go-json/decode.go

234 lines
4.8 KiB
Go

package json
import (
"encoding"
"io"
"reflect"
"strconv"
"unsafe"
)
type Delim rune
func (d Delim) String() string {
return string(d)
}
type decoder interface {
decode([]byte, int64, unsafe.Pointer) (int64, error)
decodeStream(*stream, unsafe.Pointer) error
}
type Decoder struct {
s *stream
structTypeToDecoder map[uintptr]decoder
}
var (
unmarshalJSONType = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
unmarshalTextType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
)
const (
nul = '\000'
)
// NewDecoder returns a new decoder that reads from r.
//
// The decoder introduces its own buffering and may
// read data from r beyond the JSON values requested.
func NewDecoder(r io.Reader) *Decoder {
s := newStream(r)
return &Decoder{
s: s,
}
}
// Buffered returns a reader of the data remaining in the Decoder's
// buffer. The reader is valid until the next call to Decode.
func (d *Decoder) Buffered() io.Reader {
return d.s.buffered()
}
func (d *Decoder) validateType(typ *rtype, p uintptr) error {
if typ.Kind() != reflect.Ptr || p == 0 {
return &InvalidUnmarshalError{Type: rtype2type(typ)}
}
return nil
}
func (d *Decoder) decode(src []byte, header *interfaceHeader) error {
typ := header.typ
typeptr := uintptr(unsafe.Pointer(typ))
// noescape trick for header.typ ( reflect.*rtype )
copiedType := *(**rtype)(unsafe.Pointer(&typeptr))
ptr := uintptr(header.ptr)
if err := d.validateType(copiedType, ptr); err != nil {
return err
}
dec, err := decodeCompileToGetDecoder(typeptr, typ)
if err != nil {
return err
}
if _, err := dec.decode(src, 0, header.ptr); err != nil {
return err
}
return nil
}
func (d *Decoder) decodeForUnmarshal(src []byte, v interface{}) error {
header := (*interfaceHeader)(unsafe.Pointer(&v))
header.typ.escape()
return d.decode(src, header)
}
func (d *Decoder) decodeForUnmarshalNoEscape(src []byte, v interface{}) error {
header := (*interfaceHeader)(unsafe.Pointer(&v))
return d.decode(src, header)
}
func (d *Decoder) prepareForDecode() error {
s := d.s
for {
switch s.char() {
case ' ', '\t', '\r', '\n':
s.cursor++
continue
case ',', ':':
s.cursor++
return nil
case nul:
if s.read() {
continue
}
return io.EOF
}
break
}
return nil
}
// Decode reads the next JSON-encoded value from its
// input and stores it in the value pointed to by v.
//
// See the documentation for Unmarshal for details about
// the conversion of JSON into a Go value.
func (d *Decoder) Decode(v interface{}) error {
header := (*interfaceHeader)(unsafe.Pointer(&v))
typ := header.typ
ptr := uintptr(header.ptr)
typeptr := uintptr(unsafe.Pointer(typ))
// noescape trick for header.typ ( reflect.*rtype )
copiedType := *(**rtype)(unsafe.Pointer(&typeptr))
if err := d.validateType(copiedType, ptr); err != nil {
return err
}
dec, err := decodeCompileToGetDecoder(typeptr, typ)
if err != nil {
return err
}
if err := d.prepareForDecode(); err != nil {
return err
}
s := d.s
if err := dec.decodeStream(s, header.ptr); err != nil {
return err
}
return nil
}
func (d *Decoder) More() bool {
s := d.s
for {
switch s.char() {
case ' ', '\n', '\r', '\t':
s.cursor++
continue
case '}', ']':
return false
case nul:
if s.read() {
continue
}
return false
}
break
}
return true
}
func (d *Decoder) Token() (Token, error) {
s := d.s
for {
c := s.char()
switch c {
case ' ', '\n', '\r', '\t':
s.cursor++
case '{', '[', ']', '}':
s.cursor++
return Delim(c), nil
case ',', ':':
s.cursor++
case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
bytes := floatBytes(s)
s := *(*string)(unsafe.Pointer(&bytes))
f64, err := strconv.ParseFloat(s, 64)
if err != nil {
return nil, err
}
return f64, nil
case '"':
bytes, err := stringBytes(s)
if err != nil {
return nil, err
}
return string(bytes), nil
case 't':
if err := trueBytes(s); err != nil {
return nil, err
}
return true, nil
case 'f':
if err := falseBytes(s); err != nil {
return nil, err
}
return false, nil
case 'n':
if err := nullBytes(s); err != nil {
return nil, err
}
return nil, nil
case nul:
if s.read() {
continue
}
goto END
default:
return nil, errInvalidCharacter(s.char(), "token", s.totalOffset())
}
}
END:
return nil, io.EOF
}
// DisallowUnknownFields causes the Decoder to return an error when the destination
// is a struct and the input contains object keys which do not match any
// non-ignored, exported fields in the destination.
func (d *Decoder) DisallowUnknownFields() {
d.s.disallowUnknownFields = true
}
func (d *Decoder) InputOffset() int64 {
return d.s.totalOffset()
}
// UseNumber causes the Decoder to unmarshal a number into an interface{} as a
// Number instead of as a float64.
func (d *Decoder) UseNumber() {
d.s.useNumber = true
}