snapshot of https://github.com/blevesearch/bleve.git (master, 2026-09-15; blobs > 131072B omitted)

analysis/token/reverse/reverse.go

@@ -0,0 +1,78 @@
+//  Copyright (c) 2019 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 reverse
+
+import (
+	"unicode"
+	"unicode/utf8"
+
+	"github.com/blevesearch/bleve/v2/analysis"
+	"github.com/blevesearch/bleve/v2/registry"
+)
+
+// Name is the name used to register ReverseFilter in the bleve registry
+const Name = "reverse"
+
+type ReverseFilter struct {
+}
+
+func NewReverseFilter() *ReverseFilter {
+	return &ReverseFilter{}
+}
+
+func (f *ReverseFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
+	for _, token := range input {
+		token.Term = reverse(token.Term)
+	}
+	return input
+}
+
+func ReverseFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
+	return NewReverseFilter(), nil
+}
+
+func init() {
+	err := registry.RegisterTokenFilter(Name, ReverseFilterConstructor)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// reverse(..) will generate a reversed version of the provided
+// unicode array and return it back to its caller.
+func reverse(s []byte) []byte {
+	cursorIn := 0
+	inputRunes := []rune(string(s))
+	cursorOut := len(s)
+	output := make([]byte, len(s))
+	for i := 0; i < len(inputRunes); {
+		wid := utf8.RuneLen(inputRunes[i])
+		i++
+		for i < len(inputRunes) {
+			r := inputRunes[i]
+			if unicode.Is(unicode.Mn, r) || unicode.Is(unicode.Me, r) || unicode.Is(unicode.Mc, r) {
+				wid += utf8.RuneLen(r)
+				i++
+			} else {
+				break
+			}
+		}
+		copy(output[cursorOut-wid:cursorOut], s[cursorIn:cursorIn+wid])
+		cursorIn += wid
+		cursorOut -= wid
+	}
+
+	return output
+}