vitess.io/vitess@v0.16.2/go/mysql/collations/internal/charset/helpers.go (about)

     1  /*
     2  Copyright 2022 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package charset
    18  
    19  func Slice(charset Charset, input []byte, from, to int) []byte {
    20  	if charset, ok := charset.(interface{ Slice([]byte, int, int) []byte }); ok {
    21  		return charset.Slice(input, from, to)
    22  	}
    23  	iter := input
    24  	for i := 0; i < to; i++ {
    25  		r, size := charset.DecodeRune(iter)
    26  		if r == RuneError && size < 2 {
    27  			break
    28  		}
    29  		iter = iter[size:]
    30  	}
    31  	return input[:len(input)-len(iter)]
    32  }
    33  
    34  func Validate(charset Charset, input []byte) bool {
    35  	if charset, ok := charset.(interface{ Validate([]byte) bool }); ok {
    36  		return charset.Validate(input)
    37  	}
    38  	for len(input) > 0 {
    39  		r, size := charset.DecodeRune(input)
    40  		if r == RuneError && size < 2 {
    41  			return false
    42  		}
    43  		input = input[size:]
    44  	}
    45  	return true
    46  }
    47  
    48  func Length(charset Charset, input []byte) int {
    49  	if charset, ok := charset.(interface{ Length([]byte) int }); ok {
    50  		return charset.Length(input)
    51  	}
    52  	var count int
    53  	for len(input) > 0 {
    54  		_, size := charset.DecodeRune(input)
    55  		input = input[size:]
    56  		count++
    57  	}
    58  	return count
    59  }