From 47ab3d4a42e9ab51c465c4322d2ec233f6324e6b Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sun, 28 Apr 2024 15:16:40 +0200
Subject: Adding upstream version 1.18.10.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/encoding/json/encode.go | 1419 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1419 insertions(+)
 create mode 100644 src/encoding/json/encode.go

(limited to 'src/encoding/json/encode.go')

diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
new file mode 100644
index 0000000..1f5e3e4
--- /dev/null
+++ b/src/encoding/json/encode.go
@@ -0,0 +1,1419 @@
+// 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 implements encoding and decoding of JSON as defined in
+// RFC 7159. The mapping between JSON and Go values is described
+// in the documentation for the Marshal and Unmarshal functions.
+//
+// See "JSON and Go" for an introduction to this package:
+// https://golang.org/doc/articles/json_and_go.html
+package json
+
+import (
+	"bytes"
+	"encoding"
+	"encoding/base64"
+	"fmt"
+	"math"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Marshal returns the JSON encoding of v.
+//
+// Marshal traverses the value v recursively.
+// If an encountered value implements the Marshaler interface
+// and is not a nil pointer, Marshal calls its MarshalJSON method
+// to produce JSON. If no MarshalJSON method is present but the
+// value implements encoding.TextMarshaler instead, Marshal calls
+// its MarshalText method and encodes the result as a JSON string.
+// The nil pointer exception is not strictly necessary
+// but mimics a similar, necessary exception in the behavior of
+// UnmarshalJSON.
+//
+// Otherwise, Marshal uses the following type-dependent default encodings:
+//
+// Boolean values encode as JSON booleans.
+//
+// Floating point, integer, and Number values encode as JSON numbers.
+//
+// String values encode as JSON strings coerced to valid UTF-8,
+// replacing invalid bytes with the Unicode replacement rune.
+// So that the JSON will be safe to embed inside HTML <script> tags,
+// the string is encoded using HTMLEscape,
+// which replaces "<", ">", "&", U+2028, and U+2029 are escaped
+// to "\u003c","\u003e", "\u0026", "\u2028", and "\u2029".
+// This replacement can be disabled when using an Encoder,
+// by calling SetEscapeHTML(false).
+//
+// Array and slice values encode as JSON arrays, except that
+// []byte encodes as a base64-encoded string, and a nil slice
+// encodes as the null JSON value.
+//
+// Struct values encode as JSON objects.
+// Each exported struct field becomes a member of the object, using the
+// field name as the object key, unless the field is omitted for one of the
+// reasons given below.
+//
+// The encoding of each struct field can be customized by the format string
+// stored under the "json" key in the struct field's tag.
+// The format string gives the name of the field, possibly followed by a
+// comma-separated list of options. The name may be empty in order to
+// specify options without overriding the default field name.
+//
+// The "omitempty" option specifies that the field should be omitted
+// from the encoding if the field has an empty value, defined as
+// false, 0, a nil pointer, a nil interface value, and any empty array,
+// slice, map, or string.
+//
+// As a special case, if the field tag is "-", the field is always omitted.
+// Note that a field with name "-" can still be generated using the tag "-,".
+//
+// Examples of struct field tags and their meanings:
+//
+//   // Field appears in JSON as key "myName".
+//   Field int `json:"myName"`
+//
+//   // Field appears in JSON as key "myName" and
+//   // the field is omitted from the object if its value is empty,
+//   // as defined above.
+//   Field int `json:"myName,omitempty"`
+//
+//   // Field appears in JSON as key "Field" (the default), but
+//   // the field is skipped if empty.
+//   // Note the leading comma.
+//   Field int `json:",omitempty"`
+//
+//   // Field is ignored by this package.
+//   Field int `json:"-"`
+//
+//   // Field appears in JSON as key "-".
+//   Field int `json:"-,"`
+//
+// The "string" option signals that a field is stored as JSON inside a
+// JSON-encoded string. It applies only to fields of string, floating point,
+// integer, or boolean types. This extra level of encoding is sometimes used
+// when communicating with JavaScript programs:
+//
+//    Int64String int64 `json:",string"`
+//
+// The key name will be used if it's a non-empty string consisting of
+// only Unicode letters, digits, and ASCII punctuation except quotation
+// marks, backslash, and comma.
+//
+// Anonymous struct fields are usually marshaled as if their inner exported fields
+// were fields in the outer struct, subject to the usual Go visibility rules amended
+// as described in the next paragraph.
+// An anonymous struct field with a name given in its JSON tag is treated as
+// having that name, rather than being anonymous.
