Source file src/encoding/json/decode.go

     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	// Represents JSON data structure using native Go types: booleans, floats,
     6	// strings, arrays, and maps.
     7	
     8	package json
     9	
    10	import (
    11		"bytes"
    12		"encoding"
    13		"encoding/base64"
    14		"errors"
    15		"fmt"
    16		"reflect"
    17		"runtime"
    18		"strconv"
    19		"unicode"
    20		"unicode/utf16"
    21		"unicode/utf8"
    22	)
    23	
    24	// Unmarshal parses the JSON-encoded data and stores the result
    25	// in the value pointed to by v.
    26	//
    27	// Unmarshal uses the inverse of the encodings that
    28	// Marshal uses, allocating maps, slices, and pointers as necessary,
    29	// with the following additional rules:
    30	//
    31	// To unmarshal JSON into a pointer, Unmarshal first handles the case of
    32	// the JSON being the JSON literal null. In that case, Unmarshal sets
    33	// the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into
    34	// the value pointed at by the pointer. If the pointer is nil, Unmarshal
    35	// allocates a new value for it to point to.
    36	//
    37	// To unmarshal JSON into a struct, Unmarshal matches incoming object
    38	// keys to the keys used by Marshal (either the struct field name or its tag),
    39	// preferring an exact match but also accepting a case-insensitive match.
    40	// Unmarshal will only set exported fields of the struct.
    41	//
    42	// To unmarshal JSON into an interface value,
    43	// Unmarshal stores one of these in the interface value:
    44	//
    45	//	bool, for JSON booleans
    46	//	float64, for JSON numbers
    47	//	string, for JSON strings
    48	//	[]interface{}, for JSON arrays
    49	//	map[string]interface{}, for JSON objects
    50	//	nil for JSON null
    51	//
    52	// To unmarshal a JSON array into a slice, Unmarshal resets the slice length
    53	// to zero and then appends each element to the slice.
    54	// As a special case, to unmarshal an empty JSON array into a slice,
    55	// Unmarshal replaces the slice with a new empty slice.
    56	//
    57	// To unmarshal a JSON array into a Go array, Unmarshal decodes
    58	// JSON array elements into corresponding Go array elements.
    59	// If the Go array is smaller than the JSON array,
    60	// the additional JSON array elements are discarded.
    61	// If the JSON array is smaller than the Go array,
    62	// the additional Go array elements are set to zero values.
    63	//
    64	// To unmarshal a JSON object into a map, Unmarshal first establishes a map to
    65	// use. If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal
    66	// reuses the existing map, keeping existing entries. Unmarshal then stores key-
    67	// value pairs from the JSON object into the map. The map's key type must
    68	// either be a string, an integer, or implement encoding.TextUnmarshaler.
    69	//
    70	// If a JSON value is not appropriate for a given target type,
    71	// or if a JSON number overflows the target type, Unmarshal
    72	// skips that field and completes the unmarshaling as best it can.
    73	// If no more serious errors are encountered, Unmarshal returns
    74	// an UnmarshalTypeError describing the earliest such error.
    75	//
    76	// The JSON null value unmarshals into an interface, map, pointer, or slice
    77	// by setting that Go value to nil. Because null is often used in JSON to mean
    78	// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
    79	// on the value and produces no error.
    80	//
    81	// When unmarshaling quoted strings, invalid UTF-8 or
    82	// invalid UTF-16 surrogate pairs are not treated as an error.
    83	// Instead, they are replaced by the Unicode replacement
    84	// character U+FFFD.
    85	//
    86	func Unmarshal(data []byte, v interface{}) error {
    87		// Check for well-formedness.
    88		// Avoids filling out half a data structure
    89		// before discovering a JSON syntax error.
    90		var d decodeState
    91		err := checkValid(data, &d.scan)
    92		if err != nil {
    93			return err
    94		}
    95	
    96		d.init(data)
    97		return d.unmarshal(v)
    98	}
    99	
   100	// Unmarshaler is the interface implemented by types
   101	// that can unmarshal a JSON description of themselves.
   102	// The input can be assumed to be a valid encoding of
   103	// a JSON value. UnmarshalJSON must copy the JSON data
   104	// if it wishes to retain the data after returning.
   105	type Unmarshaler interface {
   106		UnmarshalJSON([]byte) error
   107	}
   108	
   109	// An UnmarshalTypeError describes a JSON value that was
   110	// not appropriate for a value of a specific Go type.
   111	type UnmarshalTypeError struct {
   112		Value  string       // description of JSON value - "bool", "array", "number -5"
   113		Type   reflect.Type // type of Go value it could not be assigned to
   114		Offset int64        // error occurred after reading Offset bytes
   115	}
   116	
   117	func (e *UnmarshalTypeError) Error() string {
   118		return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
   119	}
   120	
   121	// An UnmarshalFieldError describes a JSON object key that
   122	// led to an unexported (and therefore unwritable) struct field.
