159 lines
4.3 KiB
C++
159 lines
4.3 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_ipc_FileDescriptor_h
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#define mozilla_ipc_FileDescriptor_h
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#include "base/basictypes.h"
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#include "base/process.h"
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#include "mozilla/DebugOnly.h"
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#include "nscore.h"
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#ifdef XP_WIN
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// Need the HANDLE typedef.
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#include <winnt.h>
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#else
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#include "base/file_descriptor_posix.h"
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#endif
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namespace mozilla {
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namespace ipc {
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// This class is used by IPDL to share file descriptors across processes. When
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// sending a FileDescriptor IPDL will first duplicate a platform-specific file
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// handle type ('PlatformHandleType') into a handle that is valid in the other
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// process. Then IPDL will convert the duplicated handle into a type suitable
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// for pickling ('PickleType') and then send that through the IPC pipe. In the
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// receiving process the pickled data is converted into a platform-specific file
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// handle and then returned to the receiver.
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//
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// To use this class add 'FileDescriptor' as an argument in the IPDL protocol
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// and then pass a file descriptor from C++ to the Call/Send method. The
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// Answer/Recv method will receive a FileDescriptor& on which PlatformHandle()
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// can be called to return the platform file handle.
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class FileDescriptor
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{
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public:
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typedef base::ProcessId ProcessId;
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#ifdef XP_WIN
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typedef HANDLE PlatformHandleType;
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typedef HANDLE PickleType;
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#else
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typedef int PlatformHandleType;
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typedef base::FileDescriptor PickleType;
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#endif
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// This should only ever be created by IPDL.
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struct IPDLPrivate
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{};
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FileDescriptor();
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FileDescriptor(const FileDescriptor& aOther)
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: mHandleCreatedByOtherProcess(false),
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mHandleCreatedByOtherProcessWasUsed(false)
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{
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// Don't use operator= here because that will call
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// CloseCurrentProcessHandle() on this (uninitialized) object.
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Assign(aOther);
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}
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explicit FileDescriptor(PlatformHandleType aHandle);
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FileDescriptor(const IPDLPrivate&, const PickleType& aPickle)
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#ifdef XP_WIN
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: mHandle(aPickle)
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#else
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: mHandle(aPickle.fd)
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#endif
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, mHandleCreatedByOtherProcess(true)
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, mHandleCreatedByOtherProcessWasUsed(false)
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{ }
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~FileDescriptor()
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{
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CloseCurrentProcessHandle();
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}
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FileDescriptor&
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operator=(const FileDescriptor& aOther)
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{
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CloseCurrentProcessHandle();
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Assign(aOther);
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return *this;
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}
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// Performs platform-specific actions to duplicate mHandle in the other
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// process (e.g. dup() on POSIX, DuplicateHandle() on Windows). Returns a
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// pickled value that can be passed to the other process via IPC.
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PickleType
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ShareTo(const IPDLPrivate&, ProcessId aTargetPid) const;
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// Tests mHandle against a well-known invalid platform-specific file handle
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// (e.g. -1 on POSIX, INVALID_HANDLE_VALUE on Windows).
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bool
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IsValid() const
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{
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return IsValid(mHandle);
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}
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PlatformHandleType
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PlatformHandle() const
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{
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if (mHandleCreatedByOtherProcess) {
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mHandleCreatedByOtherProcessWasUsed = true;
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}
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return mHandle;
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}
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bool
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operator==(const FileDescriptor& aOther) const
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{
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return mHandle == aOther.mHandle;
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}
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private:
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void
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Assign(const FileDescriptor& aOther)
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{
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if (aOther.mHandleCreatedByOtherProcess) {
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mHandleCreatedByOtherProcess = true;
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mHandleCreatedByOtherProcessWasUsed =
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aOther.mHandleCreatedByOtherProcessWasUsed;
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mHandle = aOther.PlatformHandle();
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} else {
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DuplicateInCurrentProcess(aOther.PlatformHandle());
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mHandleCreatedByOtherProcess = false;
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mHandleCreatedByOtherProcessWasUsed = false;
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}
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}
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static bool
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IsValid(PlatformHandleType aHandle);
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void
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DuplicateInCurrentProcess(PlatformHandleType aHandle);
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void
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CloseCurrentProcessHandle();
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PlatformHandleType mHandle;
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// If this is true then this instance is created by IPDL to ferry a handle to
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// its eventual consumer and we never close the handle. If this is false then
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// we are a RAII wrapper around the handle and we close the handle on
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// destruction.
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bool mHandleCreatedByOtherProcess;
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// This is to ensure that we don't leak the handle (which is only possible
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// when we're in the receiving process).
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mutable DebugOnly<bool> mHandleCreatedByOtherProcessWasUsed;
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};
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} // namespace ipc
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} // namespace mozilla
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#endif // mozilla_ipc_FileDescriptor_h
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