private void setRingCursor(ByteBuffer buffer, int newCursor) {
checkArgument(newCursor >= 0);
buffer.putInt(4, newCursor);
}
/**
* Returns the offset from the file start where the latest block should be written (end of prev
* block).
*/
private int getRingCursor(ByteBuffer buffer) {
int c = buffer.getInt(4);
checkState(c >= FILE_PROLOGUE_BYTES, "Integer overflow");
return c;
}