// Copyright 2020 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.
//go:build goexperiment.jsonv2
package jsontext
import (
"bytes"
"errors"
"io"
"slices"
"sync"
"encoding/json/internal/jsonflags"
"encoding/json/internal/jsonwire"
)
// NOTE: Value is analogous to v1 json.RawMessage.
// AppendFormat formats the JSON value in src and appends it to dst
// according to the specified options.
// See [Value.Format] for more details about the formatting behavior.
//
// The dst and src may overlap.
// If an error is reported, then the entirety of src is appended to dst.
func AppendFormat(dst, src []byte, opts ...Options) ([]byte, error) {
e := getBufferedEncoder(opts...)
defer putBufferedEncoder(e)
e.s.Flags.Set(jsonflags.OmitTopLevelNewline | 1)
if err := e.s.WriteValue(src); err != nil {
return append(dst, src...), err
}
return append(dst, e.s.Buf...), nil
}
// Value represents a single raw JSON value, which may be one of the following:
// - a JSON literal (i.e., null, true, or false)
// - a JSON string (e.g., "hello, world!")
// - a JSON number (e.g., 123.456)
// - an entire JSON object (e.g., {"fizz":"buzz"} )
// - an entire JSON array (e.g., [1,2,3] )
//
// Value can represent entire array or object values, while [Token] cannot.
// Value may contain leading and/or trailing whitespace.
type Value []byte
// Clone returns a copy of v.
func (v Value) Clone() Value {
return bytes.Clone(v)
}
// String returns the string formatting of v.
func (v Value) String() string {
if v == nil {
return "null"
}
return string(v)
}
// IsValid reports whether the raw JSON value is syntactically valid
// according to the specified options.
//
// By default (if no options are specified), it validates according to RFC 7493.
// It verifies whether the input is properly encoded as UTF-8,
// that escape sequences within strings decode to valid Unicode codepoints, and
// that all names in each object are unique.
// It does not verify whether numbers are representable within the limits
// of any common numeric type (e.g., float64, int64, or uint64).
//
// Relevant options include:
// - [AllowDuplicateNames]
// - [AllowInvalidUTF8]
//
// All other options are ignored.
func (v Value) IsValid(opts ...Options) bool {
// TODO: Document support for [WithByteLimit] and [WithDepthLimit].
d := getBufferedDecoder(v, opts...)
defer putBufferedDecoder(d)
_, errVal := d.ReadValue()
_, errEOF := d.ReadToken()
return errVal == nil && errEOF == io.EOF
}
// Format formats the raw JSON value in place.
//
// By default (if no options are specified), it validates according to RFC 7493
// and produces the minimal JSON representation, where
// all whitespace is elided and JSON strings use the shortest encoding.
//
// Relevant options include:
// - [AllowDuplicateNames]
// - [AllowInvalidUTF8]
// - [EscapeForHTML]
// - [EscapeForJS]
// - [PreserveRawStrings]
// - [CanonicalizeRawInts]
// - [CanonicalizeRawFloats]
// - [ReorderRawObjects]
// - [SpaceAfterColon]
// - [SpaceAfterComma]
// - [Multiline]
// - [WithIndent]
// - [WithIndentPrefix]
//
// All other options are ignored.
//
// It is guaranteed to succeed if the value is valid according to the same options.
// If the value is already formatted, then the buffer is not mutated.
func (v *Value) Format(opts ...Options) error {
// TODO: Document support for [WithByteLimit] and [WithDepthLimit].
return v.format(opts, nil)
}
// format accepts two []Options to avoid the allocation appending them together.
// It is equivalent to v.Format(append(opts1, opts2...)...).
func (v *Value) format(opts1, opts2 []Options) error {
e := getBufferedEncoder(opts1...)
defer putBufferedEncoder(e)
e.s.Join(opts2...)
e.s.Flags.Set(jsonflags.OmitTopLevelNewline | 1)
if err := e.s.WriteValue(*v); err != nil {
return err
}
if !bytes.Equal(*v, e.s.Buf) {
*v = append((*v)[:0], e.s.Buf...)
}
return nil
}
// Compact removes all whitespace from the raw JSON value.
//
// It does not reformat JSON strings or numbers to use any other representation.
// To maximize the set of JSON values that can be formatted,
// this permits values with duplicate names and invalid UTF-8.
//
// Compact is equivalent to calling [Value.Format] with the following options:
// - [AllowDuplicateNames](true)
// - [AllowInvalidUTF8](true)
// - [PreserveRawStrings](true)
//
// Any options specified by the caller are applied after the initial set
// and may deliberately override prior options.
func (v *Value) Compact(opts ...Options) error {
return v.format([]Options{
AllowDuplicateNames(true),
AllowInvalidUTF8(true),
PreserveRawStrings(true),
}, opts)
}
// Indent reformats the whitespace in the raw JSON value so that each element
// in a JSON object or array begins on a indented line according to the nesting.
