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package jsoniter
import (
"fmt"
"io"
"reflect"
"unsafe"
)
func decoderOfSlice(cfg *frozenConfig, typ reflect.Type) (ValDecoder, error) {
decoder, err := decoderOfType(cfg, typ.Elem())
if err != nil {
return nil, err
}
return &sliceDecoder{typ, typ.Elem(), decoder}, nil
}
func encoderOfSlice(cfg *frozenConfig, typ reflect.Type) (ValEncoder, error) {
encoder, err := encoderOfType(cfg, typ.Elem())
if err != nil {
return nil, err
}
if typ.Elem().Kind() == reflect.Map {
encoder = &optionalEncoder{encoder}
}
return &sliceEncoder{typ, typ.Elem(), encoder}, nil
}
type sliceEncoder struct {
sliceType reflect.Type
elemType reflect.Type
elemEncoder ValEncoder
}
func (encoder *sliceEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
slice := (*sliceHeader)(ptr)
if slice.Data == nil {
stream.WriteNil()
return
}
if slice.Len == 0 {
stream.WriteEmptyArray()
return
}
stream.WriteArrayStart()
elemPtr := unsafe.Pointer(slice.Data)
encoder.elemEncoder.Encode(unsafe.Pointer(elemPtr), stream)
for i := 1; i < slice.Len; i++ {
stream.WriteMore()
elemPtr = unsafe.Pointer(uintptr(elemPtr) + encoder.elemType.Size())
encoder.elemEncoder.Encode(unsafe.Pointer(elemPtr), stream)
}
stream.WriteArrayEnd()
if stream.Error != nil && stream.Error != io.EOF {
stream.Error = fmt.Errorf("%v: %s", encoder.sliceType, stream.Error.Error())
}
}
func (encoder *sliceEncoder) EncodeInterface(val interface{}, stream *Stream) {
WriteToStream(val, stream, encoder)
}
func (encoder *sliceEncoder) IsEmpty(ptr unsafe.Pointer) bool {
slice := (*sliceHeader)(ptr)
return slice.Len == 0
}
type sliceDecoder struct {
sliceType reflect.Type
elemType reflect.Type
elemDecoder ValDecoder
}
// sliceHeader is a safe version of SliceHeader used within this package.
type sliceHeader struct {
Data unsafe.Pointer
Len int
Cap int
}
func (decoder *sliceDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
decoder.doDecode(ptr, iter)
if iter.Error != nil && iter.Error != io.EOF {
iter.Error = fmt.Errorf("%v: %s", decoder.sliceType, iter.Error.Error())
}
}
func (decoder *sliceDecoder) doDecode(ptr unsafe.Pointer, iter *Iterator) {
slice := (*sliceHeader)(ptr)
if iter.ReadNil() {
slice.Len = 0
slice.Cap = 0
slice.Data = nil
return
}
reuseSlice(slice, decoder.sliceType, 4)
slice.Len = 0
offset := uintptr(0)
iter.ReadArrayCB(func(iter *Iterator) bool {
growOne(slice, decoder.sliceType, decoder.elemType)
decoder.elemDecoder.Decode(unsafe.Pointer(uintptr(slice.Data)+offset), iter)
offset += decoder.elemType.Size()
return true
})
}
// grow grows the slice s so that it can hold extra more values, allocating
// more capacity if needed. It also returns the old and new slice lengths.
func growOne(slice *sliceHeader, sliceType reflect.Type, elementType reflect.Type) {
newLen := slice.Len + 1
if newLen <= slice.Cap {
slice.Len = newLen
return
}
newCap := slice.Cap
if newCap == 0 {
newCap = 1
} else {
for newCap < newLen {
if slice.Len < 1024 {
newCap += newCap
} else {
newCap += newCap / 4
}
}
}
newVal := reflect.MakeSlice(sliceType, newLen, newCap)
dst := unsafe.Pointer(newVal.Pointer())
// copy old array into new array
originalBytesCount := uintptr(slice.Len) * elementType.Size()
srcPtr := (*[1 << 30]byte)(slice.Data)
dstPtr := (*[1 << 30]byte)(dst)
for i := uintptr(0); i < originalBytesCount; i++ {
dstPtr[i] = srcPtr[i]
}
slice.Data = dst
slice.Len = newLen
slice.Cap = newCap
}
func reuseSlice(slice *sliceHeader, sliceType reflect.Type, expectedCap int) {
if expectedCap <= slice.Cap {
return
}
newVal := reflect.MakeSlice(sliceType, 0, expectedCap)
dst := unsafe.Pointer(newVal.Pointer())
slice.Data = dst
slice.Cap = expectedCap
}
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