codec

package
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 Go to latest Published: Mar 8, 2024 License: MIT Imports: 24 Imported by: 34

Documentation

Overview

Package codec provides a High Performance, Feature-Rich Idiomatic codec/encoding library for msgpack, json.

Supported Serialization formats are:

For detailed usage information, read the primer at 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
  • Excellent code coverage ( > 90% )
  • Very High Performance. Our extensive benchmarks show us outperforming Gob, Json, Bson, etc by 2-4X.
  • Lock-free (sans mutex) concurrency for scaling to 100's of cores
  • In-place updates during decode, with option to zero value in maps and slices prior to decode
  • Coerce types where appropriate e.g. decode an int in the stream into a float, decode numbers from formatted strings, 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
  • Support IsZero() bool to determine if a value is a zero value. Analogous to time.Time.IsZero() bool.
  • 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{}
  • Mapping a non-interface type to an interface, so we can decode appropriately into any interface type with a correctly configured non-interface value.
  • Encode a struct as an array, and decode struct from an array in the data stream
  • Option to encode struct keys as numbers (instead of strings) (to support structured streams with fields encoded as numeric codes)
  • 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) and text (e.g. json) formats
  • Support indefinite-length formats to enable true streaming (for formats which support it e.g. json)
  • 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.
  • Detect and error when encoding a cyclic reference (instead of stack overflow shutdown)
  • 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 idiosyncrasies 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:

```go 

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.

## Custom Encoding and Decoding

This package maintains symmetry in the encoding and decoding halfs. We determine how to encode or decode by walking this decision tree

  • is type a codec.Selfer?
  • is there an extension registered for the type?
  • is format binary, and is type a encoding.BinaryMarshaler and BinaryUnmarshaler?
  • is format specifically json, and is type a encoding/json.Marshaler and Unmarshaler?
  • is format text-based, and type an encoding.TextMarshaler and TextUnmarshaler?
  • else we use a pair of functions based on the "kind" of the type e.g. map, slice, int64, etc

This symmetry is important to reduce chances of issues happening because the encoding and decoding sides are out of sync e.g. decoded via very specific encoding.TextUnmarshaler but encoded via kind-specific generalized mode.

Consequently, if a type only defines one-half of the symmetry (e.g. it implements UnmarshalJSON() but not MarshalJSON() ), then that type doesn't satisfy the check and we will continue walking down the decision tree.

## RPC

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

## Usage

The Handle is SAFE for concurrent READ, but NOT SAFE for concurrent modification.

The Encoder and Decoder are NOT safe for concurrent use.

Consequently, the usage model is basically:

  • Create and initialize the Handle before any use. Once created, DO NOT modify it.
  • Multiple Encoders or Decoders can now use the Handle concurrently. They only read information off the Handle (never write).
  • However, each Encoder or Decoder MUST not be used concurrently
  • To re-use an Encoder/Decoder, call Reset(...) on it first. This allows you use state maintained on the Encoder/Decoder.

Sample usage model:

```go 

// create and configure Handle
var (
  mh codec.MsgpackHandle
)

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 = &mh
)

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)

```

## Running Tests

To run tests, use the following:

``` 

go test

```

To run the full suite of tests, use the following:

``` 

go test -tags alltests -run Suite

```

You can run the tag 'safe' to run tests or build in safe mode. e.g.

``` 

go test -tags safe -run Json
go test -tags "alltests safe" -run Suite

```

## Running Benchmarks

