stream.go

Documentation: gopkg.in/go-jose/go-jose.v2/json

     1  // Copyright 2010 The Go Authors.  All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package json
     6  
     7  import (
     8  	"bytes"
     9  	"errors"
    10  	"io"
    11  )
    12  
    13  // A Decoder reads and decodes JSON objects from an input stream.
    14  type Decoder struct {
    15  	r     io.Reader
    16  	buf   []byte
    17  	d     decodeState
    18  	scanp int // start of unread data in buf
    19  	scan  scanner
    20  	err   error
    21  
    22  	tokenState int
    23  	tokenStack []int
    24  }
    25  
    26  // NewDecoder returns a new decoder that reads from r.
    27  //
    28  // The decoder introduces its own buffering and may
    29  // read data from r beyond the JSON values requested.
    30  func NewDecoder(r io.Reader) *Decoder {
    31  	return &Decoder{r: r}
    32  }
    33  
    34  // Deprecated: Use `SetNumberType` instead
    35  // UseNumber causes the Decoder to unmarshal a number into an interface{} as a
    36  // Number instead of as a float64.
    37  func (dec *Decoder) UseNumber() { dec.d.numberType = UnmarshalJSONNumber }
    38  
    39  // SetNumberType causes the Decoder to unmarshal a number into an interface{} as a
    40  // Number, float64 or int64 depending on `t` enum value.
    41  func (dec *Decoder) SetNumberType(t NumberUnmarshalType) { dec.d.numberType = t }
    42  
    43  // Decode reads the next JSON-encoded value from its
    44  // input and stores it in the value pointed to by v.
    45  //
    46  // See the documentation for Unmarshal for details about
    47  // the conversion of JSON into a Go value.
    48  func (dec *Decoder) Decode(v interface{}) error {
    49  	if dec.err != nil {
    50  		return dec.err
    51  	}
    52  
    53  	if err := dec.tokenPrepareForDecode(); err != nil {
    54  		return err
    55  	}
    56  
    57  	if !dec.tokenValueAllowed() {
    58  		return &SyntaxError{msg: "not at beginning of value"}
    59  	}
    60  
    61  	// Read whole value into buffer.
    62  	n, err := dec.readValue()
    63  	if err != nil {
    64  		return err
    65  	}
    66  	dec.d.init(dec.buf[dec.scanp : dec.scanp+n])
    67  	dec.scanp += n
    68  
    69  	// Don't save err from unmarshal into dec.err:
    70  	// the connection is still usable since we read a complete JSON
    71  	// object from it before the error happened.
    72  	err = dec.d.unmarshal(v)
    73  
    74  	// fixup token streaming state
    75  	dec.tokenValueEnd()
    76  
    77  	return err
    78  }
    79  
    80  // Buffered returns a reader of the data remaining in the Decoder's
    81  // buffer. The reader is valid until the next call to Decode.
    82  func (dec *Decoder) Buffered() io.Reader {
    83  	return bytes.NewReader(dec.buf[dec.scanp:])
    84  }
    85  
    86  // readValue reads a JSON value into dec.buf.
    87  // It returns the length of the encoding.
    88  func (dec *Decoder) readValue() (int, error) {
    89  	dec.scan.reset()
    90  
    91  	scanp := dec.scanp
    92  	var err error
    93  Input:
    94  	for {
    95  		// Look in the buffer for a new value.
    96  		for i, c := range dec.buf[scanp:] {
    97  			dec.scan.bytes++
    98  			v := dec.scan.step(&dec.scan, c)
    99  			if v == scanEnd {
   100  				scanp += i
   101  				break Input
   102  			}
   103  			// scanEnd is delayed one byte.
   104  			// We might block trying to get that byte from src,
   105  			// so instead invent a space byte.
   106  			if (v == scanEndObject || v == scanEndArray) && dec.scan.step(&dec.scan, ' ') == scanEnd {
   107  				scanp += i + 1
   108  				break Input
   109  			}
   110  			if v == scanError {
   111  				dec.err = dec.scan.err
   112  				return 0, dec.scan.err
   113  			}
   114  		}
   115  		scanp = len(dec.buf)
   116  
   117  		// Did the last read have an error?
   118  		// Delayed until now to allow buffer scan.
