// write a tuple (counter id, clock, count) at an absolute (bytebuffer-wise) offset
private void writeElementAtOffset(
ByteBuffer ctx, int offset, CounterId id, long clock, long count) {
ctx = ctx.duplicate();
ctx.position(offset);
ctx.put(id.bytes().duplicate());
ctx.putLong(clock);
ctx.putLong(count);
}
/** Finds the position of a shard with the given id within the context (via binary search). */
@VisibleForTesting
public int findPositionOf(ByteBuffer context, CounterId id) {
int headerLength = headerLength(context);
int offset = context.position() + headerLength;
int left = 0;
int right = (context.remaining() - headerLength) / STEP_LENGTH - 1;
while (right >= left) {
int middle = (left + right) / 2;
int cmp =
compareId(context, offset + middle * STEP_LENGTH, id.bytes(), id.bytes().position());
if (cmp == -1) left = middle + 1;
else if (cmp == 0) return offset + middle * STEP_LENGTH;
else right = middle - 1;
}
return -1; // position not found
}
public CounterId getCounterId() {
return CounterId.wrap(context, context.position() + bodyOffset);
}
/**
* Returns the clock and the count associated with the local counter id, or (0, 0) if no such
* shard is present.
*/
public ClockAndCount getLocalClockAndCount(ByteBuffer context) {
return getClockAndCountOf(context, CounterId.getLocalId());
}
/**
* Creates a counter context with a single local shard. For use by tests of compatibility with
* pre-2.1 counters only.
*/
public ByteBuffer createLocal(long count) {
ContextState state = ContextState.allocate(0, 1, 0);
state.writeLocal(CounterId.getLocalId(), 1L, count);
return state.context;
}
