1 files changed, 134 insertions, 0 deletions
diff --git a/PCM.h b/PCM.h
new file mode 100644
index 0000000..c9d7f7f
--- /dev/null
+++ b/PCM.h
@@ -0,0 +1,134 @@
+#pragma once
+
+#include "ClickStream.h"
+
+#include "config.h"
+
+#include <alsa/asoundlib.h>
+
+#include <iostream>
+#include <string>
+
+using namespace std::string_literals;
+
+class PCM
+{
+public:
+  PCM(ClickStream& stream): m_stream(stream)
+  {
+    // non-blocking
+    if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK)) < 0) {
+        printf("Playback open error: %s\n", snd_strerror(err));
+        exit(EXIT_FAILURE);
+    }
+    if ((err = snd_pcm_set_params(handle,
+                      SND_PCM_FORMAT_S16_LE,
+                      SND_PCM_ACCESS_RW_INTERLEAVED,
+                      1,
+                      f_sample,
+                      1,
+                      100000)) < 0) {   // latency in us
+        printf("Playback open error: %s\n", snd_strerror(err));
+        exit(EXIT_FAILURE);
+    }
+
+    m_stream.generate();
+
+    npfd = snd_pcm_poll_descriptors_count(handle);
+    if (npfd < 0) {
+      throw std::runtime_error("snd_pcm_poll_descriptors_count() failed");
+    }
+    pfd = (struct pollfd *)malloc(npfd * sizeof(struct pollfd));
+    if (pfd == nullptr) {
+      throw std::runtime_error("alloca() error for PCM");
+    }
+    if (0 > snd_pcm_poll_descriptors(handle, pfd, npfd))
+    {
+      throw std::runtime_error("snd_pcm_poll_descriptors() failure");
+    }
+
+    if (0 > snd_pcm_start(handle))
+    {
+     throw std::runtime_error("PCM could not be started");
+    }
+
+    if (npfd != 1) {
+      std::cout << "Warning: " << std::to_string(npfd) << " poll fds for pcm" << std::endl;
+    }
+  }
+
+  ~PCM()
+  {
+    // pass the remaining samples, otherwise they're dropped in close
+    err = snd_pcm_drain(handle);
+    if (err < 0)
+        printf("snd_pcm_drain failed: %s\n", snd_strerror(err));
+    snd_pcm_close(handle);
+
+    free(pfd);
+  }
+
+  int fd()
+  {
+    return pfd->fd;
+  }
+
+  // write from buffer to ALSA PCM
+  void write()
+  {
+        snd_pcm_sframes_t written = snd_pcm_writei(handle, m_stream.get_buffer(), nframes);
+        if (written < 0) {
+            if (written == -EPIPE) {
+              std::cout << "Warning: PCM underrun" << std::endl;
+            }
+            std::cout << "Recovering." << std::endl;
+            written = snd_pcm_recover(handle, written, 0);
+        }
+        if (written < 0) {
+            throw std::runtime_error("snd_pcm_writei failed: "s + snd_strerror(written));
+        }
+
+        if (written != nframes) {
+          std::cout << "Warning: written " << std::to_string(written) << " frames instead of "<< std::to_string(nframes) << std::endl;
+        }
+
+        m_stream.generate();
+  }
+
+  bool wait_for_event()
+  {
+    int result = poll(pfd, npfd, 10000);
+    if (result > 0)
+    {
+      // event
+      return true;
+    }
+    else if (result == 0) {
+      // timeout
+      return false;
+    } else {
+      throw std::runtime_error("Poll unsuccessful");
+    }
+  }
+
+  bool write_available()
+  {
+    snd_pcm_sframes_t result = snd_pcm_avail(handle);
+    if (0 > result) {
+      std::cerr << "Error: snd_pcm_avail()" << std::endl;
+      //throw std::runtime_error("snd_pcm_avail()");
+    }
+
+    return result >= nframes;
+  }
+
+private:
+  int err;
+  snd_pcm_t *handle;
+
+  int npfd;
+  struct pollfd* pfd;
+
+  ClickStream& m_stream;
+};
+