cbor

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Published: Jan 4, 2022 License: MIT Imports: 16 Imported by: 389

README

CBOR Codec in Go

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fxamacker/cbor is a modern CBOR codec in Go. It's like encoding/json for CBOR with time-saving features. It balances security, usability, speed, data size, program size, and other competing factors.

Features include CBOR tags, duplicate map key detection, float64→32→16, and Go struct tags (toarray, keyasint, omitempty). API is close to encoding/json plus predefined CBOR options like Core Deterministic Encoding, Preferred Serialization, CTAP2, etc.

Using CBOR Preferred Serialization with Go struct tags (toarray, keyasint, omitempty) reduces programming effort and creates smaller encoded data size.

fxamacker/cbor has 98% coverage and is fuzz tested. It won't exhaust RAM decoding 9 bytes of bad CBOR data. It's used by Arm Ltd., Berlin Institute of Health at Charité, Chainlink, ConsenSys, Dapper Labs, Duo Labs (cisco), EdgeX Foundry, Mozilla, Netherlands (govt), Oasis Labs, Taurus SA, Teleport, and others.

Install with go get github.com/fxamacker/cbor/v2 and import "github.com/fxamacker/cbor/v2".
See Quick Start to save time.

What is CBOR?

CBOR is a concise binary data format inspired by JSON and MessagePack. CBOR is defined in RFC 8949 (December 2020) which obsoletes RFC 7049 (October 2013).

CBOR is an Internet Standard by IETF. It's used in other standards like WebAuthn by W3C, COSE (RFC 8152), CWT (RFC 8392), CDDL (RFC 8610) and more.

Reasons for choosing CBOR vary by project. Some projects replaced protobuf, encoding/json, encoding/gob, etc. with CBOR. For example, by replacing protobuf with CBOR in gRPC.

Why fxamacker/cbor?

fxamacker/cbor balances competing factors such as speed, size, safety, usability, maintainability, and etc.

  • Killer features include Go struct tags like toarray, keyasint, etc. They reduce encoded data size, improve speed, and reduce programming effort. For example, toarray automatically translates a Go struct to/from a CBOR array.

  • Modern CBOR features include Core Deterministic Encoding and Preferred Encoding. Other features include CBOR tags, big.Int, float64→32→16, an API like encoding/json, and more.

  • Security features include the option to detect duplicate map keys and options to set various max limits. And it's designed to make concurrent use of CBOR options easy and free from side-effects.

  • To prevent crashes, it has been fuzz-tested since before release 1.0 and code coverage is kept above 98%.

  • For portability and safety, it avoids using unsafe, which makes it portable and protected by Go1's compatibility guidelines.

  • For performance, it uses safe optimizations. When used properly, fxamacker/cbor can be faster than CBOR codecs that rely on unsafe. However, speed is only one factor and should be considered together with other competing factors.

CBOR Security

fxamacker/cbor is secure. It rejects malformed CBOR data and has an option to detect duplicate map keys. It doesn't crash when decoding bad CBOR data. It has extensive tests, coverage-guided fuzzing, data validation, and avoids Go's unsafe package.

Decoding 9 or 10 bytes of malformed CBOR data shouldn't exhaust memory. For example,
[]byte{0x9B, 0x00, 0x00, 0x42, 0xFA, 0x42, 0xFA, 0x42, 0xFA, 0x42}

Decode bad 10 bytes to interface{} Decode bad 10 bytes to []byte
fxamacker/cbor
1.0-2.3
49.44 ns/op, 24 B/op, 2 allocs/op* 51.93 ns/op, 32 B/op, 2 allocs/op*
ugorji/go 1.2.6 ⚠️ 45021 ns/op, 262852 B/op, 7 allocs/op 💥 runtime: out of memory: cannot allocate
ugorji/go 1.1-1.1.7 💥 runtime: out of memory: cannot allocate 💥 runtime: out of memory: cannot allocate

*Speed and memory are for latest codec version listed in the row (compiled with Go 1.17.5).

fxamacker/cbor CBOR safety settings include: MaxNestedLevels, MaxArrayElements, MaxMapPairs, and IndefLength.

