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302 lines
7.2 KiB
302 lines
7.2 KiB
package decoder
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import (
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"reflect"
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"sync"
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"unsafe"
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"github.com/goccy/go-json/internal/errors"
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"github.com/goccy/go-json/internal/runtime"
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)
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var (
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sliceType = runtime.Type2RType(
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reflect.TypeOf((*sliceHeader)(nil)).Elem(),
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)
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nilSlice = unsafe.Pointer(&sliceHeader{})
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)
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type sliceDecoder struct {
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elemType *runtime.Type
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isElemPointerType bool
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valueDecoder Decoder
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size uintptr
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arrayPool sync.Pool
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structName string
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fieldName string
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}
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// If use reflect.SliceHeader, data type is uintptr.
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// In this case, Go compiler cannot trace reference created by newArray().
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// So, define using unsafe.Pointer as data type
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type sliceHeader struct {
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data unsafe.Pointer
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len int
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cap int
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}
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const (
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defaultSliceCapacity = 2
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)
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func newSliceDecoder(dec Decoder, elemType *runtime.Type, size uintptr, structName, fieldName string) *sliceDecoder {
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return &sliceDecoder{
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valueDecoder: dec,
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elemType: elemType,
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isElemPointerType: elemType.Kind() == reflect.Ptr || elemType.Kind() == reflect.Map,
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size: size,
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arrayPool: sync.Pool{
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New: func() interface{} {
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return &sliceHeader{
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data: newArray(elemType, defaultSliceCapacity),
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len: 0,
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cap: defaultSliceCapacity,
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}
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},
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},
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structName: structName,
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fieldName: fieldName,
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}
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}
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func (d *sliceDecoder) newSlice(src *sliceHeader) *sliceHeader {
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slice := d.arrayPool.Get().(*sliceHeader)
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if src.len > 0 {
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// copy original elem
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if slice.cap < src.cap {
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data := newArray(d.elemType, src.cap)
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slice = &sliceHeader{data: data, len: src.len, cap: src.cap}
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} else {
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slice.len = src.len
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}
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copySlice(d.elemType, *slice, *src)
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} else {
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slice.len = 0
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}
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return slice
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}
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func (d *sliceDecoder) releaseSlice(p *sliceHeader) {
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d.arrayPool.Put(p)
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}
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//go:linkname copySlice reflect.typedslicecopy
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func copySlice(elemType *runtime.Type, dst, src sliceHeader) int
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//go:linkname newArray reflect.unsafe_NewArray
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func newArray(*runtime.Type, int) unsafe.Pointer
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//go:linkname typedmemmove reflect.typedmemmove
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func typedmemmove(t *runtime.Type, dst, src unsafe.Pointer)
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func (d *sliceDecoder) errNumber(offset int64) *errors.UnmarshalTypeError {
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return &errors.UnmarshalTypeError{
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Value: "number",
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Type: reflect.SliceOf(runtime.RType2Type(d.elemType)),
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Struct: d.structName,
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Field: d.fieldName,
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Offset: offset,
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}
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}
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func (d *sliceDecoder) DecodeStream(s *Stream, depth int64, p unsafe.Pointer) error {
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depth++
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if depth > maxDecodeNestingDepth {
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return errors.ErrExceededMaxDepth(s.char(), s.cursor)
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}
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for {
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switch s.char() {
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case ' ', '\n', '\t', '\r':
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s.cursor++
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continue
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case 'n':
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if err := nullBytes(s); err != nil {
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return err
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}
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typedmemmove(sliceType, p, nilSlice)
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return nil
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case '[':
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s.cursor++
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if s.skipWhiteSpace() == ']' {
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dst := (*sliceHeader)(p)
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if dst.data == nil {
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dst.data = newArray(d.elemType, 0)
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} else {
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dst.len = 0
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}
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s.cursor++
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return nil
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}
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idx := 0
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slice := d.newSlice((*sliceHeader)(p))
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srcLen := slice.len
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capacity := slice.cap
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data := slice.data
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for {
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if capacity <= idx {
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src := sliceHeader{data: data, len: idx, cap: capacity}
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capacity *= 2
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data = newArray(d.elemType, capacity)
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dst := sliceHeader{data: data, len: idx, cap: capacity}
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copySlice(d.elemType, dst, src)
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}
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ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
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// if srcLen is greater than idx, keep the original reference
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if srcLen <= idx {
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if d.isElemPointerType {
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**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
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} else {
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// assign new element to the slice
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typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
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}
