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