+// An anonymous struct field of interface type is treated the same as having
+// that type as its name, rather than being anonymous.
+//
+// The Go visibility rules for struct fields are amended for JSON when
+// deciding which field to marshal or unmarshal. If there are
+// multiple fields at the same level, and that level is the least
+// nested (and would therefore be the nesting level selected by the
+// usual Go rules), the following extra rules apply:
+//
+// 1) Of those fields, if any are JSON-tagged, only tagged fields are considered,
+// even if there are multiple untagged fields that would otherwise conflict.
+//
+// 2) If there is exactly one field (tagged or not according to the first rule), that is selected.
+//
+// 3) Otherwise there are multiple fields, and all are ignored; no error occurs.
+//
+// Handling of anonymous struct fields is new in Go 1.1.
+// Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of
+// an anonymous struct field in both current and earlier versions, give the field
+// a JSON tag of "-".
+//
+// Map values encode as JSON objects. The map's key type must either be a
+// string, an integer type, or implement encoding.TextMarshaler. The map keys
+// are sorted and used as JSON object keys by applying the following rules,
+// subject to the UTF-8 coercion described for string values above:
+//   - keys of any string type are used directly
+//   - encoding.TextMarshalers are marshaled
+//   - integer keys are converted to strings
+//
+// Pointer values encode as the value pointed to.
+// A nil pointer encodes as the null JSON value.
+//
+// Interface values encode as the value contained in the interface.
+// A nil interface value encodes as the null JSON value.
+//
+// Channel, complex, and function values cannot be encoded in JSON.
+// Attempting to encode such a value causes Marshal to return
+// an UnsupportedTypeError.
+//
+// JSON cannot represent cyclic data structures and Marshal does not
+// handle them. Passing cyclic structures to Marshal will result in
+// an error.
+//
+func Marshal(v any) ([]byte, error) {
+	e := newEncodeState()
+
+	err := e.marshal(v, encOpts{escapeHTML: true})
+	if err != nil {
+		return nil, err
+	}
+	buf := append([]byte(nil), e.Bytes()...)
+
+	encodeStatePool.Put(e)
+
+	return buf, nil
+}
+
+// MarshalIndent is like Marshal but applies Indent to format the output.
+// Each JSON element in the output will begin on a new line beginning with prefix
+// followed by one or more copies of indent according to the indentation nesting.
+func MarshalIndent(v any, prefix, indent string) ([]byte, error) {
+	b, err := Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+	var buf bytes.Buffer
+	err = Indent(&buf, b, prefix, indent)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
+// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
+// so that the JSON will be safe to embed inside HTML <script> tags.
+// For historical reasons, web browsers don't honor standard HTML
+// escaping within <script> tags, so an alternative JSON encoding must
+// be used.
+func HTMLEscape(dst *bytes.Buffer, src []byte) {
+	// The characters can only appear in string literals,
+	// so just scan the string one byte at a time.
+	start := 0
+	for i, c := range src {
+		if c == '<' || c == '>' || c == '&' {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u00`)
+			dst.WriteByte(hex[c>>4])
+			dst.WriteByte(hex[c&0xF])
+			start = i + 1
+		}
+		// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
+		if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
+			if start < i {
+				dst.Write(src[start:i])
+			}
+			dst.WriteString(`\u202`)
+			dst.WriteByte(hex[src[i+2]&0xF])
+			start = i + 3
+		}
+	}
+	if start < len(src) {
+		dst.Write(src[start:])
+	}
+}
+
+// Marshaler is the interface implemented by types that
+// can marshal themselves into valid JSON.
+type Marshaler interface {
+	MarshalJSON() ([]byte, error)
+}
+
+// An UnsupportedTypeError is returned by Marshal when attempting
+// to encode an unsupported value type.
+type UnsupportedTypeError struct {
+	Type reflect.Type
+}
+
+func (e *UnsupportedTypeError) Error() string {
+	return "json: unsupported type: " + e.Type.String()
+}
+
+// An UnsupportedValueError is returned by Marshal when attempting
+// to encode an unsupported value.
+type UnsupportedValueError struct {
+	Value reflect.Value
+	Str   string
+}
+
+func (e *UnsupportedValueError) Error() string {
+	return "json: unsupported value: " + e.Str
+}
+
+// Before Go 1.2, an InvalidUTF8Error was returned by Marshal when
+// attempting to encode a string value with invalid UTF-8 sequences.
+// As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by
+// replacing invalid bytes with the Unicode replacement rune U+FFFD.
+//
+// Deprecated: No longer used; kept for compatibility.
