More precise comment

Author: sweeneyde

Objects/stringlib/fastsearch.h

@@ -13,9 +13,11 @@
    it has actually checked for matches, but didn't find any.  callers
    beware! */
 
-/* If the needle is long enough, use Crochemore and Perrin's Two-Way
-   algorithm, which has guaranteed O(n) runtime. Also compute a table
-   of shifts to sometimes achieve O(n/m) runtime in the best cases. */
+/* If the strings are long enough, use Crochemore and Perrin's Two-Way
+   algorithm, which has worst-case O(n) runtime and best-case O(n/k).
+   Also compute a table of shifts to achieve O(n/k) in more cases,
+   and often (data dependent) deduce larger shifts than pure C&P can
+   deduce. */
 
 #define FAST_COUNT 0
 #define FAST_SEARCH 1