Properly honor base::SharedMemory semantics for name="" to mean...

base/shared_memory.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_SHARED_MEMORY_H_
 #define BASE_SHARED_MEMORY_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <semaphore.h>
 #endif
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/process.h"
 
 namespace base {
 
 // SharedMemoryHandle is a platform specific type which represents
 // the underlying OS handle to a shared memory segment.
 #if defined(OS_WIN)
 typedef HANDLE SharedMemoryHandle;
 typedef HANDLE SharedMemoryLock;
 #elif defined(OS_POSIX)
 typedef int SharedMemoryHandle;
+// TODO(port): these semaphores can leak if we crash, causing
+// autobuilder problems.  Transition to something easier to clean up
+// (e.g. lockf/flock).
+// TODO(port): make sure what we transition to is fast enough.
 typedef sem_t* SharedMemoryLock;
 #endif
 
 // Platform abstraction for shared memory.  Provides a C++ wrapper
 // around the OS primitive for a memory mapped file.
 class SharedMemory {
  public:
   // Create a new SharedMemory object.
   SharedMemory();
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file.
   SharedMemory(SharedMemoryHandle handle, bool read_only);
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file that was created by a remote process and not shared
   // to the current process.
   SharedMemory(SharedMemoryHandle handle, bool read_only,
       base::ProcessHandle process);
 
   // Destructor.  Will close any open files.
   ~SharedMemory();
 
   // Creates or opens a shared memory segment based on a name.
   // If read_only is true, opens the memory as read-only.
   // If open_existing is true, and the shared memory already exists,
   // opens the existing shared memory and ignores the size parameter.
+  // If name is the empty string, use a unique name.
   // Returns true on success, false on failure.
   bool Create(const std::wstring& name, bool read_only, bool open_existing,
               size_t size);
 
+  // Deletes resources associated with a shared memory segment based on name.
+  // Not all platforms require this call.
+  bool Delete(const std::wstring& name);
+
   // Opens a shared memory segment based on a name.
   // If read_only is true, opens for read-only access.
+  // If name is the empty string, use a unique name.
   // Returns true on success, false on failure.
   bool Open(const std::wstring& name, bool read_only);
 
   // Maps the shared memory into the caller's address space.
   // Returns true on success, false otherwise.  The memory address
   // is accessed via the memory() accessor.
   bool Map(size_t bytes);
 
   // Unmaps the shared memory from the caller's address space.
   // Returns true if successful; returns false on error or if the
@@ skipping 43 matching lines @@
   // Lock the shared memory.
   // This is a cross-process lock which may be recursively
   // locked by the same thread.
   void Lock();
 
   // Release the shared memory lock.
   void Unlock();
 
  private:
 #if defined(OS_POSIX)
-  bool CreateOrOpen(const std::wstring &name, int posix_flags);
+  bool CreateOrOpen(const std::wstring &name, int posix_flags, size_t size);
+  bool FilenameForMemoryName(const std::wstring &memname,
+                             std::wstring *filename);
 #endif
   bool ShareToProcessCommon(ProcessHandle process,
                             SharedMemoryHandle* new_handle,
                             bool close_self);
 
   std::wstring       name_;
   SharedMemoryHandle mapped_file_;
   void*              memory_;
   bool               read_only_;
   size_t             max_size_;
   SharedMemoryLock   lock_;
+#if defined(OS_POSIX)
+  std::string        sem_name_;
+#endif
 
   DISALLOW_EVIL_CONSTRUCTORS(SharedMemory);
 };
 
 // A helper class that acquires the shared memory lock while
 // the SharedMemoryAutoLock is in scope.
 class SharedMemoryAutoLock {
  public:
   explicit SharedMemoryAutoLock(SharedMemory* shared_memory)
       : shared_memory_(shared_memory) {
     shared_memory_->Lock();
   }
 
   ~SharedMemoryAutoLock() {
     shared_memory_->Unlock();
   }
 
  private:
   SharedMemory* shared_memory_;
   DISALLOW_EVIL_CONSTRUCTORS(SharedMemoryAutoLock);
 };
 
 }  // namespace base
 
 #endif  // BASE_SHARED_MEMORY_H_