msgpack

package module
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 Go to latest Published: Nov 16, 2020 License: BSD-2-Clause Imports: 18 Imported by: 1,001

README

MessagePack encoding for Golang

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Features

Installation

msgpack supports 2 last Go versions and requires support for Go modules. So make sure to initialize a Go module:

go mod init github.com/my/repo

And then install msgpack/v5 (note v5 in the import; omitting it is a popular mistake):

go get github.com/vmihailenco/msgpack/v5

Quickstart

import "github.com/vmihailenco/msgpack/v5"

func ExampleMarshal() {
    type Item struct {
        Foo string
    }

    b, err := msgpack.Marshal(&Item{Foo: "bar"})
    if err != nil {
        panic(err)
    }

    var item Item
    err = msgpack.Unmarshal(b, &item)
    if err != nil {
        panic(err)
    }
    fmt.Println(item.Foo)
    // Output: bar
}

See also

Documentation

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func Marshal 

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

Marshal returns the MessagePack encoding of v.

Example 
type Item struct {
	Foo string
}

b, err := msgpack.Marshal(&Item{Foo: "bar"})
if err != nil {
	panic(err)
}

var item Item
err = msgpack.Unmarshal(b, &item)
if err != nil {
	panic(err)
}
fmt.Println(item.Foo)

Output:

bar
Example (AsArray) 
type Item struct {
	_msgpack struct{} `msgpack:",as_array"`
	Foo      string
	Bar      string
}

var buf bytes.Buffer
enc := msgpack.NewEncoder(&buf)
err := enc.Encode(&Item{Foo: "foo", Bar: "bar"})
if err != nil {
	panic(err)
}

dec := msgpack.NewDecoder(&buf)
v, err := dec.DecodeInterface()
if err != nil {
	panic(err)
}
fmt.Println(v)

Output:

[foo bar]
Example (MapStringInterface) 
in := map[string]interface{}{"foo": 1, "hello": "world"}
b, err := msgpack.Marshal(in)
if err != nil {
	panic(err)
}

var out map[string]interface{}
err = msgpack.Unmarshal(b, &out)
if err != nil {
	panic(err)
}

fmt.Println("foo =", out["foo"])
fmt.Println("hello =", out["hello"])

Output:

foo = 1
hello = world
Example (OmitEmpty) 
type Item struct {
	Foo string
	Bar string
}

item := &Item{
	Foo: "hello",
}
b, err := msgpack.Marshal(item)
if err != nil {
	panic(err)
}
fmt.Printf("item: %q\n", b)

type ItemOmitEmpty struct {
	_msgpack struct{} `msgpack:",omitempty"`
	Foo      string
	Bar      string
}

itemOmitEmpty := &ItemOmitEmpty{
	Foo: "hello",
}
b, err = msgpack.Marshal(itemOmitEmpty)
if err != nil {
	panic(err)
}
fmt.Printf("item2: %q\n", b)

Output:

item: "\x82\xa3Foo\xa5hello\xa3Bar\xa0"
item2: "\x81\xa3Foo\xa5hello"

func PutDecoder 

func PutDecoder(dec *Decoder)

func PutEncoder 

func PutEncoder(enc *Encoder)

func Register 

func Register(value interface{}, enc encoderFunc, dec decoderFunc)

Register registers encoder and decoder functions for a value. This is low level API and in most cases you should prefer implementing CustomEncoder/CustomDecoder or Marshaler/Unmarshaler interfaces.

func RegisterExt 

func RegisterExt(extID int8, value MarshalerUnmarshaler)
Example 
package main

import (
	"encoding/binary"
	"fmt"
	"time"

	"github.com/vmihailenco/msgpack/v5"
)

func init() {
	msgpack.RegisterExt(1, (*EventTime)(nil))
}

// https://github.com/fluent/fluentd/wiki/Forward-Protocol-Specification-v1#eventtime-ext-format
type EventTime struct {
	time.Time
}

var (
	_ msgpack.Marshaler   = (*EventTime)(nil)
	_ msgpack.Unmarshaler = (*EventTime)(nil)
)

func (tm *EventTime) MarshalMsgpack() ([]byte, error) {
	b := make([]byte, 8)
	binary.BigEndian.PutUint32(b, uint32(tm.Unix()))
	binary.BigEndian.PutUint32(b[4:], uint32(tm.Nanosecond()))
	return b, nil
}

