prepare for eventual export

src/engine/pattern.cpp

@@ -30,6 +30,81 @@ void DivChannelData::wipePatterns() {
   }
 }
 
+SafeReader* DivPattern::compile(int len, int fxRows) {
+  SafeWriter w;
+  w.init();
+  short lastNote, lastOctave, lastInstr, lastVolume, lastEffect[8], lastEffectVal[8];
+  unsigned char rows=0;
+
+  lastNote=0;
+  lastOctave=0;
+  lastInstr=-1;
+  lastVolume=-1;
+  memset(lastEffect,-1,8*sizeof(short));
+  memset(lastEffectVal,-1,8*sizeof(short));
+
+  for (int i=0; i<len; i++) {
+    unsigned char mask=0;
+    if (data[i][0]!=-1) {
+      lastNote=data[i][0];
+      lastOctave=data[i][1];
+      mask|=128;
+    }
+    if (data[i][2]!=-1 && data[i][2]!=lastInstr) {
+      lastInstr=data[i][2];
+      mask|=32;
+    }
+    if (data[i][3]!=-1 && data[i][3]!=lastVolume) {
+      lastVolume=data[i][3];
+      mask|=64;
+    }
+    for (int j=0; j<fxRows; j++) {
+      if (data[i][4+(j<<1)]!=-1) {
+        lastEffect[j]=data[i][4+(j<<1)];
+        lastEffectVal[j]=data[i][5+(j<<1)];
+        mask=(mask&0xf8)|j;
+      }
+    }
+
+    if (!mask) {
+      rows++;
+      continue;
+    }
+
+    if (rows!=0) {
+      w.writeC(rows);
+    }
+    rows=1;
+
+    w.writeC(mask);
+    if (mask&128) {
+      if (lastNote==100) {
+        w.writeC(-128);
+      } else {
+        w.writeC(lastNote+(lastOctave*12));
+      }
+    }
+    if (mask&64) {
+      w.writeC(lastVolume);
+    }
+    if (mask&32) {
+      w.writeC(lastInstr);
+    }
+    for (int j=0; j<(mask&7); j++) {
+      w.writeC(lastEffect[j]);
+      if (lastEffectVal[j]==-1) {
+        w.writeC(0);
+      } else {
+        w.writeC(lastEffectVal[j]);
+      }
+    }
+  }
+  w.writeC(rows);
+  w.writeC(0);
+
+  return w.toReader();
+}
+
 DivChannelData::DivChannelData():
   effectRows(1) {
   memset(data,0,128*sizeof(void*));