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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package lowmemjson
import (
"io"
"unicode/utf8"
"git.lukeshu.com/go/lowmemjson/internal"
)
func writeStringUnicodeEscape(w io.Writer, c rune) (int, error) {
buf := [6]byte{
'\\',
'u',
internal.Hex[(c>>12)&0xf],
internal.Hex[(c>>8)&0xf],
internal.Hex[(c>>4)&0xf],
internal.Hex[(c>>0)&0xf],
}
return w.Write(buf[:])
}
func writeStringShortEscape(w io.Writer, c rune) (int, error) {
var b byte
switch c {
case '"', '\\', '/':
b = byte(c)
case '\b':
b = 'b'
case '\f':
b = 'f'
case '\n':
b = 'n'
case '\r':
b = 'r'
case '\t':
b = 't'
default:
panic("should not happen")
}
buf := [2]byte{'\\', b}
return w.Write(buf[:])
}
func writeStringChar(w io.Writer, c rune, wasEscaped BackslashEscapeMode, escaper BackslashEscaper) (int, error) {
if escaper == nil {
escaper = EscapeDefault
}
switch escaper(c, wasEscaped) {
case BackslashEscapeNone:
switch {
case c < 0x0020: // override, gotta escape these
switch c {
case '\b', '\f', '\n', '\r', '\t': // short-escape if possible
return writeStringShortEscape(w, c)
default:
return writeStringUnicodeEscape(w, c)
}
case c == '"' || c == '\\': // override, gotta escape these
return writeStringShortEscape(w, c)
default: // obey
return writeRune(w, c)
}
case BackslashEscapeShort:
switch c {
case '"', '\\', '/', '\b', '\f', '\n', '\r', '\t': // obey
return writeStringShortEscape(w, c)
default: // override, can't short-escape these
return writeRune(w, c)
}
case BackslashEscapeUnicode:
switch {
case c > 0xFFFF: // override, can't escape these (TODO: unless we use UTF-16 surrogates?)
return writeRune(w, c)
default: // obey
return writeStringUnicodeEscape(w, c)
}
default:
panic("escaper returned an invalid escape mode")
}
}
func encodeStringFromString(w io.Writer, escaper BackslashEscaper, str string) {
encodeWriteByte(w, '"')
for _, c := range str {
if _, err := writeStringChar(w, c, BackslashEscapeNone, escaper); err != nil {
panic(encodeError{err})
}
}
encodeWriteByte(w, '"')
}
func encodeStringFromBytes(w io.Writer, escaper BackslashEscaper, str []byte) {
encodeWriteByte(w, '"')
for i := 0; i < len(str); {
c, size := utf8.DecodeRune(str[i:])
if _, err := writeStringChar(w, c, BackslashEscapeNone, escaper); err != nil {
panic(encodeError{err})
}
i += size
}
encodeWriteByte(w, '"')
}
func init() {
internal.EncodeStringFromString = func(w io.Writer, s string) { encodeStringFromString(w, nil, s) }
internal.EncodeStringFromBytes = func(w io.Writer, s []byte) { encodeStringFromBytes(w, nil, s) }
}
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