``` 

cd codec/bench
./bench.sh -d
./bench.sh -c
./bench.sh -s
go test -bench . -benchmem -benchtime 1s

```

Please see http://github.com/hashicorp/go-codec-bench .

## Caveats

Struct fields matching the following are ignored during encoding and decoding

  • struct tag value set to -
  • func, complex numbers, unsafe pointers
  • unexported and not embedded
  • unexported and embedded and not struct kind
  • unexported and embedded pointers

Every other field in a struct will be encoded/decoded.

Embedded fields are encoded as if they exist in the top-level struct, with some caveats. See Encode documentation.

Index

Constants

View Source 
const GenVersion = 10

GenVersion is the current version of codecgen.

Variables

View Source 
var GoRpc goRpc

GoRpc implements Rpc using the communication protocol defined in net/rpc package.

Note: network connection (from net.Dial, of type io.ReadWriteCloser) is not buffered.

For performance, you should configure WriterBufferSize and ReaderBufferSize on the handle. This ensures we use an adequate buffer during reading and writing. If not configured, we will internally initialize and use a buffer during reads and writes. This can be turned off via the RPCNoBuffer option on the Handle. 

var handle codec.JsonHandle
handle.RPCNoBuffer = true // turns off attempt by rpc module to initialize a buffer

Example 1: one way of configuring buffering explicitly: 

var handle codec.JsonHandle // codec handle
handle.ReaderBufferSize = 1024
handle.WriterBufferSize = 1024
var conn io.ReadWriteCloser // connection got from a socket
var serverCodec = GoRpc.ServerCodec(conn, handle)
var clientCodec = GoRpc.ClientCodec(conn, handle)

Example 2: you can also explicitly create a buffered connection yourself, and not worry about configuring the buffer sizes in the Handle. 

var handle codec.Handle     // codec handle
var conn io.ReadWriteCloser // connection got from a socket
var bufconn = struct {      // bufconn here is a buffered io.ReadWriteCloser
    io.Closer
    *bufio.Reader
    *bufio.Writer
}{conn, bufio.NewReader(conn), bufio.NewWriter(conn)}
var serverCodec = GoRpc.ServerCodec(bufconn, handle)
var clientCodec = GoRpc.ClientCodec(bufconn, handle)
View Source 
var MsgpackSpecRpc msgpackSpecRpc

MsgpackSpecRpc implements Rpc using the communication protocol defined in the msgpack spec at https://github.com/msgpack-rpc/msgpack-rpc/blob/master/spec.md .

See GoRpc documentation, for information on buffering for better performance.

Functions

func GenHelperDecoder 

func GenHelperDecoder(d *Decoder) (gd genHelperDecoder, dd genHelperDecDriver)

GenHelperDecoder is exported so that it can be used externally by codecgen.

Library users: DO NOT USE IT DIRECTLY. IT WILL CHANGE CONTINOUSLY WITHOUT NOTICE.

func GenHelperEncoder 

func GenHelperEncoder(e *Encoder) (ge genHelperEncoder, ee genHelperEncDriver)

GenHelperEncoder is exported so that it can be used externally by codecgen.

Library users: DO NOT USE IT DIRECTLY. IT WILL CHANGE CONTINOUSLY WITHOUT NOTICE.

Types

type BasicHandle deprecated 

type BasicHandle struct {

	// TypeInfos is used to get the type info for any type.
	//
	// If not configured, the default TypeInfos is used, which uses struct tag keys: codec, json
	TypeInfos *TypeInfos

	RPCOptions

	// TimeNotBuiltin configures whether time.Time should be treated as a builtin type.
	//
	// All Handlers should know how to encode/decode time.Time as part of the core
	// format specification, or as a standard extension defined by the format.
	//
	// However, users can elect to handle time.Time as a custom extension, or via the
	// standard library's encoding.Binary(M|Unm)arshaler or Text(M|Unm)arshaler interface.
	// To elect this behavior, users can set TimeNotBuiltin=true.
	// Note: Setting TimeNotBuiltin=true can be used to enable the legacy behavior
	// (for Cbor and Msgpack), where time.Time was not a builtin supported type.
	TimeNotBuiltin bool

	// ExplicitRelease configures whether Release() is implicitly called after an encode or
	// decode call.
	//
	// If you will hold onto an Encoder or Decoder for re-use, by calling Reset(...)
	// on it or calling (Must)Encode repeatedly into a given []byte or io.Writer,
	// then you do not want it to be implicitly closed after each Encode/Decode call.
	// Doing so will unnecessarily return resources to the shared pool, only for you to
	// grab them right after again to do another Encode/Decode call.
	//
	// Instead, you configure ExplicitRelease=true, and you explicitly call Release() when
	// you are truly done.
	//
	// As an alternative, you can explicitly set a finalizer - so its resources
	// are returned to the shared pool before it is garbage-collected. Do it as below:
	//    runtime.SetFinalizer(e, (*Encoder).Release)
	//    runtime.SetFinalizer(d, (*Decoder).Release)
	ExplicitRelease bool

	DecodeOptions

	EncodeOptions
	// contains filtered or unexported fields
}

BasicHandle encapsulates the common options and extension functions.

Deprecated: DO NOT USE DIRECTLY. EXPORTED FOR GODOC BENEFIT. WILL BE REMOVED.

func (*BasicHandle) AddExt deprecated 

func (o *BasicHandle) AddExt(rt reflect.Type, tag byte,
	encfn func(reflect.Value) ([]byte, error),
	decfn func(reflect.Value, []byte) error) (err error)

AddExt registes an encode and decode function for a reflect.Type. To deregister an Ext, call AddExt with nil encfn and/or nil decfn.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

func (*BasicHandle) Intf2Impl 

func (o *BasicHandle) Intf2Impl(intf, impl reflect.Type) (err error)

