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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 json
import (
"strconv"
"unicode"
"unicode/utf16"
"unicode/utf8"
"google.golang.org/protobuf/internal/strs"
)
func (d *Decoder) parseString(in []byte) (string, int, error) {
in0 := in
if len(in) == 0 {
return "", 0, ErrUnexpectedEOF
}
if in[0] != '"' {
return "", 0, d.newSyntaxError(d.currPos(), "invalid character %q at start of string", 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 "", 0, d.newSyntaxError(d.currPos(), "invalid UTF-8 in string")
case r < ' ':
return "", 0, d.newSyntaxError(d.currPos(), "invalid character %q in string", r)
case r == '"':
in = in[1:]
n := len(in0) - len(in)
return string(out), n, nil
case r == '\\':
if len(in) < 2 {
return "", 0, ErrUnexpectedEOF
}
switch r := in[1]; r {
case '"', '\\', '/':
in, out = in[2:], append(out, r)
case 'b':
in, out = in[2:], append(out, '\b')
case 'f':
in, out = in[2:], append(out, '\f')
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 'u':
if len(in) < 6 {
return "", 0, ErrUnexpectedEOF
}
v, err := strconv.ParseUint(string(in[2:6]), 16, 16)
if err != nil {
return "", 0, d.newSyntaxError(d.currPos(), "invalid escape code %q in string", in[:6])
}
in = in[6:]
r := rune(v)
if utf16.IsSurrogate(r) {
if len(in) < 6 {
return "", 0, 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 "", 0, d.newSyntaxError(d.currPos(), "invalid escape code %q in string", in[:6])
}
in = in[6:]
}
out = append(out, string(r)...)
default:
return "", 0, d.newSyntaxError(d.currPos(), "invalid escape code %q in string", in[:2])
}
default:
i := indexNeedEscapeInBytes(in[n:])
in, out = in[n+i:], append(out, in[:n+i]...)
}
}
return "", 0, ErrUnexpectedEOF
}
// indexNeedEscapeInBytes 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)) }
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