canonicaljson-go: Index | Files | Directories

package canonicaljson

import ""

Package canonicaljson implements canonical serialization of Go objects to canonical-form JSON as specified at . The provided interface should match that of standard package "encoding/json" (from which it is derived) wherever they overlap (and in fact, this package is essentially a 2016-03-09 fork from golang/go@9d77ad8d34ce56e182adc30cd21af50a4b00932c:src/encoding/json ). Notable differences:

- Object keys are sorted lexicographically by code point
- Non-integer JSON numbers are represented in capital-E exponential
  notation with significand in (-10, 10) and no insignificant signs
  or zeroes beyond those required to force a decimal point.
- JSON strings are represented in UTF-8 with minimal byte length,
  using escapes only when necessary for validity and Unicode
  escapes (uppercase hex) only when there is no shorter option.


Package Files

decode.go encode.go fold.go indent.go scanner.go stream.go tags.go

func Marshal Uses

func Marshal(v interface{}) ([]byte, error)

Marshal returns the canonical UTF-8 JSON encoding of v.

Marshal traverses the value v recursively. If an encountered value implements the json.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. The nil pointer exception is not strictly necessary but mimics a similar, necessary exception in the behavior of json.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. Non-fractional values become sequences of digits without leading spaces; fractional values are represented in capital-E exponential notation with the shortest possible significand of magnitude less than 10 that includes at least one digit both before and after the decimal point, and the shortest possible non-empty exponent.

String values encode as JSON strings, treating ill-formed UTF-8 input as an error (with the exception of "WTF-8" encodings of lone surrogates—code points U+D800 through U+DFFF [inclusive] that could not be interpreted as part of a surrogate pair). This is in contrast to encoding/json, which replaces ill-formed sequences with U+FFFD REPLACEMENT CHARACTER. Also in contrast to encoding/json, characters appear unescaped whenever possible. Control characters U+0000 through U+001F and lone surrogates U+D800 through U+DFFF are replaced with their shortest escape sequence, 4 uppercase hex characters except for the following:

- \b U+0008 BACKSPACE
- \t U+0009 CHARACTER TABULATION ("tab")
- \n U+000A LINE FEED ("newline")
- \f U+000C FORM FEED

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 object.

Struct values encode as JSON objects. Each exported struct field becomes a member of the object unless

- the field's tag is "-", or
- the field is empty and its tag specifies the "omitempty" option.

The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero. The object's default key string is the struct field name but can be specified in the struct field's tag value. The "json" key in the struct field's tag value is the key name, followed by an optional comma and options. Examples:

// Field is ignored by this package.
Field int `json:"-"`

// 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"`

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, dollar signs, percent signs, hyphens, underscores and slashes.

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. 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 be string; the map keys are used as JSON object keys, subject to the UTF-8 coercion described for string values above.

Pointer values encode as the value pointed to. A nil pointer encodes as the null JSON object.

Interface values encode as the value contained in the interface. A nil interface value encodes as the null JSON object.

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 infinite recursion.

func MarshalIndent Uses

func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error)

MarshalIndent is like Marshal, but adds whitespace for more readable output.

func Unmarshal Uses

func Unmarshal(data []byte, v interface{}) error

Unmarshal parses the JSON-encoded UTF-8 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.

Invalid UTF-8 input is always treated as an error, even if it is encountered when unmarshaling a quoted string (in contrast to encoding/json, which replaces bad octets with U+FFFD REPLACEMENT CHARACTER). However, `\uXXXX` JSON string escape sequences specifying lone surrogates (code points U+D800 through U+DFFF [inclusive] that are not part of a surrogate pair) are interpreted to produce "WTF-8" runes that cannot be losslessly serialized to UTF-8 and might produce unexpected behavior if passed to functions expecting all strings to contain valid UTF-8. This package's Marshal function checks for such runes and emits them as valid JSON escape sequences.

type Decoder Uses

type Decoder struct {
    // contains filtered or unexported fields

A Decoder reads and decodes JSON objects from an input stream.

func NewDecoder Uses

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new decoder that reads from r.

The decoder introduces its own buffering and may read data from r beyond the JSON values requested.

func (*Decoder) Buffered Uses

func (dec *Decoder) Buffered() io.Reader

Buffered returns a reader of the data remaining in the Decoder's buffer. The reader is valid until the next call to Decode.

func (*Decoder) Decode Uses

func (dec *Decoder) Decode(v interface{}) error

Decode reads the next JSON-encoded value from its input and stores it in the value pointed to by v.

See the documentation for Unmarshal for details about the conversion of JSON into a Go value.

func (*Decoder) More Uses

func (dec *Decoder) More() bool

More reports whether there is another element in the current array or object being parsed.

func (*Decoder) Token Uses

func (dec *Decoder) Token() (Token, error)

Token returns the next JSON token in the input stream. At the end of the input stream, Token returns nil, io.EOF.