   119  		if err != nil {
   120  			if err == io.EOF {
   121  				if dec.scan.step(&dec.scan, ' ') == scanEnd {
   122  					break Input
   123  				}
   124  				if nonSpace(dec.buf) {
   125  					err = io.ErrUnexpectedEOF
   126  				}
   127  			}
   128  			dec.err = err
   129  			return 0, err
   130  		}
   131  
   132  		n := scanp - dec.scanp
   133  		err = dec.refill()
   134  		scanp = dec.scanp + n
   135  	}
   136  	return scanp - dec.scanp, nil
   137  }
   138  
   139  func (dec *Decoder) refill() error {
   140  	// Make room to read more into the buffer.
   141  	// First slide down data already consumed.
   142  	if dec.scanp > 0 {
   143  		n := copy(dec.buf, dec.buf[dec.scanp:])
   144  		dec.buf = dec.buf[:n]
   145  		dec.scanp = 0
   146  	}
   147  
   148  	// Grow buffer if not large enough.
   149  	const minRead = 512
   150  	if cap(dec.buf)-len(dec.buf) < minRead {
   151  		newBuf := make([]byte, len(dec.buf), 2*cap(dec.buf)+minRead)
   152  		copy(newBuf, dec.buf)
   153  		dec.buf = newBuf
   154  	}
   155  
   156  	// Read.  Delay error for next iteration (after scan).
   157  	n, err := dec.r.Read(dec.buf[len(dec.buf):cap(dec.buf)])
   158  	dec.buf = dec.buf[0 : len(dec.buf)+n]
   159  
   160  	return err
   161  }
   162  
   163  func nonSpace(b []byte) bool {
   164  	for _, c := range b {
   165  		if !isSpace(c) {
   166  			return true
   167  		}
   168  	}
   169  	return false
   170  }
   171  
   172  // An Encoder writes JSON objects to an output stream.
   173  type Encoder struct {
   174  	w   io.Writer
   175  	err error
   176  }
   177  
   178  // NewEncoder returns a new encoder that writes to w.
   179  func NewEncoder(w io.Writer) *Encoder {
   180  	return &Encoder{w: w}
   181  }
   182  
   183  // Encode writes the JSON encoding of v to the stream,
   184  // followed by a newline character.
   185  //
   186  // See the documentation for Marshal for details about the
   187  // conversion of Go values to JSON.
   188  func (enc *Encoder) Encode(v interface{}) error {
   189  	if enc.err != nil {
   190  		return enc.err
   191  	}
   192  	e := newEncodeState()
   193  	err := e.marshal(v)
   194  	if err != nil {
   195  		return err
   196  	}
   197  
   198  	// Terminate each value with a newline.
   199  	// This makes the output look a little nicer
   200  	// when debugging, and some kind of space
   201  	// is required if the encoded value was a number,
   202  	// so that the reader knows there aren't more
   203  	// digits coming.
   204  	e.WriteByte('\n')
   205  
   206  	if _, err = enc.w.Write(e.Bytes()); err != nil {
   207  		enc.err = err
   208  	}
   209  	encodeStatePool.Put(e)
   210  	return err
   211  }
   212  
   213  // RawMessage is a raw encoded JSON object.
   214  // It implements Marshaler and Unmarshaler and can
   215  // be used to delay JSON decoding or precompute a JSON encoding.
   216  type RawMessage []byte
   217  
   218  // MarshalJSON returns *m as the JSON encoding of m.
   219  func (m *RawMessage) MarshalJSON() ([]byte, error) {
   220  	return *m, nil
   221  }
   222  
   223  // UnmarshalJSON sets *m to a copy of data.
   224  func (m *RawMessage) UnmarshalJSON(data []byte) error {
   225  	if m == nil {
   226  		return errors.New("json.RawMessage: UnmarshalJSON on nil pointer")
   227  	}
   228  	*m = append((*m)[0:0], data...)
