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200 lines
7.7 KiB
Go
200 lines
7.7 KiB
Go
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// Copyright (c) 2012-2015 Ugorji Nwoke. All rights reserved.
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// Use of this source code is governed by a MIT license found in the LICENSE file.
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/*
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High Performance, Feature-Rich Idiomatic Go codec/encoding library for
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binc, msgpack, cbor, json.
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Supported Serialization formats are:
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- msgpack: https://github.com/msgpack/msgpack
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- binc: http://github.com/ugorji/binc
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- cbor: http://cbor.io http://tools.ietf.org/html/rfc7049
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- json: http://json.org http://tools.ietf.org/html/rfc7159
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- simple:
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To install:
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go get github.com/ugorji/go/codec
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This package understands the 'unsafe' tag, to allow using unsafe semantics:
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- When decoding into a struct, you need to read the field name as a string
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so you can find the struct field it is mapped to.
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Using `unsafe` will bypass the allocation and copying overhead of []byte->string conversion.
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To install using unsafe, pass the 'unsafe' tag:
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go get -tags=unsafe github.com/ugorji/go/codec
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For detailed usage information, read the primer at http://ugorji.net/blog/go-codec-primer .
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The idiomatic Go support is as seen in other encoding packages in
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the standard library (ie json, xml, gob, etc).
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Rich Feature Set includes:
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- Simple but extremely powerful and feature-rich API
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- Very High Performance.
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Our extensive benchmarks show us outperforming Gob, Json, Bson, etc by 2-4X.
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- Multiple conversions:
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Package coerces types where appropriate
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e.g. decode an int in the stream into a float, etc.
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- Corner Cases:
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Overflows, nil maps/slices, nil values in streams are handled correctly
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- Standard field renaming via tags
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- Support for omitting empty fields during an encoding
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- Encoding from any value and decoding into pointer to any value
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(struct, slice, map, primitives, pointers, interface{}, etc)
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- Extensions to support efficient encoding/decoding of any named types
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- Support encoding.(Binary|Text)(M|Unm)arshaler interfaces
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- Decoding without a schema (into a interface{}).
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Includes Options to configure what specific map or slice type to use
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when decoding an encoded list or map into a nil interface{}
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- Encode a struct as an array, and decode struct from an array in the data stream
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- Comprehensive support for anonymous fields
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- Fast (no-reflection) encoding/decoding of common maps and slices
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- Code-generation for faster performance.
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- Support binary (e.g. messagepack, cbor) and text (e.g. json) formats
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- Support indefinite-length formats to enable true streaming
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(for formats which support it e.g. json, cbor)
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- Support canonical encoding, where a value is ALWAYS encoded as same sequence of bytes.
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This mostly applies to maps, where iteration order is non-deterministic.
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- NIL in data stream decoded as zero value
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- Never silently skip data when decoding.
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User decides whether to return an error or silently skip data when keys or indexes
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in the data stream do not map to fields in the struct.
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- Detect and error when encoding a cyclic reference (instead of stack overflow shutdown)
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- Encode/Decode from/to chan types (for iterative streaming support)
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- Drop-in replacement for encoding/json. `json:` key in struct tag supported.
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- Provides a RPC Server and Client Codec for net/rpc communication protocol.
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- Handle unique idiosynchracies of codecs e.g.
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- For messagepack, configure how ambiguities in handling raw bytes are resolved
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- For messagepack, provide rpc server/client codec to support
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msgpack-rpc protocol defined at:
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https://github.com/msgpack-rpc/msgpack-rpc/blob/master/spec.md
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Extension Support
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Users can register a function to handle the encoding or decoding of
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their custom types.
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There are no restrictions on what the custom type can be. Some examples:
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type BisSet []int
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type BitSet64 uint64
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type UUID string
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type MyStructWithUnexportedFields struct { a int; b bool; c []int; }
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type GifImage struct { ... }
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As an illustration, MyStructWithUnexportedFields would normally be
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encoded as an empty map because it has no exported fields, while UUID
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would be encoded as a string. However, with extension support, you can
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encode any of these however you like.