+type InvalidUTF8Error struct {
+	S string // the whole string value that caused the error
+}
+
+func (e *InvalidUTF8Error) Error() string {
+	return "json: invalid UTF-8 in string: " + strconv.Quote(e.S)
+}
+
+// A MarshalerError represents an error from calling a MarshalJSON or MarshalText method.
+type MarshalerError struct {
+	Type       reflect.Type
+	Err        error
+	sourceFunc string
+}
+
+func (e *MarshalerError) Error() string {
+	srcFunc := e.sourceFunc
+	if srcFunc == "" {
+		srcFunc = "MarshalJSON"
+	}
+	return "json: error calling " + srcFunc +
+		" for type " + e.Type.String() +
+		": " + e.Err.Error()
+}
+
+// Unwrap returns the underlying error.
+func (e *MarshalerError) Unwrap() error { return e.Err }
+
+var hex = "0123456789abcdef"
+
+// An encodeState encodes JSON into a bytes.Buffer.
+type encodeState struct {
+	bytes.Buffer // accumulated output
+	scratch      [64]byte
+
+	// Keep track of what pointers we've seen in the current recursive call
+	// path, to avoid cycles that could lead to a stack overflow. Only do
+	// the relatively expensive map operations if ptrLevel is larger than
+	// startDetectingCyclesAfter, so that we skip the work if we're within a
+	// reasonable amount of nested pointers deep.
+	ptrLevel uint
+	ptrSeen  map[any]struct{}
+}
+
+const startDetectingCyclesAfter = 1000
+
+var encodeStatePool sync.Pool
+
+func newEncodeState() *encodeState {
+	if v := encodeStatePool.Get(); v != nil {
+		e := v.(*encodeState)
+		e.Reset()
+		if len(e.ptrSeen) > 0 {
+			panic("ptrEncoder.encode should have emptied ptrSeen via defers")
+		}
+		e.ptrLevel = 0
+		return e
+	}
+	return &encodeState{ptrSeen: make(map[any]struct{})}
+}
+
+// jsonError is an error wrapper type for internal use only.
+// Panics with errors are wrapped in jsonError so that the top-level recover
+// can distinguish intentional panics from this package.
+type jsonError struct{ error }
+
+func (e *encodeState) marshal(v any, opts encOpts) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			if je, ok := r.(jsonError); ok {
+				err = je.error
+			} else {
+				panic(r)
+			}
+		}
+	}()
+	e.reflectValue(reflect.ValueOf(v), opts)
+	return nil
+}
+
+// error aborts the encoding by panicking with err wrapped in jsonError.
+func (e *encodeState) error(err error) {
+	panic(jsonError{err})
+}
+
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return v.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return v.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Pointer:
+		return v.IsNil()
+	}
+	return false
+}
+
+func (e *encodeState) reflectValue(v reflect.Value, opts encOpts) {
+	valueEncoder(v)(e, v, opts)
+}
+
+type encOpts struct {
+	// quoted causes primitive fields to be encoded inside JSON strings.
+	quoted bool
+	// escapeHTML causes '<', '>', and '&' to be escaped in JSON strings.
+	escapeHTML bool
+}
+
+type encoderFunc func(e *encodeState, v reflect.Value, opts encOpts)
+
+var encoderCache sync.Map // map[reflect.Type]encoderFunc
+
+func valueEncoder(v reflect.Value) encoderFunc {
+	if !v.IsValid() {
+		return invalidValueEncoder
+	}
+	return typeEncoder(v.Type())
+}
+
+func typeEncoder(t reflect.Type) encoderFunc {
+	if fi, ok := encoderCache.Load(t); ok {
+		return fi.(encoderFunc)
+	}
+
+	// To deal with recursive types, populate the map with an
+	// indirect func before we build it. This type waits on the
+	// real func (f) to be ready and then calls it. This indirect
+	// func is only used for recursive types.
+	var (
+		wg sync.WaitGroup
+		f  encoderFunc
+	)
+	wg.Add(1)
+	fi, loaded := encoderCache.LoadOrStore(t, encoderFunc(func(e *encodeState, v reflect.Value, opts encOpts) {
+		wg.Wait()
+		f(e, v, opts)
+	}))
+	if loaded {
+		return fi.(encoderFunc)
+	}
+
+	// Compute the real encoder and replace the indirect func with it.
+	f = newTypeEncoder(t, true)
+	wg.Done()
+	encoderCache.Store(t, f)
+	return f
+}
+
+var (
+	marshalerType     = reflect.TypeOf((*Marshaler)(nil)).Elem()
+	textMarshalerType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+)
+
+// newTypeEncoder constructs an encoderFunc for a type.