Token guarantees that the delimiters [ ] { } it returns are properly nested and matched: if Token encounters an unexpected delimiter in the input, it will return an error.

The input stream consists of basic JSON values—bool, string, number, and null—along with delimiters [ ] { } of type Delim to mark the start and end of arrays and objects. Commas and colons are elided.

func (*Decoder) UseNumber Uses

func (dec *Decoder) UseNumber()

UseNumber causes the Decoder to unmarshal a number into an interface{} as a Number instead of as a float64.

type Delim Uses

type Delim rune

A Delim is a JSON array or object delimiter, one of [ ] { or }.

func (Delim) String Uses

func (d Delim) String() string

type Encoder Uses

type Encoder struct {
    // contains filtered or unexported fields

An Encoder writes JSON objects to an output stream.

func NewEncoder Uses

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w.

func (*Encoder) Encode Uses

func (enc *Encoder) Encode(v interface{}) error

Encode writes the JSON encoding of v to the stream, followed by a newline character.

See the documentation for Marshal for details about the conversion of Go values to JSON.

type InvalidUnmarshalError Uses

type InvalidUnmarshalError struct {
    Type reflect.Type

An InvalidUnmarshalError describes an invalid argument passed to Unmarshal. (The argument to Unmarshal must be a non-nil pointer.)

func (*InvalidUnmarshalError) Error Uses

func (e *InvalidUnmarshalError) Error() string

type Marshaler Uses

type Marshaler interface {
    MarshalJSON() ([]byte, error)

Marshaler is the interface implemented by objects that can marshal themselves into valid JSON.

type MarshalerError Uses

type MarshalerError struct {
    Type reflect.Type
    Err  error

func (*MarshalerError) Error Uses

func (e *MarshalerError) Error() string

type Number Uses

type Number string

A Number represents a JSON number literal. TODO(go>=1.9): type Number = json.Number

func (Number) Float64 Uses

func (n Number) Float64() (float64, error)

Float64 returns the number as a float64.

func (Number) Int64 Uses

func (n Number) Int64() (int64, error)

Int64 returns the number as an int64.

func (Number) String Uses

func (n Number) String() string

String returns the literal text of the number.

type RawMessage Uses

type RawMessage []byte

RawMessage is a raw encoded JSON object. It implements Marshaler and Unmarshaler and can be used to delay JSON decoding or precompute a JSON encoding.

func (*RawMessage) MarshalJSON Uses

func (m *RawMessage) MarshalJSON() ([]byte, error)

MarshalJSON returns *m as the JSON encoding of m.

func (*RawMessage) UnmarshalJSON Uses

func (m *RawMessage) UnmarshalJSON(data []byte) error

UnmarshalJSON sets *m to a copy of data.

type SyntaxError Uses

type SyntaxError struct {
    Offset int64 // error occurred after reading Offset bytes
    // contains filtered or unexported fields

A SyntaxError is a description of a JSON syntax error.

func (*SyntaxError) Error Uses

func (e *SyntaxError) Error() string

type Token Uses

type Token interface{}

A Token holds a value of one of these types:

Delim, for the four JSON delimiters [ ] { }
bool, for JSON booleans
float64, for JSON numbers
Number, for JSON numbers
string, for JSON string literals
nil, for JSON null

type UnmarshalFieldError Uses

type UnmarshalFieldError struct {
    Key   string
    Type  reflect.Type
    Field reflect.StructField

An UnmarshalFieldError describes a JSON object key that led to an unexported (and therefore unwritable) struct field. (No longer used; kept for compatibility.)

func (*UnmarshalFieldError) Error Uses

func (e *UnmarshalFieldError) Error() string

type UnmarshalTypeError Uses

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

An UnmarshalTypeError describes a JSON value that was not appropriate for a value of a specific Go type.

func (*UnmarshalTypeError) Error Uses

func (e *UnmarshalTypeError) Error() string

type Unmarshaler Uses

type Unmarshaler interface {
    UnmarshalJSON([]byte) error

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 UnsupportedTypeError Uses

type UnsupportedTypeError struct {
    Type reflect.Type

An UnsupportedTypeError is returned by Marshal when attempting to encode an unsupported value type.

func (*UnsupportedTypeError) Error Uses

func (e *UnsupportedTypeError) Error() string

type UnsupportedValueError Uses

type UnsupportedValueError struct {
    Value reflect.Value
    Str   string

func (*UnsupportedValueError) Error Uses

func (e *UnsupportedValueError) Error() string



Package canonicaljson imports 18 packages (graph) and is imported by 23 packages. Updated 2020-01-02. Refresh now. Tools for package owners.