diff --git a/lib/TH/THAllocator.c b/lib/TH/THAllocator.c
index 6992544c..cf3fe840 100644
--- a/lib/TH/THAllocator.c
+++ b/lib/TH/THAllocator.c
@@ -1,4 +1,5 @@
 #include "THAllocator.h"
+#include "THAtomic.h"
 
 /* stuff for mapped files */
 #ifdef _WIN32
@@ -36,22 +37,40 @@ THAllocator THDefaultAllocator = {
 
 struct THMapAllocatorContext_ {
   char *filename; /* file name */
-  int shared; /* is shared or not */
+  int flags;
   long size; /* mapped size */
 };
 
-THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int shared)
+#define ALLOC_ALIGNMENT 64
+
+typedef struct {
+  int refcount;
+} THMapInfo;
+
+THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int flags)
 {
   THMapAllocatorContext *ctx = THAlloc(sizeof(THMapAllocatorContext));
 
+
+  if (!(flags & TH_ALLOCATOR_MAPPED_SHARED) && !(flags & TH_ALLOCATOR_MAPPED_SHAREDMEM))
+    flags &= ~TH_ALLOCATOR_MAPPED_NOCREATE;
+  if ((flags ^ TH_ALLOCATOR_MAPPED_EXCLUSIVE) == 0)
+    THError("TH_ALLOCATOR_MAPPED_EXCLUSIVE flag requires opening the file "
+        "in shared mode");
+
   ctx->filename = THAlloc(strlen(filename)+1);
   strcpy(ctx->filename, filename);
-  ctx->shared = shared;
+  ctx->flags = flags;
   ctx->size = 0;
 
   return ctx;
 }
 
+char * THMapAllocatorContext_filename(THMapAllocatorContext *ctx)
+{
+  return ctx->filename;
+}
+
 long THMapAllocatorContext_size(THMapAllocatorContext *ctx)
 {
   return ctx->size;
@@ -63,7 +82,7 @@ void THMapAllocatorContext_free(THMapAllocatorContext *ctx)
   THFree(ctx);
 }
 
-static void *THMapAllocator_alloc(void* ctx_, long size)
+static void *_map_alloc(void* ctx_, long size)
 {
   THMapAllocatorContext *ctx = ctx_;
   void *data = NULL;
@@ -75,9 +94,14 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
     DWORD size_hi, size_lo;
     size_t hfilesz;
 
+    if (ctx->flags & TH_ALLOCATOR_MAPPED_EXCLUSIVE)
+      THError("exclusive file mapping is not supported on Windows");
+    if (ctx->flags & TH_ALLOCATOR_MAPPED_NOCREATE)
+      THError("file mapping without creation is not supported on Windows");
+
     /* open file */
     /* FILE_FLAG_RANDOM_ACCESS ? */
-    if(ctx->shared)
+    if(ctx->flags)
     {
       hfile = CreateFileA(ctx->filename, GENERIC_READ|GENERIC_WRITE, FILE_SHARE_WRITE|FILE_SHARE_READ, 0, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);
       if (hfile == INVALID_HANDLE_VALUE)
@@ -103,7 +127,7 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
     {
       if(size > hfilesz)
       {
-        if(ctx->shared)
+        if(ctx->flags)
         {
 #if SIZEOF_SIZE_T > 4
           size_hi = (DWORD)((size) >> 32);
@@ -144,7 +168,7 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
 #endif
 
     /* get map handle */
-    if(ctx->shared)
+    if(ctx->flags)
     {
       if( (hmfile = CreateFileMapping(hfile, NULL, PAGE_READWRITE, size_hi, size_lo, NULL)) == NULL )
         THError("could not create a map on file <%s>", ctx->filename);
@@ -156,30 +180,41 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
     }
 
     /* map the stuff */
-    if(ctx->shared)
+    if(ctx->flags)
       data = MapViewOfFile(hmfile, FILE_MAP_ALL_ACCESS, 0, 0, 0);
     else
       data = MapViewOfFile(hmfile, FILE_MAP_COPY, 0, 0, 0);
 
-    CloseHandle(hfile); 
-    CloseHandle(hmfile); 
+    CloseHandle(hfile);
+    CloseHandle(hmfile);
   }
 #else /* _WIN32 */
   {
     /* open file */
     int fd;
+    int flags;
     long fdsz;
 
