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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.
// Represents JSON data structure using native Go types: booleans, floats,
// strings, arrays, and maps.
package json
import (
"bytes"
"encoding"
"encoding/base64"
"errors"
"fmt"
"reflect"
"runtime"
"strconv"
"unicode"
"unicode/utf16"
"unicode/utf8"
)
// Unmarshal parses the JSON-encoded data and stores the result
// in the value pointed to by v.
//
// Unmarshal uses the inverse of the encodings that
// Marshal uses, allocating maps, slices, and pointers as necessary,
// with the following additional rules:
//
// To unmarshal JSON into a pointer, Unmarshal first handles the case of
// the JSON being the JSON literal null. In that case, Unmarshal sets
// the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into
// the value pointed at by the pointer. If the pointer is nil, Unmarshal
// allocates a new value for it to point to.
//
// To unmarshal JSON into a struct, Unmarshal matches incoming object
// keys to the keys used by Marshal (either the struct field name or its tag),
// preferring an exact match but also accepting a case-insensitive match.
// Unmarshal will only set exported fields of the struct.
//
// To unmarshal JSON into an interface value,
// Unmarshal stores one of these in the interface value:
//
// bool, for JSON booleans
// float64, for JSON numbers
// string, for JSON strings
// []interface{}, for JSON arrays
// map[string]interface{}, for JSON objects
// nil for JSON null
//
// To unmarshal a JSON array into a slice, Unmarshal resets the slice length
// to zero and then appends each element to the slice.
// As a special case, to unmarshal an empty JSON array into a slice,
// Unmarshal replaces the slice with a new empty slice.
//
// To unmarshal a JSON array into a Go array, Unmarshal decodes
// JSON array elements into corresponding Go array elements.
// If the Go array is smaller than the JSON array,
// the additional JSON array elements are discarded.
// If the JSON array is smaller than the Go array,
// the additional Go array elements are set to zero values.
//
// To unmarshal a JSON object into a string-keyed map, Unmarshal first
// establishes a map to use, If the map is nil, Unmarshal allocates a new map.
// Otherwise Unmarshal reuses the existing map, keeping existing entries.
// Unmarshal then stores key-value pairs from the JSON object into the map.
//
// If a JSON value is not appropriate for a given target type,
// or if a JSON number overflows the target type, Unmarshal
// skips that field and completes the unmarshaling as best it can.
// If no more serious errors are encountered, Unmarshal returns
// an UnmarshalTypeError describing the earliest such error.
//
// The JSON null value unmarshals into an interface, map, pointer, or slice
// by setting that Go value to nil. Because null is often used in JSON to mean
// ``not present,'' unmarshaling a JSON null into any other Go type has no effect
// on the value and produces no error.
//
// When unmarshaling quoted strings, invalid UTF-8 or
// invalid UTF-16 surrogate pairs are not treated as an error.
// Instead, they are replaced by the Unicode replacement
// character U+FFFD.
//
func Unmarshal(data []byte, v interface{}) error {
// Check for well-formedness.
// Avoids filling out half a data structure
// before discovering a JSON syntax error.
var d decodeState
err := checkValid(data, &d.scan)
if err != nil {
return err
}
d.init(data)
return d.unmarshal(v)
}
// Unmarshaler is the interface implemented by objects
// that can unmarshal a JSON description of themselves.
// The input can be assumed to be a valid encoding of
// a JSON value. UnmarshalJSON must copy the JSON data
// if it wishes to retain the data after returning.
type Unmarshaler interface {
UnmarshalJSON([]byte) error
}
// An UnmarshalTypeError describes a JSON value that was
// not appropriate for a value of a specific Go type.
type UnmarshalTypeError struct {
Value string // description of JSON value - "bool", "array", "number -5"
Type reflect.Type // type of Go value it could not be assigned to
Offset int64 // error occurred after reading Offset bytes
}
func (e *UnmarshalTypeError) Error() string {
return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
}
// An UnmarshalFieldError describes a JSON object key that
// led to an unexported (and therefore unwritable) struct field.