   123	// (No longer used; kept for compatibility.)
   124	type UnmarshalFieldError struct {
   125		Key   string
   126		Type  reflect.Type
   127		Field reflect.StructField
   128	}
   129	
   130	func (e *UnmarshalFieldError) Error() string {
   131		return "json: cannot unmarshal object key " + strconv.Quote(e.Key) + " into unexported field " + e.Field.Name + " of type " + e.Type.String()
   132	}
   133	
   134	// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
   135	// (The argument to Unmarshal must be a non-nil pointer.)
   136	type InvalidUnmarshalError struct {
   137		Type reflect.Type
   138	}
   139	
   140	func (e *InvalidUnmarshalError) Error() string {
   141		if e.Type == nil {
   142			return "json: Unmarshal(nil)"
   143		}
   144	
   145		if e.Type.Kind() != reflect.Ptr {
   146			return "json: Unmarshal(non-pointer " + e.Type.String() + ")"
   147		}
   148		return "json: Unmarshal(nil " + e.Type.String() + ")"
   149	}
   150	
   151	func (d *decodeState) unmarshal(v interface{}) (err error) {
   152		defer func() {
   153			if r := recover(); r != nil {
   154				if _, ok := r.(runtime.Error); ok {
   155					panic(r)
   156				}
   157				err = r.(error)
   158			}
   159		}()
   160	
   161		rv := reflect.ValueOf(v)
   162		if rv.Kind() != reflect.Ptr || rv.IsNil() {
   163			return &InvalidUnmarshalError{reflect.TypeOf(v)}
   164		}
   165	
   166		d.scan.reset()
   167		// We decode rv not rv.Elem because the Unmarshaler interface
   168		// test must be applied at the top level of the value.
   169		d.value(rv)
   170		return d.savedError
   171	}
   172	
   173	// A Number represents a JSON number literal.
   174	type Number string
   175	
   176	// String returns the literal text of the number.
   177	func (n Number) String() string { return string(n) }
   178	
   179	// Float64 returns the number as a float64.
   180	func (n Number) Float64() (float64, error) {
   181		return strconv.ParseFloat(string(n), 64)
   182	}
   183	
   184	// Int64 returns the number as an int64.
   185	func (n Number) Int64() (int64, error) {
   186		return strconv.ParseInt(string(n), 10, 64)
   187	}
   188	
   189	// isValidNumber reports whether s is a valid JSON number literal.
   190	func isValidNumber(s string) bool {
   191		// This function implements the JSON numbers grammar.
   192		// See https://tools.ietf.org/html/rfc7159#section-6
   193		// and http://json.org/number.gif
   194	
   195		if s == "" {
   196			return false
   197		}
   198	
   199		// Optional -
   200		if s[0] == '-' {
   201			s = s[1:]
   202			if s == "" {
   203				return false
   204			}
   205		}
   206	
   207		// Digits
   208		switch {
   209		default:
   210			return false
   211	
   212		case s[0] == '0':
   213			s = s[1:]
   214	
   215		case '1' <= s[0] && s[0] <= '9':
   216			s = s[1:]
   217			for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
   218				s = s[1:]
   219			}
   220		}
   221	
   222		// . followed by 1 or more digits.
   223		if len(s) >= 2 && s[0] == '.' && '0' <= s[1] && s[1] <= '9' {
   224			s = s[2:]
   225			for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
   226				s = s[1:]
   227			}
   228		}
   229	
   230		// e or E followed by an optional - or + and
   231		// 1 or more digits.
   232		if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
   233			s = s[1:]
   234			if s[0] == '+' || s[0] == '-' {
   235				s = s[1:]
   236				if s == "" {
   237					return false
   238				}
   239			}
   240			for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
   241				s = s[1:]
   242			}
   243		}
   244	
   245		// Make sure we are at the end.
   246		return s == ""
   247	}
   248	
   249	// decodeState represents the state while decoding a JSON value.
   250	type decodeState struct {
   251		data       []byte
   252		off        int // read offset in data
   253		scan       scanner
   254		nextscan   scanner // for calls to nextValue
   255		savedError error
   256		useNumber  bool
   257	}
   258	
   259	// errPhase is used for errors that should not happen unless
   260	// there is a bug in the JSON decoder or something is editing
   261	// the data slice while the decoder executes.
   262	var errPhase = errors.New("JSON decoder out of sync - data changing underfoot?")
   263	
   264	func (d *decodeState) init(data []byte) *decodeState {
   265		d.data = data
   266		d.off = 0
   267		d.savedError = nil
   268		return d
   269	}
   270	
   271	// error aborts the decoding by panicking with err.
