msgpack

package module
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 Go to latest Published: Aug 5, 2022 License: BSD-3-Clause Imports: 14 Imported by: 0

README

MsgPack library for Go (DEPRECATED)

DEPRECATED as of May 29, 2013. Please use github.com/ugorji/go/codec
which is significantly faster, cleaner, more correct and more complete.
See [https://github.com/ugorji/go/tree/master/codec#readme]

A complete redesign was done which accomodates multiple codec formats. It thus became necessary to create a new repository with a different name.

I hope to retire this repository anytime from July 1, 2013.

A log message will be printed out at runtime encouraging users to upgrade.

About go-msgpack

Implements:

[http://wiki.msgpack.org/display/MSGPACK/Format+specification]

To install:

go get github.com/ugorji/go-msgpack

It provides features similar to encoding packages in the standard library (ie json, xml, gob, etc).

Supports:

  • Standard Marshal/Unmarshal interface.
  • Support for all exported fields (including anonymous fields)
  • Standard field renaming via tags
  • Encoding from any value (struct, slice, map, primitives, pointers, interface{}, etc)
  • Decoding into pointer to any non-nil value (struct, slice, map, int, float32, bool, string, etc)
  • Decoding into a nil interface{}
  • Handles time.Time transparently (stores time as 2 element array: seconds since epoch and nanosecond offset)
  • Provides a Server and Client Codec so msgpack can be used as communication protocol for net/rpc.

API docs: http://godoc.org/github.com/ugorji/go-msgpack

Usage


    dec = msgpack.NewDecoder(r, nil)  
    err = dec.Decode(&v)  
    
    enc = msgpack.NewEncoder(w)  
    err = enc.Encode(v)  
    
    //methods below are convenience methods over functions above.  
    data, err = msgpack.Marshal(v)  
    err = msgpack.Unmarshal(data, &v, nil)  
    
    //RPC Server
    conn, err := listener.Accept()
    rpcCodec := msgpack.NewRPCServerCodec(conn, nil)
    rpc.ServeCodec(rpcCodec)

    //RPC Communication (client side)
    conn, err = net.Dial("tcp", "localhost:5555")  
    rpcCodec := msgpack.NewRPCClientCodec(conn, nil)  
    client := rpc.NewClientWithCodec(rpcCodec)

Documentation

Overview

MsgPack library for Go (DEPRECATED - Replacement: go get github.com/ugorji/go/codec) 

THIS LIBRARY IS DEPRECATED (May 29, 2013)

Please use github.com/ugorji/go/codec
which is significantly faster, cleaner, more correct and more complete.
See [https://github.com/ugorji/go/tree/master/codec#readme]

A complete redesign was done which also accomodates multiple codec formats.
It thus became necessary to create a new repository with a different name.

I hope to retire this repository anytime from July 1, 2013.

A log message will be printed out at runtime encouraging users to upgrade.

Implements: 

http://wiki.msgpack.org/display/MSGPACK/Format+specification

It provides features similar to encoding packages in the standard library (ie json, xml, gob, etc).

Supports:

  • Standard Marshal/Unmarshal interface.
  • Standard field renaming via tags
  • Encoding from any value (struct, slice, map, primitives, pointers, interface{}, etc)
  • Decoding into pointer to any non-nil value (struct, slice, map, int, float32, bool, string, etc)
  • Decoding into a nil interface{}
  • Handles time.Time transparently
  • Provides a Server and Client Codec so msgpack can be used as communication protocol for net/rpc. Also includes an option for msgpack-rpc: http://wiki.msgpack.org/display/MSGPACK/RPC+specification

Usage 

dec = msgpack.NewDecoder(r, nil)
err = dec.Decode(&v)

enc = msgpack.NewEncoder(w)
err = enc.Encode(v)

//methods below are convenience methods over functions above.
data, err = msgpack.Marshal(v)
err = msgpack.Unmarshal(data, &v, nil)

//RPC Server
conn, err := listener.Accept()
rpcCodec := msgpack.NewRPCServerCodec(conn, nil)
rpc.ServeCodec(rpcCodec)

//RPC Communication (client side)
conn, err = net.Dial("tcp", "localhost:5555")
rpcCodec := msgpack.NewRPCClientCodec(conn, nil)
client := rpc.NewClientWithCodec(rpcCodec)

