pattern

README

pattern

This library is aimed to deal with simple patterns, i.e. patterns of certain length with some positions being wildcards

Samples of patterns

Pattern text	Match example	Will not match example
a..a	abba	abbba
..:..:..:..:..:..	00:11:22:33:44:55	0:11:22:33:44:5
..\...	11.22	12345

Sample rules

• As you probably noticed, . plays the role of . in regular expressions, i.e. wildcard character
• There are escape sequences, those are available

  \n
  \r
  \t
  \\
  \`
  \.
  

Code usage sample

package main

import (
	"log"
	
	"github.com/sirkon/pattern"
)

func main() {
	p, err := pattern.NewPattern("a..a")
	if err != nil {
		log.Fatal(err)
	}
	
	if !p.Match([]byte("abba")) {
		log.Fatalf("pattern %s must match against abba", p)
	}
	log.Println(string(p.Lookup([]byte("  abba-cda")))) // will output "abba-cda"
}

Benchmarking (Core i5-4670k)

Test name	Iterations	Operations per nanosecond
BenchmarkPattern_Match-4	10000000	139 ns/op
BenchmarkRegexp_Match-4	500000	3235 ns/op
BenchmarkRagel_Match-4	20000000	112 ns/op
BenchmarkPattern_Lookup-4	30000	45475 ns/op
BenchmarkRegexp_Lookup-4	300	4562271 ns/op
BenchmarkRagel_Lookup-4	10000	122183ns/op

As you see, regular expression are much-much slower (there's a room for optimization I believe though). And pattern vs ragel comparsion is bit tricky: ragel is 1.25 times faster at regular match but loses at lookup. Lookup comparison was done with this sample set.

Spaces in the head	Pattern
0	00:00:00:00:00:00
1	00:00:00:00:00:00
2	00:00:00:00:00:00
…	…
128	… 00:00:00:00:00:00

But Ragel is as fast as current implementation when limited to 16 character in the head and faster with shorter prefixes. Obviously, other patterns and source strings may lead to different results.

Documentation

Index

• func CheckPattern(pattern string) bool
• type Pattern
  • func NewPattern(pattern string) (*Pattern, error)
  • func (p *Pattern) IsPrefixOf(source []byte) bool
  • func (p *Pattern) Lookup(source []byte) []byte
  • func (p *Pattern) Match(source []byte) bool
  • func (p *Pattern) String() string

Functions

func CheckPattern

func CheckPattern(pattern string) bool

CheckPattern checks if pattern is correct

Types

type Pattern

type Pattern struct {
	// contains filtered or unexported fields
}

Pattern represents a pattern.

func NewPattern

func NewPattern(pattern string) (*Pattern, error)

NewPattern pattern constructor

func (*Pattern) IsPrefixOf

func (p *Pattern) IsPrefixOf(source []byte) bool

IsPrefixOf checks if a pattern matches first symbols of source

func (*Pattern) Lookup

func (p *Pattern) Lookup(source []byte) []byte

Lookup returns a rest of source with a head matching against current pattern. Returns nil if no matches weren't found

func (*Pattern) Match

func (p *Pattern) Match(source []byte) bool

Match matches against a source

func (*Pattern) String

func (p *Pattern) String() string