Intf2Impl maps an interface to an implementing type. This allows us support infering the concrete type and populating it when passed an interface. e.g. var v io.Reader can be decoded as a bytes.Buffer, etc.

Passing a nil impl will clear the mapping.

func (*BasicHandle) SetExt deprecated 

func (o *BasicHandle) SetExt(rt reflect.Type, tag uint64, ext Ext) (err error)

SetExt will set the extension for a tag and reflect.Type. Note that the type must be a named type, and specifically not a pointer or Interface. An error is returned if that is not honored. To Deregister an ext, call SetExt with nil Ext.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

type BytesExt 

type BytesExt interface {
	// WriteExt converts a value to a []byte.
	//
	// Note: v is a pointer iff the registered extension type is a struct or array kind.
	WriteExt(v interface{}) []byte

	// ReadExt updates a value from a []byte.
	//
	// Note: dst is always a pointer kind to the registered extension type.
	ReadExt(dst interface{}, src []byte)
}

BytesExt handles custom (de)serialization of types to/from []byte. It is used by codecs (e.g. binc, msgpack, simple) which do custom serialization of the types.

type DecodeOptions 

type DecodeOptions struct {
	// MapType specifies type to use during schema-less decoding of a map in the stream.
	// If nil (unset), we default to map[string]interface{} iff json handle and MapStringAsKey=true,
	// else map[interface{}]interface{}.
	MapType reflect.Type

	// SliceType specifies type to use during schema-less decoding of an array in the stream.
	// If nil (unset), we default to []interface{} for all formats.
	SliceType reflect.Type

	// MaxInitLen defines the maxinum initial length that we "make" a collection
	// (string, slice, map, chan). If 0 or negative, we default to a sensible value
	// based on the size of an element in the collection.
	//
	// For example, when decoding, a stream may say that it has 2^64 elements.
	// We should not auto-matically provision a slice of that size, to prevent Out-Of-Memory crash.
	// Instead, we provision up to MaxInitLen, fill that up, and start appending after that.
	MaxInitLen int

	// ReaderBufferSize is the size of the buffer used when reading.
	//
	// if > 0, we use a smart buffer internally for performance purposes.
	ReaderBufferSize int

	// MaxDepth defines the maximum depth when decoding nested
	// maps and slices. If 0 or negative, we default to a suitably large number (currently 1024).
	MaxDepth int16

	// If ErrorIfNoField, return an error when decoding a map
	// from a codec stream into a struct, and no matching struct field is found.
	ErrorIfNoField bool

	// If ErrorIfNoArrayExpand, return an error when decoding a slice/array that cannot be expanded.
	// For example, the stream contains an array of 8 items, but you are decoding into a [4]T array,
	// or you are decoding into a slice of length 4 which is non-addressable (and so cannot be set).
	ErrorIfNoArrayExpand bool

	// If SignedInteger, use the int64 during schema-less decoding of unsigned values (not uint64).
	SignedInteger bool

	// MapValueReset controls how we decode into a map value.
	//
	// By default, we MAY retrieve the mapping for a key, and then decode into that.
	// However, especially with big maps, that retrieval may be expensive and unnecessary
	// if the stream already contains all that is necessary to recreate the value.
	//
	// If true, we will never retrieve the previous mapping,
	// but rather decode into a new value and set that in the map.
	//
	// If false, we will retrieve the previous mapping if necessary e.g.
	// the previous mapping is a pointer, or is a struct or array with pre-set state,
	// or is an interface.
	MapValueReset bool

	// SliceElementReset: on decoding a slice, reset the element to a zero value first.
	//
	// concern: if the slice already contained some garbage, we will decode into that garbage.
	SliceElementReset bool

	// InterfaceReset controls how we decode into an interface.
	//
	// By default, when we see a field that is an interface{...},
	// or a map with interface{...} value, we will attempt decoding into the
	// "contained" value.
	//
	// However, this prevents us from reading a string into an interface{}
	// that formerly contained a number.
	//
	// If true, we will decode into a new "blank" value, and set that in the interface.
	// If false, we will decode into whatever is contained in the interface.
	InterfaceReset bool

	// InternString controls interning of strings during decoding.
	//
	// Some handles, e.g. json, typically will read map keys as strings.
	// If the set of keys are finite, it may help reduce allocation to
	// look them up from a map (than to allocate them afresh).
	//
	// Note: Handles will be smart when using the intern functionality.
	// Every string should not be interned.
	// An excellent use-case for interning is struct field names,
	// or map keys where key type is string.
	InternString bool

	// PreferArrayOverSlice controls whether to decode to an array or a slice.
	//
	// This only impacts decoding into a nil interface{}.
	// Consequently, it has no effect on codecgen.
	//
	// *Note*: This only applies if using go1.5 and above,
	// as it requires reflect.ArrayOf support which was absent before go1.5.
	PreferArrayOverSlice bool

	// DeleteOnNilMapValue controls how to decode a nil value in the stream.
	//
	// If true, we will delete the mapping of the key.
	// Else, just set the mapping to the zero value of the type.
	DeleteOnNilMapValue bool

	// RawToString controls how raw bytes in a stream are decoded into a nil interface{}.
