From 227da1e7a20432e056e7ab42444cb56f197c53d6 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 24 Jun 2018 17:43:58 +0300
Subject: [PATCH] Add utility functions for manipulating formats

---
 source/format.cpp     | 59 +++++++++++++++++++++++++++++++++++++++++++
 source/format.h       |  6 +++++
 source/mp3decoder.cpp |  4 +--
 source/oggdecoder.cpp | 10 ++------
 4 files changed, 69 insertions(+), 10 deletions(-)
 create mode 100644 source/format.cpp

diff --git a/source/format.cpp b/source/format.cpp
new file mode 100644
index 0000000..1cb5b23
--- /dev/null
+++ b/source/format.cpp
@@ -0,0 +1,59 @@
+#include <stdexcept>
+#include "format.h"
+
+using namespace std;
+
+namespace Msp {
+namespace AL {
+
+Format create_format(unsigned sample_size, unsigned n_channels)
+{
+	if(n_channels==1)
+	{
+		if(sample_size==1)
+			return MONO8;
+		else if(sample_size==2)
+			return MONO16;
+	}
+	else if(n_channels==2)
+	{
+		if(sample_size==1)
+			return STEREO8;
+		else if(sample_size==2)
+			return STEREO16;
+	}
+
+	throw invalid_argument("create_format");
+}
+
+unsigned get_sample_size(Format fmt)
+{
+	switch(fmt)
+	{
+	case MONO8:
+	case STEREO8: return 1;
+	case MONO16:
+	case STEREO16: return 2;
+	default: throw invalid_argument("get_sample_size");
+	}
+}
+
+unsigned get_n_channels(Format fmt)
+{
+	switch(fmt)
+	{
+	case MONO8:
+	case MONO16: return 1;
+	case STEREO8:
+	case STEREO16: return 2;
+	default: throw invalid_argument("get_n_channels");
+	}
+}
+
+unsigned get_unit_size(Format fmt)
+{
+	return get_sample_size(fmt)*get_n_channels(fmt);
+}
+
+} // namespace AL
+} // namespace Msp
diff --git a/source/format.h b/source/format.h
index ed6a144..4895377 100644
--- a/source/format.h
+++ b/source/format.h
@@ -14,6 +14,12 @@ enum Format
 	STEREO16 = AL_FORMAT_STEREO16
 };
 
+Format create_format(unsigned, unsigned);
+
+unsigned get_sample_size(Format);
+unsigned get_n_channels(Format);
+unsigned get_unit_size(Format);
+
 } // namespace AL
 } // namespace Msp
 
diff --git a/source/mp3decoder.cpp b/source/mp3decoder.cpp
index 8ddad47..00fc918 100644
--- a/source/mp3decoder.cpp
+++ b/source/mp3decoder.cpp
@@ -55,7 +55,7 @@ Mp3Decoder::Mp3Decoder(IO::Seekable &io):
 	try
 	{
 		decode_frame();
-		format = (priv->frame.header.mode==MAD_MODE_SINGLE_CHANNEL ? MONO16 : STEREO16);
+		format = create_format(2, MAD_NCHANNELS(&priv->frame.header));
 		freq = priv->frame.header.samplerate;
 	}
 	catch(...)
@@ -92,7 +92,7 @@ void Mp3Decoder::rewind()
 
 unsigned Mp3Decoder::read(char *buf, unsigned len)
 {
-	unsigned nchan = (format==STEREO16 ? 2 : 1);
+	unsigned nchan = get_n_channels(format);
 	mad_pcm &pcm = priv->synth.pcm;
 
 	unsigned pos = 0;
diff --git a/source/oggdecoder.cpp b/source/oggdecoder.cpp
index d287342..78a2b5a 100644
--- a/source/oggdecoder.cpp
+++ b/source/oggdecoder.cpp
@@ -89,15 +89,9 @@ OggDecoder::OggDecoder(IO::Seekable &io):
 
 	vorbis_info *info = ov_info(&priv->ovfile, -1);
 	freq = info->rate;
+	format = create_format(2, info->channels);
 
-	size = ov_pcm_total(&priv->ovfile, 0)*info->channels*2;
-
-	switch(info->channels)
-	{
-	case 1: format = MONO16; break;
-	case 2: format = STEREO16; break;
-	default: throw unsupported_sound(Msp::format("%d channels", info->channels));
-	}
+	size = ov_pcm_total(&priv->ovfile, 0)*get_unit_size(format);
 }
 
 OggDecoder::~OggDecoder()
-- 
2.43.0