   272	func (d *decodeState) error(err error) {
   273		panic(err)
   274	}
   275	
   276	// saveError saves the first err it is called with,
   277	// for reporting at the end of the unmarshal.
   278	func (d *decodeState) saveError(err error) {
   279		if d.savedError == nil {
   280			d.savedError = err
   281		}
   282	}
   283	
   284	// next cuts off and returns the next full JSON value in d.data[d.off:].
   285	// The next value is known to be an object or array, not a literal.
   286	func (d *decodeState) next() []byte {
   287		c := d.data[d.off]
   288		item, rest, err := nextValue(d.data[d.off:], &d.nextscan)
   289		if err != nil {
   290			d.error(err)
   291		}
   292		d.off = len(d.data) - len(rest)
   293	
   294		// Our scanner has seen the opening brace/bracket
   295		// and thinks we're still in the middle of the object.
   296		// invent a closing brace/bracket to get it out.
   297		if c == '{' {
   298			d.scan.step(&d.scan, '}')
   299		} else {
   300			d.scan.step(&d.scan, ']')
   301		}
   302	
   303		return item
   304	}
   305	
   306	// scanWhile processes bytes in d.data[d.off:] until it
   307	// receives a scan code not equal to op.
   308	// It updates d.off and returns the new scan code.
   309	func (d *decodeState) scanWhile(op int) int {
   310		var newOp int
   311		for {
   312			if d.off >= len(d.data) {
   313				newOp = d.scan.eof()
   314				d.off = len(d.data) + 1 // mark processed EOF with len+1
   315			} else {
   316				c := d.data[d.off]
   317				d.off++
   318				newOp = d.scan.step(&d.scan, c)
   319			}
   320			if newOp != op {
   321				break
   322			}
   323		}
   324		return newOp
   325	}
   326	
   327	// value decodes a JSON value from d.data[d.off:] into the value.
   328	// it updates d.off to point past the decoded value.
   329	func (d *decodeState) value(v reflect.Value) {
   330		if !v.IsValid() {
   331			_, rest, err := nextValue(d.data[d.off:], &d.nextscan)
   332			if err != nil {
   333				d.error(err)
   334			}
   335			d.off = len(d.data) - len(rest)
   336	
   337			// d.scan thinks we're still at the beginning of the item.
   338			// Feed in an empty string - the shortest, simplest value -
   339			// so that it knows we got to the end of the value.
   340			if d.scan.redo {
   341				// rewind.
   342				d.scan.redo = false
   343				d.scan.step = stateBeginValue
   344			}
   345			d.scan.step(&d.scan, '"')
   346			d.scan.step(&d.scan, '"')
   347	
   348			n := len(d.scan.parseState)
   349			if n > 0 && d.scan.parseState[n-1] == parseObjectKey {
   350				// d.scan thinks we just read an object key; finish the object
   351				d.scan.step(&d.scan, ':')
   352				d.scan.step(&d.scan, '"')
   353				d.scan.step(&d.scan, '"')
   354				d.scan.step(&d.scan, '}')
   355			}
   356	
   357			return
   358		}
   359	
   360		switch op := d.scanWhile(scanSkipSpace); op {
   361		default:
   362			d.error(errPhase)
   363	
   364		case scanBeginArray:
   365			d.array(v)
   366	
   367		case scanBeginObject:
   368			d.object(v)
   369	
   370		case scanBeginLiteral:
   371			d.literal(v)
   372		}
   373	}
   374	
   375	type unquotedValue struct{}
   376	
   377	// valueQuoted is like value but decodes a
   378	// quoted string literal or literal null into an interface value.
   379	// If it finds anything other than a quoted string literal or null,
   380	// valueQuoted returns unquotedValue{}.
   381	func (d *decodeState) valueQuoted() interface{} {
   382		switch op := d.scanWhile(scanSkipSpace); op {
   383		default:
   384			d.error(errPhase)
   385	
   386		case scanBeginArray:
   387			d.array(reflect.Value{})
   388	
   389		case scanBeginObject:
   390			d.object(reflect.Value{})
   391	
   392		case scanBeginLiteral:
   393			switch v := d.literalInterface().(type) {
   394			case nil, string:
   395				return v
   396			}
   397		}
   398		return unquotedValue{}
   399	}
   400	
   401	// indirect walks down v allocating pointers as needed,
   402	// until it gets to a non-pointer.
   403	// if it encounters an Unmarshaler, indirect stops and returns that.
   404	// if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
   405	func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
   406		// If v is a named type and is addressable,
   407		// start with its address, so that if the type has pointer methods,
   408		// we find them.
   409		if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
   410			v = v.Addr()
   411		}
   412		for {
   413			// Load value from interface, but only if the result will be
   414			// usefully addressable.