// (No longer used; kept for compatibility.)
type UnmarshalFieldError struct {
Key string
Type reflect.Type
Field reflect.StructField
}
func (e *UnmarshalFieldError) Error() string {
return "json: cannot unmarshal object key " + strconv.Quote(e.Key) + " into unexported field " + e.Field.Name + " of type " + e.Type.String()
}
// An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
// (The argument to Unmarshal must be a non-nil pointer.)
type InvalidUnmarshalError struct {
Type reflect.Type
}
func (e *InvalidUnmarshalError) Error() string {
if e.Type == nil {
return "json: Unmarshal(nil)"
}
if e.Type.Kind() != reflect.Ptr {
return "json: Unmarshal(non-pointer " + e.Type.String() + ")"
}
return "json: Unmarshal(nil " + e.Type.String() + ")"
}
func (d *decodeState) unmarshal(v interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
if _, ok := r.(runtime.Error); ok {
panic(r)
}
err = r.(error)
}
}()
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
return &InvalidUnmarshalError{reflect.TypeOf(v)}
}
d.scan.reset()
// We decode rv not rv.Elem because the Unmarshaler interface
// test must be applied at the top level of the value.
d.value(rv)
return d.savedError
}
// A Number represents a JSON number literal.
type Number string
// String returns the literal text of the number.
func (n Number) String() string { return string(n) }
// Float64 returns the number as a float64.
func (n Number) Float64() (float64, error) {
return strconv.ParseFloat(string(n), 64)
}
// Int64 returns the number as an int64.
func (n Number) Int64() (int64, error) {
return strconv.ParseInt(string(n), 10, 64)
}
// isValidNumber reports whether s is a valid JSON number literal.
func isValidNumber(s string) bool {
// This function implements the JSON numbers grammar.
// See https://tools.ietf.org/html/rfc7159#section-6
// and http://json.org/number.gif
if s == "" {
return false
}
// Optional -
if s[0] == '-' {
s = s[1:]
if s == "" {
return false
}
}
// Digits
switch {
default:
return false
case s[0] == '0':
s = s[1:]
case '1' <= s[0] && s[0] <= '9':
s = s[1:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// . followed by 1 or more digits.
if len(s) >= 2 && s[0] == '.' && '0' <= s[1] && s[1] <= '9' {
s = s[2:]
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// e or E followed by an optional - or + and
// 1 or more digits.
if len(s) >= 2 && (s[0] == 'e' || s[0] == 'E') {
s = s[1:]
if s[0] == '+' || s[0] == '-' {
s = s[1:]
if s == "" {
return false
}
}
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
s = s[1:]
}
}
// Make sure we are at the end.
return s == ""
}
// decodeState represents the state while decoding a JSON value.
type decodeState struct {
data []byte
off int // read offset in data
scan scanner
nextscan scanner // for calls to nextValue
savedError error
useNumber bool
canonical bool
}
// errPhase is used for errors that should not happen unless
// there is a bug in the JSON decoder or something is editing
// the data slice while the decoder executes.
var errPhase = errors.New("JSON decoder out of sync - data changing underfoot?")
func (d *decodeState) init(data []byte) *decodeState {
d.data = data
d.off = 0
d.savedError = nil
return d
}
// error aborts the decoding by panicking with err.
func (d *decodeState) error(err error) {
panic(err)
}
// saveError saves the first err it is called with,
// for reporting at the end of the unmarshal.
func (d *decodeState) saveError(err error) {
if d.savedError == nil {
d.savedError = err
}
}
// next cuts off and returns the next full JSON value in d.data[d.off:].
// The next value is known to be an object or array, not a literal.
func (d *decodeState) next() []byte {
c := d.data[d.off]
item, rest, err := nextValue(d.data[d.off:], &d.nextscan)
if err != nil {
d.error(err)
}
d.off = len(d.data) - len(rest)
// Our scanner has seen the opening brace/bracket
// and thinks we're still in the middle of the object.