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}
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if err := d.valueDecoder.DecodeStream(s, depth, ep); err != nil {
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return err
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}
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s.skipWhiteSpace()
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RETRY:
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switch s.char() {
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case ']':
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slice.cap = capacity
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slice.len = idx + 1
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slice.data = data
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dst := (*sliceHeader)(p)
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dst.len = idx + 1
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if dst.len > dst.cap {
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dst.data = newArray(d.elemType, dst.len)
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dst.cap = dst.len
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}
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copySlice(d.elemType, *dst, *slice)
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d.releaseSlice(slice)
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s.cursor++
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return nil
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case ',':
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idx++
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case nul:
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if s.read() {
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goto RETRY
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}
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slice.cap = capacity
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slice.data = data
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d.releaseSlice(slice)
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goto ERROR
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default:
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slice.cap = capacity
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slice.data = data
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d.releaseSlice(slice)
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goto ERROR
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}
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s.cursor++
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}
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case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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return d.errNumber(s.totalOffset())
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case nul:
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if s.read() {
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continue
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}
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goto ERROR
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default:
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goto ERROR
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}
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}
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ERROR:
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return errors.ErrUnexpectedEndOfJSON("slice", s.totalOffset())
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}
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func (d *sliceDecoder) Decode(ctx *RuntimeContext, cursor, depth int64, p unsafe.Pointer) (int64, error) {
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buf := ctx.Buf
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depth++
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if depth > maxDecodeNestingDepth {
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return 0, errors.ErrExceededMaxDepth(buf[cursor], cursor)
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}
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for {
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switch buf[cursor] {
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case ' ', '\n', '\t', '\r':
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cursor++
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continue
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case 'n':
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if err := validateNull(buf, cursor); err != nil {
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return 0, err
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}
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cursor += 4
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typedmemmove(sliceType, p, nilSlice)
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return cursor, nil
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case '[':
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cursor++
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cursor = skipWhiteSpace(buf, cursor)
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if buf[cursor] == ']' {
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dst := (*sliceHeader)(p)
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if dst.data == nil {
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dst.data = newArray(d.elemType, 0)
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} else {
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dst.len = 0
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}
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cursor++
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return cursor, nil
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}
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idx := 0
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slice := d.newSlice((*sliceHeader)(p))
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srcLen := slice.len
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capacity := slice.cap
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data := slice.data
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for {
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if capacity <= idx {
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src := sliceHeader{data: data, len: idx, cap: capacity}
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capacity *= 2
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data = newArray(d.elemType, capacity)
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dst := sliceHeader{data: data, len: idx, cap: capacity}
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copySlice(d.elemType, dst, src)
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}
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ep := unsafe.Pointer(uintptr(data) + uintptr(idx)*d.size)
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// if srcLen is greater than idx, keep the original reference
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if srcLen <= idx {
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if d.isElemPointerType {
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**(**unsafe.Pointer)(unsafe.Pointer(&ep)) = nil // initialize elem pointer
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} else {
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// assign new element to the slice
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typedmemmove(d.elemType, ep, unsafe_New(d.elemType))
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}
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}
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c, err := d.valueDecoder.Decode(ctx, cursor, depth, ep)
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if err != nil {
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return 0, err
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}
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cursor = c
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cursor = skipWhiteSpace(buf, cursor)
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switch buf[cursor] {
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case ']':
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slice.cap = capacity
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slice.len = idx + 1
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slice.data = data
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dst := (*sliceHeader)(p)
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dst.len = idx + 1
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if dst.len > dst.cap {
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dst.data = newArray(d.elemType, dst.len)
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dst.cap = dst.len
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}
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copySlice(d.elemType, *dst, *slice)
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d.releaseSlice(slice)
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cursor++
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return cursor, nil
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case ',':
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idx++
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default:
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slice.cap = capacity
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slice.data = data
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d.releaseSlice(slice)
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return 0, errors.ErrInvalidCharacter(buf[cursor], "slice", cursor)
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}
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cursor++
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}
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case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
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return 0, d.errNumber(cursor)
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default:
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return 0, errors.ErrUnexpectedEndOfJSON("slice", cursor)
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}
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}
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}
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