-    if(ctx->shared == TH_ALLOCATOR_MAPPED_SHARED)
+    if (ctx->flags)
+      flags = O_RDWR | O_CREAT;
+    else
+      flags = O_RDONLY;
+
+    if (ctx->flags & TH_ALLOCATOR_MAPPED_EXCLUSIVE)
+      flags |= O_EXCL;
+    if (ctx->flags & TH_ALLOCATOR_MAPPED_NOCREATE)
+      flags &= ~O_CREAT;
+
+    if(ctx->flags & TH_ALLOCATOR_MAPPED_SHARED)
     {
-      if((fd = open(ctx->filename, O_RDWR | O_CREAT, (mode_t)0600)) == -1)
+      if((fd = open(ctx->filename, flags, (mode_t)0600)) == -1)
         THError("unable to open file <%s> in read-write mode", ctx->filename);
     }
-    else if (ctx->shared == TH_ALLOCATOR_MAPPED_SHAREDMEM)
+    else if (ctx->flags & TH_ALLOCATOR_MAPPED_SHAREDMEM)
     {
 #ifdef HAVE_SHM_OPEN
-      if((fd = shm_open(ctx->filename, O_RDWR | O_CREAT, (mode_t)0600)) == -1)
-        THError("unable to open file <%s> in read-write mode", ctx->filename);
+      if((fd = shm_open(ctx->filename, flags, (mode_t)0600)) == -1)
+        THError("unable to open shared memory object <%s> in read-write mode", ctx->filename);
 #else
       THError("unable to open file <%s> in sharedmem mode, shm_open unavailable on this platform");
 #endif
@@ -189,19 +224,21 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
       if((fd = open(ctx->filename, O_RDONLY)) == -1)
         THError("unable to open file <%s> in read-only mode", ctx->filename);
     }
+
     if((fdsz = lseek(fd, 0, SEEK_END)) == -1)
     {
       close(fd);
       THError("unable to seek at end of file <%s>", ctx->filename);
     }
+
     if(size > 0)
     {
       if(size > fdsz)
       {
-        if(ctx->shared)
+        if(ctx->flags)
         {
           /* if it is shared mem, let's put it in correct size */
-          if (ctx->shared == TH_ALLOCATOR_MAPPED_SHAREDMEM)
+          if (ctx->flags & TH_ALLOCATOR_MAPPED_SHAREDMEM)
           {
             if(ftruncate(fd, size) == -1)
               THError("unable to resize shared memory file <%s> to the right size", ctx->filename);
@@ -228,9 +265,9 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
       size = fdsz;
 
     ctx->size = size; /* if we are here, it must be the right size */
-    
+
     /* map it */
-    if(ctx->shared)
+    if(ctx->flags)
       data = mmap(NULL, ctx->size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
     else
       data = mmap(NULL, ctx->size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
@@ -249,6 +286,10 @@ static void *THMapAllocator_alloc(void* ctx_, long size)
   return data;
 }
 
+static void * THMapAllocator_alloc(void *ctx, long size) {
+  return _map_alloc(ctx, size);
+}
+
 static void *THMapAllocator_realloc(void* ctx, void* ptr, long size) {
   THError("cannot realloc mapped data");
   return NULL;
@@ -260,10 +301,10 @@ static void THMapAllocator_free(void* ctx_, void* data) {
 #ifdef _WIN32
   if(!UnmapViewOfFile((LPINT)data))
     THError("could not unmap the shared memory file");
-#else
+#else /* _WIN32 */
   if (munmap(data, ctx->size))
     THError("could not unmap the shared memory file");
-  if (ctx->shared == TH_ALLOCATOR_MAPPED_SHAREDMEM)
+  if (ctx->flags & TH_ALLOCATOR_MAPPED_SHAREDMEM)
   {
 #ifdef HAVE_SHM_UNLINK
     if (shm_unlink(ctx->filename) == -1)
@@ -272,14 +313,14 @@ static void THMapAllocator_free(void* ctx_, void* data) {
     THError("could not unlink the shared memory file %s, shm_unlink not available on platform", ctx->filename);
 #endif
   }
-#endif
+#endif /* _WIN32 */
 
   THMapAllocatorContext_free(ctx);
 }
 
 #else
 
-THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int shared) {
+THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int flags) {
   THError("file mapping not supported on your system");
   return NULL;
 }
@@ -304,8 +345,83 @@ static void THMapAllocator_free(void* ctx, void* data) {
 
