The disclosed structures and methods are directed to decoders and to methods for decoding codes, for example, polar codes. The decoder comprises: a codeword node decoding pipeline having three logic units, and configured to, for each encoded codeword node: based on a received instruction sequence, adjust the three logic units for decoding of each encoded codeword node, and decode a set of logarithmic likelihood ratios (LLRs) corresponding to the encoded codeword node to generate decoded bits. The decoder also has an output storage configured to store the decoded bits corresponding to each encoded codeword node, and generate a decoded codeword based on the decoded bits. The decoding method comprises adjusting the codeword node decoding pipeline to each encoded codeword node based on codeword node length and a codeword node type, as well as a bit index of the encoded codeword node.