RPC

An RPC Client and Server Codec is implemented, so that msgpack can be used with the standard net/rpc package. It supports both a basic net/rpc serialization, and the custom format defined at http://wiki.msgpack.org/display/MSGPACK/RPC+specification

Index

Constants

View Source 
const (
	ContainerRawBytes = ContainerType('b')
	ContainerList     = ContainerType('a')
	ContainerMap      = ContainerType('m')
)

Variables

View Source 
var DefaultDecoderContainerResolver = SimpleDecoderContainerResolver{
	MapType:                 nil,
	SliceType:               nil,
	BytesStringLiteral:      true,
	BytesStringSliceElement: true,
	BytesStringMapValue:     true,
}

Default DecoderContainerResolver used when a nil parameter is passed to NewDecoder(). Sample Usage: 

opts := msgpack.DefaultDecoderContainerResolver // makes a copy
opts.BytesStringLiteral = false // change some options
err := msgpack.NewDecoder(r, &opts).Decode(&v)

Functions

func Marshal 

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

Marshal is a convenience function which encodes v to a stream of bytes. It delegates to Encoder.Encode.

func NewCustomRPCClientCodec 

func NewCustomRPCClientCodec(conn io.ReadWriteCloser, opts DecoderContainerResolver) rpc.ClientCodec

NewCustomRPCClientCodec uses msgpack serialization for rpc communication from client side, but uses a custom protocol defined at http://wiki.msgpack.org/display/MSGPACK/RPC+specification

func NewCustomRPCServerCodec 

func NewCustomRPCServerCodec(conn io.ReadWriteCloser, opts DecoderContainerResolver) rpc.ServerCodec

NewCustomRPCServerCodec uses msgpack serialization for rpc communication from server side, but uses a custom protocol defined at http://wiki.msgpack.org/display/MSGPACK/RPC+specification

func NewRPCClientCodec 

func NewRPCClientCodec(conn io.ReadWriteCloser, opts DecoderContainerResolver) rpc.ClientCodec

NewRPCClientCodec uses basic msgpack serialization for rpc communication from client side.

Sample Usage: 

conn, err = net.Dial("tcp", "localhost:5555")
codec, err := msgpack.NewRPCClientCodec(conn, nil)
client := rpc.NewClientWithCodec(codec)
... (see rpc package for how to use an rpc client)

func NewRPCServerCodec 

func NewRPCServerCodec(conn io.ReadWriteCloser, opts DecoderContainerResolver) rpc.ServerCodec

NewRPCServerCodec uses basic msgpack serialization for rpc communication from the server side.

func Unmarshal 

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

Unmarshal is a convenience function which decodes a stream of bytes into v. It delegates to Decoder.Decode.

Types

type ContainerType 

type ContainerType byte

type Decoder 

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

A Decoder reads and decodes an object from an input stream in the msgpack format.

func NewDecoder 

func NewDecoder(r io.Reader, dam DecoderContainerResolver) (d *Decoder)

NewDecoder returns a Decoder for decoding a stream of bytes into an object. If nil DecoderContainerResolver is passed, we use DefaultDecoderContainerResolver

func (*Decoder) Decode 

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

Decode decodes the stream from reader and stores the result in the value pointed to by v.

If v is a pointer to a non-nil value, we will decode the stream into that value (if the value type and the stream match. For example: integer in stream must go into int type (int8...int64), etc

If you do not know what type of stream it is, pass in a pointer to a nil interface. We will decode and store a value in that nil interface.

time.Time is handled transparently, by (en)decoding (to)from a []int64{Seconds since Epoch, Nanoseconds offset}.

Sample usages: 

// Decoding into a non-nil typed value
var f float32
err = msgpack.NewDecoder(r, nil).Decode(&f)

// Decoding into nil interface
var v interface{}
dec := msgpack.NewDecoder(r, nil)
err = dec.Decode(&v)

// To configure default options, see DefaultDecoderContainerResolver usage.
// or write your own DecoderContainerResolver

func (*Decoder) DecodeValue 

func (d *Decoder) DecodeValue(rv reflect.Value) (err error)

DecodeValue decodes the stream into a reflect.Value. The reflect.Value must be a pointer. See Decoder.Decode documentation. (Decode internally calls DecodeValue).