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RPC
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RPC Client and Server Codecs are implemented, so the codecs can be used
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with the standard net/rpc package.
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Usage
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The Handle is SAFE for concurrent READ, but NOT SAFE for concurrent modification.
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The Encoder and Decoder are NOT safe for concurrent use.
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Consequently, the usage model is basically:
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- Create and initialize the Handle before any use.
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Once created, DO NOT modify it.
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- Multiple Encoders or Decoders can now use the Handle concurrently.
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They only read information off the Handle (never write).
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- However, each Encoder or Decoder MUST not be used concurrently
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- To re-use an Encoder/Decoder, call Reset(...) on it first.
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This allows you use state maintained on the Encoder/Decoder.
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Sample usage model:
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// create and configure Handle
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var (
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bh codec.BincHandle
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mh codec.MsgpackHandle
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ch codec.CborHandle
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)
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mh.MapType = reflect.TypeOf(map[string]interface{}(nil))
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// configure extensions
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// e.g. for msgpack, define functions and enable Time support for tag 1
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// mh.SetExt(reflect.TypeOf(time.Time{}), 1, myExt)
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// create and use decoder/encoder
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var (
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r io.Reader
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w io.Writer
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b []byte
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h = &bh // or mh to use msgpack
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)
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dec = codec.NewDecoder(r, h)
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dec = codec.NewDecoderBytes(b, h)
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err = dec.Decode(&v)
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enc = codec.NewEncoder(w, h)
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enc = codec.NewEncoderBytes(&b, h)
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err = enc.Encode(v)
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//RPC Server
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go func() {
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for {
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conn, err := listener.Accept()
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rpcCodec := codec.GoRpc.ServerCodec(conn, h)
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//OR rpcCodec := codec.MsgpackSpecRpc.ServerCodec(conn, h)
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rpc.ServeCodec(rpcCodec)
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}
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}()
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//RPC Communication (client side)
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conn, err = net.Dial("tcp", "localhost:5555")
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rpcCodec := codec.GoRpc.ClientCodec(conn, h)
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//OR rpcCodec := codec.MsgpackSpecRpc.ClientCodec(conn, h)
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client := rpc.NewClientWithCodec(rpcCodec)
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*/
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package codec
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// Benefits of go-codec:
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//
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// - encoding/json always reads whole file into memory first.
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// This makes it unsuitable for parsing very large files.
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// - encoding/xml cannot parse into a map[string]interface{}
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// I found this out on reading https://github.com/clbanning/mxj
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// TODO:
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//
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// - optimization for codecgen:
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// if len of entity is <= 3 words, then support a value receiver for encode.
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// - (En|De)coder should store an error when it occurs.
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// Until reset, subsequent calls return that error that was stored.
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// This means that free panics must go away.
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// All errors must be raised through errorf method.
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// - Decoding using a chan is good, but incurs concurrency costs.
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// This is because there's no fast way to use a channel without it
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// having to switch goroutines constantly.
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// Callback pattern is still the best. Maybe cnsider supporting something like:
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// type X struct {
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// Name string
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// Ys []Y
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// Ys chan <- Y
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// Ys func(Y) -> call this function for each entry
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// }
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// - Consider adding a isZeroer interface { isZero() bool }
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// It is used within isEmpty, for omitEmpty support.
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// - Consider making Handle used AS-IS within the encoding/decoding session.
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// This means that we don't cache Handle information within the (En|De)coder,
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// except we really need it at Reset(...)
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// - Consider adding math/big support
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// - Consider reducing the size of the generated functions:
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// Maybe use one loop, and put the conditionals in the loop.
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// for ... { if cLen > 0 { if j == cLen { break } } else if dd.CheckBreak() { break } }
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