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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_MESSAGE_LOOP_WATCHABLE_IO_MESSAGE_PUMP_POSIX_H_
#define BASE_MESSAGE_LOOP_WATCHABLE_IO_MESSAGE_PUMP_POSIX_H_
#include "base/location.h"
namespace base {
class WatchableIOMessagePumpPosix {
public:
// Used with WatchFileDescriptor to asynchronously monitor the I/O readiness
// of a file descriptor.
class FdWatcher {
public:
virtual void OnFileCanReadWithoutBlocking(int fd) = 0;
virtual void OnFileCanWriteWithoutBlocking(int fd) = 0;
protected:
virtual ~FdWatcher() = default;
};
class FdWatchControllerInterface {
public:
explicit FdWatchControllerInterface(const Location& from_here);
FdWatchControllerInterface(const FdWatchControllerInterface&) = delete;
FdWatchControllerInterface& operator=(const FdWatchControllerInterface&) =
delete;
// Subclasses must call StopWatchingFileDescriptor() in their destructor
// (this parent class cannot generically do it for them as it must usually
// be invoked before they destroy their state which happens before the
// parent destructor is invoked).
virtual ~FdWatchControllerInterface();
// NOTE: This method isn't called StopWatching() to avoid confusion with the
// win32 ObjectWatcher class. While this doesn't really need to be virtual
// as there's only one impl per platform and users don't use pointers to the
// base class. Having this interface forces implementers to share similar
// implementations (a problem in the past).
// Stop watching the FD, always safe to call. No-op if there's nothing to
// do.
virtual bool StopWatchingFileDescriptor() = 0;
const Location& created_from_location() const {
return created_from_location_;
}
private:
const Location created_from_location_;
};
enum Mode {
WATCH_READ = 1 << 0,
WATCH_WRITE = 1 << 1,
WATCH_READ_WRITE = WATCH_READ | WATCH_WRITE
};
// Every subclass of WatchableIOMessagePumpPosix must provide a
// WatchFileDescriptor() which has the following signature where
// |FdWatchController| must be the complete type based on
// FdWatchControllerInterface.
// Registers |delegate| with the current thread's message loop so that its
// methods are invoked when file descriptor |fd| becomes ready for reading or
// writing (or both) without blocking. |mode| selects ready for reading, for
// writing, or both. See "enum Mode" above. |controller| manages the
// lifetime of registrations. ("Registrations" are also ambiguously called
// "events" in many places, for instance in libevent.) It is an error to use
// the same |controller| for different file descriptors; however, the same
// controller can be reused to add registrations with a different |mode|. If
// |controller| is already attached to one or more registrations, the new
// registration is added onto those. If an error occurs while calling this
// method, any registration previously attached to |controller| is removed.
// Returns true on success. Must be called on the same thread the MessagePump
// is running on.
// bool WatchFileDescriptor(int fd,
// bool persistent,
// int mode,
// FdWatchController* controller,
// FdWatcher* delegate) = 0;
};
} // namespace base
#endif // BASE_MESSAGE_LOOP_WATCHABLE_IO_MESSAGE_PUMP_POSIX_H_
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