|
- // 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 levenshtein2
-
- import (
- "fmt"
- "sort"
- "unicode/utf8"
- )
-
- type FullCharacteristicVector []uint32
-
- func (fcv FullCharacteristicVector) shiftAndMask(offset, mask uint32) uint32 {
- bucketID := offset / 32
- align := offset - bucketID*32
- if align == 0 {
- return fcv[bucketID] & mask
- }
- left := fcv[bucketID] >> align
- right := fcv[bucketID+1] << (32 - align)
- return (left | right) & mask
- }
-
- type tuple struct {
- char rune
- fcv FullCharacteristicVector
- }
-
- type sortRunes []rune
-
- func (s sortRunes) Less(i, j int) bool {
- return s[i] < s[j]
- }
-
- func (s sortRunes) Swap(i, j int) {
- s[i], s[j] = s[j], s[i]
- }
-
- func (s sortRunes) Len() int {
- return len(s)
- }
-
- func sortRune(r []rune) []rune {
- sort.Sort(sortRunes(r))
- return r
- }
-
- type Alphabet struct {
- charset []tuple
- index uint32
- }
-
- func (a *Alphabet) resetNext() {
- a.index = 0
- }
-
- func (a *Alphabet) next() (rune, FullCharacteristicVector, error) {
- if int(a.index) >= len(a.charset) {
- return 0, nil, fmt.Errorf("eof")
- }
-
- rv := a.charset[a.index]
- a.index++
- return rv.char, rv.fcv, nil
- }
-
- func dedupe(in string) string {
- lookUp := make(map[rune]struct{}, len(in))
- var rv string
- for len(in) > 0 {
- r, size := utf8.DecodeRuneInString(in)
- in = in[size:]
- if _, ok := lookUp[r]; !ok {
- rv += string(r)
- lookUp[r] = struct{}{}
- }
- }
- return rv
- }
-
- func queryChars(qChars string) Alphabet {
- chars := dedupe(qChars)
- inChars := sortRune([]rune(chars))
- charsets := make([]tuple, 0, len(inChars))
-
- for _, c := range inChars {
- tempChars := qChars
- var bits []uint32
- for len(tempChars) > 0 {
- var chunk string
- if len(tempChars) > 32 {
- chunk = tempChars[0:32]
- tempChars = tempChars[32:]
- } else {
- chunk = tempChars
- tempChars = tempChars[:0]
- }
-
- chunkBits := uint32(0)
- bit := uint32(1)
- for _, chr := range chunk {
- if chr == c {
- chunkBits |= bit
- }
- bit <<= 1
- }
- bits = append(bits, chunkBits)
- }
- bits = append(bits, 0)
- charsets = append(charsets, tuple{char: c, fcv: FullCharacteristicVector(bits)})
- }
- return Alphabet{charset: charsets}
- }
|