// invent a closing brace/bracket to get it out.
if c == '{' {
d.scan.step(&d.scan, '}')
} else {
d.scan.step(&d.scan, ']')
}
return item
}
// scanWhile processes bytes in d.data[d.off:] until it
// receives a scan code not equal to op.
// It updates d.off and returns the new scan code.
func (d *decodeState) scanWhile(op int) int {
var newOp int
for {
if d.off >= len(d.data) {
newOp = d.scan.eof()
d.off = len(d.data) + 1 // mark processed EOF with len+1
} else {
c := d.data[d.off]
d.off++
newOp = d.scan.step(&d.scan, c)
}
if newOp != op {
break
}
}
return newOp
}
// value decodes a JSON value from d.data[d.off:] into the value.
// it updates d.off to point past the decoded value.
func (d *decodeState) value(v reflect.Value) {
if !v.IsValid() {
_, rest, err := nextValue(d.data[d.off:], &d.nextscan)
if err != nil {
d.error(err)
}
d.off = len(d.data) - len(rest)
// d.scan thinks we're still at the beginning of the item.
// Feed in an empty string - the shortest, simplest value -
// so that it knows we got to the end of the value.
if d.scan.redo {
// rewind.
d.scan.redo = false
d.scan.step = stateBeginValue
}
d.scan.step(&d.scan, '"')
d.scan.step(&d.scan, '"')
n := len(d.scan.parseState)
if n > 0 && d.scan.parseState[n-1] == parseObjectKey {
// d.scan thinks we just read an object key; finish the object
d.scan.step(&d.scan, ':')
d.scan.step(&d.scan, '"')
d.scan.step(&d.scan, '"')
d.scan.step(&d.scan, '}')
}
return
}
switch op := d.scanWhile(scanSkipSpace); op {
default:
d.error(errPhase)
case scanBeginArray:
d.array(v)
case scanBeginObject:
d.object(v)
case scanBeginLiteral:
d.literal(v)
}
}
type unquotedValue struct{}
// valueQuoted is like value but decodes a
// quoted string literal or literal null into an interface value.
// If it finds anything other than a quoted string literal or null,
// valueQuoted returns unquotedValue{}.
func (d *decodeState) valueQuoted() interface{} {
switch op := d.scanWhile(scanSkipSpace); op {
default:
d.error(errPhase)
case scanBeginArray:
d.array(reflect.Value{})
case scanBeginObject:
d.object(reflect.Value{})
case scanBeginLiteral:
switch v := d.literalInterface().(type) {
case nil, string:
return v
}
}
return unquotedValue{}
}
// indirect walks down v allocating pointers as needed,
// until it gets to a non-pointer.
// if it encounters an Unmarshaler, indirect stops and returns that.
// if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
func (d *decodeState) indirect(v reflect.Value, decodingNull bool) (Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
// If v is a named type and is addressable,
// start with its address, so that if the type has pointer methods,
// we find them.
if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
v = v.Addr()
}
for {
// Load value from interface, but only if the result will be
// usefully addressable.
if v.Kind() == reflect.Interface && !v.IsNil() {
e := v.Elem()
if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
v = e
continue
}
}
if v.Kind() != reflect.Ptr {
break
}
if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() {
break
}
if v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
if v.Type().NumMethod() > 0 {
if u, ok := v.Interface().(Unmarshaler); ok {
return u, nil, reflect.Value{}
}
if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
return nil, u, reflect.Value{}
}
}
v = v.Elem()
}
return nil, nil, v
}
// array consumes an array from d.data[d.off-1:], decoding into the value v.
