prevent crash when playing empty sample

fixes #62

src/engine/platform/amiga.cpp

@@ -10,21 +10,25 @@ void DivPlatformAmiga::acquire(short* bufL, short* bufR, size_t start, size_t le
     bufL[h]=0;
     bufR[h]=0;
     for (int i=0; i<4; i++) {
-      if (chan[i].sample!=-1) {
+      if (chan[i].sample>=0 && chan[i].sample<parent->song.sampleLen) {
         chan[i].audSub-=AMIGA_DIVIDER;
         if (chan[i].audSub<0) {
           DivSample* s=parent->song.sample[chan[i].sample];
-          if (s->depth==8) {
+          if (s->rendLength>0) {
-            chan[i].audDat=s->rendData[chan[i].audPos++];
+            if (s->depth==8) {
-          } else {
+              chan[i].audDat=s->rendData[chan[i].audPos++];
-            chan[i].audDat=s->rendData[chan[i].audPos++]>>8;
-          }
-          if (chan[i].audPos>=s->rendLength || chan[i].audPos>=131071) {
-            if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
-              chan[i].audPos=s->loopStart;
             } else {
-              chan[i].sample=-1;
+              chan[i].audDat=s->rendData[chan[i].audPos++]>>8;
             }
+            if (chan[i].audPos>=s->rendLength || chan[i].audPos>=131071) {
+              if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
+                chan[i].audPos=s->loopStart;
+              } else {
+                chan[i].sample=-1;
+              }
+            }
+          } else {
+            chan[i].sample=-1;
           }
           /*if (chan[i].freq<124) {
             // ???

src/engine/platform/arcade.cpp

@@ -61,6 +61,10 @@ void DivPlatformArcade::acquire_nuked(short* bufL, short* bufR, size_t start, si
       for (int i=8; i<13; i++) {
         if (chan[i].pcm.sample>=0) {
           DivSample* s=parent->song.sample[chan[i].pcm.sample];
+          if (s->rendLength<=0) {
+            chan[i].pcm.sample=-1;
+            continue;
+          }
           if (!isMuted[i]) {
             if (s->depth==8) {
               pcmL+=(s->rendData[chan[i].pcm.pos>>8]*chan[i].chVolL);
@@ -123,6 +127,10 @@ void DivPlatformArcade::acquire_ymfm(short* bufL, short* bufR, size_t start, siz
       for (int i=8; i<13; i++) {
         if (chan[i].pcm.sample>=0 && chan[i].pcm.sample<parent->song.sampleLen) {
           DivSample* s=parent->song.sample[chan[i].pcm.sample];
+          if (s->rendLength<=0) {
+            chan[i].pcm.sample=-1;
+            continue;
+          }
           if (!isMuted[i]) {
             if (s->depth==8) {
               pcmL+=(s->rendData[chan[i].pcm.pos>>8]*chan[i].chVolL);

src/engine/platform/genesis.cpp

@@ -18,21 +18,25 @@ void DivPlatformGenesis::acquire(short* bufL, short* bufR, size_t start, size_t
       dacPeriod-=6;
       if (dacPeriod<1) {
         DivSample* s=parent->song.sample[dacSample];
-        if (!isMuted[5]) {
+        if (s->rendLength>0) {
-          if (s->depth==8) {
+          if (!isMuted[5]) {
-            immWrite(0x2a,(unsigned char)s->rendData[dacPos++]+0x80);
+            if (s->depth==8) {
-          } else {
+              immWrite(0x2a,(unsigned char)s->rendData[dacPos++]+0x80);
-            immWrite(0x2a,((unsigned short)s->rendData[dacPos++]+0x8000)>>8);
+            } else {
+              immWrite(0x2a,((unsigned short)s->rendData[dacPos++]+0x8000)>>8);
+            }
           }
-        }
+          if (dacPos>=s->rendLength) {
-        if (dacPos>=s->rendLength) {
+            if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
-          if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
+              dacPos=s->loopStart;
-            dacPos=s->loopStart;
+            } else {
-          } else {
+              dacSample=-1;
-            dacSample=-1;
+            }
           }
+          dacPeriod+=MAX(40,dacRate);
+        } else {
+          dacSample=-1;
         }
-        dacPeriod+=MAX(40,dacRate);
       }
     }
   

src/engine/platform/nes.cpp

@@ -15,21 +15,25 @@ void DivPlatformNES::acquire(short* bufL, short* bufR, size_t start, size_t len)
       dacPeriod+=dacRate;
       if (dacPeriod>=rate) {
         DivSample* s=parent->song.sample[dacSample];
-        if (!isMuted[4]) {
+        if (s->rendLength>0) {
-          if (s->depth==8) {
+          if (!isMuted[4]) {
-            rWrite(0x4011,((unsigned char)s->rendData[dacPos++]+0x80)>>1);
+            if (s->depth==8) {
-          } else {
+              rWrite(0x4011,((unsigned char)s->rendData[dacPos++]+0x80)>>1);
-            rWrite(0x4011,((unsigned short)s->rendData[dacPos++]+0x8000)>>9);
+            } else {
+              rWrite(0x4011,((unsigned short)s->rendData[dacPos++]+0x8000)>>9);
+            }
           }
-        }
+          if (dacPos>=s->rendLength) {
-        if (dacPos>=s->rendLength) {
+            if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
-          if (s->loopStart>=0 && s->loopStart<=(int)s->rendLength) {
+              dacPos=s->loopStart;
-            dacPos=s->loopStart;
+            } else {
-          } else {
+              dacSample=-1;
-            dacSample=-1;
+            }
           }
+          dacPeriod-=rate;
+        } else {
+          dacSample=-1;
         }
-        dacPeriod-=rate;
       }
     }
   

src/engine/platform/pce.cpp

@@ -23,6 +23,10 @@ void DivPlatformPCE::acquire(short* bufL, short* bufR, size_t start, size_t len)
         chan[i].dacPeriod-=6;
         if (chan[i].dacPeriod<1) {
           DivSample* s=parent->song.sample[chan[i].dacSample];
+          if (s->rendLength<=0) {
+            chan[i].dacSample=-1;
+            continue;
+          }
           chWrite(i,0x07,0);
           if (s->depth==8) {
             chWrite(i,0x04,0xdf);