	// By default, they are decoded as []byte, but can be decoded as string (if configured).
	RawToString bool
}

DecodeOptions captures configuration options during decode.

type Decoder 

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

Decoder reads and decodes an object from an input stream in a supported format.

Decoder is NOT safe for concurrent use i.e. a Decoder cannot be used concurrently in multiple goroutines.

However, as Decoder could be allocation heavy to initialize, a Reset method is provided so its state can be reused to decode new input streams repeatedly. This is the idiomatic way to use.

func NewDecoder 

func NewDecoder(r io.Reader, h Handle) *Decoder

NewDecoder returns a Decoder for decoding a stream of bytes from an io.Reader.

For efficiency, Users are encouraged to configure ReaderBufferSize on the handle OR pass in a memory buffered reader (eg bufio.Reader, bytes.Buffer).

func NewDecoderBytes 

func NewDecoderBytes(in []byte, h Handle) *Decoder

NewDecoderBytes returns a Decoder which efficiently decodes directly from a byte slice with zero copying.

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. v cannot be a nil pointer. v can also be a reflect.Value of a pointer.

Note that a pointer to a nil interface is not a nil pointer. 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.

Sample usages: 

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

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

When decoding into a nil interface{}, we will decode into an appropriate value based on the contents of the stream:

  • Numbers are decoded as float64, int64 or uint64.
  • Other values are decoded appropriately depending on the type: bool, string, []byte, time.Time, etc
  • Extensions are decoded as RawExt (if no ext function registered for the tag)

Configurations exist on the Handle to override defaults (e.g. for MapType, SliceType and how to decode raw bytes).

When decoding into a non-nil interface{} value, the mode of encoding is based on the type of the value. When a value is seen:

  • If an extension is registered for it, call that extension function
  • If it implements BinaryUnmarshaler, call its UnmarshalBinary(data []byte) error
  • Else decode it based on its reflect.Kind

There are some special rules when decoding into containers (slice/array/map/struct). Decode will typically use the stream contents to UPDATE the container i.e. the values in these containers will not be zero'ed before decoding.

  • A map can be decoded from a stream map, by updating matching keys.
  • A slice can be decoded from a stream array, by updating the first n elements, where n is length of the stream.
  • A slice can be decoded from a stream map, by decoding as if it contains a sequence of key-value pairs.
  • A struct can be decoded from a stream map, by updating matching fields.
  • A struct can be decoded from a stream array, by updating fields as they occur in the struct (by index).

This in-place update maintains consistency in the decoding philosophy (i.e. we ALWAYS update in place by default). However, the consequence of this is that values in slices or maps which are not zero'ed before hand, will have part of the prior values in place after decode if the stream doesn't contain an update for those parts.

This in-place update can be disabled by configuring the MapValueReset and SliceElementReset decode options available on every handle.

Furthermore, when decoding a stream map or array with length of 0 into a nil map or slice, we reset the destination map or slice to a zero-length value.

However, when decoding a stream nil, we reset the destination container to its "zero" value (e.g. nil for slice/map, etc).

Note: we allow nil values in the stream anywhere except for map keys. A nil value in the encoded stream where a map key is expected is treated as an error.

func (*Decoder) MustDecode 

func (d *Decoder) MustDecode(v interface{})

MustDecode is like Decode, but panics if unable to Decode. This provides insight to the code location that triggered the error.

func (*Decoder) NumBytesRead 

func (d *Decoder) NumBytesRead() int

NumBytesRead returns the number of bytes read

func (*Decoder) Release 

func (d *Decoder) Release()

Release releases shared (pooled) resources.

It is important to call Release() when done with a Decoder, so those resources are released instantly for use by subsequently created Decoders.

By default, Release() is automatically called unless the option ExplicitRelease is set.

func (*Decoder) Reset 

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

Reset the Decoder with a new Reader to decode from, clearing all state from last run(s).

func (*Decoder) ResetBytes 

func (d *Decoder) ResetBytes(in []byte)

ResetBytes resets the Decoder with a new []byte to decode from, clearing all state from last run(s).

type EncodeOptions 

type EncodeOptions struct {
	// WriterBufferSize is the size of the buffer used when writing.
	//
	// if > 0, we use a smart buffer internally for performance purposes.
	WriterBufferSize int

	// ChanRecvTimeout is the timeout used when selecting from a chan.
	//
	// Configuring this controls how we receive from a chan during the encoding process.
	//   - If ==0, we only consume the elements currently available in the chan.
	//   - if  <0, we consume until the chan is closed.
	//   - If  >0, we consume until this timeout.
	ChanRecvTimeout time.Duration

	// StructToArray specifies to encode a struct as an array, and not as a map
	StructToArray bool

