1. A device comprising: a controller configured to: receive a first data entry over a first input port; store the first data entry in a first data structure in a memory; store a second data entry corresponding to the first data entry in a second data structure in the memory, wherein the second data structure is separate from the first data structure, and wherein entries of the second data structure include a valid bit field; and indicate, using the valid bit field of the second data entry in the second data structure, that the first data entry in the first data structure is valid.