1 files changed, 115 insertions, 0 deletions
diff --git a/channel.cc b/channel.cc
new file mode 100644
index 0000000..d6a3039
--- /dev/null
+++ b/channel.cc
@@ -0,0 +1,115 @@
+/*
+ * 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::channel
+{
+
+Notifier::Notifier(FDWrapper&& descriptor) :
+  d_fd(std::move(descriptor))
+{
+}
+
+bool Notifier::notify() const
+{
+  char data = 'a';
+  while (true) {
+    auto sent = write(d_fd.getHandle(), &data, sizeof(data));
+    if (sent == 0) {
+      throw std::runtime_error("Unable to write to channel notifier pipe: remote end has been closed");
+    }
+    if (sent != sizeof(data)) {
+      if (errno == EINTR) {
+        continue;
+      }
+      if (errno == EAGAIN || errno == EWOULDBLOCK) {
+        return false;
+      }
+      throw std::runtime_error("Unable to write to channel notifier pipe: " + stringerror());
+    }
+    return true;
+  }
+}
+
+Waiter::Waiter(FDWrapper&& descriptor, bool throwOnEOF) :
+  d_fd(std::move(descriptor)), d_throwOnEOF(throwOnEOF)
+{
+}
+
+void Waiter::clear()
+{
+  ssize_t got{0};
+  do {
+    char data{0};
+    got = read(d_fd.getHandle(), &data, sizeof(data));
+    if (got == 0) {
+      d_closed = true;
+      if (!d_throwOnEOF) {
+        return;
+      }
+      throw std::runtime_error("EOF while clearing channel notifier pipe");
+    }
+    if (got == -1) {
+      if (errno == EINTR) {
+        continue;
+      }
+      if (errno == EAGAIN || errno == EWOULDBLOCK) {
+        break;
+      }
+      throw std::runtime_error("Error while clearing channel notifier pipe: " + stringerror());
+    }
+  } while (got > 0);
+}
+
+int Waiter::getDescriptor() const
+{
+  return d_fd.getHandle();
+}
+
+std::pair<Notifier, Waiter> createNotificationQueue(bool nonBlocking, size_t pipeBufferSize, bool throwOnEOF)
+{
+  std::array<int, 2> fds = {-1, -1};
+  if (pipe(fds.data()) < 0) {
+    throw std::runtime_error("Error creating notification channel pipe: " + stringerror());
+  }
+
+  FDWrapper sender(fds[1]);
+  FDWrapper receiver(fds[0]);
+
+  if (nonBlocking && !setNonBlocking(receiver.getHandle())) {
+    int err = errno;
+    throw std::runtime_error("Error making notification channel pipe non-blocking: " + stringerror(err));
+  }
+
+  if (nonBlocking && !setNonBlocking(sender.getHandle())) {
+    int err = errno;
+    throw std::runtime_error("Error making notification channel pipe non-blocking: " + stringerror(err));
+  }
+
+  if (pipeBufferSize > 0 && getPipeBufferSize(receiver.getHandle()) < pipeBufferSize) {
+    setPipeBufferSize(receiver.getHandle(), pipeBufferSize);
+  }
+
+  return {Notifier(std::move(sender)), Waiter(std::move(receiver), throwOnEOF)};
+}
+}