ipc/glue/SharedMemorySysV.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: sw=2 ts=8 et :
   3  */
   4 /* This Source Code Form is subject to the terms of the Mozilla Public
   5  * License, v. 2.0. If a copy of the MPL was not distributed with this
   6  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   7
   8 #ifndef mozilla_ipc_SharedMemorySysV_h
   9 #define mozilla_ipc_SharedMemorySysV_h
  10
  11 #if (defined(OS_LINUX) && !defined(ANDROID)) || defined(OS_BSD)
  12
  13 // SysV shared memory isn't available on Windows, but we define the
  14 // following macro so that #ifdefs are clearer (compared to #ifdef
  15 // OS_LINUX).
  16 #define MOZ_HAVE_SHAREDMEMORYSYSV
  17
  18 #include "SharedMemory.h"
  19
  20 #include "nsDebug.h"
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <stdio.h>
  25 #include <string.h>
  26 #include <sys/ipc.h>
  27 #include <sys/shm.h>
  28
  29 //
  30 // This is a low-level wrapper around platform shared memory.  Don't
  31 // use it directly; use Shmem allocated through IPDL interfaces.
  32 //
  33
  34 namespace mozilla {
  35 namespace ipc {
  36
  37
  38 class SharedMemorySysV : public SharedMemory
  39 {
  40 public:
  41   typedef int Handle;
  42
  43   SharedMemorySysV() :
  44     mHandle(-1),
  45     mData(nullptr)
  46   {
  47   }
  48
  49   SharedMemorySysV(Handle aHandle) :
  50     mHandle(aHandle),
  51     mData(nullptr)
  52   {
  53   }
  54
  55   virtual ~SharedMemorySysV()
  56   {
  57     shmdt(mData);
  58     mHandle = -1;
  59     mData = nullptr;
  60   }
  61
  62   virtual bool Create(size_t aNbytes) MOZ_OVERRIDE
  63   {
  64     int id = shmget(IPC_PRIVATE, aNbytes, IPC_CREAT | 0600);
  65     if (id == -1)
  66       return false;
  67
  68     mHandle = id;
  69     mAllocSize = aNbytes;
  70     Created(aNbytes);
  71
  72     return Map(aNbytes);
  73   }
  74
  75   virtual bool Map(size_t nBytes) MOZ_OVERRIDE
  76   {
  77     // already mapped
  78     if (mData)
  79       return true;
  80
  81     if (!IsHandleValid(mHandle))
  82       return false;
  83
  84     void* mem = shmat(mHandle, nullptr, 0);
  85     if (mem == (void*) -1) {
  86       char warning[256];
  87       ::snprintf(warning, sizeof(warning)-1,
  88                  "shmat(): %s (%d)\n", strerror(errno), errno);
  89
  90       NS_WARNING(warning);
  91
  92       return false;
  93     }
  94
  95     // Mark the handle as deleted so that, should this process go away, the
  96     // segment is cleaned up.
  97     shmctl(mHandle, IPC_RMID, 0);
  98
  99     mData = mem;
 100
 101 #ifdef DEBUG
 102     struct shmid_ds info;
 103     if (shmctl(mHandle, IPC_STAT, &info) < 0)
 104       return false;
 105
 106     NS_ABORT_IF_FALSE(nBytes <= info.shm_segsz,
 107                       "Segment doesn't have enough space!");
 108 #endif
 109
 110     Mapped(nBytes);
 111     return true;
 112   }
 113
 114   virtual void* memory() const MOZ_OVERRIDE
 115   {
 116     return mData;
 117   }
 118
 119   virtual SharedMemoryType Type() const MOZ_OVERRIDE
 120   {
 121     return TYPE_SYSV;
 122   }
 123
 124   Handle GetHandle() const
 125   {
 126     NS_ABORT_IF_FALSE(IsHandleValid(mHandle), "invalid handle");
 127     return mHandle;
 128   }
 129
 130   static Handle NULLHandle()
 131   {
 132     return -1;
 133   }
 134
 135   static bool IsHandleValid(Handle aHandle)
 136   {
 137     return aHandle != -1;
 138   }
 139
 140 private:
 141   Handle mHandle;
 142   void* mData;
 143 };
 144
 145 } // namespace ipc
 146 } // namespace mozilla
 147
 148 #endif // OS_LINUX
 149
 150 #endif // ifndef mozilla_ipc_SharedMemorySysV_h