	// Canonical representation means that encoding a value will always result in the same
	// sequence of bytes.
	//
	// This only affects maps, as the iteration order for maps is random.
	//
	// The implementation MAY use the natural sort order for the map keys if possible:
	//
	//     - If there is a natural sort order (ie for number, bool, string or []byte keys),
	//       then the map keys are first sorted in natural order and then written
	//       with corresponding map values to the strema.
	//     - If there is no natural sort order, then the map keys will first be
	//       encoded into []byte, and then sorted,
	//       before writing the sorted keys and the corresponding map values to the stream.
	//
	Canonical bool

	// CheckCircularRef controls whether we check for circular references
	// and error fast during an encode.
	//
	// If enabled, an error is received if a pointer to a struct
	// references itself either directly or through one of its fields (iteratively).
	//
	// This is opt-in, as there may be a performance hit to checking circular references.
	CheckCircularRef bool

	// RecursiveEmptyCheck controls whether we descend into interfaces, structs and pointers
	// when checking if a value is empty.
	//
	// Note that this may make OmitEmpty more expensive, as it incurs a lot more reflect calls.
	RecursiveEmptyCheck bool

	// Raw controls whether we encode Raw values.
	// This is a "dangerous" option and must be explicitly set.
	// If set, we blindly encode Raw values as-is, without checking
	// if they are a correct representation of a value in that format.
	// If unset, we error out.
	Raw bool

	// StringToRaw controls how strings are encoded.
	//
	// As a go string is just an (immutable) sequence of bytes,
	// it can be encoded either as raw bytes or as a UTF string.
	//
	// By default, strings are encoded as UTF-8.
	// but can be treated as []byte during an encode.
	//
	// Note that things which we know (by definition) to be UTF-8
	// are ALWAYS encoded as UTF-8 strings.
	// These include encoding.TextMarshaler, time.Format calls, struct field names, etc.
	StringToRaw bool
}

EncodeOptions captures configuration options during encode.

type Encoder 

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

Encoder writes an object to an output stream in a supported format.

Encoder is NOT safe for concurrent use i.e. a Encoder cannot be used concurrently in multiple goroutines.

However, as Encoder could be allocation heavy to initialize, a Reset method is provided so its state can be reused to decode new input streams repeatedly. This is the idiomatic way to use.

func NewEncoder 

func NewEncoder(w io.Writer, h Handle) *Encoder

NewEncoder returns an Encoder for encoding into an io.Writer.

For efficiency, Users are encouraged to configure WriterBufferSize on the handle OR pass in a memory buffered writer (eg bufio.Writer, bytes.Buffer).

func NewEncoderBytes 

func NewEncoderBytes(out *[]byte, h Handle) *Encoder

NewEncoderBytes returns an encoder for encoding directly and efficiently into a byte slice, using zero-copying to temporary slices.

It will potentially replace the output byte slice pointed to. After encoding, the out parameter contains the encoded contents.

func (*Encoder) Encode 

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

Encode writes an object into a stream.

Encoding can be configured via the struct tag for the fields. The key (in the struct tags) that we look at is configurable.

By default, we look up the "codec" key in the struct field's tags, and fall bak to the "json" key if "codec" is absent. That 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. The options which can be set on _struct are:

  • omitempty: so all fields are omitted if empty
  • toarray: so struct is encoded as an array
  • int: so struct key names are encoded as signed integers (instead of strings)
  • uint: so struct key names are encoded as unsigned integers (instead of strings)
  • float: so struct key names are encoded as floats (instead of strings)

More details on these below.

Struct values "usually" encode as maps. Each exported struct field is encoded unless:

  • the field's tag is "-", OR
  • the field is empty (empty or the zero value) and its tag specifies the "omitempty" option.

When encoding as a map, the first string in the tag (before the comma) is the map key string to use when encoding. ... This key is typically encoded as a string. However, there are instances where the encoded stream has mapping keys encoded as numbers. For example, some cbor streams have keys as integer codes in the stream, but they should map to fields in a structured object. Consequently, a struct is the natural representation in code. For these, configure the struct to encode/decode the keys as numbers (instead of string). This is done with the int,uint or float option on the _struct field (see above).

However, struct values may encode as arrays. This happens when:

  • StructToArray Encode option is set, OR
  • the tag on the _struct field sets the "toarray" option

Note that omitempty is ignored when encoding struct values as arrays, as an entry must be encoded for each field, to maintain its position.

Values with types that implement MapBySlice are encoded as stream maps.

The empty values (for omitempty option) are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero.

Anonymous fields are encoded inline except:

  • the struct tag specifies a replacement name (first value)
  • the field is of an interface type

Examples: 

// NOTE: 'json:' can be used as struct tag key, in place 'codec:' below.