 #endif
 
+#if (defined(_WIN32) || defined(HAVE_MMAP)) && defined(TH_ATOMIC_IPC_REFCOUNT)
+
+static void * THRefcountedMapAllocator_alloc(void *_ctx, long size) {
+  THMapAllocatorContext *ctx = _ctx;
+  fprintf(stderr, "%d\n", ctx->flags);
+
+  if (!(ctx->flags & TH_ALLOCATOR_MAPPED_SHAREDMEM))
+    THError("THRefcountedMapAllcator requires SHAREDMEM flag");
+
+  size = size + ALLOC_ALIGNMENT;
+  void *ptr = _map_alloc(ctx, size);
+  char *data = ((char*)ptr) + ALLOC_ALIGNMENT;
+  THMapInfo *map_info = (THMapInfo*)ptr;
+
+  if (ctx->flags & TH_ALLOCATOR_MAPPED_EXCLUSIVE)
+    map_info->refcount = 1;
+  else
+    THAtomicIncrementRef(&map_info->refcount);
+
+  return (void*)data;
+}
+
+static void *THRefcountedMapAllocator_realloc(void* ctx, void* ptr, long size) {
+  THError("cannot realloc mapped data");
+  return NULL;
+}
+
+static void THRefcountedMapAllocator_free(void* ctx_, void* data) {
+  THMapAllocatorContext *ctx = ctx_;
+
+#ifdef _WIN32
+  if(!UnmapViewOfFile((LPINT)data))
+    THError("could not unmap the shared memory file");
+#else /* _WIN32 */
+
+  THMapInfo *info = (THMapInfo*)(((char*)data) - ALLOC_ALIGNMENT);
+  if (THAtomicDecrementRef(&info->refcount)) {
+#ifdef HAVE_SHM_UNLINK
+    if (shm_unlink(ctx->filename) == -1)
+      THError("could not unlink the shared memory file %s", ctx->filename);
+#else
+    THError("could not unlink the shared memory file %s, shm_unlink not available on platform", ctx->filename);
+#endif /* HAVE_SHM_UNLINK */
+  }
+  if (munmap(info, ctx->size))
+    THError("could not unmap the shared memory file %s", ctx->filename);
+#endif /* _WIN32 */
+
+  THMapAllocatorContext_free(ctx);
+}
+
+#else
+
+static void * THRefcountedMapAllocator_alloc(void *ctx, long size) {
+  THError("refcounted file mapping not supported on your system");
+  return NULL;
+}
+
+static void *THRefcountedMapAllocator_realloc(void* ctx, void* ptr, long size) {
+  THError("refcounted file mapping not supported on your system");
+  return NULL;
+}
+
+static void THRefcountedMapAllocator_free(void* ctx_, void* data) {
+  THError("refcounted file mapping not supported on your system");
+}
+
+#endif
+
 THAllocator THMapAllocator = {
   &THMapAllocator_alloc,
   &THMapAllocator_realloc,
   &THMapAllocator_free
 };
+
+THAllocator THRefcountedMapAllocator = {
+  &THRefcountedMapAllocator_alloc,
+  &THRefcountedMapAllocator_realloc,
+  &THRefcountedMapAllocator_free
+};
diff --git a/lib/TH/THAllocator.h b/lib/TH/THAllocator.h
index dbc75a86..567c59f8 100644
--- a/lib/TH/THAllocator.h
+++ b/lib/TH/THAllocator.h
@@ -5,6 +5,8 @@
 
 #define TH_ALLOCATOR_MAPPED_SHARED 1
 #define TH_ALLOCATOR_MAPPED_SHAREDMEM 2
+#define TH_ALLOCATOR_MAPPED_EXCLUSIVE 4
+#define TH_ALLOCATOR_MAPPED_NOCREATE 8
 
 /* Custom allocator
  */
@@ -22,10 +24,12 @@ extern THAllocator THDefaultAllocator;
 /* file map allocator
  */
 typedef struct THMapAllocatorContext_  THMapAllocatorContext;
-THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int shared);
-long THMapAllocatorContext_size(THMapAllocatorContext *ctx);
-void THMapAllocatorContext_free(THMapAllocatorContext *ctx);
+TH_API THMapAllocatorContext *THMapAllocatorContext_new(const char *filename, int flags);
+TH_API char * THMapAllocatorContext_filename(THMapAllocatorContext *ctx);
+TH_API long THMapAllocatorContext_size(THMapAllocatorContext *ctx);
+TH_API void THMapAllocatorContext_free(THMapAllocatorContext *ctx);
 
 extern THAllocator THMapAllocator;
+extern THAllocator THRefcountedMapAllocator;
 