   415			if v.Kind() == reflect.Interface && !v.IsNil() {
   416				e := v.Elem()
   417				if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
   418					v = e
   419					continue
   420				}
   421			}
   422	
   423			if v.Kind() != reflect.Ptr {
   424				break
   425			}
   426	
   427			if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() {
   428				break
   429			}
   430			if v.IsNil() {
   431				v.Set(reflect.New(v.Type().Elem()))
   432			}
   433			if v.Type().NumMethod() > 0 {
   434				if u, ok := v.Interface().(Unmarshaler); ok {
   435					return u, nil, reflect.Value{}
   436				}
   437				if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
   438					return nil, u, reflect.Value{}
   439				}
   440			}
   441			v = v.Elem()
   442		}
   443		return nil, nil, v
   444	}
   445	
   446	// array consumes an array from d.data[d.off-1:], decoding into the value v.
   447	// the first byte of the array ('[') has been read already.
   448	func (d *decodeState) array(v reflect.Value) {
   449		// Check for unmarshaler.
   450		u, ut, pv := d.indirect(v, false)
   451		if u != nil {
   452			d.off--
   453			err := u.UnmarshalJSON(d.next())
   454			if err != nil {
   455				d.error(err)
   456			}
   457			return
   458		}
   459		if ut != nil {
   460			d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
   461			d.off--
   462			d.next()
   463			return
   464		}
   465	
   466		v = pv
   467	
   468		// Check type of target.
   469		switch v.Kind() {
   470		case reflect.Interface:
   471			if v.NumMethod() == 0 {
   472				// Decoding into nil interface?  Switch to non-reflect code.
   473				v.Set(reflect.ValueOf(d.arrayInterface()))
   474				return
   475			}
   476			// Otherwise it's invalid.
   477			fallthrough
   478		default:
   479			d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
   480			d.off--
   481			d.next()
   482			return
   483		case reflect.Array:
   484		case reflect.Slice:
   485			break
   486		}
   487	
   488		i := 0
   489		for {
   490			// Look ahead for ] - can only happen on first iteration.
   491			op := d.scanWhile(scanSkipSpace)
   492			if op == scanEndArray {
   493				break
   494			}
   495	
   496			// Back up so d.value can have the byte we just read.
   497			d.off--
   498			d.scan.undo(op)
   499	
   500			// Get element of array, growing if necessary.
   501			if v.Kind() == reflect.Slice {
   502				// Grow slice if necessary
   503				if i >= v.Cap() {
   504					newcap := v.Cap() + v.Cap()/2
   505					if newcap < 4 {
   506						newcap = 4
   507					}
   508					newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
   509					reflect.Copy(newv, v)
   510					v.Set(newv)
   511				}
   512				if i >= v.Len() {
   513					v.SetLen(i + 1)
   514				}
   515			}
   516	
   517			if i < v.Len() {
   518				// Decode into element.
   519				d.value(v.Index(i))
   520			} else {
   521				// Ran out of fixed array: skip.
   522				d.value(reflect.Value{})
   523			}
   524			i++
   525	
   526			// Next token must be , or ].
   527			op = d.scanWhile(scanSkipSpace)
   528			if op == scanEndArray {
   529				break
   530			}
   531			if op != scanArrayValue {
   532				d.error(errPhase)
   533			}
   534		}
   535	
   536		if i < v.Len() {
   537			if v.Kind() == reflect.Array {
   538				// Array. Zero the rest.
   539				z := reflect.Zero(v.Type().Elem())
   540				for ; i < v.Len(); i++ {
   541					v.Index(i).Set(z)
   542				}
   543			} else {
   544				v.SetLen(i)
   545			}
   546		}
   547		if i == 0 && v.Kind() == reflect.Slice {
   548			v.Set(reflect.MakeSlice(v.Type(), 0, 0))
   549		}
   550	}
   551	
   552	var nullLiteral = []byte("null")
   553	var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
   554	
   555	// object consumes an object from d.data[d.off-1:], decoding into the value v.
   556	// the first byte ('{') of the object has been read already.
   557	func (d *decodeState) object(v reflect.Value) {
   558		// Check for unmarshaler.
   559		u, ut, pv := d.indirect(v, false)
   560		if u != nil {
   561			d.off--
   562			err := u.UnmarshalJSON(d.next())
   563			if err != nil {
   564				d.error(err)
   565			}
   566			return
   567		}
   568		if ut != nil {
   569			d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
   570			d.off--
   571			d.next() // skip over { } in input
   572			return
   573		}
   574		v = pv
   575	
   576		// Decoding into nil interface?  Switch to non-reflect code.
   577		if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
   578			v.Set(reflect.ValueOf(d.objectInterface()))
   579			return
   580		}
   581	
   582		// Check type of target:
   583		//   struct or
   584		//   map[T1]T2 where T1 is string, an integer type,
   585		//             or an encoding.TextUnmarshaler
   586		switch v.Kind() {
   587		case reflect.Map:
   588			// Map key must either have string kind, have an integer kind,
   589			// or be an encoding.TextUnmarshaler.
