1. A file server comprising: an offload device coupled to receive file-access requests from a network, the offload device including: a memory, the memory allocated by the offload device, the memory storing lookup tables having entries, one or more of the entries comprising a tag storing a first variable-length string; a plurality of processing units for executing functional-level instructions, the functional-level instructions including instructions operating on operands of variable-length, the processing units including a lookup unit; wherein one of the processing units includes a plurality of processing slices operating in parallel, each processing slice processing a request, the request seeking to access a file, the request including a second variable-length string, the request having a context allocated by the offload device, the context comprising: an execution buffer that stores a variable-length operand, the variable-length operand representing the second variable-length string; a first fixed-length register storing a pointer that indicates a location for the variable-length operand; a second fixed-length register storing an operand-length that indicates a length for the variable-length operand or storing a pointer that indicates the end of the variable-length operand; wherein a functional-level instruction identifies the variable-length operand stored in the execution buffer by specifying a first register number for the first fixed-length register and a second register number for the second fixed-length register, the lookup unit searches the lookup tables for an entry, and the first variable-length string stored in the tag for the entry matches the variable-length operand.