1. A computer-implemented method of identifying M-byte wide data/stuff bytes in a mapping operation or multiplexing operation in an Optical Transport Network (OTN) comprising: organizing residues of a plurality of data/stuff decisions in rows of W residues, in order of incrementing index; generating a first row of residues and corresponding flags sequentially in order of index using an incremental method based on a first addition operation and recording the last residue of the first row; generating a subset of residues and corresponding flags in subsequent rows using a stride method based on a second addition operation; generating remaining residues and corresponding flags in subsequent rows using the incremental method based on residues derived from the stride method as starting point; deriving a word-level stuff/data decision from each residue; and expanding each word-level data/stuff decision to cover all bytes within an M byte word.