91 lines
2.5 KiB
Go
91 lines
2.5 KiB
Go
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// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package levenshtein
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import (
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"fmt"
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)
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// StateLimit is the maximum number of states allowed
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const StateLimit = 10000
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// ErrTooManyStates is returned if you attempt to build a Levenshtein
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// automaton which requries too many states.
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var ErrTooManyStates = fmt.Errorf("dfa contains more than %d states", StateLimit)
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// Levenshtein implements the vellum.Automaton interface for matching
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// terms within the specified Levenshtein edit-distance of the queried
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// term. This automaton recognizes utf-8 encoded bytes and computes
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// the edit distance on the result code-points, not on the raw bytes.
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type Levenshtein struct {
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prog *dynamicLevenshtein
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dfa *dfa
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}
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// New creates a new Levenshtein automaton for the specified
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// query string and edit distance.
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func New(query string, distance int) (*Levenshtein, error) {
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lev := &dynamicLevenshtein{
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query: query,
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distance: uint(distance),
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}
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dfabuilder := newDfaBuilder(lev)
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dfa, err := dfabuilder.build()
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if err != nil {
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return nil, err
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}
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return &Levenshtein{
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prog: lev,
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dfa: dfa,
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}, nil
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}
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// Start returns the start state of this automaton.
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func (l *Levenshtein) Start() int {
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return 1
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}
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// IsMatch returns if the specified state is a matching state.
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func (l *Levenshtein) IsMatch(s int) bool {
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if s < len(l.dfa.states) {
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return l.dfa.states[s].match
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}
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return false
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}
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// CanMatch returns if the specified state can ever transition to a matching
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// state.
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func (l *Levenshtein) CanMatch(s int) bool {
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if s < len(l.dfa.states) && s > 0 {
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return true
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}
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return false
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}
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// WillAlwaysMatch returns if the specified state will always end in a
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// matching state.
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func (l *Levenshtein) WillAlwaysMatch(s int) bool {
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return false
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}
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// Accept returns the new state, resulting from the transite byte b
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// when currently in the state s.
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func (l *Levenshtein) Accept(s int, b byte) int {
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if s < len(l.dfa.states) {
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return l.dfa.states[s].next[b]
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}
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return 0
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}
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