   590			t := v.Type()
   591			switch t.Key().Kind() {
   592			case reflect.String,
   593				reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   594				reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   595			default:
   596				if !reflect.PtrTo(t.Key()).Implements(textUnmarshalerType) {
   597					d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
   598					d.off--
   599					d.next() // skip over { } in input
   600					return
   601				}
   602			}
   603			if v.IsNil() {
   604				v.Set(reflect.MakeMap(t))
   605			}
   606		case reflect.Struct:
   607	
   608		default:
   609			d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
   610			d.off--
   611			d.next() // skip over { } in input
   612			return
   613		}
   614	
   615		var mapElem reflect.Value
   616	
   617		for {
   618			// Read opening " of string key or closing }.
   619			op := d.scanWhile(scanSkipSpace)
   620			if op == scanEndObject {
   621				// closing } - can only happen on first iteration.
   622				break
   623			}
   624			if op != scanBeginLiteral {
   625				d.error(errPhase)
   626			}
   627	
   628			// Read key.
   629			start := d.off - 1
   630			op = d.scanWhile(scanContinue)
   631			item := d.data[start : d.off-1]
   632			key, ok := unquoteBytes(item)
   633			if !ok {
   634				d.error(errPhase)
   635			}
   636	
   637			// Figure out field corresponding to key.
   638			var subv reflect.Value
   639			destring := false // whether the value is wrapped in a string to be decoded first
   640	
   641			if v.Kind() == reflect.Map {
   642				elemType := v.Type().Elem()
   643				if !mapElem.IsValid() {
   644					mapElem = reflect.New(elemType).Elem()
   645				} else {
   646					mapElem.Set(reflect.Zero(elemType))
   647				}
   648				subv = mapElem
   649			} else {
   650				var f *field
   651				fields := cachedTypeFields(v.Type())
   652				for i := range fields {
   653					ff := &fields[i]
   654					if bytes.Equal(ff.nameBytes, key) {
   655						f = ff
   656						break
   657					}
   658					if f == nil && ff.equalFold(ff.nameBytes, key) {
   659						f = ff
   660					}
   661				}
   662				if f != nil {
   663					subv = v
   664					destring = f.quoted
   665					for _, i := range f.index {
   666						if subv.Kind() == reflect.Ptr {
   667							if subv.IsNil() {
   668								subv.Set(reflect.New(subv.Type().Elem()))
   669							}
   670							subv = subv.Elem()
   671						}
   672						subv = subv.Field(i)
   673					}
   674				}
   675			}
   676	
   677			// Read : before value.
   678			if op == scanSkipSpace {
   679				op = d.scanWhile(scanSkipSpace)
   680			}
   681			if op != scanObjectKey {
   682				d.error(errPhase)
   683			}
   684	
   685			// Read value.
   686			if destring {
   687				switch qv := d.valueQuoted().(type) {
   688				case nil:
   689					d.literalStore(nullLiteral, subv, false)
   690				case string:
   691					d.literalStore([]byte(qv), subv, true)
   692				default:
   693					d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
   694				}
   695			} else {
   696				d.value(subv)
   697			}
   698	
   699			// Write value back to map;
   700			// if using struct, subv points into struct already.
   701			if v.Kind() == reflect.Map {
   702				kt := v.Type().Key()
   703				var kv reflect.Value
   704				switch {
   705				case kt.Kind() == reflect.String:
   706					kv = reflect.ValueOf(key).Convert(kt)
   707				case reflect.PtrTo(kt).Implements(textUnmarshalerType):
   708					kv = reflect.New(v.Type().Key())
   709					d.literalStore(item, kv, true)
   710					kv = kv.Elem()
   711				default:
   712					switch kt.Kind() {
   713					case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   714						s := string(key)
   715						n, err := strconv.ParseInt(s, 10, 64)
   716						if err != nil || reflect.Zero(kt).OverflowInt(n) {
   717							d.saveError(&UnmarshalTypeError{"number " + s, kt, int64(start + 1)})
   718							return
   719						}
   720						kv = reflect.ValueOf(n).Convert(kt)
   721					case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   722						s := string(key)
   723						n, err := strconv.ParseUint(s, 10, 64)
   724						if err != nil || reflect.Zero(kt).OverflowUint(n) {
   725							d.saveError(&UnmarshalTypeError{"number " + s, kt, int64(start + 1)})
   726							return
   727						}
   728						kv = reflect.ValueOf(n).Convert(kt)
   729					default:
   730						panic("json: Unexpected key type") // should never occur
   731					}
   732				}
   733				v.SetMapIndex(kv, subv)
   734			}
   735	
   736			// Next token must be , or }.
