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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/jsonparse"
)
type runeTypeScanner struct {
// everything that is not "initialized by constructor" starts
// out as the zero value.
inner io.RuneScanner // initialized by constructor
parser jsonparse.Parser // initialized by constructor
offset int64
rTypeOK bool
repeat bool
rRune rune
rSize int
rIsRune bool
rType jsonparse.RuneType
rErr error
}
// The returned error is a *ReadError, a *SyntaxError, or nil.
// An EOF condition is represented as one of:
//
// end of value: (_, 0, RuneTypeEOF, nil)
// end of file in middle of value: (_, 0, RuneTypeError, &DecodeSyntaxError{Offset: offset: Err: io.ErrUnexepctedEOF})
// end of file at start of value: (_, 0, RuneTypeError, &DecodeSyntaxError{Offset: offset: Err: io.EOF})
func (sc *runeTypeScanner) ReadRuneType() (rune, int, jsonparse.RuneType, error) {
switch {
case sc.rTypeOK && (sc.rType == jsonparse.RuneTypeError || sc.rType == jsonparse.RuneTypeEOF):
// do nothing
case sc.repeat:
sc.offset += int64(sc.rSize)
_, _, _ = sc.inner.ReadRune()
case sc.parser.IsAtBarrier():
sc.rTypeOK = true
sc.rType = jsonparse.RuneTypeEOF
sc.rRune = 0
sc.rSize = 0
sc.rErr = nil
default:
sc.rTypeOK = true
again:
var err error
sc.rRune, sc.rSize, err = sc.inner.ReadRune()
sc.offset += int64(sc.rSize)
switch err {
case nil:
sc.rIsRune = true
if sc.rRune == utf8.RuneError && sc.rSize == 1 {
if bs, ok := sc.inner.(io.ByteScanner); ok {
_ = bs.UnreadByte() // UnreadRune doesn't back up the ReadByte-pos
b, _ := bs.ReadByte()
_ = bs.UnreadByte()
_, _, _ = sc.inner.ReadRune()
sc.rRune = rune(b)
sc.rIsRune = false
}
}
sc.rType, err = sc.parser.HandleRune(sc.rRune, sc.rIsRune)
if err != nil {
sc.rErr = &DecodeSyntaxError{
Offset: sc.offset - int64(sc.rSize),
Err: err,
}
} else {
sc.rErr = nil
}
switch sc.rType {
case jsonparse.RuneTypeSpace:
goto again
case jsonparse.RuneTypeEOF:
sc.offset -= int64(sc.rSize)
sc.rRune = 0
sc.rSize = 0
_ = sc.inner.UnreadRune()
}
case io.EOF:
sc.rType, err = sc.parser.HandleEOF()
if err != nil {
sc.rErr = &DecodeSyntaxError{
Offset: sc.offset,
Err: err,
}
} else {
sc.rErr = nil
}
default:
sc.rType = 0
sc.rErr = &DecodeReadError{
Offset: sc.offset,
Err: err,
}
}
}
sc.repeat = false
if sc.rSize > 0 && !sc.rIsRune {
return utf8.RuneError, sc.rSize, sc.rType, sc.rErr
}
return sc.rRune, sc.rSize, sc.rType, sc.rErr
}
// UnreadRune undoes a call to .ReadRuneType().
//
// If the last call to .ReadRuneType() has already been unread, or if
// that call returned a rune with size 0, then ErrInvalidUnreadRune is
// returned. Otherwise, nil is returned.
func (sc *runeTypeScanner) UnreadRune() error {
if sc.repeat || sc.rSize == 0 {
return ErrInvalidUnreadRune
}
sc.repeat = true
sc.offset -= int64(sc.rSize)
_ = sc.inner.UnreadRune()
return nil
}
func (sc *runeTypeScanner) InputOffset() int64 {
return sc.offset
}
func (sc *runeTypeScanner) PushReadBarrier() {
sc.parser.PushReadBarrier()
}
func (sc *runeTypeScanner) PopReadBarrier() {
sc.parser.PopBarrier()
switch {
case sc.repeat:
// re-figure the rType and rErr
var err error
sc.rType, err = sc.parser.HandleRune(sc.rRune, sc.rIsRune)
if err != nil {
sc.rErr = &DecodeSyntaxError{
Offset: sc.offset - int64(sc.rSize),
Err: err,
}
} else {
sc.rErr = nil
}
case sc.rTypeOK && sc.rType == jsonparse.RuneTypeEOF:
sc.rTypeOK = false // forget the sticky EOF
}
}
func (sc *runeTypeScanner) Reset() {
sc.parser.Reset()
sc.rTypeOK = false // forget any sticky errors/EOF
sc.repeat = false // feed the rune (if any) through the parser again
}
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