The Tor Browser: ipc/chromium/src/base/shared_memory.h@6474c204b198 (annotated)

ipc/chromium/src/base/shared_memory.h@6474c204b198 (annotated)

ipc/chromium/src/base/shared_memory.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // 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 <sys/types.h>
 #include <semaphore.h>
 #include "base/file_descriptor_posix.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)
 // 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.
 #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();
   // Return true iff the given handle is valid (i.e. not the distingished
   // invalid value; NULL for a HANDLE and -1 for a file descriptor)
   static bool IsHandleValid(const SharedMemoryHandle& handle);
   // Return invalid handle (see comment above for exact definition).
   static SharedMemoryHandle NULLHandle();
   // 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::string& 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
   // 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;
 #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();
   // 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(base::ProcessHandle process,
                       SharedMemoryHandle* new_handle) {
     return ShareToProcessCommon(process, new_handle, false);
   }
   // Logically equivalent to:
   //   bool ok = ShareToProcess(process, new_handle);
   //   Close();
   //   return ok;
   // Note that the memory is unmapped by calling this method, regardless of the
   // return value.
   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.
   // TODO(port):
   // WARNING: on POSIX the lock only works across processes, not
   // across threads.  2 threads in the same process can both grab the
   // lock at the same time.  There are several solutions for this
   // (futex, lockf+anon_semaphore) but none are both clean and common
   // across Mac and Linux.
   void Lock();
   // Release the shared memory lock.
   void Unlock();
  private:
 #if defined(OS_POSIX)
   bool CreateOrOpen(const std::wstring &name, int posix_flags, size_t size);
   bool FilenameForMemoryName(const std::wstring &memname,
                              std::wstring *filename);
   void LockOrUnlockCommon(int function);
 #endif
   bool ShareToProcessCommon(ProcessHandle process,
                             SharedMemoryHandle* new_handle,
                             bool close_self);
 #if defined(OS_WIN)
   std::wstring       name_;
   HANDLE             mapped_file_;
 #elif defined(OS_POSIX)
   int                mapped_file_;
   ino_t              inode_;
 #endif
   void*              memory_;
   bool               read_only_;
   size_t             max_size_;
 #if !defined(OS_POSIX)
   SharedMemoryLock   lock_;
 #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_

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ipc/chromium/src/base/shared_memory.h@6474c204b198 (annotated)

ipc/chromium/src/base/shared_memory.h