func (tm *EventTime) UnmarshalMsgpack(b []byte) error {
	if len(b) != 8 {
		return fmt.Errorf("invalid data length: got %d, wanted 8", len(b))
	}
	sec := binary.BigEndian.Uint32(b)
	usec := binary.BigEndian.Uint32(b[4:])
	tm.Time = time.Unix(int64(sec), int64(usec))
	return nil
}

func main() {
	b, err := msgpack.Marshal(&EventTime{time.Unix(123456789, 123)})
	if err != nil {
		panic(err)
	}

	var v interface{}
	err = msgpack.Unmarshal(b, &v)
	if err != nil {
		panic(err)
	}
	fmt.Println(v.(*EventTime).UTC())

	tm := new(EventTime)
	err = msgpack.Unmarshal(b, &tm)
	if err != nil {
		panic(err)
	}
	fmt.Println(tm.UTC())

}

Output:

1973-11-29 21:33:09.000000123 +0000 UTC
1973-11-29 21:33:09.000000123 +0000 UTC

func RegisterExtDecoder 

func RegisterExtDecoder(
	extID int8,
	value interface{},
	decoder func(dec *Decoder, v reflect.Value, extLen int) error,
)

func RegisterExtEncoder 

func RegisterExtEncoder(
	extID int8,
	value interface{},
	encoder func(enc *Encoder, v reflect.Value) ([]byte, error),
)

func Unmarshal 

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

Unmarshal decodes the MessagePack-encoded data and stores the result in the value pointed to by v.

Types

type CustomDecoder 

type CustomDecoder interface {
	DecodeMsgpack(*Decoder) error
}

type CustomEncoder 

type CustomEncoder interface {
	EncodeMsgpack(*Encoder) error
}
Example 
package main

import (
	"fmt"

	"github.com/vmihailenco/msgpack/v5"
)

type customStruct struct {
	S string
	N int
}

var _ msgpack.CustomEncoder = (*customStruct)(nil)
var _ msgpack.CustomDecoder = (*customStruct)(nil)

func (s *customStruct) EncodeMsgpack(enc *msgpack.Encoder) error {
	return enc.EncodeMulti(s.S, s.N)
}

func (s *customStruct) DecodeMsgpack(dec *msgpack.Decoder) error {
	return dec.DecodeMulti(&s.S, &s.N)
}

func main() {
	b, err := msgpack.Marshal(&customStruct{S: "hello", N: 42})
	if err != nil {
		panic(err)
	}

	var v customStruct
	err = msgpack.Unmarshal(b, &v)
	if err != nil {
		panic(err)
	}
	fmt.Printf("%#v", v)
}

Output:

msgpack_test.customStruct{S:"hello", N:42}

type Decoder 

type Decoder struct {
	// contains filtered or unexported fields
}

A Decoder reads and decodes MessagePack values from an input stream.

func GetDecoder 

func GetDecoder() *Decoder

func NewDecoder 

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 requested msgpack values. Buffering can be disabled by passing a reader that implements io.ByteScanner interface.

func (*Decoder) Buffered 

func (d *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 

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

func (*Decoder) DecodeArrayLen 

func (d *Decoder) DecodeArrayLen() (int, error)

DecodeArrayLen decodes array length. Length is -1 when array is nil.

func (*Decoder) DecodeBool 

func (d *Decoder) DecodeBool() (bool, error)

func (*Decoder) DecodeBytes 

func (d *Decoder) DecodeBytes() ([]byte, error)

func (*Decoder) DecodeBytesLen 

func (d *Decoder) DecodeBytesLen() (int, error)

func (*Decoder) DecodeDuration 

func (d *Decoder) DecodeDuration() (time.Duration, error)

func (*Decoder) DecodeExtHeader 

func (d *Decoder) DecodeExtHeader() (extID int8, extLen int, err error)

func (*Decoder) DecodeFloat32 

func (d *Decoder) DecodeFloat32() (float32, error)

func (*Decoder) DecodeFloat64 

func (d *Decoder) DecodeFloat64() (float64, error)

DecodeFloat64 decodes msgpack float32/64 into Go float64.

func (*Decoder) DecodeInt 

func (d *Decoder) DecodeInt() (int, error)

func (*Decoder) DecodeInt16 

func (d *Decoder) DecodeInt16() (int16, error)

func (*Decoder) DecodeInt32 

func (d *Decoder) DecodeInt32() (int32, error)

func (*Decoder) DecodeInt64 

func (d *Decoder) DecodeInt64() (int64, error)

DecodeInt64 decodes msgpack int8/16/32/64 and uint8/16/32/64 into Go int64.

func (*Decoder) DecodeInt8 

func (d *Decoder) DecodeInt8() (int8, error)

func (*Decoder) DecodeInterface 

func (d *Decoder) DecodeInterface() (interface{}, error)

DecodeInterface decodes value into interface. It returns following types:

  • nil,
  • bool,
  • int8, int16, int32, int64,
  • uint8, uint16, uint32, uint64,
  • float32 and float64,
  • string,
  • []byte,
  • slices of any of the above,
  • maps of any of the above.

