Added support for libsndfile (sound input)

sound/sources/libsndfile.cpp

@@ -0,0 +1,50 @@
+#include "libsndfile.hpp"
+
+#include "../../tools/str_exception.hpp"
+#include <sndfile.h>
+
+using namespace Mangle::Stream;
+
+static void fail(const std::string &msg)
+{ throw str_exception("Mangle::libsndfile: " + msg); }
+
+using namespace Mangle::Sound;
+
+void SndFileSource::getInfo(int32_t *_rate, int32_t *_channels, int32_t *_bits)
+{
+  *_rate = rate;
+  *_channels = channels;
+  *_bits = bits;
+}
+
+size_t SndFileSource::readSamples(void *data, size_t length)
+{
+  // Read frames. We count channels as part of the frame. Even though
+  // libsndfile does not, since it still requires the number of frames
+  // read to be a multiple of channels.
+  return channels*sf_read_short((SNDFILE*)handle, (short*)data, length*channels);
+}
+
+SndFileSource::SndFileSource(const std::string &file)
+{
+  SF_INFO info;
+  info.format = 0;
+  handle = sf_open(file.c_str(), SFM_READ, &info);
+  if(handle == NULL)
+    fail("Failed to open " + file);
+
+  // I THINK that using sf_read_short forces the library to convert to
+  // 16 bits no matter what, but the libsndfile docs aren't exactly
+  // very clear on this point.
+  channels = info.channels;
+  rate = info.samplerate;
+  bits = 16;
+
+  // 16 bits per sample times number of channels
+  setup(2*channels);
+}
+
+SndFileSource::~SndFileSource()
+{
+  sf_close((SNDFILE*)handle);
+}