gtsocial-umbx

stream.go (11888B)

---

 // 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
 	scanp int // start of unread data in buf
 	scan  scanner
 	err   error
 
 	tokenState int
 	tokenStack []int
 }
 
 // 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}
 }
 
 // Deprecated: Use `SetNumberType` instead
 // 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.numberType = UnmarshalJSONNumber }
 
 // SetNumberType causes the Decoder to unmarshal a number into an interface{} as a
 // Number, float64 or int64 depending on `t` enum value.
 func (dec *Decoder) SetNumberType(t NumberUnmarshalType) { dec.d.numberType = t }
 
 // 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
 	}
 
 	if err := dec.tokenPrepareForDecode(); err != nil {
 		return err
 	}
 
 	if !dec.tokenValueAllowed() {
 		return &SyntaxError{msg: "not at beginning of value"}
 	}
 
 	// Read whole value into buffer.
 	n, err := dec.readValue()
 	if err != nil {
 		return err
 	}
 	dec.d.init(dec.buf[dec.scanp : dec.scanp+n])
 	dec.scanp += n
 
 	// 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.
 	err = dec.d.unmarshal(v)
 
 	// fixup token streaming state
 	dec.tokenValueEnd()
 
 	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[dec.scanp:])
 }
 
 // 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 := dec.scanp
 	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, 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
 		}
 
 		n := scanp - dec.scanp
 		err = dec.refill()
 		scanp = dec.scanp + n
 	}
 	return scanp - dec.scanp, nil
 }
 
 func (dec *Decoder) refill() error {
 	// Make room to read more into the buffer.
 	// First slide down data already consumed.
 	if dec.scanp > 0 {
 		n := copy(dec.buf, dec.buf[dec.scanp:])
 		dec.buf = dec.buf[:n]
 		dec.scanp = 0
 	}
 
 	// Grow buffer if not large enough.
 	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).
 	n, err := dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
 	dec.buf = dec.buf[0 : len(dec.buf)+n]
 
 	return err
 }
 
 func nonSpace(b []byte) bool {
 	for _, c := range b {
 		if !isSpace(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)
 
 // A Token holds a value of one of these types:
 //
 //	Delim, for the four JSON delimiters [ ] { }
 //	bool, for JSON booleans
 //	float64, for JSON numbers
 //	Number, for JSON numbers
 //	string, for JSON string literals
 //	nil, for JSON null
 //
 type Token interface{}
 
 const (
 	tokenTopValue = iota
 	tokenArrayStart
 	tokenArrayValue
 	tokenArrayComma
 	tokenObjectStart
 	tokenObjectKey
 	tokenObjectColon
 	tokenObjectValue
 	tokenObjectComma
 )
 
 // advance tokenstate from a separator state to a value state
 func (dec *Decoder) tokenPrepareForDecode() error {
 	// Note: Not calling peek before switch, to avoid
 	// putting peek into the standard Decode path.
 	// peek is only called when using the Token API.
 	switch dec.tokenState {
 	case tokenArrayComma:
 		c, err := dec.peek()
 		if err != nil {
 			return err
 		}
 		if c != ',' {
 			return &SyntaxError{"expected comma after array element", 0}
 		}
 		dec.scanp++
 		dec.tokenState = tokenArrayValue
 	case tokenObjectColon:
 		c, err := dec.peek()
 		if err != nil {
 			return err
 		}
 		if c != ':' {
 			return &SyntaxError{"expected colon after object key", 0}
 		}
 		dec.scanp++
 		dec.tokenState = tokenObjectValue
 	}
 	return nil
 }
 
 func (dec *Decoder) tokenValueAllowed() bool {
 	switch dec.tokenState {
 	case tokenTopValue, tokenArrayStart, tokenArrayValue, tokenObjectValue:
 		return true
 	}
 	return false
 }
 
 func (dec *Decoder) tokenValueEnd() {
 	switch dec.tokenState {
 	case tokenArrayStart, tokenArrayValue:
 		dec.tokenState = tokenArrayComma
 	case tokenObjectValue:
 		dec.tokenState = tokenObjectComma
 	}
 }
 
