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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package quoted provides string manipulation utilities.
package quoted
import (
"flag"
"fmt"
"strings"
"unicode"
)
func isSpaceByte(c byte) bool {
return c == ' ' || c == '\t' || c == '\n' || c == '\r'
}
// Split splits s into a list of fields,
// allowing single or double quotes around elements.
// There is no unescaping or other processing within
// quoted fields.
func Split(s string) ([]string, error) {
// Split fields allowing '' or "" around elements.
// Quotes further inside the string do not count.
var f []string
for len(s) > 0 {
for len(s) > 0 && isSpaceByte(s[0]) {
s = s[1:]
}
if len(s) == 0 {
break
}
// Accepted quoted string. No unescaping inside.
if s[0] == '"' || s[0] == '\'' {
quote := s[0]
s = s[1:]
i := 0
for i < len(s) && s[i] != quote {
i++
}
if i >= len(s) {
return nil, fmt.Errorf("unterminated %c string", quote)
}
f = append(f, s[:i])
s = s[i+1:]
continue
}
i := 0
for i < len(s) && !isSpaceByte(s[i]) {
i++
}
f = append(f, s[:i])
s = s[i:]
}
return f, nil
}
// Join joins a list of arguments into a string that can be parsed
// with Split. Arguments are quoted only if necessary; arguments
// without spaces or quotes are kept as-is. No argument may contain both
// single and double quotes.
func Join(args []string) (string, error) {
var buf []byte
for i, arg := range args {
if i > 0 {
buf = append(buf, ' ')
}
var sawSpace, sawSingleQuote, sawDoubleQuote bool
for _, c := range arg {
switch {
case c > unicode.MaxASCII:
continue
case isSpaceByte(byte(c)):
sawSpace = true
case c == '\'':
sawSingleQuote = true
case c == '"':
sawDoubleQuote = true
}
}
switch {
case !sawSpace && !sawSingleQuote && !sawDoubleQuote:
buf = append(buf, []byte(arg)...)
case !sawSingleQuote:
buf = append(buf, '\'')
buf = append(buf, []byte(arg)...)
buf = append(buf, '\'')
case !sawDoubleQuote:
buf = append(buf, '"')
buf = append(buf, []byte(arg)...)
buf = append(buf, '"')
default:
return "", fmt.Errorf("argument %q contains both single and double quotes and cannot be quoted", arg)
}
}
return string(buf), nil
}
// A Flag parses a list of string arguments encoded with Join.
// It is useful for flags like cmd/link's -extldflags.
type Flag []string
var _ flag.Value = (*Flag)(nil)
func (f *Flag) Set(v string) error {
fs, err := Split(v)
if err != nil {
return err
}
*f = fs[:len(fs):len(fs)]
return nil
}
func (f *Flag) String() string {
if f == nil {
return ""
}
s, err := Join(*f)
if err != nil {
return strings.Join(*f, " ")
}
return s
}
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