   229  	return nil
   230  }
   231  
   232  var _ Marshaler = (*RawMessage)(nil)
   233  var _ Unmarshaler = (*RawMessage)(nil)
   234  
   235  // A Token holds a value of one of these types:
   236  //
   237  //	Delim, for the four JSON delimiters [ ] { }
   238  //	bool, for JSON booleans
   239  //	float64, for JSON numbers
   240  //	Number, for JSON numbers
   241  //	string, for JSON string literals
   242  //	nil, for JSON null
   243  //
   244  type Token interface{}
   245  
   246  const (
   247  	tokenTopValue = iota
   248  	tokenArrayStart
   249  	tokenArrayValue
   250  	tokenArrayComma
   251  	tokenObjectStart
   252  	tokenObjectKey
   253  	tokenObjectColon
   254  	tokenObjectValue
   255  	tokenObjectComma
   256  )
   257  
   258  // advance tokenstate from a separator state to a value state
   259  func (dec *Decoder) tokenPrepareForDecode() error {
   260  	// Note: Not calling peek before switch, to avoid
   261  	// putting peek into the standard Decode path.
   262  	// peek is only called when using the Token API.
   263  	switch dec.tokenState {
   264  	case tokenArrayComma:
   265  		c, err := dec.peek()
   266  		if err != nil {
   267  			return err
   268  		}
   269  		if c != ',' {
   270  			return &SyntaxError{"expected comma after array element", 0}
   271  		}
   272  		dec.scanp++
   273  		dec.tokenState = tokenArrayValue
   274  	case tokenObjectColon:
   275  		c, err := dec.peek()
   276  		if err != nil {
   277  			return err
   278  		}
   279  		if c != ':' {
   280  			return &SyntaxError{"expected colon after object key", 0}
   281  		}
   282  		dec.scanp++
   283  		dec.tokenState = tokenObjectValue
   284  	}
   285  	return nil
   286  }
   287  
   288  func (dec *Decoder) tokenValueAllowed() bool {
   289  	switch dec.tokenState {
   290  	case tokenTopValue, tokenArrayStart, tokenArrayValue, tokenObjectValue:
   291  		return true
   292  	}
   293  	return false
   294  }
   295  
   296  func (dec *Decoder) tokenValueEnd() {
   297  	switch dec.tokenState {
   298  	case tokenArrayStart, tokenArrayValue:
   299  		dec.tokenState = tokenArrayComma
   300  	case tokenObjectValue:
   301  		dec.tokenState = tokenObjectComma
   302  	}
   303  }
   304  
   305  // A Delim is a JSON array or object delimiter, one of [ ] { or }.
   306  type Delim rune
   307  
   308  func (d Delim) String() string {
   309  	return string(d)
   310  }
   311  
   312  // Token returns the next JSON token in the input stream.
   313  // At the end of the input stream, Token returns nil, io.EOF.
   314  //
   315  // Token guarantees that the delimiters [ ] { } it returns are
   316  // properly nested and matched: if Token encounters an unexpected
   317  // delimiter in the input, it will return an error.
   318  //
   319  // The input stream consists of basic JSON values—bool, string,
   320  // number, and null—along with delimiters [ ] { } of type Delim
   321  // to mark the start and end of arrays and objects.
   322  // Commas and colons are elided.
   323  func (dec *Decoder) Token() (Token, error) {
   324  	for {
   325  		c, err := dec.peek()
   326  		if err != nil {
   327  			return nil, err
   328  		}
   329  		switch c {
   330  		case '[':
   331  			if !dec.tokenValueAllowed() {
   332  				return dec.tokenError(c)
   333  			}
   334  			dec.scanp++
   335  			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
   336  			dec.tokenState = tokenArrayStart
   337  			return Delim('['), nil
   338  
   339  		case ']':
   340  			if dec.tokenState != tokenArrayStart && dec.tokenState != tokenArrayComma {
   341  				return dec.tokenError(c)
   342  			}
   343  			dec.scanp++
   344  			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
   345  			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
   346  			dec.tokenValueEnd()
   347  			return Delim(']'), nil
   348  
   349  		case '{':
   350  			if !dec.tokenValueAllowed() {
   351  				return dec.tokenError(c)
   352  			}
   353  			dec.scanp++
   354  			dec.tokenStack = append(dec.tokenStack, dec.tokenState)
   355  			dec.tokenState = tokenObjectStart
   356  			return Delim('{'), nil
