mirror of
https://github.com/go-gitea/gitea.git
synced 2024-08-22 20:33:46 +02:00
251 lines
6.4 KiB
Go
251 lines
6.4 KiB
Go
// Copyright (c) 2018 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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"math"
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)
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const SinkState = uint32(0)
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type DFA struct {
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transitions [][256]uint32
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distances []Distance
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initState int
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ed uint8
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}
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/// Returns the initial state
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func (d *DFA) initialState() int {
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return d.initState
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}
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/// Returns the Levenshtein distance associated to the
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/// current state.
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func (d *DFA) distance(stateId int) Distance {
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return d.distances[stateId]
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}
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/// Returns the number of states in the `DFA`.
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func (d *DFA) numStates() int {
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return len(d.transitions)
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}
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/// Returns the destination state reached after consuming a given byte.
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func (d *DFA) transition(fromState int, b uint8) int {
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return int(d.transitions[fromState][b])
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}
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func (d *DFA) eval(bytes []uint8) Distance {
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state := d.initialState()
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for _, b := range bytes {
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state = d.transition(state, b)
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}
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return d.distance(state)
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}
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func (d *DFA) Start() int {
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return int(d.initialState())
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}
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func (d *DFA) IsMatch(state int) bool {
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if _, ok := d.distance(state).(Exact); ok {
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return true
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}
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return false
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}
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func (d *DFA) CanMatch(state int) bool {
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return state > 0 && state < d.numStates()
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}
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func (d *DFA) Accept(state int, b byte) int {
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return int(d.transition(state, b))
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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 (d *DFA) WillAlwaysMatch(state int) bool {
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return false
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}
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func fill(dest []uint32, val uint32) {
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for i := range dest {
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dest[i] = val
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}
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}
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func fillTransitions(dest *[256]uint32, val uint32) {
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for i := range dest {
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dest[i] = val
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}
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}
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type Utf8DFAStateBuilder struct {
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dfaBuilder *Utf8DFABuilder
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stateID uint32
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defaultSuccessor []uint32
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}
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func (sb *Utf8DFAStateBuilder) addTransitionID(fromStateID uint32, b uint8,
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toStateID uint32) {
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sb.dfaBuilder.transitions[fromStateID][b] = toStateID
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}
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func (sb *Utf8DFAStateBuilder) addTransition(in rune, toStateID uint32) {
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fromStateID := sb.stateID
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chars := []byte(string(in))
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lastByte := chars[len(chars)-1]
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for i, ch := range chars[:len(chars)-1] {
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remNumBytes := len(chars) - i - 1
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defaultSuccessor := sb.defaultSuccessor[remNumBytes]
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intermediateStateID := sb.dfaBuilder.transitions[fromStateID][ch]
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if intermediateStateID == defaultSuccessor {
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intermediateStateID = sb.dfaBuilder.allocate()
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fillTransitions(&sb.dfaBuilder.transitions[intermediateStateID],
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sb.defaultSuccessor[remNumBytes-1])
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}
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sb.addTransitionID(fromStateID, ch, intermediateStateID)
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fromStateID = intermediateStateID
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}
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toStateIDDecoded := sb.dfaBuilder.getOrAllocate(original(toStateID))
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sb.addTransitionID(fromStateID, lastByte, toStateIDDecoded)
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}
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type Utf8StateId uint32
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func original(stateId uint32) Utf8StateId {
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return predecessor(stateId, 0)
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}
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func predecessor(stateId uint32, numSteps uint8) Utf8StateId {
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return Utf8StateId(stateId*4 + uint32(numSteps))
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}
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// Utf8DFABuilder makes it possible to define a DFA
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// that takes unicode character, and build a `DFA`
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// that operates on utf-8 encoded
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type Utf8DFABuilder struct {
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index []uint32
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distances []Distance
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transitions [][256]uint32
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initialState uint32
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numStates uint32
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maxNumStates uint32
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}
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func withMaxStates(maxStates uint32) *Utf8DFABuilder {
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rv := &Utf8DFABuilder{
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index: make([]uint32, maxStates*2+100),
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distances: make([]Distance, 0, maxStates),
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transitions: make([][256]uint32, 0, maxStates),
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maxNumStates: maxStates,
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}
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for i := range rv.index {
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rv.index[i] = math.MaxUint32
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}
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return rv
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}
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func (dfab *Utf8DFABuilder) allocate() uint32 {
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newState := dfab.numStates
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dfab.numStates++
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dfab.distances = append(dfab.distances, Atleast{d: 255})
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dfab.transitions = append(dfab.transitions, [256]uint32{})
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return newState
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}
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func (dfab *Utf8DFABuilder) getOrAllocate(state Utf8StateId) uint32 {
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if int(state) >= cap(dfab.index) {
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cloneIndex := make([]uint32, int(state)*2)
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copy(cloneIndex, dfab.index)
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dfab.index = cloneIndex
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}
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if dfab.index[state] != math.MaxUint32 {
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return dfab.index[state]
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}
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nstate := dfab.allocate()
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dfab.index[state] = nstate
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return nstate
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}
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func (dfab *Utf8DFABuilder) setInitialState(iState uint32) {
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decodedID := dfab.getOrAllocate(original(iState))
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dfab.initialState = decodedID
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}
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func (dfab *Utf8DFABuilder) build(ed uint8) *DFA {
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return &DFA{
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transitions: dfab.transitions,
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distances: dfab.distances,
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initState: int(dfab.initialState),
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ed: ed,
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}
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}
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func (dfab *Utf8DFABuilder) addState(state, default_suc_orig uint32,
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distance Distance) (*Utf8DFAStateBuilder, error) {
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if state > dfab.maxNumStates {
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return nil, fmt.Errorf("State id is larger than maxNumStates")
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}
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stateID := dfab.getOrAllocate(original(state))
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dfab.distances[stateID] = distance
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defaultSuccID := dfab.getOrAllocate(original(default_suc_orig))
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// creates a chain of states of predecessors of `default_suc_orig`.
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// Accepting k-bytes (whatever the bytes are) from `predecessor_states[k-1]`
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// leads to the `default_suc_orig` state.
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predecessorStates := []uint32{defaultSuccID,
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defaultSuccID,
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defaultSuccID,
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defaultSuccID}
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for numBytes := uint8(1); numBytes < 4; numBytes++ {
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predecessorState := predecessor(default_suc_orig, numBytes)
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predecessorStateID := dfab.getOrAllocate(predecessorState)
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predecessorStates[numBytes] = predecessorStateID
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succ := predecessorStates[numBytes-1]
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fillTransitions(&dfab.transitions[predecessorStateID], succ)
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}
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// 1-byte encoded chars.
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fill(dfab.transitions[stateID][0:192], predecessorStates[0])
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// 2-bytes encoded chars.
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fill(dfab.transitions[stateID][192:224], predecessorStates[1])
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// 3-bytes encoded chars.
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fill(dfab.transitions[stateID][224:240], predecessorStates[2])
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// 4-bytes encoded chars.
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fill(dfab.transitions[stateID][240:256], predecessorStates[3])
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return &Utf8DFAStateBuilder{
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dfaBuilder: dfab,
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stateID: stateID,
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defaultSuccessor: predecessorStates}, nil
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}
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