Add Pipe-to-command export backend

A first step towards allowing external encoders without intermediate
temporary file.

diff --git a/libs/audiographer/audiographer/general/cmdpipe_writer.h b/libs/audiographer/audiographer/general/cmdpipe_writer.h
new file mode 100644 (file)
index 0000000..74dc604
--- /dev/null
+++ b/libs/audiographer/audiographer/general/cmdpipe_writer.h
@@ -0,0 +1,87 @@
+#ifndef AUDIOGRAPHER_CMDPIPE_WRITER_H
+#define AUDIOGRAPHER_CMDPIPE_WRITER_H
+
+#include <string>
+
+#include <boost/format.hpp>
+
+#include "audiographer/flag_debuggable.h"
+#include "audiographer/sink.h"
+#include "audiographer/types.h"
+
+#include "pbd/signals.h"
+#include "pbd/system_exec.h"
+
+namespace AudioGrapher
+{
+
+/** Writer for audio files using libsndfile.
+  * Only short, int and float are valid template parameters
+  */
+template <typename T = DefaultSampleType>
+class CmdPipeWriter
+  : public Sink<T>
+  , public Throwing<>
+  , public FlagDebuggable<>
+{
+public:
+       CmdPipeWriter (PBD::SystemExec* proc, std::string const& path)
+               : samples_written (0)
+               , _proc (proc)
+               , _path (path)
+       {
+               add_supported_flag (ProcessContext<T>::EndOfInput);
+       }
+
+       virtual ~CmdPipeWriter () {
+               delete _proc;
+       }
+
+       samplecnt_t get_samples_written() const { return samples_written; }
+       void       reset_samples_written_count() { samples_written = 0; }
+
+       void close (void)
+       {
+               _proc->terminate ();
+       }
+
+       virtual void process (ProcessContext<T> const & c)
+       {
+               check_flags (*this, c);
+
+               if (!_proc || !_proc->is_running()) {
+                       throw Exception (*this, boost::str (boost::format
+                                               ("Target encoder process is not running")));
+               }
+
+               const size_t bytes_per_sample = sizeof (T);
+               samplecnt_t const written = _proc->write_to_stdin ((const void*) c.data(), c.samples() * bytes_per_sample) / bytes_per_sample;
+               samples_written += written;
+
+               if (throw_level (ThrowProcess) && written != c.samples()) {
+                       throw Exception (*this, boost::str (boost::format
+                                               ("Could not write data to output file")));
+               }
+
+               if (c.has_flag(ProcessContext<T>::EndOfInput)) {
+                       _proc->close_stdin ();
+                       FileWritten (_path);
+               }
+       }
+
+       using Sink<T>::process;
+
+       PBD::Signal1<void, std::string> FileWritten;
+
+private:
+       CmdPipeWriter (CmdPipeWriter const & other) {}
+
+       samplecnt_t samples_written;
+       PBD::SystemExec* _proc;
+       std::string _path;
+};
+
+} // namespace
+
+#endif
+