For more info, see:

CBOR Performance

fxamacker/cbor is fast without sacrificing security. It can be faster than libraries relying on unsafe package.

alt text

Click to expand:

👉 CBOR Program Size Comparison

fxamacker/cbor produces smaller programs without sacrificing features.

alt text

👉 fxamacker/cbor 2.3.0 (safe) vs ugorji/go 1.2.6 (unsafe)

fxamacker/cbor 2.3.0 (not using unsafe) is faster than ugorji/go 1.2.6 (using unsafe).

benchstat results/bench-ugorji-go-count20.txt results/bench-fxamacker-cbor-count20.txt 
name                                 old time/op    new time/op    delta
DecodeCWTClaims-8                      1.08µs ± 0%    0.67µs ± 0%  -38.10%  (p=0.000 n=16+20)
DecodeCOSE/128-Bit_Symmetric_Key-8      715ns ± 0%     501ns ± 0%  -29.97%  (p=0.000 n=20+19)
DecodeCOSE/256-Bit_Symmetric_Key-8      722ns ± 0%     507ns ± 0%  -29.72%  (p=0.000 n=19+18)
DecodeCOSE/ECDSA_P256_256-Bit_Key-8    1.11µs ± 0%    0.83µs ± 0%  -25.27%  (p=0.000 n=19+20)
DecodeWebAuthn-8                        880ns ± 0%     727ns ± 0%  -17.31%  (p=0.000 n=18+20)
EncodeCWTClaims-8                       785ns ± 0%     388ns ± 0%  -50.51%  (p=0.000 n=20+20)
EncodeCOSE/128-Bit_Symmetric_Key-8      973ns ± 0%     433ns ± 0%  -55.45%  (p=0.000 n=20+19)
EncodeCOSE/256-Bit_Symmetric_Key-8      974ns ± 0%     435ns ± 0%  -55.37%  (p=0.000 n=20+19)
EncodeCOSE/ECDSA_P256_256-Bit_Key-8    1.14µs ± 0%    0.55µs ± 0%  -52.10%  (p=0.000 n=19+19)
EncodeWebAuthn-8                        564ns ± 0%     450ns ± 1%  -20.18%  (p=0.000 n=18+20)

name                                 old alloc/op   new alloc/op   delta
DecodeCWTClaims-8                        744B ± 0%      160B ± 0%  -78.49%  (p=0.000 n=20+20)
DecodeCOSE/128-Bit_Symmetric_Key-8       792B ± 0%      232B ± 0%  -70.71%  (p=0.000 n=20+20)
DecodeCOSE/256-Bit_Symmetric_Key-8       816B ± 0%      256B ± 0%  -68.63%  (p=0.000 n=20+20)
DecodeCOSE/ECDSA_P256_256-Bit_Key-8      905B ± 0%      344B ± 0%  -61.99%  (p=0.000 n=20+20)
DecodeWebAuthn-8                       1.56kB ± 0%    0.99kB ± 0%  -36.41%  (p=0.000 n=20+20)
EncodeCWTClaims-8                      1.35kB ± 0%    0.18kB ± 0%  -86.98%  (p=0.000 n=20+20)
EncodeCOSE/128-Bit_Symmetric_Key-8     1.95kB ± 0%    0.22kB ± 0%  -88.52%  (p=0.000 n=20+20)
EncodeCOSE/256-Bit_Symmetric_Key-8     1.95kB ± 0%    0.24kB ± 0%  -87.70%  (p=0.000 n=20+20)
EncodeCOSE/ECDSA_P256_256-Bit_Key-8    1.95kB ± 0%    0.32kB ± 0%  -83.61%  (p=0.000 n=20+20)
EncodeWebAuthn-8                       1.30kB ± 0%    1.09kB ± 0%  -16.56%  (p=0.000 n=20+20)

name                                 old allocs/op  new allocs/op  delta
DecodeCWTClaims-8                        6.00 ± 0%      6.00 ± 0%     ~     (all equal)
DecodeCOSE/128-Bit_Symmetric_Key-8       4.00 ± 0%      4.00 ± 0%     ~     (all equal)
DecodeCOSE/256-Bit_Symmetric_Key-8       4.00 ± 0%      4.00 ± 0%     ~     (all equal)
DecodeCOSE/ECDSA_P256_256-Bit_Key-8      7.00 ± 0%      7.00 ± 0%     ~     (all equal)
DecodeWebAuthn-8                         5.00 ± 0%      5.00 ± 0%     ~     (all equal)
EncodeCWTClaims-8                        4.00 ± 0%      2.00 ± 0%  -50.00%  (p=0.000 n=20+20)
EncodeCOSE/128-Bit_Symmetric_Key-8       6.00 ± 0%      2.00 ± 0%  -66.67%  (p=0.000 n=20+20)
EncodeCOSE/256-Bit_Symmetric_Key-8       6.00 ± 0%      2.00 ± 0%  -66.67%  (p=0.000 n=20+20)
EncodeCOSE/ECDSA_P256_256-Bit_Key-8      6.00 ± 0%      2.00 ± 0%  -66.67%  (p=0.000 n=20+20)
EncodeWebAuthn-8                         4.00 ± 0%      2.00 ± 0%  -50.00%  (p=0.000 n=20+20)

