Methods and systems for locating occurrences of a search pattern in a body of text. A processor searches the text for one or more occurrences of a pattern. Both the text and the pattern comprise symbols of some alphabet. In preparation for the search, the processor defines a respective bit-map for each alphabet symbol. Using the bit-maps, the processor carries out a highly efficient process of searching the text for occurrences of the pattern. The processor then scans the pattern backwards using the bit-maps, symbol by symbol, attempting to match the symbols of the pattern to the corresponding symbols of the text. If a match is not found, the processor calculates the size of the jump to the next position in the text based on the accumulated results of the evaluations up to the current position.