base/memory/shared_memory_handle.h

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
   6 #define BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
   7
   8 #include "build/build_config.h"
   9
  10 #if defined(OS_WIN)
  11 #include <windows.h>
  12 #elif defined(OS_MACOSX)
  13 #include <sys/types.h>
  14 #include "base/base_export.h"
  15 #include "base/file_descriptor_posix.h"
  16 #include "base/macros.h"
  17 #elif defined(OS_POSIX)
  18 #include <sys/types.h>
  19 #include "base/file_descriptor_posix.h"
  20 #endif
  21
  22 namespace base {
  23
  24 class Pickle;
  25
  26 // SharedMemoryHandle is a platform specific type which represents
  27 // the underlying OS handle to a shared memory segment.
  28 #if defined(OS_WIN)
  29 typedef HANDLE SharedMemoryHandle;
  30 #elif defined(OS_POSIX) && !defined(OS_MACOSX)
  31 typedef FileDescriptor SharedMemoryHandle;
  32 #else
  33 class BASE_EXPORT SharedMemoryHandle {
  34  public:
  35   enum Type {
  36     // Indicates that the SharedMemoryHandle is backed by a POSIX fd.
  37     POSIX,
  38     // Indicates that the SharedMemoryHandle is backed by the Mach primitive
  39     // "memory object".
  40     MACH,
  41   };
  42
  43   // The format that should be used to transmit |Type| over the wire.
  44   typedef int TypeWireFormat;
  45
  46   // The default constructor returns an invalid SharedMemoryHandle.
  47   SharedMemoryHandle();
  48
  49   // Constructs a SharedMemoryHandle backed by the components of a
  50   // FileDescriptor. The newly created instance has the same ownership semantics
  51   // as base::FileDescriptor. This typically means that the SharedMemoryHandle
  52   // takes ownership of the |fd| if |auto_close| is true. Unfortunately, it's
  53   // common for existing code to make shallow copies of SharedMemoryHandle, and
  54   // the one that is finally passed into a base::SharedMemory is the one that
  55   // "consumes" the fd.
  56   explicit SharedMemoryHandle(const base::FileDescriptor& file_descriptor);
  57   SharedMemoryHandle(int fd, bool auto_close);
  58
  59   // Standard copy constructor. The new instance shares the underlying OS
  60   // primitives.
  61   SharedMemoryHandle(const SharedMemoryHandle& handle);
  62
  63   // Standard assignment operator. The updated instance shares the underlying
  64   // OS primitives.
  65   SharedMemoryHandle& operator=(const SharedMemoryHandle& handle);
  66
  67   // Duplicates the underlying OS resources.
  68   SharedMemoryHandle Duplicate() const;
  69
  70   // Comparison operators.
  71   bool operator==(const SharedMemoryHandle& handle) const;
  72   bool operator!=(const SharedMemoryHandle& handle) const;
  73
  74   // Returns the type.
  75   Type GetType() const;
  76
  77   // Whether the underlying OS primitive is valid.
  78   bool IsValid() const;
  79
  80   // Sets the POSIX fd backing the SharedMemoryHandle. Requires that the
  81   // SharedMemoryHandle be backed by a POSIX fd.
  82   void SetFileHandle(int fd, bool auto_close);
  83
  84   // This method assumes that the SharedMemoryHandle is backed by a POSIX fd.
  85   // This is eventually no longer going to be true, so please avoid adding new
  86   // uses of this method.
  87   const FileDescriptor GetFileDescriptor() const;
  88
  89  private:
  90   Type type_;
  91   FileDescriptor file_descriptor_;
  92 };
  93 #endif
  94
  95 }  // namespace base
  96
  97 #endif  // BASE_MEMORY_SHARED_MEMORY_HANDLE_H_