SNES: implement getSamplePos()

but gotta fix one thing

src/engine/platform/snes.cpp

@@ -681,6 +681,20 @@ DivMacroInt* DivPlatformSNES::getChanMacroInt(int ch) {
   return &chan[ch].std;
 }
 
+DivSamplePos DivPlatformSNES::getSamplePos(int ch) {
+  if (ch>=8) return DivSamplePos();
+  if (!chan[ch].active) return DivSamplePos();
+  if (chan[ch].sample<0 || chan[ch].sample>=parent->song.sampleLen) return DivSamplePos();
+  const SPC_DSP::voice_t* v=dsp.get_voice(ch);
+  // TODO: fix?
+  if (sampleMem[v->brr_addr&0xffff]==0) return DivSamplePos();
+  return DivSamplePos(
+    chan[ch].sample,
+    ((v->brr_addr-sampleOff[chan[ch].sample])*16/9)+v->brr_offset,
+    (chan[ch].freq*125)/16
+  );
+}
+
 DivDispatchOscBuffer* DivPlatformSNES::getOscBuffer(int ch) {
   return oscBuf[ch];
 }

src/engine/platform/snes.h

@@ -97,6 +97,7 @@ class DivPlatformSNES: public DivDispatch {
     int dispatch(DivCommand c);
     void* getChanState(int chan);
     DivMacroInt* getChanMacroInt(int ch);
+    DivSamplePos getSamplePos(int ch);
     DivDispatchOscBuffer* getOscBuffer(int chan);
     unsigned char* getRegisterPool();
     int getRegisterPoolSize();

src/engine/platform/sound/snes/SPC_DSP.h

@@ -123,6 +123,9 @@ public:
 		uint8_t t_envx_out;
 		sample_t out[2];        // Furnace addition, for per-channel oscilloscope
 	};
+
+  // Furnace addition, gets a voice
+  const voice_t* get_voice(int n);
 private:
 	enum { brr_block_size = 9 };
 	
@@ -298,6 +301,10 @@ inline void SPC_DSP::get_voice_outputs( sample_t* outs )
 	}
 }
 
+inline const SPC_DSP::voice_t* SPC_DSP::get_voice(int n) {
+  return &m.voices[n];
+}
+
 #if !SPC_NO_COPY_STATE_FUNCS
 
 class SPC_State_Copier {