   357  
   358  		case '}':
   359  			if dec.tokenState != tokenObjectStart && dec.tokenState != tokenObjectComma {
   360  				return dec.tokenError(c)
   361  			}
   362  			dec.scanp++
   363  			dec.tokenState = dec.tokenStack[len(dec.tokenStack)-1]
   364  			dec.tokenStack = dec.tokenStack[:len(dec.tokenStack)-1]
   365  			dec.tokenValueEnd()
   366  			return Delim('}'), nil
   367  
   368  		case ':':
   369  			if dec.tokenState != tokenObjectColon {
   370  				return dec.tokenError(c)
   371  			}
   372  			dec.scanp++
   373  			dec.tokenState = tokenObjectValue
   374  			continue
   375  
   376  		case ',':
   377  			if dec.tokenState == tokenArrayComma {
   378  				dec.scanp++
   379  				dec.tokenState = tokenArrayValue
   380  				continue
   381  			}
   382  			if dec.tokenState == tokenObjectComma {
   383  				dec.scanp++
   384  				dec.tokenState = tokenObjectKey
   385  				continue
   386  			}
   387  			return dec.tokenError(c)
   388  
   389  		case '"':
   390  			if dec.tokenState == tokenObjectStart || dec.tokenState == tokenObjectKey {
   391  				var x string
   392  				old := dec.tokenState
   393  				dec.tokenState = tokenTopValue
   394  				err := dec.Decode(&x)
   395  				dec.tokenState = old
   396  				if err != nil {
   397  					clearOffset(err)
   398  					return nil, err
   399  				}
   400  				dec.tokenState = tokenObjectColon
   401  				return x, nil
   402  			}
   403  			fallthrough
   404  
   405  		default:
   406  			if !dec.tokenValueAllowed() {
   407  				return dec.tokenError(c)
   408  			}
   409  			var x interface{}
   410  			if err := dec.Decode(&x); err != nil {
   411  				clearOffset(err)
   412  				return nil, err
   413  			}
   414  			return x, nil
   415  		}
   416  	}
   417  }
   418  
   419  func clearOffset(err error) {
   420  	if s, ok := err.(*SyntaxError); ok {
   421  		s.Offset = 0
   422  	}
   423  }
   424  
   425  func (dec *Decoder) tokenError(c byte) (Token, error) {
   426  	var context string
   427  	switch dec.tokenState {
   428  	case tokenTopValue:
   429  		context = " looking for beginning of value"
   430  	case tokenArrayStart, tokenArrayValue, tokenObjectValue:
   431  		context = " looking for beginning of value"
   432  	case tokenArrayComma:
   433  		context = " after array element"
   434  	case tokenObjectKey:
   435  		context = " looking for beginning of object key string"
   436  	case tokenObjectColon:
   437  		context = " after object key"
   438  	case tokenObjectComma:
   439  		context = " after object key:value pair"
   440  	}
   441  	return nil, &SyntaxError{"invalid character " + quoteChar(c) + " " + context, 0}
   442  }
   443  
   444  // More reports whether there is another element in the
   445  // current array or object being parsed.
   446  func (dec *Decoder) More() bool {
   447  	c, err := dec.peek()
   448  	return err == nil && c != ']' && c != '}'
   449  }
   450  
   451  func (dec *Decoder) peek() (byte, error) {
   452  	var err error
   453  	for {
   454  		for i := dec.scanp; i < len(dec.buf); i++ {
   455  			c := dec.buf[i]
   456  			if isSpace(c) {
   457  				continue
   458  			}
   459  			dec.scanp = i
   460  			return c, nil
   461  		}
   462  		// buffer has been scanned, now report any error
   463  		if err != nil {
   464  			return 0, err
   465  		}
   466  		err = dec.refill()
   467  	}
   468  }
   469  
   470  /*
   471  TODO
   472  
   473  // EncodeToken writes the given JSON token to the stream.
   474  // It returns an error if the delimiters [ ] { } are not properly used.
   475  //
   476  // EncodeToken does not call Flush, because usually it is part of
   477  // a larger operation such as Encode, and those will call Flush when finished.
   478  // Callers that create an Encoder and then invoke EncodeToken directly,
   479  // without using Encode, need to call Flush when finished to ensure that
   480  // the JSON is written to the underlying writer.
   481  func (e *Encoder) EncodeToken(t Token) error  {
   482  	...
   483  }
   484  
   485  */
   486
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