//
// It does not reformat JSON strings or numbers to use any other representation.
// To maximize the set of JSON values that can be formatted,
// this permits values with duplicate names and invalid UTF-8.
//
// Indent is equivalent to calling [Value.Format] with the following options:
// - [AllowDuplicateNames](true)
// - [AllowInvalidUTF8](true)
// - [PreserveRawStrings](true)
// - [Multiline](true)
//
// Any options specified by the caller are applied after the initial set
// and may deliberately override prior options.
func (v *Value) Indent(opts ...Options) error {
return v.format([]Options{
AllowDuplicateNames(true),
AllowInvalidUTF8(true),
PreserveRawStrings(true),
Multiline(true),
}, opts)
}
// Canonicalize canonicalizes the raw JSON value according to the
// JSON Canonicalization Scheme (JCS) as defined by RFC 8785
// where it produces a stable representation of a JSON value.
//
// JSON strings are formatted to use their minimal representation,
// JSON numbers are formatted as double precision numbers according
// to some stable serialization algorithm.
// JSON object members are sorted in ascending order by name.
// All whitespace is removed.
//
// The output stability is dependent on the stability of the application data
// (see RFC 8785, Appendix E). It cannot produce stable output from
// fundamentally unstable input. For example, if the JSON value
// contains ephemeral data (e.g., a frequently changing timestamp),
// then the value is still unstable regardless of whether this is called.
//
// Canonicalize is equivalent to calling [Value.Format] with the following options:
// - [CanonicalizeRawInts](true)
// - [CanonicalizeRawFloats](true)
// - [ReorderRawObjects](true)
//
// Any options specified by the caller are applied after the initial set
// and may deliberately override prior options.
//
// Note that JCS treats all JSON numbers as IEEE 754 double precision numbers.
// Any numbers with precision beyond what is representable by that form
// will lose their precision when canonicalized. For example, integer values
// beyond ±2⁵³ will lose their precision. To preserve the original representation
// of JSON integers, additionally set [CanonicalizeRawInts] to false:
//
// v.Canonicalize(jsontext.CanonicalizeRawInts(false))
func (v *Value) Canonicalize(opts ...Options) error {
return v.format([]Options{
CanonicalizeRawInts(true),
CanonicalizeRawFloats(true),
ReorderRawObjects(true),
}, opts)
}
// MarshalJSON returns v as the JSON encoding of v.
// It returns the stored value as the raw JSON output without any validation.
// If v is nil, then this returns a JSON null.
func (v Value) MarshalJSON() ([]byte, error) {
// NOTE: This matches the behavior of v1 json.RawMessage.MarshalJSON.
if v == nil {
return []byte("null"), nil
}
return v, nil
}
// UnmarshalJSON sets v as the JSON encoding of b.
// It stores a copy of the provided raw JSON input without any validation.
func (v *Value) UnmarshalJSON(b []byte) error {
// NOTE: This matches the behavior of v1 json.RawMessage.UnmarshalJSON.
if v == nil {
return errors.New("jsontext.Value: UnmarshalJSON on nil pointer")
}
*v = append((*v)[:0], b...)
return nil
}
// Kind returns the starting token kind.
// For a valid value, this will never include '}' or ']'.
func (v Value) Kind() Kind {
if v := v[jsonwire.ConsumeWhitespace(v):]; len(v) > 0 {
return Kind(v[0]).normalize()
}
return invalidKind
}
const commaAndWhitespace = ", \n\r\t"
type objectMember struct {
// name is the unquoted name.
name []byte // e.g., "name"
// buffer is the entirety of the raw JSON object member
// starting from right after the previous member (or opening '{')
// until right after the member value.
buffer []byte // e.g., `, \n\r\t"name": "value"`
}
func (x objectMember) Compare(y objectMember) int {
if c := jsonwire.CompareUTF16(x.name, y.name); c != 0 {
return c
}
// With [AllowDuplicateNames] or [AllowInvalidUTF8],
// names could be identical, so also sort using the member value.
return jsonwire.CompareUTF16(
bytes.TrimLeft(x.buffer, commaAndWhitespace),
bytes.TrimLeft(y.buffer, commaAndWhitespace))
}
var objectMemberPool = sync.Pool{New: func() any { return new([]objectMember) }}
func getObjectMembers() *[]objectMember {
ns := objectMemberPool.Get().(*[]objectMember)
*ns = (*ns)[:0]
return ns
}
func putObjectMembers(ns *[]objectMember) {
if cap(*ns) < 1<<10 {
clear(*ns) // avoid pinning name and buffer
objectMemberPool.Put(ns)
}
}
// mustReorderObjects reorders in-place all object members in a JSON value,
// which must be valid otherwise it panics.