+// The returned encoder only checks CanAddr when allowAddr is true.
+func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
+	// If we have a non-pointer value whose type implements
+	// Marshaler with a value receiver, then we're better off taking
+	// the address of the value - otherwise we end up with an
+	// allocation as we cast the value to an interface.
+	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(marshalerType) {
+		return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
+	}
+	if t.Implements(marshalerType) {
+		return marshalerEncoder
+	}
+	if t.Kind() != reflect.Pointer && allowAddr && reflect.PointerTo(t).Implements(textMarshalerType) {
+		return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
+	}
+	if t.Implements(textMarshalerType) {
+		return textMarshalerEncoder
+	}
+
+	switch t.Kind() {
+	case reflect.Bool:
+		return boolEncoder
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return intEncoder
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return uintEncoder
+	case reflect.Float32:
+		return float32Encoder
+	case reflect.Float64:
+		return float64Encoder
+	case reflect.String:
+		return stringEncoder
+	case reflect.Interface:
+		return interfaceEncoder
+	case reflect.Struct:
+		return newStructEncoder(t)
+	case reflect.Map:
+		return newMapEncoder(t)
+	case reflect.Slice:
+		return newSliceEncoder(t)
+	case reflect.Array:
+		return newArrayEncoder(t)
+	case reflect.Pointer:
+		return newPtrEncoder(t)
+	default:
+		return unsupportedTypeEncoder
+	}
+}
+
+func invalidValueEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.WriteString("null")
+}
+
+func marshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m, ok := v.Interface().(Marshaler)
+	if !ok {
+		e.WriteString("null")
+		return
+	}
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, opts.escapeHTML)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
+	}
+}
+
+func addrMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(Marshaler)
+	b, err := m.MarshalJSON()
+	if err == nil {
+		// copy JSON into buffer, checking validity.
+		err = compact(&e.Buffer, b, opts.escapeHTML)
+	}
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalJSON"})
+	}
+}
+
+func textMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Kind() == reflect.Pointer && v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m, ok := v.Interface().(encoding.TextMarshaler)
+	if !ok {
+		e.WriteString("null")
+		return
+	}
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	va := v.Addr()
+	if va.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	m := va.Interface().(encoding.TextMarshaler)
+	b, err := m.MarshalText()
+	if err != nil {
+		e.error(&MarshalerError{v.Type(), err, "MarshalText"})
+	}
+	e.stringBytes(b, opts.escapeHTML)
+}
+
+func boolEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	if v.Bool() {
+		e.WriteString("true")
+	} else {
+		e.WriteString("false")
+	}
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func intEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+func uintEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+type floatEncoder int // number of bits
+
+func (bits floatEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	f := v.Float()
+	if math.IsInf(f, 0) || math.IsNaN(f) {
+		e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
+	}
+
+	// Convert as if by ES6 number to string conversion.
+	// This matches most other JSON generators.
+	// See golang.org/issue/6384 and golang.org/issue/14135.
+	// Like fmt %g, but the exponent cutoffs are different
+	// and exponents themselves are not padded to two digits.
+	b := e.scratch[:0]
+	abs := math.Abs(f)
+	fmt := byte('f')
+	// Note: Must use float32 comparisons for underlying float32 value to get precise cutoffs right.
+	if abs != 0 {
+		if bits == 64 && (abs < 1e-6 || abs >= 1e21) || bits == 32 && (float32(abs) < 1e-6 || float32(abs) >= 1e21) {
+			fmt = 'e'
+		}
+	}
+	b = strconv.AppendFloat(b, f, fmt, -1, int(bits))
+	if fmt == 'e' {
+		// clean up e-09 to e-9
+		n := len(b)
+		if n >= 4 && b[n-4] == 'e' && b[n-3] == '-' && b[n-2] == '0' {
+			b[n-2] = b[n-1]
+			b = b[:n-1]
+		}
+	}
+
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+	e.Write(b)
+	if opts.quoted {
+		e.WriteByte('"')
+	}
+}
+
+var (
+	float32Encoder = (floatEncoder(32)).encode
+	float64Encoder = (floatEncoder(64)).encode
+)
+
+func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.Type() == numberType {
+		numStr := v.String()
+		// In Go1.5 the empty string encodes to "0", while this is not a valid number literal
+		// we keep compatibility so check validity after this.