// the first byte of the array ('[') has been read already.
func (d *decodeState) array(v reflect.Value) {
// Check for unmarshaler.
u, ut, pv := d.indirect(v, false)
if u != nil {
d.off--
err := u.UnmarshalJSON(d.next())
if err != nil {
d.error(err)
}
return
}
if ut != nil {
d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
d.off--
d.next()
return
}
v = pv
// Check type of target.
switch v.Kind() {
case reflect.Interface:
if v.NumMethod() == 0 {
// Decoding into nil interface? Switch to non-reflect code.
v.Set(reflect.ValueOf(d.arrayInterface()))
return
}
// Otherwise it's invalid.
fallthrough
default:
d.saveError(&UnmarshalTypeError{"array", v.Type(), int64(d.off)})
d.off--
d.next()
return
case reflect.Array:
case reflect.Slice:
break
}
i := 0
for {
// Look ahead for ] - can only happen on first iteration.
op := d.scanWhile(scanSkipSpace)
if op == scanEndArray {
break
}
// Back up so d.value can have the byte we just read.
d.off--
d.scan.undo(op)
// Get element of array, growing if necessary.
if v.Kind() == reflect.Slice {
// Grow slice if necessary
if i >= v.Cap() {
newcap := v.Cap() + v.Cap()/2
if newcap < 4 {
newcap = 4
}
newv := reflect.MakeSlice(v.Type(), v.Len(), newcap)
reflect.Copy(newv, v)
v.Set(newv)
}
if i >= v.Len() {
v.SetLen(i + 1)
}
}
if i < v.Len() {
// Decode into element.
d.value(v.Index(i))
} else {
// Ran out of fixed array: skip.
d.value(reflect.Value{})
}
i++
// Next token must be , or ].
op = d.scanWhile(scanSkipSpace)
if op == scanEndArray {
break
}
if op != scanArrayValue {
d.error(errPhase)
}
}
if i < v.Len() {
if v.Kind() == reflect.Array {
// Array. Zero the rest.
z := reflect.Zero(v.Type().Elem())
for ; i < v.Len(); i++ {
v.Index(i).Set(z)
}
} else {
v.SetLen(i)
}
}
if i == 0 && v.Kind() == reflect.Slice {
v.Set(reflect.MakeSlice(v.Type(), 0, 0))
}
}
var nullLiteral = []byte("null")
// object consumes an object from d.data[d.off-1:], decoding into the value v.
// the first byte ('{') of the object has been read already.
func (d *decodeState) object(v reflect.Value) {
// Check for unmarshaler.
u, ut, pv := d.indirect(v, false)
if u != nil {
d.off--
err := u.UnmarshalJSON(d.next())
if err != nil {
d.error(err)
}
return
}
if ut != nil {
d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
d.off--
d.next() // skip over { } in input
return
}
v = pv
// Decoding into nil interface? Switch to non-reflect code.
if v.Kind() == reflect.Interface && v.NumMethod() == 0 {
v.Set(reflect.ValueOf(d.objectInterface()))
return
}
// Check type of target: struct or map[string]T
switch v.Kind() {
case reflect.Map:
// map must have string kind
t := v.Type()
if t.Key().Kind() != reflect.String {
d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
d.off--
d.next() // skip over { } in input
return
}
if v.IsNil() {
v.Set(reflect.MakeMap(t))
}
case reflect.Struct:
default:
d.saveError(&UnmarshalTypeError{"object", v.Type(), int64(d.off)})
d.off--
d.next() // skip over { } in input
return
}
var mapElem reflect.Value
for {
// Read opening " of string key or closing }.
op := d.scanWhile(scanSkipSpace)
if op == scanEndObject {
// closing } - can only happen on first iteration.
break
}
if op != scanBeginLiteral {
d.error(errPhase)
}
// Read key.
start := d.off - 1
op = d.scanWhile(scanContinue)
item := d.data[start : d.off-1]
key, ok := unquoteBytes(item)
if !ok {
d.error(errPhase)
}
// Figure out field corresponding to key.