   737			op = d.scanWhile(scanSkipSpace)
   738			if op == scanEndObject {
   739				break
   740			}
   741			if op != scanObjectValue {
   742				d.error(errPhase)
   743			}
   744		}
   745	}
   746	
   747	// literal consumes a literal from d.data[d.off-1:], decoding into the value v.
   748	// The first byte of the literal has been read already
   749	// (that's how the caller knows it's a literal).
   750	func (d *decodeState) literal(v reflect.Value) {
   751		// All bytes inside literal return scanContinue op code.
   752		start := d.off - 1
   753		op := d.scanWhile(scanContinue)
   754	
   755		// Scan read one byte too far; back up.
   756		d.off--
   757		d.scan.undo(op)
   758	
   759		d.literalStore(d.data[start:d.off], v, false)
   760	}
   761	
   762	// convertNumber converts the number literal s to a float64 or a Number
   763	// depending on the setting of d.useNumber.
   764	func (d *decodeState) convertNumber(s string) (interface{}, error) {
   765		if d.useNumber {
   766			return Number(s), nil
   767		}
   768		f, err := strconv.ParseFloat(s, 64)
   769		if err != nil {
   770			return nil, &UnmarshalTypeError{"number " + s, reflect.TypeOf(0.0), int64(d.off)}
   771		}
   772		return f, nil
   773	}
   774	
   775	var numberType = reflect.TypeOf(Number(""))
   776	
   777	// literalStore decodes a literal stored in item into v.
   778	//
   779	// fromQuoted indicates whether this literal came from unwrapping a
   780	// string from the ",string" struct tag option. this is used only to
   781	// produce more helpful error messages.
   782	func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool) {
   783		// Check for unmarshaler.
   784		if len(item) == 0 {
   785			//Empty string given
   786			d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   787			return
   788		}
   789		wantptr := item[0] == 'n' // null
   790		u, ut, pv := d.indirect(v, wantptr)
   791		if u != nil {
   792			err := u.UnmarshalJSON(item)
   793			if err != nil {
   794				d.error(err)
   795			}
   796			return
   797		}
   798		if ut != nil {
   799			if item[0] != '"' {
   800				if fromQuoted {
   801					d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   802				} else {
   803					d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
   804				}
   805				return
   806			}
   807			s, ok := unquoteBytes(item)
   808			if !ok {
   809				if fromQuoted {
   810					d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   811				} else {
   812					d.error(errPhase)
   813				}
   814			}
   815			err := ut.UnmarshalText(s)
   816			if err != nil {
   817				d.error(err)
   818			}
   819			return
   820		}
   821	
   822		v = pv
   823	
   824		switch c := item[0]; c {
   825		case 'n': // null
   826			switch v.Kind() {
   827			case reflect.Interface, reflect.Ptr, reflect.Map, reflect.Slice:
   828				v.Set(reflect.Zero(v.Type()))
   829				// otherwise, ignore null for primitives/string
   830			}
   831		case 't', 'f': // true, false
   832			value := c == 't'
   833			switch v.Kind() {
   834			default:
   835				if fromQuoted {
   836					d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   837				} else {
   838					d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
   839				}
   840			case reflect.Bool:
   841				v.SetBool(value)
   842			case reflect.Interface:
   843				if v.NumMethod() == 0 {
   844					v.Set(reflect.ValueOf(value))
   845				} else {
   846					d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
   847				}
   848			}
   849	
   850		case '"': // string
   851			s, ok := unquoteBytes(item)
   852			if !ok {
   853				if fromQuoted {
   854					d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   855				} else {
   856					d.error(errPhase)
   857				}
   858			}
   859			switch v.Kind() {
   860			default:
   861				d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
   862			case reflect.Slice:
   863				if v.Type().Elem().Kind() != reflect.Uint8 {
   864					d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
   865					break
   866				}
   867				b := make([]byte, base64.StdEncoding.DecodedLen(len(s)))
   868				n, err := base64.StdEncoding.Decode(b, s)
   869				if err != nil {
   870					d.saveError(err)
   871					break
   872				}
   873				v.SetBytes(b[:n])
   874			case reflect.String:
   875				v.SetString(string(s))
   876			case reflect.Interface:
   877				if v.NumMethod() == 0 {
   878					v.Set(reflect.ValueOf(string(s)))
   879				} else {
   880					d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
   881				}
   882			}
   883	
   884		default: // number
   885			if c != '-' && (c < '0' || c > '9') {
   886				if fromQuoted {
   887					d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   888				} else {
   889					d.error(errPhase)
   890				}
   891			}
   892			s := string(item)
   893			switch v.Kind() {
   894			default:
   895				if v.Kind() == reflect.String && v.Type() == numberType {
   896					v.SetString(s)
   897					if !isValidNumber(s) {
   898						d.error(fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item))
   899					}
   900					break
   901				}
   902				if fromQuoted {
   903					d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
   904				} else {
   905					d.error(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
   906				}
   907			case reflect.Interface:
   908				n, err := d.convertNumber(s)
   909				if err != nil {
   910					d.saveError(err)
   911					break
   912				}
   913				if v.NumMethod() != 0 {
   914					d.saveError(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
   915					break
   916				}
   917				v.Set(reflect.ValueOf(n))
   918	
   919			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   920				n, err := strconv.ParseInt(s, 10, 64)
   921				if err != nil || v.OverflowInt(n) {
   922					d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
   923					break
   924				}
   925				v.SetInt(n)
   926	
   927			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
   928				n, err := strconv.ParseUint(s, 10, 64)
   929				if err != nil || v.OverflowUint(n) {
   930					d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
   931					break
   932				}
   933				v.SetUint(n)
   934	
   935			case reflect.Float32, reflect.Float64:
   936				n, err := strconv.ParseFloat(s, v.Type().Bits())
   937				if err != nil || v.OverflowFloat(n) {
   938					d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
   939					break
   940				}
   941				v.SetFloat(n)
   942			}
   943		}
   944	}
   945	
   946	// The xxxInterface routines build up a value to be stored
   947	// in an empty interface. They are not strictly necessary,
   948	// but they avoid the weight of reflection in this common case.
