--- /dev/null
+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "channel.hh"
+
+namespace pdns
+{
+namespace channel
+{
+
+ Notifier::Notifier(FDWrapper&& fd) :
+ d_fd(std::move(fd))
+ {
+ }
+
+ bool Notifier::notify() const
+ {
+ char data = 'a';
+ auto sent = write(d_fd.getHandle(), &data, sizeof(data));
+ if (sent != sizeof(data)) {
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ return false;
+ }
+ else {
+ throw std::runtime_error("Unable to write to channel notifier pipe: " + stringerror());
+ }
+ }
+ return true;
+ }
+
+ Waiter::Waiter(FDWrapper&& fd) :
+ d_fd(std::move(fd))
+ {
+ }
+
+ void Waiter::clear() const
+ {
+ ssize_t got;
+ do {
+ char data;
+ got = read(d_fd.getHandle(), &data, sizeof(data));
+ if (got == 0) {
+ throw std::runtime_error("EOF while clearing channel notifier pipe");
+ }
+ else if (got == -1) {
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ break;
+ }
+ throw std::runtime_error("Error while clearing channel notifier pipe: " + stringerror());
+ }
+ } while (got);
+ }
+
+ int Waiter::getDescriptor() const
+ {
+ return d_fd.getHandle();
+ }
+
+ std::pair<Notifier, Waiter> createNotificationQueue(bool nonBlocking, size_t pipeBufferSize)
+ {
+ int fds[2] = { -1, -1};
+ if (pipe(fds) < 0) {
+ throw std::runtime_error("Error creating notification channel pipe: " + stringerror());
+ }
+
+ if (nonBlocking && !setNonBlocking(fds[0])) {
+ int err = errno;
+ close(fds[0]);
+ close(fds[1]);
+ throw std::runtime_error("Error making notification channel pipe non-blocking: " + stringerror(err));
+ }
+
+ if (nonBlocking && !setNonBlocking(fds[1])) {
+ int err = errno;
+ close(fds[0]);
+ close(fds[1]);
+ throw std::runtime_error("Error making notification channel pipe non-blocking: " + stringerror(err));
+ }
+
+ if (pipeBufferSize > 0 && getPipeBufferSize(fds[0]) < pipeBufferSize) {
+ setPipeBufferSize(fds[0], pipeBufferSize);
+ }
+
+ FDWrapper sender(fds[1]);
+ FDWrapper receiver(fds[0]);
+
+ return std::pair(Notifier(std::move(sender)), Waiter(std::move(receiver)));
+ }
+}
+}
--- /dev/null
+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#pragma once
+#include <memory>
+#include <optional>
+
+#include "misc.hh"
+
+namespace pdns
+{
+namespace channel
+{
+ /**
+ * The sender's end of a channel used to pass objects between threads.
+ *
+ * A sender can be used by several threads in a safe way.
+ */
+ template <typename T>
+ class Sender
+ {
+ public:
+ Sender()
+ {
+ }
+ Sender(FDWrapper&& fd) :
+ d_fd(std::move(fd))
+ {
+ }
+ Sender(const Sender&) = delete;
+ Sender& operator=(const Sender&) = delete;
+ Sender(Sender&&) = default;
+ Sender& operator=(Sender&&) = default;
+ /**
+ * \brief Try to send the supplied object to the other end of that channel. Might block if the channel was created in blocking mode.
+ *
+ * \return True if the object was properly sent, False if the channel is full.
+ *
+ * \throw runtime_error if the channel is broken, for example if the other end has been closed.
+ */
+ bool send(std::unique_ptr<T>&&) const;
+
+ private:
+ FDWrapper d_fd;
+ };
+
+ /**
+ * The receiver's end of a channel used to pass objects between threads.
+ *
+ * A receiver can be used by several threads in a safe way, but in that case spurious wake up might happen.
+ */
+ template <typename T>
+ class Receiver
+ {
+ public:
+ Receiver()
+ {
+ }
+ Receiver(FDWrapper&& fd) :
+ d_fd(std::move(fd))
+ {
+ }
+ Receiver(const Receiver&) = delete;
+ Receiver& operator=(const Receiver&) = delete;
+ Receiver(Receiver&&) = default;
+ Receiver& operator=(Receiver&&) = default;
+ /**
+ * \brief Try to read an object sent by the other end of that channel. Might block if the channel was created in blocking mode.
+ *
+ * \return An object if one was available, and std::nullopt otherwise.
+ *
+ * \throw runtime_error if the channel is broken, for example if the other end has been closed.
+ */
+ std::optional<std::unique_ptr<T>> receive() const;
+
+ /**
+ * \brief Get a descriptor that can be used with an I/O multiplexer to wait for an object to become available.
+ *
+ * \return A valid descriptor or -1 if the Receiver was not properly initialized.
+ */
+ int getDescriptor() const
+ {
+ return d_fd.getHandle();
+ }
+
+ private:
+ FDWrapper d_fd;
+ };
+
+ /**
+ * \brief Create a channel to pass objects between threads, accepting multiple senders and receivers.
+ *
+ * \return A pair of Sender and Receiver objects.
