recalcBitMap method
Rebuilds the bitmap component at bitmapIndex from the fields present.
A no-op while the message is unchanged, exactly as in the Java.
Implementation
void recalcBitMap([int bitmapIndex = 1]) {
if (!_dirty || bitmapIndex < 0) return;
final int highest = maxField < 192 ? maxField : 192;
final IsoBitSet bitmap = IsoBitSet();
for (int i = bitmapIndex + 1; i <= highest; i++) {
if (fields[i] != null) bitmap.set(i);
}
setComponent(bitmapIndex, IsoBitMapField(bitmap));
_dirty = false;
}