type MyStruct struct {
    _struct bool    `codec:",omitempty"`   //set omitempty for every field
    Field1 string   `codec:"-"`            //skip this field
    Field2 int      `codec:"myName"`       //Use key "myName" in encode stream
    Field3 int32    `codec:",omitempty"`   //use key "Field3". Omit if empty.
    Field4 bool     `codec:"f4,omitempty"` //use key "f4". Omit if empty.
    io.Reader                              //use key "Reader".
    MyStruct        `codec:"my1"           //use key "my1".
    MyStruct                               //inline it
    ...
}

type MyStruct struct {
    _struct bool    `codec:",toarray"`     //encode struct as an array
}

type MyStruct struct {
    _struct bool    `codec:",uint"`        //encode struct with "unsigned integer" keys
    Field1 string   `codec:"1"`            //encode Field1 key using: EncodeInt(1)
    Field2 string   `codec:"2"`            //encode Field2 key using: EncodeInt(2)
}

The mode of encoding is based on the type of the value. When a value is seen:

  • If a Selfer, call its CodecEncodeSelf method
  • If an extension is registered for it, call that extension function
  • If implements encoding.(Binary|Text|JSON)Marshaler, call Marshal(Binary|Text|JSON) method
  • Else encode it based on its reflect.Kind

Note that struct field names and keys in map[string]XXX will be treated as symbols. Some formats support symbols (e.g. binc) and will properly encode the string only once in the stream, and use a tag to refer to it thereafter.

func (*Encoder) MustEncode 

func (e *Encoder) MustEncode(v interface{})

MustEncode is like Encode, but panics if unable to Encode. This provides insight to the code location that triggered the error.

func (*Encoder) Release 

func (e *Encoder) Release()

Release releases shared (pooled) resources.

It is important to call Release() when done with an Encoder, so those resources are released instantly for use by subsequently created Encoders.

func (*Encoder) Reset 

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

Reset resets the Encoder with a new output stream.

This accommodates using the state of the Encoder, where it has "cached" information about sub-engines.

func (*Encoder) ResetBytes 

func (e *Encoder) ResetBytes(out *[]byte)

ResetBytes resets the Encoder with a new destination output []byte.

type Ext 

type Ext interface {
	BytesExt
	InterfaceExt
}

Ext handles custom (de)serialization of custom types / extensions.

type Handle 

type Handle interface {
	Name() string
	// contains filtered or unexported methods
}

Handle defines a specific encoding format. It also stores any runtime state used during an Encoding or Decoding session e.g. stored state about Types, etc.

Once a handle is configured, it can be shared across multiple Encoders and Decoders.

Note that a Handle is NOT safe for concurrent modification. Consequently, do not modify it after it is configured if shared among multiple Encoders and Decoders in different goroutines.

Consequently, the typical usage model is that a Handle is pre-configured before first time use, and not modified while in use. Such a pre-configured Handle is safe for concurrent access.

type InterfaceExt 

type InterfaceExt interface {
	// ConvertExt converts a value into a simpler interface for easy encoding
	// e.g. convert time.Time to int64.
	//
	// Note: v is a pointer iff the registered extension type is a struct or array kind.
	ConvertExt(v interface{}) interface{}

	// UpdateExt updates a value from a simpler interface for easy decoding
	// e.g. convert int64 to time.Time.
	//
	// Note: dst is always a pointer kind to the registered extension type.
	UpdateExt(dst interface{}, src interface{})
}

InterfaceExt handles custom (de)serialization of types to/from another interface{} value. The Encoder or Decoder will then handle the further (de)serialization of that known type.

It is used by codecs (e.g. cbor, json) which use the format to do custom serialization of types.

type JsonHandle 

type JsonHandle struct {
	BasicHandle

	// Indent indicates how a value is encoded.
	//   - If positive, indent by that number of spaces.
	//   - If negative, indent by that number of tabs.
	Indent int8

	// IntegerAsString controls how integers (signed and unsigned) are encoded.
	//
	// Per the JSON Spec, JSON numbers are 64-bit floating point numbers.
	// Consequently, integers > 2^53 cannot be represented as a JSON number without losing precision.
	// This can be mitigated by configuring how to encode integers.
	//
	// IntegerAsString interpretes the following values:
	//   - if 'L', then encode integers > 2^53 as a json string.
	//   - if 'A', then encode all integers as a json string
	//             containing the exact integer representation as a decimal.
	//   - else    encode all integers as a json number (default)
	IntegerAsString byte

	// HTMLCharsAsIs controls how to encode some special characters to html: < > &
	//
	// By default, we encode them as \uXXX
	// to prevent security holes when served from some browsers.
	HTMLCharsAsIs bool

	// PreferFloat says that we will default to decoding a number as a float.
	// If not set, we will examine the characters of the number and decode as an
	// integer type if it doesn't have any of the characters [.eE].
	PreferFloat bool

	// TermWhitespace says that we add a whitespace character
	// at the end of an encoding.
	//
	// The whitespace is important, especially if using numbers in a context
	// where multiple items are written to a stream.
	TermWhitespace bool

	// MapKeyAsString says to encode all map keys as strings.
