections), FileShare.ReadWrite,
DefaultBufferSize, FileOptions.DeleteOnClose);
fs.SetLength(capacity);
return(fs);
}
private static FileStream CreateSharedBackingObject(
Interop.libc.MemoryMappedProtections protections, long capacity,
out string mapName, out SafeMemoryMappedFileHandle.FileStreamSource fileStreamSource)
{
// The POSIX shared memory object name must begin with '/'. After that we just want something short and unique.
mapName = "/" + MemoryMapObjectFilePrefix + Guid.NewGuid().ToString("N");
fileStreamSource = SafeMemoryMappedFileHandle.FileStreamSource.ManufacturedSharedMemory;
// Determine the flags to use when creating the shared memory object
Interop.libc.OpenFlags flags = (protections & Interop.libc.MemoryMappedProtections.PROT_WRITE) != 0 ?
Interop.libc.OpenFlags.O_RDWR :
Interop.libc.OpenFlags.O_RDONLY;
flags |= Interop.libc.OpenFlags.O_CREAT | Interop.libc.OpenFlags.O_EXCL; // CreateNew
// Determine the permissions with which to create the file
Interop.libc.Permissions perms = default(Interop.libc.Permissions);
if ((protections & Interop.libc.MemoryMappedProtections.PROT_READ) != 0)
{
perms |= Interop.libc.Permissions.S_IRUSR;
}
if ((protections & Interop.libc.MemoryMappedProtections.PROT_WRITE) != 0)
{
perms |= Interop.libc.Permissions.S_IWUSR;
}
if ((protections & Interop.libc.MemoryMappedProtections.PROT_EXEC) != 0)
{
perms |= Interop.libc.Permissions.S_IXUSR;
}
// Create the shared memory object. Then enlarge it to the requested capacity.
int fd;
Interop.CheckIo(fd = Interop.libc.shm_open(mapName, flags, (int)perms), mapName);
SafeFileHandle fileHandle = new SafeFileHandle((IntPtr)fd, ownsHandle: true);
// Wrap the handle in a stream and return it.
var fs = new FileStream(fileHandle, TranslateProtectionsToFileAccess(protections));
fs.SetLength(capacity);
return(fs);
}