   949	
   950	// valueInterface is like value but returns interface{}
   951	func (d *decodeState) valueInterface() interface{} {
   952		switch d.scanWhile(scanSkipSpace) {
   953		default:
   954			d.error(errPhase)
   955			panic("unreachable")
   956		case scanBeginArray:
   957			return d.arrayInterface()
   958		case scanBeginObject:
   959			return d.objectInterface()
   960		case scanBeginLiteral:
   961			return d.literalInterface()
   962		}
   963	}
   964	
   965	// arrayInterface is like array but returns []interface{}.
   966	func (d *decodeState) arrayInterface() []interface{} {
   967		var v = make([]interface{}, 0)
   968		for {
   969			// Look ahead for ] - can only happen on first iteration.
   970			op := d.scanWhile(scanSkipSpace)
   971			if op == scanEndArray {
   972				break
   973			}
   974	
   975			// Back up so d.value can have the byte we just read.
   976			d.off--
   977			d.scan.undo(op)
   978	
   979			v = append(v, d.valueInterface())
   980	
   981			// Next token must be , or ].
   982			op = d.scanWhile(scanSkipSpace)
   983			if op == scanEndArray {
   984				break
   985			}
   986			if op != scanArrayValue {
   987				d.error(errPhase)
   988			}
   989		}
   990		return v
   991	}
   992	
   993	// objectInterface is like object but returns map[string]interface{}.
   994	func (d *decodeState) objectInterface() map[string]interface{} {
   995		m := make(map[string]interface{})
   996		for {
   997			// Read opening " of string key or closing }.
   998			op := d.scanWhile(scanSkipSpace)
   999			if op == scanEndObject {
  1000				// closing } - can only happen on first iteration.
  1001				break
  1002			}
  1003			if op != scanBeginLiteral {
  1004				d.error(errPhase)
  1005			}
  1006	
  1007			// Read string key.
  1008			start := d.off - 1
  1009			op = d.scanWhile(scanContinue)
  1010			item := d.data[start : d.off-1]
  1011			key, ok := unquote(item)
  1012			if !ok {
  1013				d.error(errPhase)
  1014			}
  1015	
  1016			// Read : before value.
  1017			if op == scanSkipSpace {
  1018				op = d.scanWhile(scanSkipSpace)
  1019			}
  1020			if op != scanObjectKey {
  1021				d.error(errPhase)
  1022			}
  1023	
  1024			// Read value.
  1025			m[key] = d.valueInterface()
  1026	
  1027			// Next token must be , or }.
  1028			op = d.scanWhile(scanSkipSpace)
  1029			if op == scanEndObject {
  1030				break
  1031			}
  1032			if op != scanObjectValue {
  1033				d.error(errPhase)
  1034			}
  1035		}
  1036		return m
  1037	}
  1038	
  1039	// literalInterface is like literal but returns an interface value.
  1040	func (d *decodeState) literalInterface() interface{} {
  1041		// All bytes inside literal return scanContinue op code.
  1042		start := d.off - 1
  1043		op := d.scanWhile(scanContinue)
  1044	
  1045		// Scan read one byte too far; back up.
