gotosocial/vendor/github.com/goccy/go-json/decode_slice.go

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package json
import (
"reflect"
"sync"
"unsafe"
)
type sliceDecoder struct {
elemType *rtype
isElemPointerType bool
valueDecoder decoder
size uintptr
arrayPool sync.Pool
structName string
fieldName string
}
// If use reflect.SliceHeader, data type is uintptr.
// In this case, Go compiler cannot trace reference created by newArray().
// So, define using unsafe.Pointer as data type
type sliceHeader struct {
data unsafe.Pointer
len int
cap int
}
const (
defaultSliceCapacity = 2
)
func newSliceDecoder(dec decoder, elemType *rtype, size uintptr, structName, fieldName string) *sliceDecoder {
return &sliceDecoder{
valueDecoder: dec,
elemType: elemType,
isElemPointerType: elemType.Kind() == reflect.Ptr || elemType.Kind() == reflect.Map,
size: size,
arrayPool: sync.Pool{
New: func() interface{} {
return &sliceHeader{
data: newArray(elemType, defaultSliceCapacity),
len: 0,
cap: defaultSliceCapacity,
}
},
},
structName: structName,
fieldName: fieldName,
}
}
func (d *sliceDecoder) newSlice(src *sliceHeader) *sliceHeader {
slice := d.arrayPool.Get().(*sliceHeader)
if src.len > 0 {
// copy original elem
if slice.cap < src.cap {
data := newArray(d.elemType, src.cap)
slice = &sliceHeader{data: data, len: src.len, cap: src.cap}
} else {
slice.len = src.len
}
copySlice(d.elemType, *slice, *src)
} else {
slice.len = 0
}
return slice
}
func (d *sliceDecoder) releaseSlice(p *sliceHeader) {
d.arrayPool.Put(p)
}
//go:linkname copySlice reflect.typedslicecopy
func copySlice(elemType *rtype, dst, src sliceHeader) int
//go:linkname newArray reflect.unsafe_NewArray
func newArray(*rtype, int) unsafe.Pointer
//go:linkname typedmemmove reflect.typedmemmove
func typedmemmove(t *rtype, dst, src unsafe.Pointer)
func (d *sliceDecoder) errNumber(offset int64) *UnmarshalTypeError {
return &UnmarshalTypeError{
Value: "number",
Type: reflect.SliceOf(rtype2type(d.elemType)),
Struct: d.structName,
Field: d.fieldName,
Offset: offset,
}
}
func (d *sliceDecoder) decodeStream(s *stream, depth int64, p unsafe.Pointer) error {
depth++
if depth > maxDecodeNestingDepth {
return errExceededMaxDepth(s.char(), s.cursor)
}
for {
switch s.char() {
case ' ', '\n', '\t', '\r':
s.cursor++
continue
case 'n':
if err := nullBytes(s); err != nil {
return err
}
*(*unsafe.Pointer)(p) = nil
return nil
case '[':
s.cursor++
s.skipWhiteSpace()
if s.char() == ']' {
dst := (*sliceHeader)(p)
if dst.data == nil {
dst.data = newArray(d.elemType, 0)
} else {
dst.len = 0
}
s.cursor++
return nil
}
idx := 0
slice := d.newSlice((*sliceHeader)(p))
srcLen := slice.len
capacity := slice.cap
data := slice.data
for {
if capacity <= idx {
src := sliceHeader{data: data, len: idx, cap: capacity}
capacity *= 2
data = newArray(d.elemType, capacity)
dst := sliceHeader{data: data, len: idx, cap: capacity}
copySlice(d.elemType, dst, src)
}
ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
// if srcLen is greater than idx, keep the original reference
if srcLen <= idx {
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
}
}
if err := d.valueDecoder.decodeStream(s, depth, ep); err != nil {
return err
}
s.skipWhiteSpace()
RETRY:
switch s.char() {
case ']':
slice.cap = capacity
slice.len = idx + 1
slice.data = data
dst := (*sliceHeader)(p)
dst.len = idx + 1
if dst.len > dst.cap {
dst.data = newArray(d.elemType, dst.len)
dst.cap = dst.len
}
copySlice(d.elemType, *dst, *slice)
d.releaseSlice(slice)
s.cursor++
return nil
case ',':
idx++
case nul:
if s.read() {
goto RETRY
}
slice.cap = capacity
slice.data = data
d.releaseSlice(slice)
goto ERROR
default:
slice.cap = capacity
slice.data = data
d.releaseSlice(slice)
goto ERROR
}
s.cursor++
}
case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return d.errNumber(s.totalOffset())
case nul:
if s.read() {
continue
}
goto ERROR
default:
goto ERROR
}
}
ERROR:
return errUnexpectedEndOfJSON("slice", s.totalOffset())
}
func (d *sliceDecoder) decode(buf []byte, cursor, depth int64, p unsafe.Pointer) (int64, error) {
depth++
if depth > maxDecodeNestingDepth {
return 0, errExceededMaxDepth(buf[cursor], cursor)
}
for {
switch buf[cursor] {
case ' ', '\n', '\t', '\r':
cursor++
continue
case 'n':
if err := validateNull(buf, cursor); err != nil {
return 0, err
}
cursor += 4
*(*unsafe.Pointer)(p) = nil
return cursor, nil
case '[':
cursor++
cursor = skipWhiteSpace(buf, cursor)
if buf[cursor] == ']' {
dst := (*sliceHeader)(p)
if dst.data == nil {
dst.data = newArray(d.elemType, 0)
} else {
dst.len = 0
}
cursor++
return cursor, nil
}
idx := 0
slice := d.newSlice((*sliceHeader)(p))
srcLen := slice.len
capacity := slice.cap
data := slice.data
for {
if capacity <= idx {
src := sliceHeader{data: data, len: idx, cap: capacity}
capacity *= 2
data = newArray(d.elemType, capacity)
dst := sliceHeader{data: data, len: idx, cap: capacity}
copySlice(d.elemType, dst, src)
}
ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
// if srcLen is greater than idx, keep the original reference
if srcLen <= idx {
if d.isElemPointerType {
**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
} else {
// assign new element to the slice
typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
}
}
c, err := d.valueDecoder.decode(buf, cursor, depth, ep)
if err != nil {
return 0, err
}
cursor = c
cursor = skipWhiteSpace(buf, cursor)
switch buf[cursor] {
case ']':
slice.cap = capacity
slice.len = idx + 1
slice.data = data
dst := (*sliceHeader)(p)
dst.len = idx + 1
if dst.len > dst.cap {
dst.data = newArray(d.elemType, dst.len)
dst.cap = dst.len
}
copySlice(d.elemType, *dst, *slice)
d.releaseSlice(slice)
cursor++
return cursor, nil
case ',':
idx++
default:
slice.cap = capacity
slice.data = data
d.releaseSlice(slice)
return 0, errInvalidCharacter(buf[cursor], "slice", cursor)
}
cursor++
}
case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return 0, d.errNumber(cursor)
default:
return 0, errUnexpectedEndOfJSON("slice", cursor)
}
}
}