# Codec

High Performance, Feature-Rich Idiomatic Go codec/encoding library for
binc, msgpack, cbor, json.

Supported Serialization formats are:

  - msgpack: https://github.com/msgpack/msgpack
  - binc:    http://github.com/ugorji/binc
  - cbor:    http://cbor.io http://tools.ietf.org/html/rfc7049
  - json:    http://json.org http://tools.ietf.org/html/rfc7159
  - simple:

To install:

    go get github.com/ugorji/go/codec

This package understands the `unsafe` tag, to allow using unsafe semantics:

  - When decoding into a struct, you need to read the field name as a string
    so you can find the struct field it is mapped to.
    Using `unsafe` will bypass the allocation and copying overhead of `[]byte->string` conversion.

To use it, you must pass the `unsafe` tag during install:

```
go install -tags=unsafe github.com/ugorji/go/codec
```

Online documentation: http://godoc.org/github.com/ugorji/go/codec
Detailed Usage/How-to Primer: http://ugorji.net/blog/go-codec-primer

The idiomatic Go support is as seen in other encoding packages in
the standard library (ie json, xml, gob, etc).

Rich Feature Set includes:

  - Simple but extremely powerful and feature-rich API
  - Very High Performance.
    Our extensive benchmarks show us outperforming Gob, Json, Bson, etc by 2-4X.
  - Multiple conversions:
    Package coerces types where appropriate
    e.g. decode an int in the stream into a float, etc.
  - Corner Cases:
    Overflows, nil maps/slices, nil values in streams are handled correctly
  - Standard field renaming via tags
  - Support for omitting empty fields during an encoding
  - Encoding from any value and decoding into pointer to any value
    (struct, slice, map, primitives, pointers, interface{}, etc)
  - Extensions to support efficient encoding/decoding of any named types
  - Support encoding.(Binary|Text)(M|Unm)arshaler interfaces
  - Decoding without a schema (into a interface{}).
    Includes Options to configure what specific map or slice type to use
    when decoding an encoded list or map into a nil interface{}
  - Encode a struct as an array, and decode struct from an array in the data stream
  - Comprehensive support for anonymous fields
  - Fast (no-reflection) encoding/decoding of common maps and slices
  - Code-generation for faster performance.
  - Support binary (e.g. messagepack, cbor) and text (e.g. json) formats
  - Support indefinite-length formats to enable true streaming
    (for formats which support it e.g. json, cbor)
  - Support canonical encoding, where a value is ALWAYS encoded as same sequence of bytes.
    This mostly applies to maps, where iteration order is non-deterministic.
  - NIL in data stream decoded as zero value
  - Never silently skip data when decoding.
    User decides whether to return an error or silently skip data when keys or indexes
    in the data stream do not map to fields in the struct.
  - Encode/Decode from/to chan types (for iterative streaming support)
  - Drop-in replacement for encoding/json. `json:` key in struct tag supported.
  - Provides a RPC Server and Client Codec for net/rpc communication protocol.
  - Handle unique idiosynchracies of codecs e.g.
    - For messagepack, configure how ambiguities in handling raw bytes are resolved
    - For messagepack, provide rpc server/client codec to support
      msgpack-rpc protocol defined at:
      https://github.com/msgpack-rpc/msgpack-rpc/blob/master/spec.md

## Extension Support

Users can register a function to handle the encoding or decoding of
their custom types.

There are no restrictions on what the custom type can be. Some examples:

    type BisSet   []int
    type BitSet64 uint64
    type UUID     string
    type MyStructWithUnexportedFields struct { a int; b bool; c []int; }
    type GifImage struct { ... }

As an illustration, MyStructWithUnexportedFields would normally be
encoded as an empty map because it has no exported fields, while UUID
would be encoded as a string. However, with extension support, you can
encode any of these however you like.

## RPC

RPC Client and Server Codecs are implemented, so the codecs can be used
with the standard net/rpc package.

## Usage

Typical usage model:

    // create and configure Handle
    var (
      bh codec.BincHandle
      mh codec.MsgpackHandle
      ch codec.CborHandle
    )

    mh.MapType = reflect.TypeOf(map[string]interface{}(nil))

    // configure extensions
    // e.g. for msgpack, define functions and enable Time support for tag 1
    // mh.SetExt(reflect.TypeOf(time.Time{}), 1, myExt)

    // create and use decoder/encoder
    var (
      r io.Reader
      w io.Writer
      b []byte
      h = &bh // or mh to use msgpack
    )

    dec = codec.NewDecoder(r, h)
    dec = codec.NewDecoderBytes(b, h)
    err = dec.Decode(&v)

    enc = codec.NewEncoder(w, h)
    enc = codec.NewEncoderBytes(&b, h)
    err = enc.Encode(v)

    //RPC Server
    go func() {
        for {
            conn, err := listener.Accept()
            rpcCodec := codec.GoRpc.ServerCodec(conn, h)
            //OR rpcCodec := codec.MsgpackSpecRpc.ServerCodec(conn, h)
            rpc.ServeCodec(rpcCodec)
        }
    }()

    //RPC Communication (client side)
    conn, err = net.Dial("tcp", "localhost:5555")
    rpcCodec := codec.GoRpc.ClientCodec(conn, h)
    //OR rpcCodec := codec.MsgpackSpecRpc.ClientCodec(conn, h)
    client := rpc.NewClientWithCodec(rpcCodec)