  1046		d.off--
  1047		d.scan.undo(op)
  1048		item := d.data[start:d.off]
  1049	
  1050		switch c := item[0]; c {
  1051		case 'n': // null
  1052			return nil
  1053	
  1054		case 't', 'f': // true, false
  1055			return c == 't'
  1056	
  1057		case '"': // string
  1058			s, ok := unquote(item)
  1059			if !ok {
  1060				d.error(errPhase)
  1061			}
  1062			return s
  1063	
  1064		default: // number
  1065			if c != '-' && (c < '0' || c > '9') {
  1066				d.error(errPhase)
  1067			}
  1068			n, err := d.convertNumber(string(item))
  1069			if err != nil {
  1070				d.saveError(err)
  1071			}
  1072			return n
  1073		}
  1074	}
  1075	
  1076	// getu4 decodes \uXXXX from the beginning of s, returning the hex value,
  1077	// or it returns -1.
  1078	func getu4(s []byte) rune {
  1079		if len(s) < 6 || s[0] != '\\' || s[1] != 'u' {
  1080			return -1
  1081		}
  1082		r, err := strconv.ParseUint(string(s[2:6]), 16, 64)
  1083		if err != nil {
  1084			return -1
  1085		}
  1086		return rune(r)
  1087	}
  1088	
  1089	// unquote converts a quoted JSON string literal s into an actual string t.
  1090	// The rules are different than for Go, so cannot use strconv.Unquote.
  1091	func unquote(s []byte) (t string, ok bool) {
  1092		s, ok = unquoteBytes(s)
  1093		t = string(s)
  1094		return
  1095	}
  1096	
  1097	func unquoteBytes(s []byte) (t []byte, ok bool) {
  1098		if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
  1099			return
  1100		}
  1101		s = s[1 : len(s)-1]
  1102	
  1103		// Check for unusual characters. If there are none,
  1104		// then no unquoting is needed, so return a slice of the
  1105		// original bytes.
  1106		r := 0
  1107		for r < len(s) {
  1108			c := s[r]
  1109			if c == '\\' || c == '"' || c < ' ' {
  1110				break
  1111			}
  1112			if c < utf8.RuneSelf {
  1113				r++
  1114				continue
  1115			}
  1116			rr, size := utf8.DecodeRune(s[r:])
  1117			if rr == utf8.RuneError && size == 1 {
  1118				break
  1119			}
  1120			r += size
  1121		}
  1122		if r == len(s) {
  1123			return s, true
  1124		}
  1125	
  1126		b := make([]byte, len(s)+2*utf8.UTFMax)
  1127		w := copy(b, s[0:r])
  1128		for r < len(s) {
  1129			// Out of room?  Can only happen if s is full of
  1130			// malformed UTF-8 and we're replacing each
  1131			// byte with RuneError.
  1132			if w >= len(b)-2*utf8.UTFMax {
  1133				nb := make([]byte, (len(b)+utf8.UTFMax)*2)
  1134				copy(nb, b[0:w])
  1135				b = nb
  1136			}
  1137			switch c := s[r]; {
  1138			case c == '\\':
  1139				r++
  1140				if r >= len(s) {
  1141					return
  1142				}
  1143				switch s[r] {
  1144				default:
  1145					return
  1146				case '"', '\\', '/', '\'':
  1147					b[w] = s[r]
  1148					r++
  1149					w++
  1150				case 'b':
  1151					b[w] = '\b'
  1152					r++
  1153					w++
  1154				case 'f':
  1155					b[w] = '\f'
  1156					r++
  1157					w++
  1158				case 'n':
  1159					b[w] = '\n'
  1160					r++
  1161					w++
  1162				case 'r':
  1163					b[w] = '\r'
  1164					r++
  1165					w++
  1166				case 't':
  1167					b[w] = '\t'
  1168					r++
  1169					w++
  1170				case 'u':
  1171					r--
  1172					rr := getu4(s[r:])
  1173					if rr < 0 {
  1174						return
  1175					}
  1176					r += 6
  1177					if utf16.IsSurrogate(rr) {
  1178						rr1 := getu4(s[r:])
  1179						if dec := utf16.DecodeRune(rr, rr1); dec != unicode.ReplacementChar {
  1180							// A valid pair; consume.
  1181							r += 6
  1182							w += utf8.EncodeRune(b[w:], dec)
  1183							break
  1184						}
  1185						// Invalid surrogate; fall back to replacement rune.
  1186						rr = unicode.ReplacementChar
  1187					}
  1188					w += utf8.EncodeRune(b[w:], rr)
  1189				}
  1190	
  1191			// Quote, control characters are invalid.
  1192			case c == '"', c < ' ':
  1193				return
  1194	
  1195			// ASCII
  1196			case c < utf8.RuneSelf:
  1197				b[w] = c
  1198				r++
  1199				w++
  1200	
  1201			// Coerce to well-formed UTF-8.
  1202			default:
  1203				rr, size := utf8.DecodeRune(s[r:])
  1204				r += size
  1205				w += utf8.EncodeRune(b[w:], rr)
  1206			}
  1207		}
  1208		return b[0:w], true
  1209	}
  1210	

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