forked from Shiloh/githaven
65 lines
2.2 KiB
Go
65 lines
2.2 KiB
Go
// Copyright (c) 2018 Couchbase, Inc.
|
|
//
|
|
// 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 levenshtein
|
|
|
|
import "fmt"
|
|
|
|
// StateLimit is the maximum number of states allowed
|
|
const StateLimit = 10000
|
|
|
|
// ErrTooManyStates is returned if you attempt to build a Levenshtein
|
|
// automaton which requires too many states.
|
|
var ErrTooManyStates = fmt.Errorf("dfa contains more than %d states",
|
|
StateLimit)
|
|
|
|
// LevenshteinAutomatonBuilder wraps a precomputed
|
|
// datastructure that allows to produce small (but not minimal) DFA.
|
|
type LevenshteinAutomatonBuilder struct {
|
|
pDfa *ParametricDFA
|
|
}
|
|
|
|
// NewLevenshteinAutomatonBuilder creates a
|
|
// reusable, threadsafe Levenshtein automaton builder.
|
|
// `maxDistance` - maximum distance considered by the automaton.
|
|
// `transposition` - assign a distance of 1 for transposition
|
|
//
|
|
// Building this automaton builder is computationally intensive.
|
|
// While it takes only a few milliseconds for `d=2`, it grows
|
|
// exponentially with `d`. It is only reasonable to `d <= 5`.
|
|
func NewLevenshteinAutomatonBuilder(maxDistance uint8,
|
|
transposition bool) (*LevenshteinAutomatonBuilder, error) {
|
|
lnfa := newLevenshtein(maxDistance, transposition)
|
|
|
|
pdfa, err := fromNfa(lnfa)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &LevenshteinAutomatonBuilder{pDfa: pdfa}, nil
|
|
}
|
|
|
|
// BuildDfa builds the levenshtein automaton for serving
|
|
// queries with a given edit distance.
|
|
func (lab *LevenshteinAutomatonBuilder) BuildDfa(query string,
|
|
fuzziness uint8) (*DFA, error) {
|
|
return lab.pDfa.buildDfa(query, fuzziness, false)
|
|
}
|
|
|
|
// MaxDistance returns the MaxEdit distance supported by the
|
|
// LevenshteinAutomatonBuilder builder.
|
|
func (lab *LevenshteinAutomatonBuilder) MaxDistance() uint8 {
|
|
return lab.pDfa.maxDistance
|
|
}
|