public void removeStart(final int len) {
        if (len < 0) {
            throw new IllegalArgumentException("You cannot remove a negative number of characters");
        }
        setLength(length - len);
        offset += len;
        offset = offset % buffer.length;
    }
Create a buffer with a specified initial size.

@param initialSize The initial size of the buffer.
stroom-pipeline/src/main/java/stroom/pipeline/xml/converter/ds3/RingBuffer.java