	//
	// Use this to enforce strict json output.
	// The only caveat is that nil value is ALWAYS written as null (never as "null")
	MapKeyAsString bool

	// RawBytesExt, if configured, is used to encode and decode raw bytes in a custom way.
	// If not configured, raw bytes are encoded to/from base64 text.
	RawBytesExt InterfaceExt
	// contains filtered or unexported fields
}

JsonHandle is a handle for JSON encoding format.

Json is comprehensively supported:

  • decodes numbers into interface{} as int, uint or float64 based on how the number looks and some config parameters e.g. PreferFloat, SignedInt, etc.
  • decode integers from float formatted numbers e.g. 1.27e+8
  • decode any json value (numbers, bool, etc) from quoted strings
  • configurable way to encode/decode []byte . by default, encodes and decodes []byte using base64 Std Encoding
  • UTF-8 support for encoding and decoding

It has better performance than the json library in the standard library, by leveraging the performance improvements of the codec library.

In addition, it doesn't read more bytes than necessary during a decode, which allows reading multiple values from a stream containing json and non-json content. For example, a user can read a json value, then a cbor value, then a msgpack value, all from the same stream in sequence.

Note that, when decoding quoted strings, invalid UTF-8 or invalid UTF-16 surrogate pairs are not treated as an error. Instead, they are replaced by the Unicode replacement character U+FFFD.

func (*JsonHandle) AddExt deprecated 

func (o *JsonHandle) AddExt(rt reflect.Type, tag byte,
	encfn func(reflect.Value) ([]byte, error),
	decfn func(reflect.Value, []byte) error) (err error)

AddExt registes an encode and decode function for a reflect.Type. To deregister an Ext, call AddExt with nil encfn and/or nil decfn.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

func (*JsonHandle) Intf2Impl 

func (o *JsonHandle) Intf2Impl(intf, impl reflect.Type) (err error)

Intf2Impl maps an interface to an implementing type. This allows us support infering the concrete type and populating it when passed an interface. e.g. var v io.Reader can be decoded as a bytes.Buffer, etc.

Passing a nil impl will clear the mapping.

func (*JsonHandle) Name 

func (h *JsonHandle) Name() string

Name returns the name of the handle: json

func (*JsonHandle) SetExt deprecated 

func (o *JsonHandle) SetExt(rt reflect.Type, tag uint64, ext Ext) (err error)

SetExt will set the extension for a tag and reflect.Type. Note that the type must be a named type, and specifically not a pointer or Interface. An error is returned if that is not honored. To Deregister an ext, call SetExt with nil Ext.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

func (*JsonHandle) SetInterfaceExt 

func (h *JsonHandle) SetInterfaceExt(rt reflect.Type, tag uint64, ext InterfaceExt) (err error)

SetInterfaceExt sets an extension

type MapBySlice 

type MapBySlice interface {
	MapBySlice()
}

MapBySlice is a tag interface that denotes wrapped slice should encode as a map in the stream. The slice contains a sequence of key-value pairs. This affords storing a map in a specific sequence in the stream.

Example usage: 

type T1 []string         // or []int or []Point or any other "slice" type
func (_ T1) MapBySlice{} // T1 now implements MapBySlice, and will be encoded as a map
type T2 struct { KeyValues T1 }

var kvs = []string{"one", "1", "two", "2", "three", "3"}
var v2 = T2{ KeyValues: T1(kvs) }
// v2 will be encoded like the map: {"KeyValues": {"one": "1", "two": "2", "three": "3"} }

The support of MapBySlice affords the following:

  • A slice type which implements MapBySlice will be encoded as a map
  • A slice can be decoded from a map in the stream
  • It MUST be a slice type (not a pointer receiver) that implements MapBySlice

type MissingFielder 

type MissingFielder interface {
	// CodecMissingField is called to set a missing field and value pair.
	//
	// It returns true if the missing field was set on the struct.
	CodecMissingField(field []byte, value interface{}) bool

	// CodecMissingFields returns the set of fields which are not struct fields
	CodecMissingFields() map[string]interface{}
}

MissingFielder defines the interface allowing structs to internally decode or encode values which do not map to struct fields.

We expect that this interface is bound to a pointer type (so the mutation function works).

A use-case is if a version of a type unexports a field, but you want compatibility between both versions during encoding and decoding.

Note that the interface is completely ignored during codecgen.

type MsgpackHandle 

type MsgpackHandle struct {
	BasicHandle

	// NoFixedNum says to output all signed integers as 2-bytes, never as 1-byte fixednum.
	NoFixedNum bool

	// WriteExt controls whether the new spec is honored.
	//
	// With WriteExt=true, we can encode configured extensions with extension tags
	// and encode string/[]byte/extensions in a way compatible with the new spec
	// but incompatible with the old spec.
	//
	// For compatibility with the old spec, set WriteExt=false.
	//
	// With WriteExt=false:
	//    configured extensions are serialized as raw bytes (not msgpack extensions).
	//    reserved byte descriptors like Str8 and those enabling the new msgpack Binary type
	//    are not encoded.
	WriteExt bool

	// PositiveIntUnsigned says to encode positive integers as unsigned.
	PositiveIntUnsigned bool
	// contains filtered or unexported fields
}

MsgpackHandle is a Handle for the Msgpack Schema-Free Encoding Format.

