Added mpg123 sound source

sound/sources/mpg123_source.cpp

@@ -0,0 +1,121 @@
+#include "mpg123_source.hpp"
+
+#include "../../tools/str_exception.hpp"
+
+#include <mpg123.h>
+
+using namespace Mangle::Stream;
+
+/*
+  TODOs:
+
+  - mpg123 impressively enough supports custom stream reading. Which
+    means we could (and SHOULD!) support reading from Mangle::Streams
+    as well. But I'll save it til I need it.
+
+    An alternative way to do this is through feeding (which they also
+    support), but that's more messy.
+
+  - the library also supports output, via various other sources,
+    including ALSO, OSS, PortAudio, PulseAudio and SDL. Using this
+    library as a pure output library (if that is possible) would be a
+    nice shortcut over using those libraries - OTOH it's another
+    dependency. But it also means we could scavenge the mpg123 source
+    for these parts if we want them.
+
+  - we could implement seek(), tell() and size(), but they aren't
+    really necessary. Further more, since the returned size is only a
+    guess, it is not safe to rely on it.
+ */
+
+static void fail(const std::string &msg)
+{ throw str_exception("Mangle::Mpg123 exception: " + msg); }
+
+static void checkError(int err, void *mh = NULL)
+{
+  if(err != MPG123_OK)
+    {
+      std::string msg;
+      if(mh) msg = mpg123_strerror((mpg123_handle*)mh);
+      else msg = mpg123_plain_strerror(err);
+      fail(msg);
+    }
+}
+
+using namespace Mangle::Sound;
+
+void Mpg123Source::getInfo(int32_t *pRate, int32_t *pChannels, int32_t *pBits)
+{
+  // Use the values we found in the constructor
+  *pRate = rate;
+  *pChannels = channels;
+  *pBits = bits;
+}
+
+size_t Mpg123Source::read(void *data, size_t length)
+{
+  size_t done;
+  // This is extraordinarily nice. I like this library.
+  int err = mpg123_read((mpg123_handle*)mh, (unsigned char*)data, length, &done);
+  assert(done <= length);
+  if(err == MPG123_DONE)
+    isEof = true;
+  else
+    checkError(err, mh);
+  return done;
+}
+
+Mpg123Loader::Mpg123Loader(bool setup)
+{
+  // Do as we're told
+  if(setup)
+    {
+      int err = mpg123_init();
+      checkError(err);
+    }
+  didSetup = setup;
+}
+
+Mpg123Loader::~Mpg123Loader()
+{
+  // Deinitialize the library on exit
+  if(didSetup)
+    mpg123_exit();
+}
+
+Mpg123Source::Mpg123Source(const std::string &file)
+{
+  int err;
+
+  // Create a new handle
+  mh = mpg123_new(NULL, &err);
+  if(mh == NULL)
+    checkError(err, mh);
+
+  mpg123_handle *mhh = (mpg123_handle*)mh;
+
+  // Open the file
+  err = mpg123_open(mhh, file.c_str());
+  checkError(err, mh);
+
+  // Get the format
+  int encoding;
+  err = mpg123_getformat(mhh, &rate, &channels, &encoding);
+  checkError(err, mh);
+  if(encoding != MPG123_ENC_SIGNED_16)
+    fail("Bad encoding");
+
+  // This is the only bit size we support.
+  bits = 16;
+
+  // Ensure the output format does not change. (The tutorial on the
+  // mpg123 site did this, I assume it's kosher.)
+  mpg123_format_none(mhh);
+  mpg123_format(mhh,rate,channels,encoding);
+}
+
+Mpg123Source::~Mpg123Source()
+{
+  mpg123_close((mpg123_handle*)mh);
+  mpg123_delete((mpg123_handle*)mh);
+}