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util.go
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util.go
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// 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 analysis
import (
"bytes"
"unicode/utf8"
)
func DeleteRune(in []rune, pos int) []rune {
if pos >= len(in) {
return in
}
copy(in[pos:], in[pos+1:])
return in[:len(in)-1]
}
func InsertRune(in []rune, pos int, r rune) []rune {
// create a new slice 1 rune larger
rv := make([]rune, len(in)+1)
// copy the characters before the insert pos
copy(rv[0:pos], in[0:pos])
// set the inserted rune
rv[pos] = r
// copy the characters after the insert pos
copy(rv[pos+1:], in[pos:])
return rv
}
// BuildTermFromRunesOptimistic will build a term from the provided runes
// AND optimistically attempt to encode into the provided buffer
// if at any point it appears the buffer is too small, a new buffer is
// allocated and that is used instead
// this should be used in cases where frequently the new term is the same
// length or shorter than the original term (in number of bytes)
func BuildTermFromRunesOptimistic(buf []byte, runes []rune) []byte {
rv := buf
used := 0
for _, r := range runes {
nextLen := utf8.RuneLen(r)
if used+nextLen > len(rv) {
// alloc new buf
buf = make([]byte, len(runes)*utf8.UTFMax)
// copy work we've already done
copy(buf, rv[:used])
rv = buf
}
written := utf8.EncodeRune(rv[used:], r)
used += written
}
return rv[:used]
}
func BuildTermFromRunes(runes []rune) []byte {
return BuildTermFromRunesOptimistic(make([]byte, len(runes)*utf8.UTFMax), runes)
}
func TruncateRunes(input []byte, num int) []byte {
runes := bytes.Runes(input)
runes = runes[:len(runes)-num]
out := BuildTermFromRunes(runes)
return out
}
func RunesEndsWith(input []rune, suffix string) bool {
inputLen := len(input)
suffixRunes := []rune(suffix)
suffixLen := len(suffixRunes)
if suffixLen > inputLen {
return false
}
for i := suffixLen - 1; i >= 0; i-- {
if input[inputLen-(suffixLen-i)] != suffixRunes[i] {
return false
}
}
return true
}