very, very simple WP with midi CC out

include/libremidi/backends/alsa_raw/config.hpp

@@ -0,0 +1,79 @@
+#pragma once
+#include <libremidi/config.hpp>
+
+#include <chrono>
+#include <functional>
+#include <optional>
+#include <span>
+#include <thread>
+
+#if __has_include(<poll.h>)
+  #include <poll.h>
+namespace libremidi
+{
+using poll_descriptors = pollfd;
+}
+#else
+namespace libremidi
+{
+struct poll_descriptors
+{
+  int fd;
+  short int events;
+  short int revents;
+};
+}
+#endif
+
+namespace libremidi
+{
+
+/**
+ * Used to determine how large sent messages will be chunked.
+ */
+struct LIBREMIDI_EXPORT chunking_parameters
+{
+  std::chrono::milliseconds interval{};
+  int32_t size{};
+
+  /**
+   * @brief Will be called by the chunking code to allow the API user to wait.
+   *
+   * By default just calls sleep.
+   * Arguments are: the time that must be waited, the bytes currently written.
+   * Return false if you want to abort the transfer, and true otherwise.
+   */
+  std::function<bool(std::chrono::microseconds, int64_t)> wait = chunking_parameters::default_wait;
+
+  static bool default_wait(std::chrono::microseconds time_to_wait, int64_t /*written_bytes*/)
+  {
+    std::this_thread::sleep_for(time_to_wait);
+    return true;
+  }
+};
+
+struct manual_poll_parameters
+{
+  std::span<poll_descriptors> fds;
+  std::function<int64_t(std::span<poll_descriptors> fds)> callback;
+};
+
+struct alsa_raw_input_configuration
+{
+  std::function<bool(const manual_poll_parameters&)> manual_poll;
+};
+
+struct alsa_raw_output_configuration
+{
+  /**
+   * For large messages, chunk their content and wait.
+   * Setting a null optional will disable chunking.
+   */
+  std::optional<chunking_parameters> chunking;
+};
+
+struct alsa_raw_observer_configuration
+{
+  std::chrono::milliseconds poll_period{100};
+};
+}