pavmon, a simple tool to monitor the volume of a PulseAudio sinkHEADmain

1 files changed, 184 insertions, 0 deletions

diff --git a/pavmon.cc b/pavmon.cc
new file mode 100644
index 0000000..df639e4
--- /dev/null
+++ b/pavmon.cc
@@ -0,0 +1,184 @@
+// Copyright 2022 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include <getopt.h>
+#include <pulse/def.h>
+#include <pulse/error.h>
+#include <pulse/introspect.h>
+#include <pulse/volume.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <iomanip>
+#include <ios>
+#include <iostream>
+#include <locale>
+#include <string>
+#include <string_view>
+
+#include "pulse.h"
+
+namespace {
+
+constexpr std::string_view kShortUsage = "Usage: pavmon SINK_NAME\n";
+
+constexpr std::string_view kHelp = R"(
+Monitor the volume level of a PulseAudio sink, printing a new line each time it
+changes.
+
+Options:
+      --help                  display this help and exit
+      --version               display version information and exit
+)";
+
+constexpr std::string_view kAskForHelp =
+    "Try \"pavmon --help\" for more information.\n";
+
+constexpr std::string_view kVersionInfo = R"(pavmon 1.0.0
+Copyright 2022 Benjamin Barenblat
+Licensed under the Apache License, Version 2.0
+)";
+
+enum {
+  kHelpLongOption = 128,
+  kVersionLongOption,
+};
+
+void GetAndPrintVolume(const std::string& sink_name, pulse::PollMainLoop& loop,
+                       pulse::Context& ctx) noexcept {
+  ctx.GetSinkInfo(
+      sink_name.c_str(),
+      [&]() noexcept {
+        std::clog << "pavmon: failed to get volume" << std::endl;
+        loop.Quit(1);
+      },
+      [&](const pa_sink_info& info) noexcept {
+        if (info.mute) {
+          std::cout << "muted (";
+        }
+        std::cout << std::fixed << std::setprecision(1)
+                  << pa_sw_volume_to_dB(pa_cvolume_avg(&info.volume)) << " dB";
+        if (info.mute) {
+          std::cout << ')';
+        }
+        std::cout << std::endl;
+      });
+}
+
+void SubscribeToEvents(const std::string& sink_name, pulse::PollMainLoop& loop,
+                       pulse::Context& ctx) noexcept {
+  ctx.Subscribe(
+      PA_SUBSCRIPTION_MASK_SINK,
+      [&]() noexcept {
+        std::clog << "pavmon: failed to subscribe to events" << std::endl;
+        loop.Quit(1);
+      },
+      [&](pa_subscription_event_type_t) noexcept {
+        GetAndPrintVolume(sink_name, loop, ctx);
+      });
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+  std::locale loc("");
+  std::locale::global(loc);
+  std::cin.imbue(loc);
+  std::cout.imbue(loc);
+  std::cerr.imbue(loc);
+  std::clog.imbue(loc);
+  std::wcin.imbue(loc);
+  std::wcout.imbue(loc);
+  std::wcerr.imbue(loc);
+  std::wclog.imbue(loc);
+
+  std::ios_base::sync_with_stdio(false);
+
+  static option long_options[] = {
+      {"help", no_argument, nullptr, kHelpLongOption},
+      {"version", no_argument, nullptr, kVersionLongOption},
+      {nullptr, 0, nullptr, 0},
+  };
+  while (true) {
+    int c = getopt_long(argc, argv, "", long_options, /*longindex=*/nullptr);
+    if (c == -1) {
+      break;
+    }
+    switch (c) {
+      case kHelpLongOption:
+        std::cout << kShortUsage << kHelp;
+        return 0;
+      case kVersionLongOption:
+        std::cout << kVersionInfo;
+        return 0;
+      case '?':
+        std::clog << kAskForHelp;
+        return 1;
+      default:
+        std::clog << "Internal error; please report.\n";
+        return 1;
+    }
+  }
+  if (optind != argc - 1) {
+    std::clog << kShortUsage << kAskForHelp;
+    return 1;
+  }
+
+  std::string sink_name = argv[1];
+
+  pulse::PollMainLoop loop;
+
+  loop.HandleSignals();
+  auto quit_on_signal = [&]() noexcept { loop.Quit(0); };
+  pulse::SignalEventSource quit_on_sigterm(SIGTERM, quit_on_signal);
+  pulse::SignalEventSource quit_on_sigint(SIGINT, quit_on_signal);
+
+  pulse::PropertyList proplist;
+  proplist.Set(PA_PROP_APPLICATION_NAME, "PulseAudio volume monitor");
+  proplist.Set(PA_PROP_APPLICATION_ID, "pavmon");
+  proplist.Set(PA_PROP_APPLICATION_VERSION, "1.0.0");
+  proplist.Set(PA_PROP_APPLICATION_PROCESS_ID, std::to_string(getpid()));
+  if (const char* user = getlogin(); user != nullptr) {
+    proplist.Set(PA_PROP_APPLICATION_PROCESS_USER, user);
+  }
+  // TODO(bbarenblat@gmail.com): More of these?
+
+  pulse::Context ctx("PulseAudio volume meter", proplist, loop);
+  ctx.Connect(PA_CONTEXT_NOFAIL, [&](pa_context_state_t state) noexcept {
+    switch (state) {
+      case PA_CONTEXT_UNCONNECTED:
+      case PA_CONTEXT_CONNECTING:
+      case PA_CONTEXT_AUTHORIZING:
+      case PA_CONTEXT_SETTING_NAME:
+        break;
+
+      case PA_CONTEXT_READY:
+        GetAndPrintVolume(sink_name, loop, ctx);
+        SubscribeToEvents(sink_name, loop, ctx);
+        break;
+
+      case PA_CONTEXT_TERMINATED:
+        loop.Quit(0);
+        break;
+
+      case PA_CONTEXT_FAILED:
+      default:
+        std::clog << "pavmon: failed to connect to PulseAudio" << std::endl;
+        loop.Quit(1);
+        break;
+    }
+  });
+
+  return loop.Run();
+}