+		if numStr == "" {
+			numStr = "0" // Number's zero-val
+		}
+		if !isValidNumber(numStr) {
+			e.error(fmt.Errorf("json: invalid number literal %q", numStr))
+		}
+		if opts.quoted {
+			e.WriteByte('"')
+		}
+		e.WriteString(numStr)
+		if opts.quoted {
+			e.WriteByte('"')
+		}
+		return
+	}
+	if opts.quoted {
+		e2 := newEncodeState()
+		// Since we encode the string twice, we only need to escape HTML
+		// the first time.
+		e2.string(v.String(), opts.escapeHTML)
+		e.stringBytes(e2.Bytes(), false)
+		encodeStatePool.Put(e2)
+	} else {
+		e.string(v.String(), opts.escapeHTML)
+	}
+}
+
+// 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 https://www.json.org/img/number.png
+
+	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 == ""
+}
+
+func interfaceEncoder(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	e.reflectValue(v.Elem(), opts)
+}
+
+func unsupportedTypeEncoder(e *encodeState, v reflect.Value, _ encOpts) {
+	e.error(&UnsupportedTypeError{v.Type()})
+}
+
+type structEncoder struct {
+	fields structFields
+}
+
+type structFields struct {
+	list      []field
+	nameIndex map[string]int
+}
+
+func (se structEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	next := byte('{')
+FieldLoop:
+	for i := range se.fields.list {
+		f := &se.fields.list[i]
+
+		// Find the nested struct field by following f.index.
+		fv := v
+		for _, i := range f.index {
+			if fv.Kind() == reflect.Pointer {
+				if fv.IsNil() {
+					continue FieldLoop
+				}
+				fv = fv.Elem()
+			}
+			fv = fv.Field(i)
+		}
+
+		if f.omitEmpty && isEmptyValue(fv) {
+			continue
+		}
+		e.WriteByte(next)
+		next = ','
+		if opts.escapeHTML {
+			e.WriteString(f.nameEscHTML)
+		} else {
+			e.WriteString(f.nameNonEsc)
+		}
+		opts.quoted = f.quoted
+		f.encoder(e, fv, opts)
+	}
+	if next == '{' {
+		e.WriteString("{}")
+	} else {
+		e.WriteByte('}')
+	}
+}
+
+func newStructEncoder(t reflect.Type) encoderFunc {
+	se := structEncoder{fields: cachedTypeFields(t)}
+	return se.encode
+}
+
+type mapEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		ptr := v.Pointer()
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	e.WriteByte('{')
+
+	// Extract and sort the keys.
+	sv := make([]reflectWithString, v.Len())
+	mi := v.MapRange()
+	for i := 0; mi.Next(); i++ {
+		sv[i].k = mi.Key()
+		sv[i].v = mi.Value()
+		if err := sv[i].resolve(); err != nil {
+			e.error(fmt.Errorf("json: encoding error for type %q: %q", v.Type().String(), err.Error()))
+		}
+	}
+	sort.Slice(sv, func(i, j int) bool { return sv[i].ks < sv[j].ks })
+
+	for i, kv := range sv {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		e.string(kv.ks, opts.escapeHTML)
+		e.WriteByte(':')
+		me.elemEnc(e, kv.v, opts)
+	}
+	e.WriteByte('}')
+	e.ptrLevel--
+}
+
+func newMapEncoder(t reflect.Type) encoderFunc {
+	switch t.Key().Kind() {
+	case reflect.String,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+	default:
+		if !t.Key().Implements(textMarshalerType) {
+			return unsupportedTypeEncoder
+		}
+	}
+	me := mapEncoder{typeEncoder(t.Elem())}
+	return me.encode
+}
+
+func encodeByteSlice(e *encodeState, v reflect.Value, _ encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	s := v.Bytes()
+	e.WriteByte('"')
+	encodedLen := base64.StdEncoding.EncodedLen(len(s))
+	if encodedLen <= len(e.scratch) {
+		// If the encoded bytes fit in e.scratch, avoid an extra
+		// allocation and use the cheaper Encoding.Encode.
+		dst := e.scratch[:encodedLen]
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else if encodedLen <= 1024 {
+		// The encoded bytes are short enough to allocate for, and
+		// Encoding.Encode is still cheaper.
+		dst := make([]byte, encodedLen)
+		base64.StdEncoding.Encode(dst, s)
+		e.Write(dst)
+	} else {
+		// The encoded bytes are too long to cheaply allocate, and
+		// Encoding.Encode is no longer noticeably cheaper.
