| // Copyright 2008, Google Inc. |
| // All rights reserved. |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following disclaimer |
| // in the documentation and/or other materials provided with the |
| // distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived from |
| // this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #ifndef BASE_SHARED_MEMORY_H_ |
| #define BASE_SHARED_MEMORY_H_ |
| |
| #include "base/basictypes.h" |
| #include "base/process_util.h" |
| |
| // 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) |
| #include <semaphore.h> |
| typedef int SharedMemoryHandle; |
| 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, |
| 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. |
| // Returns true on success, false on failure. |
| bool Create(const std::wstring &name, bool read_only, bool open_existing, |
| size_t size); |
| |
| // Opens a shared memory segment based on a name. |
| // If read_only is true, opens for read-only access. |
| // 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 |
| // memory is not mapped. |
| bool Unmap(); |
| |
| // Get the size of the opened shared memory backing file. |
| // Note: This size is only available to the creator of the |
| // shared memory, and not to those that opened shared memory |
| // created externally. |
| // Returns 0 if not opened or unknown. |
| size_t max_size() const { return max_size_; } |
| |
| // Gets a pointer to the opened memory space if it has been |
| // Mapped via Map(). Returns NULL if it is not mapped. |
| void *memory() const { return memory_; } |
| |
| // Get access to the underlying OS handle for this segment. |
| // Use of this handle for anything other than an opaque |
| // identifier is not portable. |
| SharedMemoryHandle handle() const { return mapped_file_; } |
| |
| // Closes the open shared memory segment. |
| // It is safe to call Close repeatedly. |
| void Close(); |
| |
| // Share the shared memory to another process. Attempts |
| // to create a platform-specific new_handle which can be |
| // used in a remote process to access the shared memory |
| // file. new_handle is an ouput parameter to receive |
| // the handle for use in the remote process. |
| // Returns true on success, false otherwise. |
| bool ShareToProcess(ProcessHandle process, |
| SharedMemoryHandle *new_handle) { |
| return ShareToProcessCommon(process, new_handle, false); |
| } |
| |
| // Logically equivalent to: |
| // bool ok = ShareToProcess(process, new_handle); |
| // Close(); |
| // return ok; |
| bool GiveToProcess(ProcessHandle process, |
| SharedMemoryHandle *new_handle) { |
| return ShareToProcessCommon(process, new_handle, true); |
| } |
| |
| // 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); |
| #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_; |
| |
| 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); |
| }; |
| |
| |
| #endif // BASE_SHARED_MEMORY_H_ |