ipc/glue/SharedMemorySysV.h

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  39
  40 #ifndef mozilla_ipc_SharedMemorySysV_h
  41 #define mozilla_ipc_SharedMemorySysV_h
  42
  43 #ifdef OS_LINUX
  44
  45 // SysV shared memory isn't available on Windows, but we define the
  46 // following macro so that #ifdefs are clearer (compared to #ifdef
  47 // OS_LINUX).
  48 #define MOZ_HAVE_SHAREDMEMORYSYSV
  49
  50 #include "SharedMemory.h"
  51
  52 #include "nsDebug.h"
  53
  54 #include <errno.h>
  55 #include <fcntl.h>
  56 #include <string.h>
  57 #include <sys/ipc.h>
  58 #include <sys/shm.h>
  59
  60 //
  61 // This is a low-level wrapper around platform shared memory.  Don't
  62 // use it directly; use Shmem allocated through IPDL interfaces.
  63 //
  64
  65 namespace mozilla {
  66 namespace ipc {
  67
  68
  69 class SharedMemorySysV : public SharedMemory
  70 {
  71 public:
  72   typedef int Handle;
  73
  74   SharedMemorySysV() :
  75     mHandle(-1),
  76     mData(nsnull),
  77     mSize(0)
  78   {
  79   }
  80
  81   SharedMemorySysV(Handle aHandle) :
  82     mHandle(aHandle),
  83     mData(nsnull),
  84     mSize(0)
  85   {
  86   }
  87
  88   virtual ~SharedMemorySysV()
  89   {
  90     shmdt(mData);
  91     mHandle = -1;
  92     mData = nsnull;
  93     mSize = 0;
  94
  95   }
  96
  97   NS_OVERRIDE
  98   virtual bool Create(size_t aNbytes)
  99   {
 100     int id = shmget(IPC_PRIVATE, aNbytes, IPC_CREAT | 0600);
 101     if (id == -1)
 102       return false;
 103
 104     mHandle = id;
 105
 106     if (!Map(aNbytes))
 107       return false;
 108
 109     return true;
 110   }
 111
 112   NS_OVERRIDE
 113   virtual bool Map(size_t nBytes)
 114   {
 115     // already mapped
 116     if (mData)
 117       return true;
 118
 119     if (!IsHandleValid(mHandle))
 120       return false;
 121
 122     void* mem = shmat(mHandle, nsnull, 0);
 123     if (mem == (void*) -1) {
 124       char warning[256];
 125       snprintf(warning, sizeof(warning)-1,
 126                "shmat(): %s (%d)\n", strerror(errno), errno);
 127
 128       NS_WARNING(warning);
 129
 130       return false;
 131     }
 132
 133     // Mark the handle as deleted so that, should this process go away, the
 134     // segment is cleaned up.
 135     shmctl(mHandle, IPC_RMID, 0);
 136
 137     mData = mem;
 138     mSize = nBytes;
 139
 140 #ifdef NS_DEBUG
 141     struct shmid_ds info;
 142     if (shmctl(mHandle, IPC_STAT, &info) < 0)
 143       return false;
 144
 145     NS_ABORT_IF_FALSE(nBytes <= info.shm_segsz,
 146                       "Segment doesn't have enough space!");
 147 #endif
 148
 149     return true;
 150   }
 151
 152   NS_OVERRIDE
 153   virtual size_t Size() const
 154   {
 155     return mSize;
 156   }
 157
 158   NS_OVERRIDE
 159   virtual void* memory() const
 160   {
 161     return mData;
 162   }
 163
 164   NS_OVERRIDE
 165   virtual SharedMemoryType Type() const
 166   {
 167     return TYPE_SYSV;
 168   }
 169
 170   Handle GetHandle() const
 171   {
 172     NS_ABORT_IF_FALSE(IsHandleValid(mHandle), "invalid handle");
 173     return mHandle;
 174   }
 175
 176   static Handle NULLHandle()
 177   {
 178     return -1;
 179   }
 180
 181   static bool IsHandleValid(Handle aHandle)
 182   {
 183     return aHandle != -1;
 184   }
 185
 186 private:
 187   Handle mHandle;
 188   void* mData;
 189   size_t mSize;
 190 };
 191
 192 } // namespace ipc
 193 } // namespace mozilla
 194
 195 #endif // OS_LINUX
 196
 197 #endif // ifndef mozilla_ipc_SharedMemorySysV_h