type DecoderContainerResolver 

type DecoderContainerResolver interface {
	// DecoderContainer is used to get a proper reflect.Value when decoding
	// a msgpack map, array or raw bytes (for which the stream defines the length and
	// corresponding containerType) into a nil interface{}.
	//
	// This may be within the context of a container: ([]interface{} or map[XXX]interface{}),
	// or just a top-level literal.
	//
	// The parentcontainer and parentkey define the context
	//   - If decoding into a map, they will be the map and the key in the map (a reflect.Value)
	//   - If decoding into a slice, they will be the slice and the index into the slice (an int)
	//   - Else they will be Invalid/nil
	//
	// Custom code can use this callback to determine how specifically to decode something.
	// A simple implementation exists which just uses some options to do it
	// (see SimpleDecoderContainerResolver).
	DecoderContainer(parentcontainer reflect.Value, parentkey interface{},
		length int, ct ContainerType) (val reflect.Value)
}

DecoderContainerResolver has the DecoderContainer method for getting a usable reflect.Value when decoding a container (map, array, raw bytes) from a stream into a nil interface{}.

type Encoder 

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

An Encoder writes an object to an output stream in the msgpack format.

func NewEncoder 

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

NewDecoder returns an Encoder for encoding an object.

func (*Encoder) Encode 

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

Encode writes an object into a stream in the MsgPack format.

time.Time is handled transparently, by (en)decoding (to)from a []int64{Seconds since Epoch, Nanoseconds offset}.

Struct values encode as maps. Each exported struct field is encoded 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.

Anonymous fields are encoded inline if no msgpack tag is present. Else they are encoded as regular fields.

The object's default key string is the struct field name but can be specified in the struct field's tag value. The "msgpack" key in struct field's tag value is the key name, followed by an optional comma and options.

To set an option on all fields (e.g. omitempty on all fields), you can create a field called _struct, and set flags on it.

Examples: 

type MyStruct struct {
    _struct bool    `msgpack:",omitempty"`   //set omitempty for every field
    Field1 string   `msgpack:"-"`            //skip this field
    Field2 int      `msgpack:"myName"`       //Use key "myName" in encode stream
    Field3 int32    `msgpack:",omitempty"`   //use key "Field3". Omit if empty.
    Field4 bool     `msgpack:"f4,omitempty"` //use key "f4". Omit if empty.
    ...
}

func (*Encoder) EncodeValue 

func (e *Encoder) EncodeValue(rv reflect.Value) (err error)

EncodeValue encodes a reflect.Value.

type SimpleDecoderContainerResolver 

type SimpleDecoderContainerResolver struct {
	// If decoding into a nil interface{} and we detect a map in the stream,
	// we create a map of the type specified. It defaults to creating a
	// map[interface{}]interface{} if not specified.
	MapType reflect.Type
	// If decoding into a nil interface{} and we detect a slice/array in the stream,
	// we create a slice of the type specified. It defaults to creating a
	// []interface{} if not specified.
	SliceType reflect.Type
	// convert to a string if raw bytes are detected while decoding
	// into a interface{},
	BytesStringLiteral bool
	// convert to a string if raw bytes are detected while decoding
	// into a []interface{},
	BytesStringSliceElement bool
	// convert to a string if raw bytes are detected while decoding
	// into a value in a map[XXX]interface{},
	BytesStringMapValue bool
}

SimpleDecoderContainerResolver is a simple DecoderContainerResolver which uses some simple options to determine how to decode into a nil interface{}. Most applications will work fine with just this.

func (SimpleDecoderContainerResolver) DecoderContainer 

func (d SimpleDecoderContainerResolver) DecoderContainer(
	parentcontainer reflect.Value, parentkey interface{},
	length int, ct ContainerType) (rvn reflect.Value)

DecoderContainer supports common cases for decoding into a nil interface{} depending on the context.

When decoding into a nil interface{}, the following rules apply as we have to make assumptions about the specific types you want.

  • Maps are decoded as map[interface{}]interface{} unless you provide a default map type when creating your decoder. option: MapType
  • Lists are always decoded as []interface{} unless you provide a default slice type when creating your decoder. option: SliceType
  • raw bytes are decoded into []byte or string depending on setting of: option: BytesStringMapValue (if within a map value, use this setting) option: BytesStringSliceElement (else if within a slice, use this setting) option: BytesStringLiteral (else use this setting)

Source Files

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