+		enc := base64.NewEncoder(base64.StdEncoding, e)
+		enc.Write(s)
+		enc.Close()
+	}
+	e.WriteByte('"')
+}
+
+// sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
+type sliceEncoder struct {
+	arrayEnc encoderFunc
+}
+
+func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		// Here we use a struct to memorize the pointer to the first element of the slice
+		// and its length.
+		ptr := struct {
+			ptr uintptr
+			len int
+		}{v.Pointer(), v.Len()}
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	se.arrayEnc(e, v, opts)
+	e.ptrLevel--
+}
+
+func newSliceEncoder(t reflect.Type) encoderFunc {
+	// Byte slices get special treatment; arrays don't.
+	if t.Elem().Kind() == reflect.Uint8 {
+		p := reflect.PointerTo(t.Elem())
+		if !p.Implements(marshalerType) && !p.Implements(textMarshalerType) {
+			return encodeByteSlice
+		}
+	}
+	enc := sliceEncoder{newArrayEncoder(t)}
+	return enc.encode
+}
+
+type arrayEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (ae arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	e.WriteByte('[')
+	n := v.Len()
+	for i := 0; i < n; i++ {
+		if i > 0 {
+			e.WriteByte(',')
+		}
+		ae.elemEnc(e, v.Index(i), opts)
+	}
+	e.WriteByte(']')
+}
+
+func newArrayEncoder(t reflect.Type) encoderFunc {
+	enc := arrayEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type ptrEncoder struct {
+	elemEnc encoderFunc
+}
+
+func (pe ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.IsNil() {
+		e.WriteString("null")
+		return
+	}
+	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
+		// We're a large number of nested ptrEncoder.encode calls deep;
+		// start checking if we've run into a pointer cycle.
+		ptr := v.Interface()
+		if _, ok := e.ptrSeen[ptr]; ok {
+			e.error(&UnsupportedValueError{v, fmt.Sprintf("encountered a cycle via %s", v.Type())})
+		}
+		e.ptrSeen[ptr] = struct{}{}
+		defer delete(e.ptrSeen, ptr)
+	}
+	pe.elemEnc(e, v.Elem(), opts)
+	e.ptrLevel--
+}
+
+func newPtrEncoder(t reflect.Type) encoderFunc {
+	enc := ptrEncoder{typeEncoder(t.Elem())}
+	return enc.encode
+}
+
+type condAddrEncoder struct {
+	canAddrEnc, elseEnc encoderFunc
+}
+
+func (ce condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+	if v.CanAddr() {
+		ce.canAddrEnc(e, v, opts)
+	} else {
+		ce.elseEnc(e, v, opts)
+	}
+}
+
+// newCondAddrEncoder returns an encoder that checks whether its value
+// CanAddr and delegates to canAddrEnc if so, else to elseEnc.
+func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
+	enc := condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+	return enc.encode
+}
+
+func isValidTag(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		switch {
+		case strings.ContainsRune("!#$%&()*+-./:;<=>?@[]^_{|}~ ", c):
+			// Backslash and quote chars are reserved, but
+			// otherwise any punctuation chars are allowed
+			// in a tag name.
+		case !unicode.IsLetter(c) && !unicode.IsDigit(c):
+			return false
+		}
+	}
+	return true
+}
+
+func typeByIndex(t reflect.Type, index []int) reflect.Type {
+	for _, i := range index {
+		if t.Kind() == reflect.Pointer {
+			t = t.Elem()
+		}
+		t = t.Field(i).Type
+	}
+	return t
+}
+
+type reflectWithString struct {
+	k  reflect.Value
+	v  reflect.Value
+	ks string
+}
+
+func (w *reflectWithString) resolve() error {
+	if w.k.Kind() == reflect.String {
+		w.ks = w.k.String()
+		return nil
+	}
+	if tm, ok := w.k.Interface().(encoding.TextMarshaler); ok {
+		if w.k.Kind() == reflect.Pointer && w.k.IsNil() {
+			return nil
+		}
+		buf, err := tm.MarshalText()
+		w.ks = string(buf)
+		return err
+	}
+	switch w.k.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		w.ks = strconv.FormatInt(w.k.Int(), 10)
+		return nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		w.ks = strconv.FormatUint(w.k.Uint(), 10)
+		return nil
+	}
+	panic("unexpected map key type")
+}
+
+// NOTE: keep in sync with stringBytes below.
+func (e *encodeState) string(s string, escapeHTML bool) {
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
+				i++
+				continue
+			}
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteByte('\\')
+			switch b {
+			case '\\', '"':
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRuneInString(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.WriteString(s[start:])
+	}
+	e.WriteByte('"')
+}
+
+// NOTE: keep in sync with string above.
