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// Copyright 2018 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 text
import (
"bytes"
"strconv"
"strings"
"unicode"
"unicode/utf16"
"unicode/utf8"
"google.golang.org/protobuf/internal/strs"
)
// parseStringValue parses string field token.
// This differs from parseString since the text format allows
// multiple back-to-back string literals where they are semantically treated
// as a single large string with all values concatenated.
//
// E.g., `"foo" "bar" "baz"` => "foobarbaz"
func (d *Decoder) parseStringValue() (Token, error) {
// Note that the ending quote is sufficient to unambiguously mark the end
// of a string. Thus, the text grammar does not require intervening
// whitespace or control characters in-between strings.
// Thus, the following is valid:
// `"foo"'bar'"baz"` => "foobarbaz"
in0 := d.in
var ss []string
for len(d.in) > 0 && (d.in[0] == '"' || d.in[0] == '\'') {
s, err := d.parseString()
if err != nil {
return Token{}, err
}
ss = append(ss, s)
}
// d.in already points to the end of the value at this point.
return Token{
kind: Scalar,
attrs: stringValue,
pos: len(d.orig) - len(in0),
raw: in0[:len(in0)-len(d.in)],
str: strings.Join(ss, ""),
}, nil
}
// parseString parses a string value enclosed in " or '.
func (d *Decoder) parseString() (string, error) {
in := d.in
if len(in) == 0 {
return "", ErrUnexpectedEOF
}
quote := in[0]
in = in[1:]
i := indexNeedEscapeInBytes(in)
in, out := in[i:], in[:i:i] // set cap to prevent mutations
for len(in) > 0 {
switch r, n := utf8.DecodeRune(in); {
case r == utf8.RuneError && n == 1:
return "", d.newSyntaxError("invalid UTF-8 detected")
case r == 0 || r == '\n':
return "", d.newSyntaxError("invalid character %q in string", r)
case r == rune(quote):
in = in[1:]
d.consume(len(d.in) - len(in))
return string(out), nil
case r == '\\':
if len(in) < 2 {
return "", ErrUnexpectedEOF
}
switch r := in[1]; r {
case '"', '\'', '\\', '?':
in, out = in[2:], append(out, r)
case 'a':
in, out = in[2:], append(out, '\a')
case 'b':
in, out = in[2:], append(out, '\b')
case 'n':
in, out = in[2:], append(out, '\n')
case 'r':
in, out = in[2:], append(out, '\r')
case 't':
in, out = in[2:], append(out, '\t')
case 'v':
in, out = in[2:], append(out, '\v')
case 'f':
in, out = in[2:], append(out, '\f')
case '0', '1', '2', '3', '4', '5', '6', '7':
// One, two, or three octal characters.
n := len(in[1:]) - len(bytes.TrimLeft(in[1:], "01234567"))
if n > 3 {
n = 3
}
v, err := strconv.ParseUint(string(in[1:1+n]), 8, 8)
if err != nil {
return "", d.newSyntaxError("invalid octal escape code %q in string", in[:1+n])
}
in, out = in[1+n:], append(out, byte(v))
case 'x':
// One or two hexadecimal characters.
n := len(in[2:]) - len(bytes.TrimLeft(in[2:], "0123456789abcdefABCDEF"))
if n > 2 {
n = 2
}
v, err := strconv.ParseUint(string(in[2:2+n]), 16, 8)
if err != nil {
return "", d.newSyntaxError("invalid hex escape code %q in string", in[:2+n])
}
in, out = in[2+n:], append(out, byte(v))
case 'u', 'U':
// Four or eight hexadecimal characters
n := 6
if r == 'U' {
n = 10
}
if len(in) < n {
return "", ErrUnexpectedEOF
}
v, err := strconv.ParseUint(string(in[2:n]), 16, 32)
if utf8.MaxRune < v || err != nil {
return "", d.newSyntaxError("invalid Unicode escape code %q in string", in[:n])
}
in = in[n:]
r := rune(v)
if utf16.IsSurrogate(r) {
if len(in) < 6 {
return "", ErrUnexpectedEOF
}
v, err := strconv.ParseUint(string(in[2:6]), 16, 16)
r = utf16.DecodeRune(r, rune(v))
if in[0] != '\\' || in[1] != 'u' || r == unicode.ReplacementChar || err != nil {
return "", d.newSyntaxError("invalid Unicode escape code %q in string", in[:6])
}
in = in[6:]
}
out = append(out, string(r)...)
default:
return "", d.newSyntaxError("invalid escape code %q in string", in[:2])
}
default:
i := indexNeedEscapeInBytes(in[n:])
in, out = in[n+i:], append(out, in[:n+i]...)
}
}
return "", ErrUnexpectedEOF
}
// indexNeedEscapeInString returns the index of the character that needs
// escaping. If no characters need escaping, this returns the input length.
func indexNeedEscapeInBytes(b []byte) int { return indexNeedEscapeInString(strs.UnsafeString(b)) }
// UnmarshalString returns an unescaped string given a textproto string value.
// String value needs to contain single or double quotes. This is only used by
// internal/encoding/defval package for unmarshaling bytes.
func UnmarshalString(s string) (string, error) {
d := NewDecoder([]byte(s))
return d.parseString()
}
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