 // A Delim is a JSON array or object delimiter, one of [ ] { or }.
 type Delim rune
 
 func (d Delim) String() string {
 	return string(d)
 }
 
 // Token returns the next JSON token in the input stream.
 // At the end of the input stream, Token returns nil, io.EOF.
 //
 // Token guarantees that the delimiters [ ] { } it returns are
 // properly nested and matched: if Token encounters an unexpected
 // delimiter in the input, it will return an error.
 //
 // The input stream consists of basic JSON values—bool, string,
 // number, and null—along with delimiters [ ] { } of type Delim
 // to mark the start and end of arrays and objects.
 // Commas and colons are elided.
 func (dec *Decoder) Token() (Token, error) {
 	for {
 		c, err := dec.peek()
 		if err != nil {
 			return nil, err
 		}
 		switch c {
 		case '[':
 			if !dec.tokenValueAllowed() {
 				return dec.tokenError(c)
 			}
 			dec.scanp++
 			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
 			dec.tokenState = tokenArrayStart
 			return Delim('['), nil
 
 		case ']':
 			if dec.tokenState != tokenArrayStart && dec.tokenState != tokenArrayComma {
 				return dec.tokenError(c)
 			}
 			dec.scanp++
 			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
 			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
 			dec.tokenValueEnd()
 			return Delim(']'), nil
 
 		case '{':
 			if !dec.tokenValueAllowed() {
 				return dec.tokenError(c)
 			}
 			dec.scanp++
 			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
 			dec.tokenState = tokenObjectStart
 			return Delim('{'), nil
 
 		case '}':
 			if dec.tokenState != tokenObjectStart && dec.tokenState != tokenObjectComma {
 				return dec.tokenError(c)
 			}
 			dec.scanp++
 			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
 			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
 			dec.tokenValueEnd()
 			return Delim('}'), nil
 
 		case ':':
 			if dec.tokenState != tokenObjectColon {
 				return dec.tokenError(c)
 			}
 			dec.scanp++
 			dec.tokenState = tokenObjectValue
 			continue
 
 		case ',':
 			if dec.tokenState == tokenArrayComma {
 				dec.scanp++
 				dec.tokenState = tokenArrayValue
 				continue
 			}
 			if dec.tokenState == tokenObjectComma {
 				dec.scanp++
 				dec.tokenState = tokenObjectKey
 				continue
 			}
 			return dec.tokenError(c)
 
 		case '"':
 			if dec.tokenState == tokenObjectStart || dec.tokenState == tokenObjectKey {
 				var x string
 				old := dec.tokenState
 				dec.tokenState = tokenTopValue
 				err := dec.Decode(&x)
 				dec.tokenState = old
 				if err != nil {
 					clearOffset(err)
 					return nil, err
 				}
 				dec.tokenState = tokenObjectColon
 				return x, nil
 			}
 			fallthrough
 
 		default:
 			if !dec.tokenValueAllowed() {
 				return dec.tokenError(c)
 			}
 			var x interface{}
 			if err := dec.Decode(&x); err != nil {
 				clearOffset(err)
 				return nil, err
 			}
 			return x, nil
 		}
 	}
 }
 
 func clearOffset(err error) {
 	if s, ok := err.(*SyntaxError); ok {
 		s.Offset = 0
 	}
 }
 
 func (dec *Decoder) tokenError(c byte) (Token, error) {
 	var context string
 	switch dec.tokenState {
 	case tokenTopValue:
 		context = " looking for beginning of value"
 	case tokenArrayStart, tokenArrayValue, tokenObjectValue:
 		context = " looking for beginning of value"
 	case tokenArrayComma:
 		context = " after array element"
 	case tokenObjectKey:
 		context = " looking for beginning of object key string"
 	case tokenObjectColon:
 		context = " after object key"
 	case tokenObjectComma:
 		context = " after object key:value pair"
 	}
 	return nil, &SyntaxError{"invalid character " + quoteChar(c) + " " + context, 0}
 }
 
 // More reports whether there is another element in the
 // current array or object being parsed.
 func (dec *Decoder) More() bool {
 	c, err := dec.peek()
 	return err == nil && c != ']' && c != '}'
 }
 
 func (dec *Decoder) peek() (byte, error) {
 	var err error
 	for {
 		for i := dec.scanp; i < len(dec.buf); i++ {
 			c := dec.buf[i]
 			if isSpace(c) {
 				continue
 			}
 			dec.scanp = i
 			return c, nil
 		}
 		// buffer has been scanned, now report any error
 		if err != nil {
 			return 0, err
 		}
 		err = dec.refill()
 	}
 }
 
 /*
 TODO
 
 // EncodeToken writes the given JSON token to the stream.
 // It returns an error if the delimiters [ ] { } are not properly used.
 //
 // EncodeToken does not call Flush, because usually it is part of
 // a larger operation such as Encode, and those will call Flush when finished.
 // Callers that create an Encoder and then invoke EncodeToken directly,
 // without using Encode, need to call Flush when finished to ensure that
 // the JSON is written to the underlying writer.
 func (e *Encoder) EncodeToken(t Token) error  {
 	...
 }
 
 */