func (*MsgpackHandle) AddExt deprecated 

func (o *MsgpackHandle) AddExt(rt reflect.Type, tag byte,
	encfn func(reflect.Value) ([]byte, error),
	decfn func(reflect.Value, []byte) error) (err error)

AddExt registes an encode and decode function for a reflect.Type. To deregister an Ext, call AddExt with nil encfn and/or nil decfn.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

func (*MsgpackHandle) Intf2Impl 

func (o *MsgpackHandle) Intf2Impl(intf, impl reflect.Type) (err error)

Intf2Impl maps an interface to an implementing type. This allows us support infering the concrete type and populating it when passed an interface. e.g. var v io.Reader can be decoded as a bytes.Buffer, etc.

Passing a nil impl will clear the mapping.

func (*MsgpackHandle) Name 

func (h *MsgpackHandle) Name() string

Name returns the name of the handle: msgpack

func (*MsgpackHandle) SetBytesExt 

func (h *MsgpackHandle) SetBytesExt(rt reflect.Type, tag uint64, ext BytesExt) (err error)

SetBytesExt sets an extension

func (*MsgpackHandle) SetExt deprecated 

func (o *MsgpackHandle) SetExt(rt reflect.Type, tag uint64, ext Ext) (err error)

SetExt will set the extension for a tag and reflect.Type. Note that the type must be a named type, and specifically not a pointer or Interface. An error is returned if that is not honored. To Deregister an ext, call SetExt with nil Ext.

Deprecated: Use SetBytesExt or SetInterfaceExt on the Handle instead.

type MsgpackSpecRpcMultiArgs 

type MsgpackSpecRpcMultiArgs []interface{}

MsgpackSpecRpcMultiArgs is a special type which signifies to the MsgpackSpecRpcCodec that the backend RPC service takes multiple arguments, which have been arranged in sequence in the slice.

The Codec then passes it AS-IS to the rpc service (without wrapping it in an array of 1 element).

type RPCOptions 

type RPCOptions struct {
	// RPCNoBuffer configures whether we attempt to buffer reads and writes during RPC calls.
	//
	// Set RPCNoBuffer=true to turn buffering off.
	// Buffering can still be done if buffered connections are passed in, or
	// buffering is configured on the handle.
	RPCNoBuffer bool
}

RPCOptions holds options specific to rpc functionality

type Raw 

type Raw []byte

Raw represents raw formatted bytes. We "blindly" store it during encode and retrieve the raw bytes during decode. Note: it is dangerous during encode, so we may gate the behaviour behind an Encode flag which must be explicitly set.

type RawExt 

type RawExt struct {
	Tag uint64
	// Data is the []byte which represents the raw ext. If nil, ext is exposed in Value.
	// Data is used by codecs (e.g. binc, msgpack, simple) which do custom serialization of types
	Data []byte
	// Value represents the extension, if Data is nil.
	// Value is used by codecs (e.g. cbor, json) which leverage the format to do
	// custom serialization of the types.
	Value interface{}
}

RawExt represents raw unprocessed extension data. Some codecs will decode extension data as a *RawExt if there is no registered extension for the tag.

Only one of Data or Value is nil. If Data is nil, then the content of the RawExt is in the Value.

type Rpc 

type Rpc interface {
	ServerCodec(conn io.ReadWriteCloser, h Handle) rpc.ServerCodec
	ClientCodec(conn io.ReadWriteCloser, h Handle) rpc.ClientCodec
}

Rpc provides a rpc Server or Client Codec for rpc communication.

type Selfer 

type Selfer interface {
	CodecEncodeSelf(*Encoder)
	CodecDecodeSelf(*Decoder)
}

Selfer defines methods by which a value can encode or decode itself.

Any type which implements Selfer will be able to encode or decode itself. Consequently, during (en|de)code, this takes precedence over (text|binary)(M|Unm)arshal or extension support.

By definition, it is not allowed for a Selfer to directly call Encode or Decode on itself. If that is done, Encode/Decode will rightfully fail with a Stack Overflow style error. For example, the snippet below will cause such an error. 

type testSelferRecur struct{}
func (s *testSelferRecur) CodecEncodeSelf(e *Encoder) { e.MustEncode(s) }
func (s *testSelferRecur) CodecDecodeSelf(d *Decoder) { d.MustDecode(s) }

Note: *the first set of bytes of any value MUST NOT represent nil in the format*. This is because, during each decode, we first check the the next set of bytes represent nil, and if so, we just set the value to nil.

type TypeInfos 

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

TypeInfos caches typeInfo for each type on first inspection.

It is configured with a set of tag keys, which are used to get configuration for the type.

func NewTypeInfos 

func NewTypeInfos(tags []string) *TypeInfos

NewTypeInfos creates a TypeInfos given a set of struct tags keys.

This allows users customize the struct tag keys which contain configuration of their types.

Source Files

View all Source files

Directories

Path Synopsis
Package codec provides a High Performance, Feature-Rich Idiomatic Go 1.4+ codec/encoding library for binc, msgpack, cbor, json.
 Package codec provides a High Performance, Feature-Rich Idiomatic Go 1.4+ codec/encoding library for binc, msgpack, cbor, json.
codecgen generates static implementations of the encoder and decoder functions for a given type, bypassing reflection, and giving some performance benefits in terms of wall and cpu time, and memory usage.
 codecgen generates static implementations of the encoder and decoder functions for a given type, bypassing reflection, and giving some performance benefits in terms of wall and cpu time, and memory usage.

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