Benchmarks used Go 1.17.5, linux_amd64, and data from RFC 8392 Appendix A.1. Default build options were used for all CBOR libraries. Library init code was put outside the benchmark loop for all libraries compared.

CBOR API

fxamacker/cbor is easy to use. It provides standard API and interfaces.

Standard API. Function signatures identical to encoding/json include:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, and (*Decoder).Decode.

Standard Interfaces. Custom encoding and decoding is handled by implementing:
BinaryMarshaler, BinaryUnmarshaler, Marshaler, and Unmarshaler.

Predefined Encoding Options. Encoding options are easy to use and are customizable.

func CoreDetEncOptions() EncOptions {}              // RFC 8949 Core Deterministic Encoding
func PreferredUnsortedEncOptions() EncOptions {}    // RFC 8949 Preferred Serialization
func CanonicalEncOptions() EncOptions {}            // RFC 7049 Canonical CBOR
func CTAP2EncOptions() EncOptions {}                // FIDO2 CTAP2 Canonical CBOR

fxamacker/cbor designed to simplify concurrency. CBOR options can be used without creating unintended runtime side-effects.

Go Struct Tags

fxamacker/cbor provides Go struct tags like toarray and keyasint to save time and reduce encoded size of data.


alt text

CBOR Features

fxamacker/cbor is a full-featured CBOR encoder and decoder.

CBOR Feature Description
☑️ CBOR tags API supports built-in and user-defined tags.
☑️ Preferred serialization Integers encode to fewest bytes. Optional float64 → float32 → float16.
☑️ Map key sorting Unsorted, length-first (Canonical CBOR), and bytewise-lexicographic (CTAP2).
☑️ Duplicate map keys Always forbid for encoding and option to allow/forbid for decoding.
☑️ Indefinite length data Option to allow/forbid for encoding and decoding.
☑️ Well-formedness Always checked and enforced.
☑️ Basic validity checks Check UTF-8 validity and optionally check duplicate map keys.
☑️ Security considerations Prevent integer overflow and resource exhaustion (RFC 8949 Section 10).

CBOR Library Installation

fxamacker/cbor supports Go 1.12 and newer versions. Init the Go module, go get v2, and begin coding.

go mod init github.com/my_name/my_repo
go get github.com/fxamacker/cbor/v2
import "github.com/fxamacker/cbor/v2"  // imports as cbor

Quick Start

🛡️ Use Go's io.LimitReader to limit size when decoding very large or indefinite size data.

Import using "/v2" like this: import "github.com/fxamacker/cbor/v2", and
it will import version 2.x as package "cbor" (when using Go modules).

Functions with identical signatures to encoding/json include:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, (*Decoder).Decode.

Default Mode

If default options are acceptable, package level functions can be used for encoding and decoding.

b, err := cbor.Marshal(v)        // encode v to []byte b
err := cbor.Unmarshal(b, &v)     // decode []byte b to v
encoder := cbor.NewEncoder(w)    // create encoder with io.Writer w
decoder := cbor.NewDecoder(r)    // create decoder with io.Reader r

Modes

If you need to use options or CBOR tags, then you'll want to create a mode.

"Mode" means defined way of encoding or decoding -- it links the standard API to your CBOR options and CBOR tags. This way, you don't pass around options and the API remains identical to encoding/json.

EncMode and DecMode are interfaces created from EncOptions or DecOptions structs.
For example, em, err := cbor.EncOptions{...}.EncMode() or em, err := cbor.CanonicalEncOptions().EncMode().

EncMode and DecMode use immutable options so their behavior won't accidentally change at runtime. Modes are reusable, safe for concurrent use, and allow fast parallelism.

Creating and Using Encoding Modes

💡 Avoid using init(). For best performance, reuse EncMode and DecMode after creating them.