+func (e *encodeState) stringBytes(s []byte, escapeHTML bool) {
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if htmlSafeSet[b] || (!escapeHTML && safeSet[b]) {
+				i++
+				continue
+			}
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteByte('\\')
+			switch b {
+			case '\\', '"':
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('r')
+			case '\t':
+				e.WriteByte('t')
+			default:
+				// This encodes bytes < 0x20 except for \t, \n and \r.
+				// If escapeHTML is set, it also escapes <, >, and &
+				// because they can lead to security holes when
+				// user-controlled strings are rendered into JSON
+				// and served to some browsers.
+				e.WriteString(`u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRune(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\ufffd`)
+			i += size
+			start = i
+			continue
+		}
+		// U+2028 is LINE SEPARATOR.
+		// U+2029 is PARAGRAPH SEPARATOR.
+		// They are both technically valid characters in JSON strings,
+		// but don't work in JSONP, which has to be evaluated as JavaScript,
+		// and can lead to security holes there. It is valid JSON to
+		// escape them, so we do so unconditionally.
+		// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+		if c == '\u2028' || c == '\u2029' {
+			if start < i {
+				e.Write(s[start:i])
+			}
+			e.WriteString(`\u202`)
+			e.WriteByte(hex[c&0xF])
+			i += size
+			start = i
+			continue
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.Write(s[start:])
+	}
+	e.WriteByte('"')
+}
+
+// A field represents a single field found in a struct.
+type field struct {
+	name      string
+	nameBytes []byte                 // []byte(name)
+	equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
+
+	nameNonEsc  string // `"` + name + `":`
+	nameEscHTML string // `"` + HTMLEscape(name) + `":`
+
+	tag       bool
+	index     []int
+	typ       reflect.Type
+	omitEmpty bool
+	quoted    bool
+
+	encoder encoderFunc
+}
+
+// byIndex sorts field by index sequence.
+type byIndex []field
+
+func (x byIndex) Len() int { return len(x) }
+
+func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+func (x byIndex) Less(i, j int) bool {
+	for k, xik := range x[i].index {
+		if k >= len(x[j].index) {
+			return false
+		}
+		if xik != x[j].index[k] {
+			return xik < x[j].index[k]
+		}
+	}
+	return len(x[i].index) < len(x[j].index)
+}
+
+// typeFields returns a list of fields that JSON should recognize for the given type.
+// The algorithm is breadth-first search over the set of structs to include - the top struct
+// and then any reachable anonymous structs.
+func typeFields(t reflect.Type) structFields {
+	// Anonymous fields to explore at the current level and the next.
+	current := []field{}
+	next := []field{{typ: t}}
+
+	// Count of queued names for current level and the next.
+	var count, nextCount map[reflect.Type]int
+
+	// Types already visited at an earlier level.
+	visited := map[reflect.Type]bool{}
+
+	// Fields found.
+	var fields []field
+
+	// Buffer to run HTMLEscape on field names.
+	var nameEscBuf bytes.Buffer
+
+	for len(next) > 0 {
+		current, next = next, current[:0]
+		count, nextCount = nextCount, map[reflect.Type]int{}
+
+		for _, f := range current {
+			if visited[f.typ] {
+				continue
+			}
+			visited[f.typ] = true
+
+			// Scan f.typ for fields to include.
+			for i := 0; i < f.typ.NumField(); i++ {
+				sf := f.typ.Field(i)
+				if sf.Anonymous {
+					t := sf.Type
+					if t.Kind() == reflect.Pointer {
+						t = t.Elem()
+					}
+					if !sf.IsExported() && t.Kind() != reflect.Struct {
+						// Ignore embedded fields of unexported non-struct types.
+						continue
+					}
+					// Do not ignore embedded fields of unexported struct types
+					// since they may have exported fields.
+				} else if !sf.IsExported() {
+					// Ignore unexported non-embedded fields.
+					continue
+				}
+				tag := sf.Tag.Get("json")
+				if tag == "-" {
+					continue
+				}
+				name, opts := parseTag(tag)
+				if !isValidTag(name) {
+					name = ""
+				}
+				index := make([]int, len(f.index)+1)
+				copy(index, f.index)
+				index[len(f.index)] = i
+
+				ft := sf.Type
+				if ft.Name() == "" && ft.Kind() == reflect.Pointer {
+					// Follow pointer.
+					ft = ft.Elem()
+				}
+
+				// Only strings, floats, integers, and booleans can be quoted.