DecodeInterface should be used only when you don't know the type of value you are decoding. For example, if you are decoding number it is better to use DecodeInt64 for negative numbers and DecodeUint64 for positive numbers.

func (*Decoder) DecodeInterfaceLoose 

func (d *Decoder) DecodeInterfaceLoose() (interface{}, error)

DecodeInterfaceLoose is like DecodeInterface except that:

  • int8, int16, and int32 are converted to int64,
  • uint8, uint16, and uint32 are converted to uint64,
  • float32 is converted to float64.

func (*Decoder) DecodeMap 

func (d *Decoder) DecodeMap() (map[string]interface{}, error)

func (*Decoder) DecodeMapLen 

func (d *Decoder) DecodeMapLen() (int, error)

DecodeMapLen decodes map length. Length is -1 when map is nil.

func (*Decoder) DecodeMulti 

func (d *Decoder) DecodeMulti(v ...interface{}) error

func (*Decoder) DecodeNil 

func (d *Decoder) DecodeNil() error

func (*Decoder) DecodeRaw 

func (d *Decoder) DecodeRaw() (RawMessage, error)

func (*Decoder) DecodeSlice 

func (d *Decoder) DecodeSlice() ([]interface{}, error)

func (*Decoder) DecodeString 

func (d *Decoder) DecodeString() (string, error)

func (*Decoder) DecodeTime 

func (d *Decoder) DecodeTime() (time.Time, error)

func (*Decoder) DecodeTypedMap 

func (d *Decoder) DecodeTypedMap() (interface{}, error)

DecodeTypedMap decodes a typed map. Typed map is a map that has a fixed type for keys and values. Key and value types may be different.

func (*Decoder) DecodeUint 

func (d *Decoder) DecodeUint() (uint, error)

func (*Decoder) DecodeUint16 

func (d *Decoder) DecodeUint16() (uint16, error)

func (*Decoder) DecodeUint32 

func (d *Decoder) DecodeUint32() (uint32, error)

func (*Decoder) DecodeUint64 

func (d *Decoder) DecodeUint64() (uint64, error)

DecodeUint64 decodes msgpack int8/16/32/64 and uint8/16/32/64 into Go uint64.

func (*Decoder) DecodeUint8 

func (d *Decoder) DecodeUint8() (uint8, error)

func (*Decoder) DecodeUntypedMap 

func (d *Decoder) DecodeUntypedMap() (map[interface{}]interface{}, error)

func (*Decoder) DecodeValue 

func (d *Decoder) DecodeValue(v reflect.Value) error

func (*Decoder) DisallowUnknownFields 

func (d *Decoder) DisallowUnknownFields(on bool)

DisallowUnknownFields causes the Decoder to return an error when the destination is a struct and the input contains object keys which do not match any non-ignored, exported fields in the destination.

func (*Decoder) PeekCode 

func (d *Decoder) PeekCode() (byte, error)

PeekCode returns the next MessagePack code without advancing the reader. Subpackage msgpack/codes defines the list of available msgpcode.

func (*Decoder) Query 

func (d *Decoder) Query(query string) ([]interface{}, error)

Query extracts data specified by the query from the msgpack stream skipping any other data. Query consists of map keys and array indexes separated with dot, e.g. key1.0.key2.

Example 
b, err := msgpack.Marshal([]map[string]interface{}{
	{"id": 1, "attrs": map[string]interface{}{"phone": 12345}},
	{"id": 2, "attrs": map[string]interface{}{"phone": 54321}},
})
if err != nil {
	panic(err)
}

dec := msgpack.NewDecoder(bytes.NewBuffer(b))
values, err := dec.Query("*.attrs.phone")
if err != nil {
	panic(err)
}
fmt.Println("phones are", values)

dec.Reset(bytes.NewBuffer(b))
values, err = dec.Query("1.attrs.phone")
if err != nil {
	panic(err)
}
fmt.Println("2nd phone is", values[0])