Most apps will probably create one EncMode and DecMode before init(). There's no limit and each can use different options.

// Create EncOptions using either struct literal or a function.
opts := cbor.CanonicalEncOptions()

// If needed, modify opts. For example: opts.Time = cbor.TimeUnix

// Create reusable EncMode interface with immutable options, safe for concurrent use.
em, err := opts.EncMode()   

// Use EncMode like encoding/json, with same function signatures.
b, err := em.Marshal(v)      // encode v to []byte b

encoder := em.NewEncoder(w)  // create encoder with io.Writer w
err := encoder.Encode(v)     // encode v to io.Writer w

Both em.Marshal(v) and encoder.Encode(v) use encoding options specified during creation of encoding mode em.

Creating Modes With CBOR Tags

A TagSet is used to specify CBOR tags.

em, err := opts.EncMode()                  // no tags
em, err := opts.EncModeWithTags(ts)        // immutable tags
em, err := opts.EncModeWithSharedTags(ts)  // mutable shared tags

TagSet and all modes using it are safe for concurrent use. Equivalent API is available for DecMode.

Predefined Encoding Options

func CoreDetEncOptions() EncOptions {}              // RFC 8949 Core Deterministic Encoding
func PreferredUnsortedEncOptions() EncOptions {}    // RFC 8949 Preferred Serialization
func CanonicalEncOptions() EncOptions {}            // RFC 7049 Canonical CBOR
func CTAP2EncOptions() EncOptions {}                // FIDO2 CTAP2 Canonical CBOR

The empty curly braces prevent a syntax highlighting bug on GitHub, please ignore them.

Struct Tags (keyasint, toarray, omitempty)

The keyasint, toarray, and omitempty struct tags make it easy to use compact CBOR message formats. Internet standards often use CBOR arrays and CBOR maps with int keys to save space.

The following sections provide more info:


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Features

Standard API

Many function signatures are identical to encoding/json, including:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, (*Decoder).Decode.

RawMessage can be used to delay CBOR decoding or precompute CBOR encoding, like encoding/json.

Standard interfaces allow user-defined types to have custom CBOR encoding and decoding. They include:
BinaryMarshaler, BinaryUnmarshaler, Marshaler, and Unmarshaler.

Marshaler and Unmarshaler interfaces are satisfied by MarshalCBOR and UnmarshalCBOR functions using same params and return types as Go's MarshalJSON and UnmarshalJSON.

Struct Tags

Support "cbor" and "json" keys in Go's struct tags. If both are specified for the same field, then "cbor" is used.

  • a different field name can be specified, like encoding/json.
  • omitempty omits (ignores) field if value is empty, like encoding/json.
  • - always omits (ignores) field, like encoding/json.
  • keyasint treats fields as elements of CBOR maps with specified int key.
  • toarray treats fields as elements of CBOR arrays.

See Struct Tags for more info.

CBOR Tags (New in v2.1)

There are three categories of CBOR tags:

  • Default built-in CBOR tags currently include tag numbers 0 (Standard Date/Time), 1 (Epoch Date/Time), 2 (Unsigned Bignum), 3 (Negative Bignum), 55799 (Self-Described CBOR).

  • Optional built-in CBOR tags may be provided in the future via build flags or optional package(s) to help reduce bloat.

  • User-defined CBOR tags are easy by using TagSet to associate tag numbers to user-defined Go types.

Preferred Serialization

Preferred serialization encodes integers and floating-point values using the fewest bytes possible.

  • Integers are always encoded using the fewest bytes possible.
  • Floating-point values can optionally encode from float64->float32->float16 when values fit.
Compact Data Size

The combination of preferred serialization and struct tags (toarray, keyasint, omitempty) allows very compact data size.

Predefined Encoding Options

Easy-to-use functions (no params) return preset EncOptions struct:
CanonicalEncOptions, CTAP2EncOptions, CoreDetEncOptions, PreferredUnsortedEncOptions

Encoding Options

Integers always encode to the shortest form that preserves value. By default, time values are encoded without tags.

Encoding of other data types and map key sort order are determined by encoder options.