var subv reflect.Value
destring := false // whether the value is wrapped in a string to be decoded first
if v.Kind() == reflect.Map {
elemType := v.Type().Elem()
if !mapElem.IsValid() {
mapElem = reflect.New(elemType).Elem()
} else {
mapElem.Set(reflect.Zero(elemType))
}
subv = mapElem
} else {
var f *field
fields := cachedTypeFields(v.Type(), false)
for i := range fields {
ff := &fields[i]
if bytes.Equal(ff.nameBytes, key) {
f = ff
break
}
if f == nil && ff.equalFold(ff.nameBytes, key) {
f = ff
}
}
if f != nil {
subv = v
destring = f.quoted
for _, i := range f.index {
if subv.Kind() == reflect.Ptr {
if subv.IsNil() {
subv.Set(reflect.New(subv.Type().Elem()))
}
subv = subv.Elem()
}
subv = subv.Field(i)
}
}
}
// Read : before value.
if op == scanSkipSpace {
op = d.scanWhile(scanSkipSpace)
}
if op != scanObjectKey {
d.error(errPhase)
}
// Read value.
if destring {
switch qv := d.valueQuoted().(type) {
case nil:
d.literalStore(nullLiteral, subv, false)
case string:
d.literalStore([]byte(qv), subv, true)
default:
d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal unquoted value into %v", subv.Type()))
}
} else {
d.value(subv)
}
// Write value back to map;
// if using struct, subv points into struct already.
if v.Kind() == reflect.Map {
kv := reflect.ValueOf(key).Convert(v.Type().Key())
v.SetMapIndex(kv, subv)
}
// Next token must be , or }.
op = d.scanWhile(scanSkipSpace)
if op == scanEndObject {
break
}
if op != scanObjectValue {
d.error(errPhase)
}
}
}
// literal consumes a literal from d.data[d.off-1:], decoding into the value v.
// The first byte of the literal has been read already
// (that's how the caller knows it's a literal).
func (d *decodeState) literal(v reflect.Value) {
// All bytes inside literal return scanContinue op code.
start := d.off - 1
op := d.scanWhile(scanContinue)
// Scan read one byte too far; back up.
d.off--
d.scan.undo(op)
d.literalStore(d.data[start:d.off], v, false)
}
// convertNumber converts the number literal s to a float64 or a Number
// depending on the setting of d.useNumber.
func (d *decodeState) convertNumber(s string) (interface{}, error) {
if d.useNumber {
return Number(s), nil
}
f, err := strconv.ParseFloat(s, 64)
if err != nil {
return nil, &UnmarshalTypeError{"number " + s, reflect.TypeOf(0.0), int64(d.off)}
}
return f, nil
}
var numberType = reflect.TypeOf(Number(""))
// literalStore decodes a literal stored in item into v.
//
// fromQuoted indicates whether this literal came from unwrapping a
// string from the ",string" struct tag option. this is used only to
// produce more helpful error messages.
func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool) {
// Check for unmarshaler.
if len(item) == 0 {
//Empty string given
d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
return
}
wantptr := item[0] == 'n' // null
u, ut, pv := d.indirect(v, wantptr)
if u != nil {
err := u.UnmarshalJSON(item)
if err != nil {
d.error(err)
}
return
}
if ut != nil {
if item[0] != '"' {
if fromQuoted {
d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
}
return
}
s, ok := unquoteBytes(item)
if !ok {
if fromQuoted {
d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.error(errPhase)
}
}
err := ut.UnmarshalText(s)
if err != nil {
d.error(err)
}
return
}
v = pv
switch c := item[0]; c {
case 'n': // null
switch v.Kind() {
case reflect.Interface, reflect.Ptr, reflect.Map, reflect.Slice:
v.Set(reflect.Zero(v.Type()))
// otherwise, ignore null for primitives/string
}
case 't', 'f': // true, false
value := c == 't'
switch v.Kind() {
default:
if fromQuoted {
d.saveError(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
}
case reflect.Bool:
v.SetBool(value)
case reflect.Interface:
if v.NumMethod() == 0 {
v.Set(reflect.ValueOf(value))
} else {
d.saveError(&UnmarshalTypeError{"bool", v.Type(), int64(d.off)})
}
}
case '"': // string