Output:

phones are [12345 54321]
2nd phone is 54321

func (*Decoder) ReadFull 

func (d *Decoder) ReadFull(buf []byte) error

ReadFull reads exactly len(buf) bytes into the buf.

func (*Decoder) Reset 

func (d *Decoder) Reset(r io.Reader)

Reset discards any buffered data, resets all state, and switches the buffered reader to read from r.

func (*Decoder) ResetDict 

func (d *Decoder) ResetDict(r io.Reader, dict []string)

ResetDict is like Reset, but also resets the dict.

func (*Decoder) SetCustomStructTag 

func (d *Decoder) SetCustomStructTag(tag string)

SetCustomStructTag causes the decoder to use the supplied tag as a fallback option if there is no msgpack tag.

func (*Decoder) SetMapDecoder 

func (d *Decoder) SetMapDecoder(fn func(*Decoder) (interface{}, error))
Example 
buf := new(bytes.Buffer)

enc := msgpack.NewEncoder(buf)
in := map[string]string{"hello": "world"}
err := enc.Encode(in)
if err != nil {
	panic(err)
}

dec := msgpack.NewDecoder(buf)

// Causes decoder to produce map[string]string instead of map[string]interface{}.
dec.SetMapDecoder(func(d *msgpack.Decoder) (interface{}, error) {
	n, err := d.DecodeMapLen()
	if err != nil {
		return nil, err
	}

	m := make(map[string]string, n)
	for i := 0; i < n; i++ {
		mk, err := d.DecodeString()
		if err != nil {
			return nil, err
		}

		mv, err := d.DecodeString()
		if err != nil {
			return nil, err
		}

		m[mk] = mv
	}
	return m, nil
})

out, err := dec.DecodeInterface()
if err != nil {
	panic(err)
}
fmt.Printf("%#v", out)

Output:

map[string]string{"hello":"world"}

func (*Decoder) Skip 

func (d *Decoder) Skip() error

Skip skips next value.

func (*Decoder) UseInternedStrings 

func (d *Decoder) UseInternedStrings(on bool)

UseInternedStrings enables support for decoding interned strings.

func (*Decoder) UseLooseInterfaceDecoding 

func (d *Decoder) UseLooseInterfaceDecoding(on bool)

UseLooseInterfaceDecoding causes decoder to use DecodeInterfaceLoose to decode msgpack value into Go interface{}.

type Encoder 

type Encoder struct {
	// contains filtered or unexported fields
}

func GetEncoder 

func GetEncoder() *Encoder

func NewEncoder 

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w.

func (*Encoder) Encode 

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

func (*Encoder) EncodeArrayLen 

func (e *Encoder) EncodeArrayLen(l int) error

func (*Encoder) EncodeBool 

func (e *Encoder) EncodeBool(value bool) error

func (*Encoder) EncodeBytes 

func (e *Encoder) EncodeBytes(v []byte) error

func (*Encoder) EncodeBytesLen 

func (e *Encoder) EncodeBytesLen(l int) error

func (*Encoder) EncodeDuration 

func (e *Encoder) EncodeDuration(d time.Duration) error

func (*Encoder) EncodeExtHeader 

func (e *Encoder) EncodeExtHeader(extID int8, extLen int) error

func (*Encoder) EncodeFloat32 

func (e *Encoder) EncodeFloat32(n float32) error

func (*Encoder) EncodeFloat64 

func (e *Encoder) EncodeFloat64(n float64) error

func (*Encoder) EncodeInt 

func (e *Encoder) EncodeInt(n int64) error

EncodeNumber encodes an int64 in 1, 2, 3, 5, or 9 bytes. Type of the number is lost during encoding.

func (*Encoder) EncodeInt16 

func (e *Encoder) EncodeInt16(n int16) error

EncodeInt16 encodes an int16 in 3 bytes preserving type of the number.

func (*Encoder) EncodeInt32 

func (e *Encoder) EncodeInt32(n int32) error

EncodeInt32 encodes an int32 in 5 bytes preserving type of the number.

func (*Encoder) EncodeInt64 

func (e *Encoder) EncodeInt64(n int64) error

EncodeInt64 encodes an int64 in 9 bytes preserving type of the number.

func (*Encoder) EncodeInt8 

func (e *Encoder) EncodeInt8(n int8) error

EncodeInt8 encodes an int8 in 2 bytes preserving type of the number.

