mirror of https://github.com/goccy/go-json.git
119 lines
2.7 KiB
Go
119 lines
2.7 KiB
Go
package json
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import (
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"reflect"
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"sync"
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"unsafe"
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)
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type sliceDecoder struct {
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elemType *rtype
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valueDecoder decoder
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size uintptr
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arrayPool sync.Pool
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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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func newSliceDecoder(dec decoder, elemType *rtype, size uintptr) *sliceDecoder {
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return &sliceDecoder{
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valueDecoder: dec,
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elemType: elemType,
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size: size,
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arrayPool: sync.Pool{
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New: func() interface{} {
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cap := 2
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return &sliceHeader{
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data: newArray(elemType, cap),
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len: 0,
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cap: cap,
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}
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},
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},
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}
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}
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func (d *sliceDecoder) newSlice() *sliceHeader {
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slice := d.arrayPool.Get().(*sliceHeader)
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slice.len = 0
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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 *rtype, dst, src reflect.SliceHeader) int
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//go:linkname newArray reflect.unsafe_NewArray
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func newArray(*rtype, int) unsafe.Pointer
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func (d *sliceDecoder) decode(buf []byte, cursor int64, p uintptr) (int64, error) {
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buflen := int64(len(buf))
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for ; cursor < buflen; cursor++ {
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switch buf[cursor] {
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case ' ', '\n', '\t', '\r':
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continue
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case '[':
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idx := 0
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slice := d.newSlice()
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cap := slice.cap
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data := slice.data
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for {
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cursor++
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if cap <= idx {
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src := reflect.SliceHeader{Data: uintptr(data), Len: idx, Cap: cap}
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cap *= 2
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data = newArray(d.elemType, cap)
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dst := reflect.SliceHeader{Data: uintptr(data), Len: idx, Cap: cap}
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copySlice(d.elemType, dst, src)
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}
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c, err := d.valueDecoder.decode(buf, cursor, uintptr(data)+uintptr(idx)*d.size)
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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 = cap
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slice.len = idx + 1
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slice.data = data
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dstCap := idx + 1
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dst := reflect.SliceHeader{
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Data: uintptr(newArray(d.elemType, dstCap)),
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Len: idx + 1,
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Cap: dstCap,
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}
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copySlice(d.elemType, dst, reflect.SliceHeader{
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Data: uintptr(slice.data),
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Len: slice.len,
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Cap: slice.cap,
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})
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*(*reflect.SliceHeader)(unsafe.Pointer(p)) = dst
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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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continue
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default:
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slice.cap = cap
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slice.data = data
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d.releaseSlice(slice)
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return 0, errInvalidCharacter(buf[cursor], "slice", cursor)
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}
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}
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}
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}
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return 0, errUnexpectedEndOfJSON("slice", cursor)
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}
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