EncOptions Available Settings (defaults listed first)
Sort SortNone, SortLengthFirst, SortBytewiseLexical
Aliases: SortCanonical, SortCTAP2, SortCoreDeterministic
Time TimeUnix, TimeUnixMicro, TimeUnixDynamic, TimeRFC3339, TimeRFC3339Nano
TimeTag EncTagNone, EncTagRequired
ShortestFloat ShortestFloatNone, ShortestFloat16
BigIntConvert BigIntConvertShortest, BigIntConvertNone
InfConvert InfConvertFloat16, InfConvertNone
NaNConvert NaNConvert7e00, NaNConvertNone, NaNConvertQuiet, NaNConvertPreserveSignal
IndefLength IndefLengthAllowed, IndefLengthForbidden
TagsMd TagsAllowed, TagsForbidden

See Options section for details about each setting.

Decoding Options
DecOptions Available Settings (defaults listed first)
TimeTag DecTagIgnored, DecTagOptional, DecTagRequired
DupMapKey DupMapKeyQuiet, DupMapKeyEnforcedAPF
IntDec IntDecConvertNone, IntDecConvertSigned
IndefLength IndefLengthAllowed, IndefLengthForbidden
TagsMd TagsAllowed, TagsForbidden
ExtraReturnErrors ExtraDecErrorNone, ExtraDecErrorUnknownField
MaxNestedLevels 32, can be set to [4, 256]
MaxArrayElements 131072, can be set to [16, 2147483647]
MaxMapPairs 131072, can be set to [16, 2147483647]

See Options section for details about each setting.

Additional Features
  • Decoder always checks for invalid UTF-8 string errors.
  • Decoder always decodes in-place to slices, maps, and structs.
  • Decoder tries case-sensitive first and falls back to case-insensitive field name match when decoding to structs.
  • Decoder supports decoding registered CBOR tag data to interface types.
  • Both encoder and decoder support indefinite length CBOR data ("streaming").
  • Both encoder and decoder correctly handles nil slice, map, pointer, and interface values.

Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Standards

This library is a full-featured generic CBOR (RFC 8949) encoder and decoder. Notable CBOR features include:

CBOR Feature Description
☑️ CBOR tags API supports built-in and user-defined tags.
☑️ Preferred serialization Integers encode to fewest bytes. Optional float64 → float32 → float16.
☑️ Map key sorting Unsorted, length-first (Canonical CBOR), and bytewise-lexicographic (CTAP2).
☑️ Duplicate map keys Always forbid for encoding and option to allow/forbid for decoding.
☑️ Indefinite length data Option to allow/forbid for encoding and decoding.
☑️ Well-formedness Always checked and enforced.
☑️ Basic validity checks Check UTF-8 validity and optionally check duplicate map keys.
☑️ Security considerations Prevent integer overflow and resource exhaustion (RFC 8949 Section 10).

See the Features section for list of Encoding Options and Decoding Options.

Known limitations are noted in the Limitations section.

Go nil values for slices, maps, pointers, etc. are encoded as CBOR null. Empty slices, maps, etc. are encoded as empty CBOR arrays and maps.

Decoder checks for all required well-formedness errors, including all "subkinds" of syntax errors and too little data.

After well-formedness is verified, basic validity errors are handled as follows:

  • Invalid UTF-8 string: Decoder always checks and returns invalid UTF-8 string error.
  • Duplicate keys in a map: Decoder has options to ignore or enforce rejection of duplicate map keys.

When decoding well-formed CBOR arrays and maps, decoder saves the first error it encounters and continues with the next item. Options to handle this differently may be added in the future.

By default, decoder treats time values of floating-point NaN and Infinity as if they are CBOR Null or CBOR Undefined.

See Options section for detailed settings or Features section for a summary of options.

Click to expand topic:

Duplicate Map Keys

This library provides options for fast detection and rejection of duplicate map keys based on applying a Go-specific data model to CBOR's extended generic data model in order to determine duplicate vs distinct map keys. Detection relies on whether the CBOR map key would be a duplicate "key" when decoded and applied to the user-provided Go map or struct.

DupMapKeyQuiet turns off detection of duplicate map keys. It tries to use a "keep fastest" method by choosing either "keep first" or "keep last" depending on the Go data type.

DupMapKeyEnforcedAPF enforces detection and rejection of duplidate map keys. Decoding stops immediately and returns DupMapKeyError when the first duplicate key is detected. The error includes the duplicate map key and the index number.

APF suffix means "Allow Partial Fill" so the destination map or struct can contain some decoded values at the time of error. It is the caller's responsibility to respond to the DupMapKeyError by discarding the partially filled result if that's required by their protocol.

