78 lines
2 KiB
Go
78 lines
2 KiB
Go
// Copyright (c) 2019 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 reverse
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import (
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"unicode"
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"unicode/utf8"
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"github.com/blevesearch/bleve/v2/analysis"
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"github.com/blevesearch/bleve/v2/registry"
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)
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// Name is the name used to register ReverseFilter in the bleve registry
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const Name = "reverse"
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type ReverseFilter struct {
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}
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func NewReverseFilter() *ReverseFilter {
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return &ReverseFilter{}
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}
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func (f *ReverseFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
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for _, token := range input {
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token.Term = reverse(token.Term)
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}
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return input
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}
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func ReverseFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
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return NewReverseFilter(), nil
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}
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func init() {
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err := registry.RegisterTokenFilter(Name, ReverseFilterConstructor)
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if err != nil {
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panic(err)
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}
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}
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// reverse(..) will generate a reversed version of the provided
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// unicode array and return it back to its caller.
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func reverse(s []byte) []byte {
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cursorIn := 0
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inputRunes := []rune(string(s))
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cursorOut := len(s)
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output := make([]byte, len(s))
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for i := 0; i < len(inputRunes); {
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wid := utf8.RuneLen(inputRunes[i])
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i++
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for i < len(inputRunes) {
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r := inputRunes[i]
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if unicode.Is(unicode.Mn, r) || unicode.Is(unicode.Me, r) || unicode.Is(unicode.Mc, r) {
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wid += utf8.RuneLen(r)
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i++
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} else {
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break
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}
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}
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copy(output[cursorOut-wid:cursorOut], s[cursorIn:cursorIn+wid])
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cursorIn += wid
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cursorOut -= wid
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}
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return output
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}
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