func mustReorderObjects(b []byte) {
// Obtain a buffered encoder just to use its internal buffer as
// a scratch buffer for reordering object members.
e2 := getBufferedEncoder()
defer putBufferedEncoder(e2)
// Disable unnecessary checks to syntactically parse the JSON value.
d := getBufferedDecoder(b)
defer putBufferedDecoder(d)
d.s.Flags.Set(jsonflags.AllowDuplicateNames | jsonflags.AllowInvalidUTF8 | 1)
mustReorderObjectsFromDecoder(d, &e2.s.Buf) // per RFC 8785, section 3.2.3
}
// mustReorderObjectsFromDecoder recursively reorders all object members in place
// according to the ordering specified in RFC 8785, section 3.2.3.
//
// Pre-conditions:
// - The value is valid (i.e., no decoder errors should ever occur).
// - Initial call is provided a Decoder reading from the start of v.
//
// Post-conditions:
// - Exactly one JSON value is read from the Decoder.
// - All fully-parsed JSON objects are reordered by directly moving
// the members in the value buffer.
//
// The runtime is approximately O(n·log(n)) + O(m·log(m)),
// where n is len(v) and m is the total number of object members.
func mustReorderObjectsFromDecoder(d *Decoder, scratch *[]byte) {
switch tok, err := d.ReadToken(); tok.Kind() {
case '{':
// Iterate and collect the name and offsets for every object member.
members := getObjectMembers()
defer putObjectMembers(members)
var prevMember objectMember
isSorted := true
beforeBody := d.InputOffset() // offset after '{'
for d.PeekKind() != '}' {
beforeName := d.InputOffset()
var flags jsonwire.ValueFlags
name, _ := d.s.ReadValue(&flags)
name = jsonwire.UnquoteMayCopy(name, flags.IsVerbatim())
mustReorderObjectsFromDecoder(d, scratch)
afterValue := d.InputOffset()
currMember := objectMember{name, d.s.buf[beforeName:afterValue]}
if isSorted && len(*members) > 0 {
isSorted = objectMember.Compare(prevMember, currMember) < 0
}
*members = append(*members, currMember)
prevMember = currMember
}
afterBody := d.InputOffset() // offset before '}'
d.ReadToken()
// Sort the members; return early if it's already sorted.
if isSorted {
return
}
firstBufferBeforeSorting := (*members)[0].buffer
slices.SortFunc(*members, objectMember.Compare)
firstBufferAfterSorting := (*members)[0].buffer
// Append the reordered members to a new buffer,
// then copy the reordered members back over the original members.
// Avoid swapping in place since each member may be a different size
// where moving a member over a smaller member may corrupt the data
// for subsequent members before they have been moved.
//
// The following invariant must hold:
// sum([m.after-m.before for m in members]) == afterBody-beforeBody
commaAndWhitespacePrefix := func(b []byte) []byte {
return b[:len(b)-len(bytes.TrimLeft(b, commaAndWhitespace))]
}
sorted := (*scratch)[:0]
for i, member := range *members {
switch {
case i == 0 && &member.buffer[0] != &firstBufferBeforeSorting[0]:
// First member after sorting is not the first member before sorting,
// so use the prefix of the first member before sorting.
sorted = append(sorted, commaAndWhitespacePrefix(firstBufferBeforeSorting)...)
sorted = append(sorted, bytes.TrimLeft(member.buffer, commaAndWhitespace)...)
case i != 0 && &member.buffer[0] == &firstBufferBeforeSorting[0]:
// Later member after sorting is the first member before sorting,
// so use the prefix of the first member after sorting.
sorted = append(sorted, commaAndWhitespacePrefix(firstBufferAfterSorting)...)
sorted = append(sorted, bytes.TrimLeft(member.buffer, commaAndWhitespace)...)
default:
sorted = append(sorted, member.buffer...)
}
}
if int(afterBody-beforeBody) != len(sorted) {
panic("BUG: length invariant violated")
}
copy(d.s.buf[beforeBody:afterBody], sorted)
// Update scratch buffer to the largest amount ever used.
if len(sorted) > len(*scratch) {
*scratch = sorted
}
case '[':
for d.PeekKind() != ']' {
mustReorderObjectsFromDecoder(d, scratch)
}
d.ReadToken()
default:
if err != nil {
panic("BUG: " + err.Error())
}
}
}
