POSIX: Transfer network data using shared memory

base/shared_memory.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_SHARED_MEMORY_H_
 #define BASE_SHARED_MEMORY_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <semaphore.h>
+#include "base/file_descriptor_posix.h"
 #endif
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/process.h"
 
 namespace base {
 
 // SharedMemoryHandle is a platform specific type which represents
 // the underlying OS handle to a shared memory segment.
 #if defined(OS_WIN)
 typedef HANDLE SharedMemoryHandle;
 typedef HANDLE SharedMemoryLock;
 #elif defined(OS_POSIX)
-typedef int SharedMemoryHandle;
+typedef FileDescriptor SharedMemoryHandle;
 // On POSIX, the lock is implemented as a lockf() on the mapped file,
 // so no additional member (or definition of SharedMemoryLock) is
 // needed.
 #endif
 
 // Platform abstraction for shared memory.  Provides a C++ wrapper
 // around the OS primitive for a memory mapped file.
 class SharedMemory {
  public:
   // Create a new SharedMemory object.
   SharedMemory();
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file.
   SharedMemory(SharedMemoryHandle handle, bool read_only);
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file that was created by a remote process and not shared
   // to the current process.
   SharedMemory(SharedMemoryHandle handle, bool read_only,
       base::ProcessHandle process);
 
   // Destructor.  Will close any open files.
   ~SharedMemory();
 
+  // Return true iff the given handle is valid (i.e. not the distingished
+  // invalid value; NULL for a HANDLE and -1 for a file descriptor)
+  static bool IsHandleValid(const SharedMemoryHandle& handle);
+
   // Creates or opens a shared memory segment based on a name.
   // If read_only is true, opens the memory as read-only.
   // If open_existing is true, and the shared memory already exists,
   // opens the existing shared memory and ignores the size parameter.
   // If name is the empty string, use a unique name.
   // Returns true on success, false on failure.
   bool Create(const std::wstring& name, bool read_only, bool open_existing,
               size_t size);
 
   // Deletes resources associated with a shared memory segment based on name.
@@ skipping 23 matching lines @@
   // Returns 0 if not opened or unknown.
   size_t max_size() const { return max_size_; }
 
   // Gets a pointer to the opened memory space if it has been
   // Mapped via Map().  Returns NULL if it is not mapped.
   void *memory() const { return memory_; }
 
   // Get access to the underlying OS handle for this segment.
   // Use of this handle for anything other than an opaque
   // identifier is not portable.
-  SharedMemoryHandle handle() const { return mapped_file_; }
+  SharedMemoryHandle handle() const;
 
   // Closes the open shared memory segment.
   // It is safe to call Close repeatedly.
   void Close();
 
   // Share the shared memory to another process.  Attempts
   // to create a platform-specific new_handle which can be
   // used in a remote process to access the shared memory
   // file.  new_handle is an ouput parameter to receive
   // the handle for use in the remote process.
@@ skipping 34 matching lines @@
   bool FilenameForMemoryName(const std::wstring &memname,
                              std::wstring *filename);
   void LockOrUnlockCommon(int function);
 
 #endif
   bool ShareToProcessCommon(ProcessHandle process,
                             SharedMemoryHandle* new_handle,
                             bool close_self);
 
   std::wstring       name_;
-  SharedMemoryHandle mapped_file_;
+#if defined(OS_WIN)
+  HANDLE mapped_file_;
+#elif defined(OS_POSIX)
+  int mapped_file_;
+#endif
   void*              memory_;
   bool               read_only_;
   size_t             max_size_;
 #if !defined(OS_POSIX)
   SharedMemoryLock   lock_;
 #endif
 
   DISALLOW_EVIL_CONSTRUCTORS(SharedMemory);
 };
 
@@ skipping 11 matching lines @@
   }
 
  private:
   SharedMemory* shared_memory_;
   DISALLOW_EVIL_CONSTRUCTORS(SharedMemoryAutoLock);
 };
 
 }  // namespace base
 
 #endif  // BASE_SHARED_MEMORY_H_