134 lines
3.8 KiB
Go
134 lines
3.8 KiB
Go
// Copyright 2015 PingCAP, 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,
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package stringutil
|
|
|
|
import (
|
|
"strings"
|
|
"unicode/utf8"
|
|
|
|
"github.com/juju/errors"
|
|
)
|
|
|
|
// ErrSyntax indicates that a value does not have the right syntax for the target type.
|
|
var ErrSyntax = errors.New("invalid syntax")
|
|
|
|
// Reverse returns its argument string reversed rune-wise left to right.
|
|
func Reverse(s string) string {
|
|
r := []rune(s)
|
|
for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
|
|
r[i], r[j] = r[j], r[i]
|
|
}
|
|
return string(r)
|
|
}
|
|
|
|
// UnquoteChar decodes the first character or byte in the escaped string
|
|
// or character literal represented by the string s.
|
|
// It returns four values:
|
|
//
|
|
//1) value, the decoded Unicode code point or byte value;
|
|
//2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
|
|
//3) tail, the remainder of the string after the character; and
|
|
//4) an error that will be nil if the character is syntactically valid.
|
|
//
|
|
// The second argument, quote, specifies the type of literal being parsed
|
|
// and therefore which escaped quote character is permitted.
|
|
// If set to a single quote, it permits the sequence \' and disallows unescaped '.
|
|
// If set to a double quote, it permits \" and disallows unescaped ".
|
|
// If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
|
|
// Different with strconv.UnquoteChar, it permits unnecessary backslash.
|
|
func UnquoteChar(s string, quote byte) (value []byte, tail string, err error) {
|
|
// easy cases
|
|
switch c := s[0]; {
|
|
case c == quote:
|
|
err = errors.Trace(ErrSyntax)
|
|
return
|
|
case c >= utf8.RuneSelf:
|
|
r, size := utf8.DecodeRuneInString(s)
|
|
if r == utf8.RuneError {
|
|
value = append(value, c)
|
|
return value, s[1:], nil
|
|
}
|
|
value = append(value, string(r)...)
|
|
return value, s[size:], nil
|
|
case c != '\\':
|
|
value = append(value, c)
|
|
return value, s[1:], nil
|
|
}
|
|
// hard case: c is backslash
|
|
if len(s) <= 1 {
|
|
err = errors.Trace(ErrSyntax)
|
|
return
|
|
}
|
|
c := s[1]
|
|
s = s[2:]
|
|
switch c {
|
|
case 'b':
|
|
value = append(value, '\b')
|
|
case 'n':
|
|
value = append(value, '\n')
|
|
case 'r':
|
|
value = append(value, '\r')
|
|
case 't':
|
|
value = append(value, '\t')
|
|
case 'Z':
|
|
value = append(value, '\032')
|
|
case '0':
|
|
value = append(value, '\000')
|
|
case '_', '%':
|
|
value = append(value, '\\')
|
|
value = append(value, c)
|
|
case '\\':
|
|
value = append(value, '\\')
|
|
case '\'', '"':
|
|
value = append(value, c)
|
|
default:
|
|
value = append(value, c)
|
|
}
|
|
tail = s
|
|
return
|
|
}
|
|
|
|
// Unquote interprets s as a single-quoted, double-quoted,
|
|
// or backquoted Go string literal, returning the string value
|
|
// that s quotes. For example: test=`"\"\n"` (hex: 22 5c 22 5c 6e 22)
|
|
// should be converted to `"\n` (hex: 22 0a).
|
|
func Unquote(s string) (t string, err error) {
|
|
n := len(s)
|
|
if n < 2 {
|
|
return "", errors.Trace(ErrSyntax)
|
|
}
|
|
quote := s[0]
|
|
if quote != s[n-1] {
|
|
return "", errors.Trace(ErrSyntax)
|
|
}
|
|
s = s[1 : n-1]
|
|
if quote != '"' && quote != '\'' {
|
|
return "", errors.Trace(ErrSyntax)
|
|
}
|
|
// Avoid allocation. No need to convert if there is no '\'
|
|
if strings.IndexByte(s, '\\') == -1 && strings.IndexByte(s, quote) == -1 {
|
|
return s, nil
|
|
}
|
|
buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
|
|
for len(s) > 0 {
|
|
mb, ss, err := UnquoteChar(s, quote)
|
|
if err != nil {
|
|
return "", errors.Trace(err)
|
|
}
|
|
s = ss
|
|
buf = append(buf, mb...)
|
|
}
|
|
return string(buf), nil
|
|
}
|