private void upgradeRatings(BinaryFormat newFormat) throws IOException {
Preconditions.checkArgument(
newFormat.getRatingSize() > format.getRatingSize(), "new format is not wider than old");
logger.info("upgrading {} ratings from {} to {}", index, format, newFormat);
ByteBuffer oldBuffer = ByteBuffer.allocateDirect(format.getRatingSize());
ByteBuffer newBuffer = ByteBuffer.allocateDirect(newFormat.getRatingSize());
MutableRating scratch = new MutableRating();
long oldPos = BinaryHeader.HEADER_SIZE + index * format.getRatingSize();
Preconditions.checkState(channel.position() == oldPos, "channel is at the wrong position");
long newPos = BinaryHeader.HEADER_SIZE + index * newFormat.getRatingSize();
channel.position(newPos);
// loop backwards, coping each rating to later in the file
for (int i = index - 1; i >= 0; i--) {
oldPos -= format.getRatingSize();
newPos -= newFormat.getRatingSize();
// read the old rating
BinaryUtils.readBuffer(channel, oldBuffer, oldPos);
oldBuffer.flip();
format.readRating(oldBuffer, scratch);
oldBuffer.clear();
// write the new rating
newFormat.renderRating(scratch, newBuffer);
newBuffer.flip();
BinaryUtils.writeBuffer(channel, newBuffer, newPos);
newBuffer.clear();
}
assert oldPos == BinaryHeader.HEADER_SIZE;
assert newPos == BinaryHeader.HEADER_SIZE;
format = newFormat;
ratingBuffer = ByteBuffer.allocateDirect(newFormat.getRatingSize());
}
