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// Copyright (c) 2012 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.
// TODO(jamiewalch): Add unit tests for this.
#include "remoting/host/posix/signal_handler.h"
#include <errno.h>
#include <signal.h>
#include <list>
#include <utility>
#include "base/compiler_specific.h"
#include "base/eintr_wrapper.h"
#include "base/message_loop.h"
#include "base/message_pump_libevent.h"
#include "base/threading/platform_thread.h"
namespace remoting {
namespace {
class SignalListener : public base::MessagePumpLibevent::Watcher {
public:
SignalListener();
void AddSignalHandler(int signal, const SignalHandler& handler);
virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE {}
// WatchFileDescriptor needs a controller through which the operation can be
// canceled. We don't use it, but this is as good a place as any to store it.
base::MessagePumpLibevent::FileDescriptorWatcher controller;
private:
typedef std::pair<int, SignalHandler> SignalAndHandler;
typedef std::list<SignalAndHandler> SignalHandlers;
SignalHandlers signal_handlers_;
};
SignalListener::SignalListener() {
}
void SignalListener::AddSignalHandler(int signal,
const SignalHandler& handler) {
signal_handlers_.push_back(SignalAndHandler(signal, handler));
}
void SignalListener::OnFileCanReadWithoutBlocking(int fd) {
char buffer;
int result = HANDLE_EINTR(read(fd, &buffer, sizeof(buffer)));
if (result > 0) {
for (SignalHandlers::const_iterator i = signal_handlers_.begin();
i != signal_handlers_.end();
++i) {
if (i->first == buffer) {
i->second.Run(i->first);
}
}
}
}
SignalListener* g_signal_listener = NULL;
int g_write_fd = 0;
void GlobalSignalHandler(int signal) {
char byte = signal;
int r ALLOW_UNUSED = write(g_write_fd, &byte, 1);
}
} // namespace
// RegisterSignalHandler registers a signal handler that writes a byte to a
// pipe each time a signal is received. The read end of the pipe is registered
// with the current MessageLoop (which must be of type IO); whenever the pipe
// is readable, it invokes the specified callback.
//
// This arrangement is required because the set of system APIs that are safe to
// call from a signal handler is very limited (but does include write).
bool RegisterSignalHandler(int signal_number, const SignalHandler& handler) {
CHECK(signal_number < 256); // Don't want to worry about multi-byte writes.
if (!g_signal_listener) {
g_signal_listener = new SignalListener();
}
if (!g_write_fd) {
int pipe_fd[2];
int result = pipe(pipe_fd);
if (result < 0) {
LOG(ERROR) << "Could not create signal pipe: " << errno;
return false;
}
MessageLoopForIO* message_loop = MessageLoopForIO::current();
result = message_loop->WatchFileDescriptor(
pipe_fd[0], true, MessageLoopForIO::WATCH_READ,
&g_signal_listener->controller, g_signal_listener);
if (!result) {
LOG(ERROR) << "Failed to create signal detector task.";
close(pipe_fd[0]);
close(pipe_fd[1]);
return false;
}
g_write_fd = pipe_fd[1];
}
if (signal(signal_number, GlobalSignalHandler) == SIG_ERR) {
LOG(ERROR) << "signal() failed: " << errno;
return false;
}
g_signal_listener->AddSignalHandler(signal_number, handler);
return true;
}
} // namespace remoting
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