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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package lowmemjson
import (
"errors"
"io"
)
type runeTypeScanner interface {
// The returned error is a *ReadError, a *SyntaxError, or nil.
// An EOF condition is represented either as
//
// (char, size, RuneTypeEOF, nil)
//
// or
//
// (char, size, RuneTypeError, &DecodeSyntaxError{Offset: offset: Err: io.ErrUnexepctedEOF})
ReadRuneType() (rune, int, RuneType, error)
// The returned error is a *DecodeReadError, a *DecodeSyntaxError, io.EOF, or nil.
ReadRune() (rune, int, error)
UnreadRune() error
Reset()
InputOffset() int64
}
// runeTypeScannerImpl /////////////////////////////////////////////////////////////////////////////
type runeTypeScannerImpl struct {
inner io.RuneReader
parser Parser
offset int64
repeat bool
stuck bool
rRune rune
rRuneOK bool
rSize int
rType RuneType
rErr error
}
var _ runeTypeScanner = (*runeTypeScannerImpl)(nil)
func (sc *runeTypeScannerImpl) Reset() {
sc.parser.Reset()
unread := sc.stuck && sc.rType == RuneTypeEOF && sc.rRuneOK
sc.stuck = false
sc.repeat = false
if unread {
// re-figure the rType and rErr
var err error
sc.rType, err = sc.parser.HandleRune(sc.rRune)
if err != nil {
sc.rErr = &DecodeSyntaxError{
Offset: sc.offset,
Err: err,
}
} else {
sc.rErr = nil
}
// tell it to use that rType and rErr
sc.UnreadRune()
}
}
func (sc *runeTypeScannerImpl) ReadRuneType() (rune, int, RuneType, error) {
switch {
case sc.stuck:
// do nothing
case sc.repeat:
if _, ok := sc.inner.(io.RuneScanner); ok {
sc.inner.ReadRune()
}
default:
var err error
sc.rRune, sc.rSize, err = sc.inner.ReadRune()
sc.offset += int64(sc.rSize)
sc.rRuneOK = err == nil
switch err {
case nil:
sc.rType, err = sc.parser.HandleRune(sc.rRune)
if err != nil {
sc.rErr = &DecodeSyntaxError{
Offset: sc.offset,
Err: err,
}
} else {
sc.rErr = nil
}
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
sc.stuck = sc.rType == RuneTypeEOF || sc.rType == RuneTypeError
return sc.rRune, sc.rSize, sc.rType, sc.rErr
}
func (sc *runeTypeScannerImpl) ReadRune() (rune, int, error) {
r, s, t, e := sc.ReadRuneType()
switch t {
case RuneTypeEOF:
return 0, 0, io.EOF
case RuneTypeError:
return 0, 0, e
default:
return r, s, nil
}
}
var ErrInvalidUnreadRune = errors.New("lowmemjson: invalid use of UnreadRune")
// UnreadRune undoes a call to .ReadRune() or .ReadRuneType(). If the
// last call to .ReadRune() or .ReadRuneType() has already been
// unread, or if that call returned an error or RuneTypeEOF, then
// ErrInvalidRune is returned. Otherwise, nil is returned.
func (sc *runeTypeScannerImpl) UnreadRune() error {
if sc.stuck || sc.repeat {
return ErrInvalidUnreadRune
}
sc.repeat = true
if rs, ok := sc.inner.(io.RuneScanner); ok {
_ = rs.UnreadRune()
}
return nil
}
func (sc *runeTypeScannerImpl) InputOffset() int64 {
ret := sc.offset
if sc.repeat {
ret -= int64(sc.rSize)
}
return ret
}
// noWSRuneTypeScanner /////////////////////////////////////////////////////////////////////////////
type noWSRuneTypeScanner struct {
inner runeTypeScanner
}
var _ runeTypeScanner = (*noWSRuneTypeScanner)(nil)
func (sc *noWSRuneTypeScanner) ReadRuneType() (rune, int, RuneType, error) {
again:
r, s, t, e := sc.inner.ReadRuneType()
if t == RuneTypeSpace {
goto again
}
return r, s, t, e
}
func (sc *noWSRuneTypeScanner) ReadRune() (rune, int, error) {
r, s, t, e := sc.ReadRuneType()
switch t {
case RuneTypeEOF:
return 0, 0, io.EOF
case RuneTypeError:
return 0, 0, e
default:
return r, s, nil
}
}
func (sc *noWSRuneTypeScanner) UnreadRune() error { return sc.inner.UnreadRune() }
func (sc *noWSRuneTypeScanner) Reset() { sc.inner.Reset() }
func (sc *noWSRuneTypeScanner) InputOffset() int64 { return sc.inner.InputOffset() }
// elemRuneTypeScanner /////////////////////////////////////////////////////////////////////////////
type elemRuneTypeScanner struct {
inner runeTypeScanner
parser Parser
repeat bool
rType RuneType
}
var _ runeTypeScanner = (*elemRuneTypeScanner)(nil)
func (sc *elemRuneTypeScanner) ReadRuneType() (rune, int, RuneType, error) {
r, s, t, e := sc.inner.ReadRuneType()
// Check if we need to insert a premature EOF
if t != RuneTypeError && t != RuneTypeEOF {
if sc.repeat {
sc.repeat = false
} else {
sc.rType, _ = sc.parser.HandleRune(r)
}
if sc.rType == RuneTypeEOF {
_ = sc.inner.UnreadRune()
}
t = sc.rType
}
if t == RuneTypeEOF {
return 0, 0, RuneTypeEOF, nil
}
return r, s, t, e
}
func (sc *elemRuneTypeScanner) ReadRune() (rune, int, error) {
r, s, t, e := sc.ReadRuneType()
switch t {
case RuneTypeEOF:
return 0, 0, io.EOF
case RuneTypeError:
return 0, 0, e
default:
return r, s, nil
}
}
func (sc *elemRuneTypeScanner) UnreadRune() error {
sc.repeat = true
return sc.inner.UnreadRune()
}
func (sc *elemRuneTypeScanner) InputOffset() int64 { return sc.inner.InputOffset() }
func (sc *elemRuneTypeScanner) Reset() {}
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