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base/shared_memory.h

Index: base/shared_memory.h
diff --git a/base/shared_memory.h b/base/shared_memory.h
index b44367a7fcc875e16e91e6e486f73c0316debd15..744b3489e7d9d7fb21c6d7d5878019faa7091a86 100644
--- a/base/shared_memory.h
+++ b/base/shared_memory.h
@@ -8,6 +8,7 @@
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
+#include <sys/types.h>
 #include <semaphore.h>
 #include "base/file_descriptor_posix.h"
 #endif
@@ -24,7 +25,10 @@ namespace base {
 typedef HANDLE SharedMemoryHandle;
 typedef HANDLE SharedMemoryLock;
 #elif defined(OS_POSIX)
+// A SharedMemoryId is sufficient to identify a given shared memory segment on a
+// system, but insufficient to map it.
 typedef FileDescriptor SharedMemoryHandle;
+typedef ino_t SharedMemoryId;
 // On POSIX, the lock is implemented as a lockf() on the mapped file,
 // so no additional member (or definition of SharedMemoryLock) is
 // needed.
@@ -99,6 +103,14 @@ class SharedMemory {
   // identifier is not portable.
   SharedMemoryHandle handle() const;
 
+#if defined(OS_POSIX)
+  // Return a unique identifier for this shared memory segment. Inode numbers
+  // are technically only unique to a single filesystem. However, we always
+  // allocate shared memory backing files from the same directory, so will end
+  // up on the same filesystem.
+  SharedMemoryId id() const { return inode_; }
+#endif
+
   // Closes the open shared memory segment.
   // It is safe to call Close repeatedly.
   void Close();
@@ -153,9 +165,10 @@ class SharedMemory {
 
   std::wstring       name_;
 #if defined(OS_WIN)
-  HANDLE mapped_file_;
+  HANDLE             mapped_file_;
 #elif defined(OS_POSIX)
-  int mapped_file_;
+  int                mapped_file_;
+  ino_t              inode_;
 #endif
   void*              memory_;
   bool               read_only_;