s, ok := unquoteBytes(item)
if !ok {
if fromQuoted {
d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.error(errPhase)
}
}
switch v.Kind() {
default:
d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
case reflect.Slice:
if v.Type().Elem().Kind() != reflect.Uint8 {
d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
break
}
b := make([]byte, base64.StdEncoding.DecodedLen(len(s)))
n, err := base64.StdEncoding.Decode(b, s)
if err != nil {
d.saveError(err)
break
}
v.SetBytes(b[:n])
case reflect.String:
v.SetString(string(s))
case reflect.Interface:
if v.NumMethod() == 0 {
v.Set(reflect.ValueOf(string(s)))
} else {
d.saveError(&UnmarshalTypeError{"string", v.Type(), int64(d.off)})
}
}
default: // number
if c != '-' && (c < '0' || c > '9') {
if fromQuoted {
d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.error(errPhase)
}
}
s := string(item)
switch v.Kind() {
default:
if v.Kind() == reflect.String && v.Type() == numberType {
v.SetString(s)
if !isValidNumber(s) {
d.error(fmt.Errorf("json: invalid number literal, trying to unmarshal %q into Number", item))
}
break
}
if fromQuoted {
d.error(fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type()))
} else {
d.error(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
}
case reflect.Interface:
n, err := d.convertNumber(s)
if err != nil {
d.saveError(err)
break
}
if v.NumMethod() != 0 {
d.saveError(&UnmarshalTypeError{"number", v.Type(), int64(d.off)})
break
}
v.Set(reflect.ValueOf(n))
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
n, err := strconv.ParseInt(s, 10, 64)
if err != nil || v.OverflowInt(n) {
d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
break
}
v.SetInt(n)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
n, err := strconv.ParseUint(s, 10, 64)
if err != nil || v.OverflowUint(n) {
d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
break
}
v.SetUint(n)
case reflect.Float32, reflect.Float64:
n, err := strconv.ParseFloat(s, v.Type().Bits())
if err != nil || v.OverflowFloat(n) {
d.saveError(&UnmarshalTypeError{"number " + s, v.Type(), int64(d.off)})
break
}
v.SetFloat(n)
}
}
}
// The xxxInterface routines build up a value to be stored
// in an empty interface. They are not strictly necessary,
// but they avoid the weight of reflection in this common case.
// valueInterface is like value but returns interface{}
func (d *decodeState) valueInterface() interface{} {
switch d.scanWhile(scanSkipSpace) {
default:
d.error(errPhase)
panic("unreachable")
case scanBeginArray:
return d.arrayInterface()
case scanBeginObject:
return d.objectInterface()
case scanBeginLiteral:
return d.literalInterface()
}
}
// arrayInterface is like array but returns []interface{}.
func (d *decodeState) arrayInterface() []interface{} {
var v = make([]interface{}, 0)
for {
// Look ahead for ] - can only happen on first iteration.
op := d.scanWhile(scanSkipSpace)
if op == scanEndArray {
break
}
// Back up so d.value can have the byte we just read.
d.off--
d.scan.undo(op)
v = append(v, d.valueInterface())
// Next token must be , or ].
op = d.scanWhile(scanSkipSpace)
if op == scanEndArray {
break
}
if op != scanArrayValue {
d.error(errPhase)
}
}
return v
}
// objectInterface is like object but returns map[string]interface{}.
func (d *decodeState) objectInterface() map[string]interface{} {
m := make(map[string]interface{})
for {
// Read opening " of string key or closing }.
op := d.scanWhile(scanSkipSpace)
if op == scanEndObject {
// closing } - can only happen on first iteration.
break
}
if op != scanBeginLiteral {
d.error(errPhase)
}
// Read string key.
start := d.off - 1
op = d.scanWhile(scanContinue)
item := d.data[start : d.off-1]
key, ok := unquote(item)
if !ok {
d.error(errPhase)
}
// Read : before value.
if op == scanSkipSpace {
op = d.scanWhile(scanSkipSpace)
}
if op != scanObjectKey {
d.error(errPhase)
}
// Read value.
