|Maintainer||Daniel Fischer <email@example.com>|
Fast search of lazy
ByteString values using the
A description of the algorithm can be found at http://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm.
Original authors: Justin Bailey (jgbailey at gmail.com) and Chris Kuklewicz (haskell at list.mightyreason.com).
This module provides two functions for finding the occurrences of a
pattern in a target string using the Knuth-Morris-Pratt algorithm.
It exists mostly for systematic reasons, the functions from
Data.ByteString.Lazy.Search are much faster, except for very short
patterns or long patterns with a short period if overlap is allowed.
In the latter case,
indices from this module may be the best choice
since the Boyer-Moore function's performance degrades if there are many
matches and the DFA function's automaton needs much space for long
In the former case, for some pattern/target combinations DFA has better
performance, for others KMP, usually the difference is small.
Complexity and Performance
The preprocessing of the pattern is O(
patternLength) in time and space.
The time complexity of the searching phase is O(
targetLength) for both
In most cases, these functions are considerably slower than the Boyer-Moore variants, performance is close to that of those from Data.ByteString.Search.DFA.
Both functions can be usefully partially applied. Given only a pattern, the auxiliary data will be computed only once, allowing for efficient re-use.
indices finds the starting indices of all possibly overlapping
occurrences of the pattern in the target string.
If the pattern is empty, the result is
[0 .. .
nonOverlappingIndices finds the starting indices of all
non-overlapping occurrences of the pattern in the target string.
It is more efficient than removing indices from the list produced