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

analysis/token/ngram/ngram.go

@@ -0,0 +1,116 @@
+//  Copyright (c) 2014 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 ngram
+
+import (
+	"bytes"
+	"fmt"
+	"unicode/utf8"
+
+	"github.com/blevesearch/bleve/v2/analysis"
+	"github.com/blevesearch/bleve/v2/registry"
+)
+
+const Name = "ngram"
+
+type NgramFilter struct {
+	minLength int
+	maxLength int
+}
+
+func NewNgramFilter(minLength, maxLength int) *NgramFilter {
+	return &NgramFilter{
+		minLength: minLength,
+		maxLength: maxLength,
+	}
+}
+
+func (s *NgramFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
+	rv := make(analysis.TokenStream, 0, len(input))
+
+	for _, token := range input {
+		runeCount := utf8.RuneCount(token.Term)
+		runes := bytes.Runes(token.Term)
+		for i := 0; i < runeCount; i++ {
+			// index of the starting rune for this token
+			for ngramSize := s.minLength; ngramSize <= s.maxLength; ngramSize++ {
+				// build an ngram of this size starting at i
+				if i+ngramSize <= runeCount {
+					ngramTerm := analysis.BuildTermFromRunes(runes[i : i+ngramSize])
+					token := analysis.Token{
+						Position: token.Position,
+						Start:    token.Start,
+						End:      token.End,
+						Type:     token.Type,
+						Term:     ngramTerm,
+					}
+					rv = append(rv, &token)
+				}
+			}
+		}
+	}
+
+	return rv
+}
+
+func NgramFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
+	minVal, ok := config["min"]
+	if !ok {
+		return nil, fmt.Errorf("must specify min")
+	}
+
+	min, err := convertToInt(minVal)
+	if err != nil {
+		return nil, err
+	}
+
+	maxVal, ok := config["max"]
+	if !ok {
+		return nil, fmt.Errorf("must specify max")
+	}
+
+	max, err := convertToInt(maxVal)
+	if err != nil {
+		return nil, err
+	}
+
+	return NewNgramFilter(min, max), nil
+}
+
+func init() {
+	err := registry.RegisterTokenFilter(Name, NgramFilterConstructor)
+	if err != nil {
+		panic(err)
+	}
+}
+
+// Expects either an int or a flaot64 value
+func convertToInt(val interface{}) (int, error) {
+	var intVal int
+	var floatVal float64
+	var ok bool
+
+	intVal, ok = val.(int)
+	if ok {
+		return intVal, nil
+	}
+
+	floatVal, ok = val.(float64)
+	if ok {
+		return int(floatVal), nil
+	}
+
+	return 0, fmt.Errorf("failed to convert to int value")
+}