m[key] = d.valueInterface()
// Next token must be , or }.
op = d.scanWhile(scanSkipSpace)
if op == scanEndObject {
break
}
if op != scanObjectValue {
d.error(errPhase)
}
}
return m
}
// literalInterface is like literal but returns an interface value.
func (d *decodeState) literalInterface() interface{} {
// All bytes inside literal return scanContinue op code.
start := d.off - 1
op := d.scanWhile(scanContinue)
// Scan read one byte too far; back up.
d.off--
d.scan.undo(op)
item := d.data[start:d.off]
switch c := item[0]; c {
case 'n': // null
return nil
case 't', 'f': // true, false
return c == 't'
case '"': // string
s, ok := unquote(item)
if !ok {
d.error(errPhase)
}
return s
default: // number
if c != '-' && (c < '0' || c > '9') {
d.error(errPhase)
}
n, err := d.convertNumber(string(item))
if err != nil {
d.saveError(err)
}
return n
}
}
// getu4 decodes \uXXXX from the beginning of s, returning the hex value,
// or it returns -1.
func getu4(s []byte) rune {
if len(s) < 6 || s[0] != '\\' || s[1] != 'u' {
return -1
}
r, err := strconv.ParseUint(string(s[2:6]), 16, 64)
if err != nil {
return -1
}
return rune(r)
}
// unquote converts a quoted JSON string literal s into an actual string t.
// The rules are different than for Go, so cannot use strconv.Unquote.
func unquote(s []byte) (t string, ok bool) {
s, ok = unquoteBytes(s)
t = string(s)
return
}
func unquoteBytes(s []byte) (t []byte, ok bool) {
if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
return
}
s = s[1 : len(s)-1]
// Check for unusual characters. If there are none,
// then no unquoting is needed, so return a slice of the
// original bytes.
r := 0
for r < len(s) {
c := s[r]
if c == '\\' || c == '"' || c < ' ' {
break
}
if c < utf8.RuneSelf {
r++
continue
}
rr, size := utf8.DecodeRune(s[r:])
if rr == utf8.RuneError && size == 1 {
break
}
r += size
}
if r == len(s) {
return s, true
}
b := make([]byte, len(s)+2*utf8.UTFMax)
w := copy(b, s[0:r])
for r < len(s) {
// Out of room? Can only happen if s is full of
// malformed UTF-8 and we're replacing each
// byte with RuneError.
if w >= len(b)-2*utf8.UTFMax {
nb := make([]byte, (len(b)+utf8.UTFMax)*2)
copy(nb, b[0:w])
b = nb
}
switch c := s[r]; {
case c == '\\':
r++
if r >= len(s) {
return
}
switch s[r] {
default:
return
case '"', '\\', '/', '\'':
b[w] = s[r]
r++
w++
case 'b':
b[w] = '\b'
r++
w++
case 'f':
b[w] = '\f'
r++
w++
case 'n':
b[w] = '\n'
r++
w++
case 'r':
b[w] = '\r'
r++
w++
case 't':
b[w] = '\t'
r++
w++
case 'u':
r--
rr := getu4(s[r:])
if rr < 0 {
return
}
r += 6
if utf16.IsSurrogate(rr) {
rr1 := getu4(s[r:])
if dec := utf16.DecodeRune(rr, rr1); dec != unicode.ReplacementChar {
// A valid pair; consume.
r += 6
w += utf8.EncodeRune(b[w:], dec)
break
}
// Invalid surrogate; fall back to replacement rune.
rr = unicode.ReplacementChar
}
w += utf8.EncodeRune(b[w:], rr)
}
// Quote, control characters are invalid.
case c == '"', c < ' ':
return
// ASCII
case c < utf8.RuneSelf:
b[w] = c
r++
w++
// Coerce to well-formed UTF-8.
default:
rr, size := utf8.DecodeRune(s[r:])
r += size
w += utf8.EncodeRune(b[w:], rr)
}
}
return b[0:w], true
}
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