1dc466a800
often the result stream was the same length, so can reuse the existing token stream also, in cases where a new stream was required, set capacity to the length of the input stream. most output stream are at least as long as the input, so this may avoid some subsequent resizing
144 lines
4.6 KiB
Go
144 lines
4.6 KiB
Go
// Copyright (c) 2014 Couchbase, Inc.
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
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// except in compliance with the License. You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed under the
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// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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package ckb
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import (
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"bytes"
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"unicode/utf8"
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"github.com/blevesearch/bleve/analysis"
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"github.com/blevesearch/bleve/registry"
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)
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const StemmerName = "stemmer_ckb"
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type SoraniStemmerFilter struct {
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}
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func NewSoraniStemmerFilter() *SoraniStemmerFilter {
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return &SoraniStemmerFilter{}
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}
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func (s *SoraniStemmerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
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for _, token := range input {
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// if not protected keyword, stem it
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if !token.KeyWord {
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stemmed := stem(token.Term)
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token.Term = stemmed
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}
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}
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return input
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}
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func stem(input []byte) []byte {
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inputLen := utf8.RuneCount(input)
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// postposition
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if inputLen > 5 && bytes.HasSuffix(input, []byte("دا")) {
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input = truncateRunes(input, 2)
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inputLen = utf8.RuneCount(input)
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} else if inputLen > 4 && bytes.HasSuffix(input, []byte("نا")) {
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input = truncateRunes(input, 1)
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inputLen = utf8.RuneCount(input)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("ەوە")) {
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input = truncateRunes(input, 3)
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inputLen = utf8.RuneCount(input)
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}
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// possessive pronoun
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if inputLen > 6 &&
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(bytes.HasSuffix(input, []byte("مان")) ||
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bytes.HasSuffix(input, []byte("یان")) ||
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bytes.HasSuffix(input, []byte("تان"))) {
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input = truncateRunes(input, 3)
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inputLen = utf8.RuneCount(input)
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}
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// indefinite singular ezafe
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if inputLen > 6 && bytes.HasSuffix(input, []byte("ێکی")) {
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return truncateRunes(input, 3)
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} else if inputLen > 7 && bytes.HasSuffix(input, []byte("یەکی")) {
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return truncateRunes(input, 4)
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}
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if inputLen > 5 && bytes.HasSuffix(input, []byte("ێک")) {
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// indefinite singular
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return truncateRunes(input, 2)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("یەک")) {
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// indefinite singular
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return truncateRunes(input, 3)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("ەکە")) {
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// definite singular
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return truncateRunes(input, 3)
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} else if inputLen > 5 && bytes.HasSuffix(input, []byte("کە")) {
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// definite singular
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return truncateRunes(input, 2)
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} else if inputLen > 7 && bytes.HasSuffix(input, []byte("ەکان")) {
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// definite plural
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return truncateRunes(input, 4)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("کان")) {
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// definite plural
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return truncateRunes(input, 3)
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} else if inputLen > 7 && bytes.HasSuffix(input, []byte("یانی")) {
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// indefinite plural ezafe
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return truncateRunes(input, 4)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("انی")) {
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// indefinite plural ezafe
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return truncateRunes(input, 3)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("یان")) {
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// indefinite plural
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return truncateRunes(input, 3)
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} else if inputLen > 5 && bytes.HasSuffix(input, []byte("ان")) {
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// indefinite plural
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return truncateRunes(input, 2)
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} else if inputLen > 7 && bytes.HasSuffix(input, []byte("یانە")) {
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// demonstrative plural
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return truncateRunes(input, 4)
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} else if inputLen > 6 && bytes.HasSuffix(input, []byte("انە")) {
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// demonstrative plural
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return truncateRunes(input, 3)
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} else if inputLen > 5 && (bytes.HasSuffix(input, []byte("ایە")) || bytes.HasSuffix(input, []byte("ەیە"))) {
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// demonstrative singular
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return truncateRunes(input, 2)
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} else if inputLen > 4 && bytes.HasSuffix(input, []byte("ە")) {
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// demonstrative singular
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return truncateRunes(input, 1)
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} else if inputLen > 4 && bytes.HasSuffix(input, []byte("ی")) {
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// absolute singular ezafe
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return truncateRunes(input, 1)
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}
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return input
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}
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func truncateRunes(input []byte, num int) []byte {
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runes := bytes.Runes(input)
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runes = runes[:len(runes)-num]
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out := buildTermFromRunes(runes)
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return out
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}
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func buildTermFromRunes(runes []rune) []byte {
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rv := make([]byte, 0, len(runes)*4)
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for _, r := range runes {
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runeBytes := make([]byte, utf8.RuneLen(r))
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utf8.EncodeRune(runeBytes, r)
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rv = append(rv, runeBytes...)
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}
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return rv
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}
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func StemmerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
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return NewSoraniStemmerFilter(), nil
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}
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func init() {
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registry.RegisterTokenFilter(StemmerName, StemmerFilterConstructor)
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}
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