+ *
+ * \throw runtime_error if the channel creation failed.
+ */
+ template <typename T>
+ std::pair<Sender<T>, Receiver<T>> createObjectQueue(bool nonBlocking = true, size_t pipeBufferSize = 0);
+
+ /**
+ * The notifier's end of a channel used to communicate between threads.
+ *
+ * A notifier can be used by several threads in a safe way.
+ */
+ class Notifier
+ {
+ public:
+ Notifier()
+ {
+ }
+ Notifier(FDWrapper&&);
+ Notifier(const Notifier&) = delete;
+ Notifier& operator=(const Notifier&) = delete;
+ Notifier(Notifier&&) = default;
+ Notifier& operator=(Notifier&&) = default;
+
+ /**
+ * \brief Queue a notification to wake up the other end of the channel.
+ *
+ * \return True if the notification was properly sent, False if the channel is full.
+ *
+ * \throw runtime_error if the channel is broken, for example if the other end has been closed.
+ */
+ bool notify() const;
+
+ private:
+ FDWrapper d_fd;
+ };
+
+ /**
+ * The waiter's end of a channel used to communicate between threads.
+ *
+ * A waiter can be used by several threads in a safe way, but in that case spurious wake up might happen.
+ */
+ class Waiter
+ {
+ public:
+ Waiter(FDWrapper&&);
+ Waiter(const Waiter&) = delete;
+ Waiter& operator=(const Waiter&) = delete;
+ Waiter(Waiter&&) = default;
+ Waiter& operator=(Waiter&&) = default;
+
+ /**
+ * \brief Clear all notifications queued on that channel, if any.
+ */
+ void clear() const;
+ /**
+ * \brief Get a descriptor that can be used with an I/O multiplexer to wait for a notification to arrive.
+ *
+ * \return A valid descriptor or -1 if the Waiter was not properly initialized.
+ */
+ int getDescriptor() const;
+
+ private:
+ FDWrapper d_fd;
+ };
+
+ /**
+ * \brief Create a channel to notify one thread from another one, accepting multiple senders and receivers.
+ *
+ * \return A pair of Notifier and Sender objects.
+ *
+ * \throw runtime_error if the channel creation failed.
+ */
+ std::pair<Notifier, Waiter> createNotificationQueue(bool nonBlocking = true, size_t pipeBufferSize = 0);
+
+ template <typename T>
+ bool Sender<T>::send(std::unique_ptr<T>&& object) const
+ {
+ auto ptr = object.release();
+ static_assert(sizeof(ptr) <= PIPE_BUF, "Writes up to PIPE_BUF are guaranted not to interleaved and to either fully succeed or fail");
+ ssize_t sent = write(d_fd.getHandle(), &ptr, sizeof(ptr));
+
+ if (sent != sizeof(ptr)) {
+ if (errno == EAGAIN || errno == EWOULDBLOCK) {
+ return false;
+ }
+ else {
+ throw std::runtime_error("Unable to write to channel:" + stringerror());
+ }
+ delete ptr;
+ }
+
+ return true;
+ }
+
+ template <typename T>
+ std::optional<std::unique_ptr<T>> Receiver<T>::receive() const
+ {
+ std::optional<std::unique_ptr<T>> result;
+ T* obj{nullptr};
+ ssize_t got = read(d_fd.getHandle(), &obj, sizeof(obj));
+ if (got == sizeof(obj)) {
+ return std::unique_ptr<T>(obj);
+ }
+ else if (got == 0) {
+ throw std::runtime_error("EOF while reading from Channel receiver");
+ }
+ else if (got == -1) {
+ if (errno == EAGAIN || errno == EINTR) {
+ return result;
+ }
+ throw std::runtime_error("Error while reading from Channel receiver: " + stringerror());
+ }
+ else {
+ throw std::runtime_error("Partial read from Channel receiver");
+ }
+ }
+
+ template <typename T>
+ std::pair<Sender<T>, Receiver<T>> createObjectQueue(bool nonBlocking, size_t pipeBufferSize)
+ {
+ int fds[2] = { -1, -1};
+ if (pipe(fds) < 0) {
+ throw std::runtime_error("Error creating channel pipe: " + stringerror());
+ }
+
+ if (nonBlocking && !setNonBlocking(fds[0])) {
+ int err = errno;
+ close(fds[0]);
+ close(fds[1]);
+ throw std::runtime_error("Error making channel pipe non-blocking: " + stringerror(err));
+ }
+
+ if (nonBlocking && !setNonBlocking(fds[1])) {
+ int err = errno;
+ close(fds[0]);
+ close(fds[1]);
+ throw std::runtime_error("Error making channel pipe non-blocking: " + stringerror(err));
+ }
+
+ if (pipeBufferSize > 0 && getPipeBufferSize(fds[0]) < pipeBufferSize) {
+ setPipeBufferSize(fds[0], pipeBufferSize);
+ }
+
+ FDWrapper sender(fds[1]);
+ FDWrapper receiver(fds[0]);
+
+ return std::pair(Sender<T>(std::move(sender)), Receiver<T>(std::move(receiver)));
+ }
+}
+}
projects / thirdparty / pdns.git / commitdiff
