Optimized version of strstr (search has constant length)

Question

My C program had a lot of strstr function calls. The standard library strstr is already fast but in my case the search string has always length of 5 characters. I replaced i

Answer 1

Your code may access cs beyond the bounds of its allocation if cs is shorter than 4 characters.

A common optimisation for string search is to use the Boyer-Moore algorithm where you start looking in cs from the end of what would be ct. See the linked page for a full description of the algorithm.