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overlap.go
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overlap.go
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// Copyright 2019 Richard Lehane. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package patterns
// func Overlap calculates the max distance before a possible overlap with multiple matches of the same Pattern
// e.g. 0xAABBAA has a length of 3 but returns 2
func Overlap(p Pattern) int {
return aggregateOverlap(p, overlap)
}
// func OverlapR calculates the max distance before a possible overlap with multiple matches of the same Pattern,
// matching in reverse
// e.g. EOFE has a length of 4 but returns 3
func OverlapR(p Pattern) int {
return aggregateOverlap(p, overlapR)
}
func aggregateOverlap(p Pattern, of overlapFunc) int {
var counter int // prevent combinatorial explosions
seqs := p.Sequences()
if len(seqs) < 1 {
return 1
}
ret := len(seqs[0])
for _, v := range seqs {
for _, vv := range seqs {
counter++
if counter > 1000000 {
//panic("counter exploded!")
return ret
}
if r := of(v, vv); r < ret {
ret = r
}
}
}
return ret
}
type overlapFunc func([]byte, []byte) int
func overlap(a, b []byte) int {
var ret int = 1
for ; ret < len(a); ret++ {
success := true
for i := 0; ret+i < len(a) && i < len(b); i++ {
if a[ret+i] != b[i] {
success = false
break
}
}
if success {
break
}
}
return ret
}
func overlapR(a, b []byte) int {
var ret int = 1
for ; ret < len(a); ret++ {
success := true
for i := 0; ret+i < len(a) && i < len(b); i++ {
if a[len(a)-ret-i-1] != b[len(b)-i-1] {
success = false
break
}
}
if success {
break
}
}
return ret
}