func (*Encoder) EncodeMap 

func (e *Encoder) EncodeMap(m map[string]interface{}) error

func (*Encoder) EncodeMapLen 

func (e *Encoder) EncodeMapLen(l int) error

func (*Encoder) EncodeMapSorted 

func (e *Encoder) EncodeMapSorted(m map[string]interface{}) error

func (*Encoder) EncodeMulti 

func (e *Encoder) EncodeMulti(v ...interface{}) error

func (*Encoder) EncodeNil 

func (e *Encoder) EncodeNil() error

func (*Encoder) EncodeString 

func (e *Encoder) EncodeString(v string) error

func (*Encoder) EncodeTime 

func (e *Encoder) EncodeTime(tm time.Time) error

func (*Encoder) EncodeUint 

func (e *Encoder) EncodeUint(n uint64) error

EncodeUnsignedNumber encodes an uint64 in 1, 2, 3, 5, or 9 bytes. Type of the number is lost during encoding.

func (*Encoder) EncodeUint16 

func (e *Encoder) EncodeUint16(n uint16) error

EncodeUint16 encodes an uint16 in 3 bytes preserving type of the number.

func (*Encoder) EncodeUint32 

func (e *Encoder) EncodeUint32(n uint32) error

EncodeUint32 encodes an uint16 in 5 bytes preserving type of the number.

func (*Encoder) EncodeUint64 

func (e *Encoder) EncodeUint64(n uint64) error

EncodeUint64 encodes an uint16 in 9 bytes preserving type of the number.

func (*Encoder) EncodeUint8 

func (e *Encoder) EncodeUint8(n uint8) error

EncodeUint8 encodes an uint8 in 2 bytes preserving type of the number.

func (*Encoder) EncodeValue 

func (e *Encoder) EncodeValue(v reflect.Value) error

func (*Encoder) Reset 

func (e *Encoder) Reset(w io.Writer)

Reset discards any buffered data, resets all state, and switches the writer to write to w.

func (*Encoder) ResetDict 

func (e *Encoder) ResetDict(w io.Writer, dict map[string]int)

ResetDict is like Reset, but also resets the dict.

func (*Encoder) SetCustomStructTag 

func (e *Encoder) SetCustomStructTag(tag string)

SetCustomStructTag causes the Encoder to use a custom struct tag as fallback option if there is no msgpack tag.

func (*Encoder) SetSortMapKeys 

func (e *Encoder) SetSortMapKeys(on bool) *Encoder

SetSortMapKeys causes the Encoder to encode map keys in increasing order. Supported map types are:

  • map[string]string
  • map[string]interface{}

func (*Encoder) UseArrayEncodedStructs 

func (e *Encoder) UseArrayEncodedStructs(on bool)

UseArrayEncodedStructs causes the Encoder to encode Go structs as msgpack arrays.

Example 
type Item struct {
	Foo string
	Bar string
}

var buf bytes.Buffer
enc := msgpack.NewEncoder(&buf)
enc.UseArrayEncodedStructs(true)

err := enc.Encode(&Item{Foo: "foo", Bar: "bar"})
if err != nil {
	panic(err)
}

dec := msgpack.NewDecoder(&buf)
v, err := dec.DecodeInterface()
if err != nil {
	panic(err)
}
fmt.Println(v)

Output:

[foo bar]

func (*Encoder) UseCompactFloats 

func (e *Encoder) UseCompactFloats(on bool)

UseCompactFloats causes the Encoder to chose a compact integer encoding for floats that can be represented as integers.

func (*Encoder) UseCompactInts 

func (e *Encoder) UseCompactInts(on bool)

UseCompactEncoding causes the Encoder to chose the most compact encoding. For example, it allows to encode small Go int64 as msgpack int8 saving 7 bytes.

func (*Encoder) UseInternedStrings 

func (e *Encoder) UseInternedStrings(on bool)

UseInternedStrings causes the Encoder to intern strings.

func (*Encoder) Writer 

func (e *Encoder) Writer() io.Writer

Writer returns the Encoder's writer.

type Marshaler 

type Marshaler interface {
	MarshalMsgpack() ([]byte, error)
}

type MarshalerUnmarshaler 

type MarshalerUnmarshaler interface {
	Marshaler
	Unmarshaler
}

type RawMessage 

type RawMessage []byte

func (*RawMessage) DecodeMsgpack 

func (m *RawMessage) DecodeMsgpack(dec *Decoder) error

func (RawMessage) EncodeMsgpack 

func (m RawMessage) EncodeMsgpack(enc *Encoder) error

type Unmarshaler 

type Unmarshaler interface {
	UnmarshalMsgpack([]byte) error
}

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