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- // Copyright 2010 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
- package json
- import (
- "bytes"
- "errors"
- "io"
- )
- // A Decoder reads and decodes JSON objects from an input stream.
- type Decoder struct {
- r io.Reader
- buf []byte
- d decodeState
- scan Scanner
- err error
- }
- // 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 {
- return &Decoder{r: r}
- }
- // UseNumber causes the Decoder to unmarshal a number into an interface{} as a
- // Number instead of as a float64.
- func (dec *Decoder) UseNumber() { dec.d.useNumber = true }
- // 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 (dec *Decoder) Decode(v interface{}) error {
- if dec.err != nil {
- return dec.err
- }
- n, err := dec.readValue()
- if err != nil {
- return err
- }
- // Don't save err from unmarshal into dec.err:
- // the connection is still usable since we read a complete JSON
- // object from it before the error happened.
- dec.d.init(dec.buf[0:n])
- err = dec.d.unmarshal(v)
- // Slide rest of data down.
- rest := copy(dec.buf, dec.buf[n:])
- dec.buf = dec.buf[0:rest]
- return err
- }
- // Buffered returns a reader of the data remaining in the Decoder's
- // buffer. The reader is valid until the next call to Decode.
- func (dec *Decoder) Buffered() io.Reader {
- return bytes.NewReader(dec.buf)
- }
- // readValue reads a JSON value into dec.buf.
- // It returns the length of the encoding.
- func (dec *Decoder) readValue() (int, error) {
- dec.scan.Reset()
- scanp := 0
- var err error
- Input:
- for {
- // Look in the buffer for a new value.
- for i, c := range dec.buf[scanp:] {
- dec.scan.bytes++
- v := dec.scan.Step(&dec.scan, int(c))
- if v == ScanEnd {
- scanp += i
- break Input
- }
- // scanEnd is delayed one byte.
- // We might block trying to get that byte from src,
- // so instead invent a space byte.
- if (v == ScanEndObject || v == ScanEndArray) && dec.scan.Step(&dec.scan, ' ') == ScanEnd {
- scanp += i + 1
- break Input
- }
- if v == ScanError {
- dec.err = dec.scan.Err
- return 0, dec.scan.Err
- }
- }
- scanp = len(dec.buf)
- // Did the last read have an error?
- // Delayed until now to allow buffer scan.
- if err != nil {
- if err == io.EOF {
- if dec.scan.Step(&dec.scan, ' ') == ScanEnd {
- break Input
- }
- if nonSpace(dec.buf) {
- err = io.ErrUnexpectedEOF
- }
- }
- dec.err = err
- return 0, err
- }
- // Make room to read more into the buffer.
- const minRead = 512
- if cap(dec.buf)-len(dec.buf) < minRead {
- newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
- copy(newBuf, dec.buf)
- dec.buf = newBuf
- }
- // Read. Delay error for next iteration (after scan).
- var n int
- n, err = dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
- dec.buf = dec.buf[0 : len(dec.buf)+n]
- }
- return scanp, nil
- }
- func nonSpace(b []byte) bool {
- for _, c := range b {
- if !isSpace(rune(c)) {
- return true
- }
- }
- return false
- }
- // An Encoder writes JSON objects to an output stream.
- type Encoder struct {
- w io.Writer
- err error
- }
- // NewEncoder returns a new encoder that writes to w.
- func NewEncoder(w io.Writer) *Encoder {
- return &Encoder{w: w}
- }
- // Encode writes the JSON encoding of v to the stream,
- // followed by a newline character.
- //
- // See the documentation for Marshal for details about the
- // conversion of Go values to JSON.
- func (enc *Encoder) Encode(v interface{}) error {
- if enc.err != nil {
- return enc.err
- }
- e := newEncodeState()
- err := e.marshal(v)
- if err != nil {
- return err
- }
- // Terminate each value with a newline.
- // This makes the output look a little nicer
- // when debugging, and some kind of space
- // is required if the encoded value was a number,
- // so that the reader knows there aren't more
- // digits coming.
- e.WriteByte('\n')
- if _, err = enc.w.Write(e.Bytes()); err != nil {
- enc.err = err
- }
- encodeStatePool.Put(e)
- return err
- }
- // RawMessage is a raw encoded JSON object.
- // It implements Marshaler and Unmarshaler and can
- // be used to delay JSON decoding or precompute a JSON encoding.
- type RawMessage []byte
- // MarshalJSON returns *m as the JSON encoding of m.
- func (m *RawMessage) MarshalJSON() ([]byte, error) {
- return *m, nil
- }
- // UnmarshalJSON sets *m to a copy of data.
- func (m *RawMessage) UnmarshalJSON(data []byte) error {
- if m == nil {
- return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
- }
- *m = append((*m)[0:0], data...)
- return nil
- }
- var _ Marshaler = (*RawMessage)(nil)
- var _ Unmarshaler = (*RawMessage)(nil)
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