+				quoted := false
+				if opts.Contains("string") {
+					switch ft.Kind() {
+					case reflect.Bool,
+						reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+						reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
+						reflect.Float32, reflect.Float64,
+						reflect.String:
+						quoted = true
+					}
+				}
+
+				// Record found field and index sequence.
+				if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
+					tagged := name != ""
+					if name == "" {
+						name = sf.Name
+					}
+					field := field{
+						name:      name,
+						tag:       tagged,
+						index:     index,
+						typ:       ft,
+						omitEmpty: opts.Contains("omitempty"),
+						quoted:    quoted,
+					}
+					field.nameBytes = []byte(field.name)
+					field.equalFold = foldFunc(field.nameBytes)
+
+					// Build nameEscHTML and nameNonEsc ahead of time.
+					nameEscBuf.Reset()
+					nameEscBuf.WriteString(`"`)
+					HTMLEscape(&nameEscBuf, field.nameBytes)
+					nameEscBuf.WriteString(`":`)
+					field.nameEscHTML = nameEscBuf.String()
+					field.nameNonEsc = `"` + field.name + `":`
+
+					fields = append(fields, field)
+					if count[f.typ] > 1 {
+						// If there were multiple instances, add a second,
+						// so that the annihilation code will see a duplicate.
+						// It only cares about the distinction between 1 or 2,
+						// so don't bother generating any more copies.
+						fields = append(fields, fields[len(fields)-1])
+					}
+					continue
+				}
+
+				// Record new anonymous struct to explore in next round.
+				nextCount[ft]++
+				if nextCount[ft] == 1 {
+					next = append(next, field{name: ft.Name(), index: index, typ: ft})
+				}
+			}
+		}
+	}
+
+	sort.Slice(fields, func(i, j int) bool {
+		x := fields
+		// sort field by name, breaking ties with depth, then
+		// breaking ties with "name came from json tag", then
+		// breaking ties with index sequence.
+		if x[i].name != x[j].name {
+			return x[i].name < x[j].name
+		}
+		if len(x[i].index) != len(x[j].index) {
+			return len(x[i].index) < len(x[j].index)
+		}
+		if x[i].tag != x[j].tag {
+			return x[i].tag
+		}
+		return byIndex(x).Less(i, j)
+	})
+
+	// Delete all fields that are hidden by the Go rules for embedded fields,
+	// except that fields with JSON tags are promoted.
+
+	// The fields are sorted in primary order of name, secondary order
+	// of field index length. Loop over names; for each name, delete
+	// hidden fields by choosing the one dominant field that survives.
+	out := fields[:0]
+	for advance, i := 0, 0; i < len(fields); i += advance {
+		// One iteration per name.
+		// Find the sequence of fields with the name of this first field.
+		fi := fields[i]
+		name := fi.name
+		for advance = 1; i+advance < len(fields); advance++ {
+			fj := fields[i+advance]
+			if fj.name != name {
+				break
+			}
+		}
+		if advance == 1 { // Only one field with this name
+			out = append(out, fi)
+			continue
+		}
+		dominant, ok := dominantField(fields[i : i+advance])
+		if ok {
+			out = append(out, dominant)
+		}
+	}
+
+	fields = out
+	sort.Sort(byIndex(fields))
+
+	for i := range fields {
+		f := &fields[i]
+		f.encoder = typeEncoder(typeByIndex(t, f.index))
+	}
+	nameIndex := make(map[string]int, len(fields))
+	for i, field := range fields {
+		nameIndex[field.name] = i
+	}
+	return structFields{fields, nameIndex}
+}
+
+// dominantField looks through the fields, all of which are known to
+// have the same name, to find the single field that dominates the
+// others using Go's embedding rules, modified by the presence of
+// JSON tags. If there are multiple top-level fields, the boolean
+// will be false: This condition is an error in Go and we skip all
+// the fields.
+func dominantField(fields []field) (field, bool) {
+	// The fields are sorted in increasing index-length order, then by presence of tag.
+	// That means that the first field is the dominant one. We need only check
+	// for error cases: two fields at top level, either both tagged or neither tagged.
+	if len(fields) > 1 && len(fields[0].index) == len(fields[1].index) && fields[0].tag == fields[1].tag {
+		return field{}, false
+	}
+	return fields[0], true
+}
+
+var fieldCache sync.Map // map[reflect.Type]structFields
+
+// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
+func cachedTypeFields(t reflect.Type) structFields {
+	if f, ok := fieldCache.Load(t); ok {
+		return f.(structFields)
+	}
+	f, _ := fieldCache.LoadOrStore(t, typeFields(t))
+	return f.(structFields)
+}
-- 
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