Returns the offset into the backing array of the first element in the buffer. The caller
should have checked the {@link #hasArray()} method before calling this method.
@return the offset into the backing array of the first element in the buffer.
@throws UnsupportedOperationException if this {@link ReadableBuffer} doesn't support array access.
@throws ReadOnlyBufferException if the ReadableBuffer is read-only.
Returns the offset into the backing array of the first element in the buffer. The caller should have checked the {@link #hasArray()} method before calling this method.
@return the offset into the backing array of the first element in the buffer.
@throws UnsupportedOperationException if this {@link ReadableBuffer} doesn't support array access. @throws ReadOnlyBufferException if the ReadableBuffer is read-only.