 #endif
diff --git a/lib/TH/THAtomic.h b/lib/TH/THAtomic.h
index 3a37c311..3a0b6fa0 100644
--- a/lib/TH/THAtomic.h
+++ b/lib/TH/THAtomic.h
@@ -86,4 +86,11 @@ TH_API long THAtomicAddLong(long volatile *a, long value);
 */
 TH_API long THAtomicCompareAndSwapLong(long volatile *a, long oldvalue, long newvalue);
 
+#if defined(USE_C11_ATOMICS) && defined(ATOMIC_INT_LOCK_FREE) && \
+  ATOMIC_INT_LOCK_FREE == 2
+#define TH_ATOMIC_IPC_REFCOUNT 1
+#elif defined(USE_MSC_ATOMICS) || defined(USE_GCC_ATOMICS)
+#define TH_ATOMIC_IPC_REFCOUNT 1
+#endif
+
 #endif
diff --git a/lib/TH/generic/THStorage.c b/lib/TH/generic/THStorage.c
index cac043ed..788f6c77 100644
--- a/lib/TH/generic/THStorage.c
+++ b/lib/TH/generic/THStorage.c
@@ -41,9 +41,9 @@ THStorage* THStorage_(newWithAllocator)(long size,
   return storage;
 }
 
-THStorage* THStorage_(newWithMapping)(const char *filename, long size, int shared)
+THStorage* THStorage_(newWithMapping)(const char *filename, long size, int flags)
 {
-  THMapAllocatorContext *ctx = THMapAllocatorContext_new(filename, shared);
+  THMapAllocatorContext *ctx = THMapAllocatorContext_new(filename, flags);
 
   THStorage *storage = THStorage_(newWithAllocator)(size,
                                                     &THMapAllocator,
@@ -203,4 +203,24 @@ real THStorage_(get)(const THStorage *self, long idx)
   return self->data[idx];
 }
 
+void THStorage_(swap)(THStorage *storage1, THStorage *storage2)
+{
+#define SWAP(val) { val = storage1->val; storage1->val = storage2->val; storage2->val = val; }
+    real *data;
+    long size;
+    char flag;
+    THAllocator *allocator;
+    void *allocatorContext;
+    struct THStorage *view;
+
+    SWAP(data);
+    SWAP(size);
+    SWAP(flag);
+    // don't swap refcount!
+    SWAP(allocator);
+    SWAP(allocatorContext);
+    SWAP(view);
+#undef SWAP
+}
+
 #endif
diff --git a/lib/TH/generic/THStorage.h b/lib/TH/generic/THStorage.h
index 79013d8e..0f6dcca4 100644
--- a/lib/TH/generic/THStorage.h
+++ b/lib/TH/generic/THStorage.h
@@ -46,7 +46,7 @@ TH_API THStorage* THStorage_(newWithSize1)(real);
 TH_API THStorage* THStorage_(newWithSize2)(real, real);
 TH_API THStorage* THStorage_(newWithSize3)(real, real, real);
 TH_API THStorage* THStorage_(newWithSize4)(real, real, real, real);
-TH_API THStorage* THStorage_(newWithMapping)(const char *filename, long size, int shared);
+TH_API THStorage* THStorage_(newWithMapping)(const char *filename, long size, int flags);
 
 /* takes ownership of data */
 TH_API THStorage* THStorage_(newWithData)(real *data, long size);
@@ -61,6 +61,7 @@ TH_API THStorage* THStorage_(newWithDataAndAllocator)(
 TH_API void THStorage_(setFlag)(THStorage *storage, const char flag);
 TH_API void THStorage_(clearFlag)(THStorage *storage, const char flag);
 TH_API void THStorage_(retain)(THStorage *storage);
+TH_API void THStorage_(swap)(THStorage *storage1, THStorage *storage2);
 
 /* might differ with other API (like CUDA) */
 TH_API void THStorage_(free)(THStorage *storage);