Tag Validity

This library checks tag validity for built-in tags (currently tag numbers 0, 1, 2, 3, and 55799):

  • Inadmissible type for tag content
  • Inadmissible value for tag content

Unknown tag data items (not tag number 0, 1, 2, 3, or 55799) are handled in two ways:

  • When decoding into an empty interface, unknown tag data item will be decoded into cbor.Tag data type, which contains tag number and tag content. The tag content will be decoded into the default Go data type for the CBOR data type.
  • When decoding into other Go types, unknown tag data item is decoded into the specified Go type. If Go type is registered with a tag number, the tag number can optionally be verified.

Decoder also has an option to forbid tag data items (treat any tag data item as error) which is specified by protocols such as CTAP2 Canonical CBOR.

For more information, see decoding options and tag options.

Limitations

If any of these limitations prevent you from using this library, please open an issue along with a link to your project.

  • CBOR Undefined (0xf7) value decodes to Go's nil value. CBOR Null (0xf6) more closely matches Go's nil.
  • CBOR map keys with data types not supported by Go for map keys are ignored and an error is returned after continuing to decode remaining items.
  • When using io.Reader interface to read very large or indefinite length CBOR data, Go's io.LimitReader should be used to limit size.
  • When decoding registered CBOR tag data to interface type, decoder creates a pointer to registered Go type matching CBOR tag number. Requiring a pointer for this is a Go limitation.

Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

API

Many function signatures are identical to Go's encoding/json, such as:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, and (*Decoder).Decode.

Interfaces identical or comparable to Go's encoding, encoding/json, or encoding/gob include:
Marshaler, Unmarshaler, BinaryMarshaler, and BinaryUnmarshaler.

Like encoding/json, RawMessage can be used to delay CBOR decoding or precompute CBOR encoding.

"Mode" in this API means defined way of encoding or decoding -- it links the standard API to CBOR options and CBOR tags.

EncMode and DecMode are interfaces created from EncOptions or DecOptions structs.
For example, em, err := cbor.EncOptions{...}.EncMode() or em, err := cbor.CanonicalEncOptions().EncMode().

EncMode and DecMode use immutable options so their behavior won't accidentally change at runtime. Modes are intended to be reused and are safe for concurrent use.

API for Default Mode

If default options are acceptable, then you don't need to create EncMode or DecMode.

Marshal(v interface{}) ([]byte, error)
NewEncoder(w io.Writer) *Encoder

Unmarshal(data []byte, v interface{}) error
NewDecoder(r io.Reader) *Decoder

API for Creating & Using Encoding Modes

// EncMode interface uses immutable options and is safe for concurrent use.
type EncMode interface {
	Marshal(v interface{}) ([]byte, error)
	NewEncoder(w io.Writer) *Encoder
	EncOptions() EncOptions  // returns copy of options
}

// EncOptions specifies encoding options.
type EncOptions struct {
...
}

// EncMode returns an EncMode interface created from EncOptions.
func (opts EncOptions) EncMode() (EncMode, error) {}

// EncModeWithTags returns EncMode with options and tags that are both immutable. 
func (opts EncOptions) EncModeWithTags(tags TagSet) (EncMode, error) {}

// EncModeWithSharedTags returns EncMode with immutable options and mutable shared tags. 
func (opts EncOptions) EncModeWithSharedTags(tags TagSet) (EncMode, error) {}

The empty curly braces prevent a syntax highlighting bug, please ignore them.

API for Predefined Encoding Options

func CoreDetEncOptions() EncOptions {}              // RFC 8949 Core Deterministic Encoding
func PreferredUnsortedEncOptions() EncOptions {}    // RFC 8949 Preferred Serialization
func CanonicalEncOptions() EncOptions {}            // RFC 7049 Canonical CBOR
func CTAP2EncOptions() EncOptions {}                // FIDO2 CTAP2 Canonical CBOR

API for Creating & Using Decoding Modes

// DecMode interface uses immutable options and is safe for concurrent use.
type DecMode interface {
	Unmarshal(data []byte, v interface{}) error
	NewDecoder(r io.Reader) *Decoder
	DecOptions() DecOptions  // returns copy of options
}

// DecOptions specifies decoding options.
type DecOptions struct {
...
}

// DecMode returns a DecMode interface created from DecOptions.
func (opts DecOptions) DecMode() (DecMode, error) {}

// DecModeWithTags returns DecMode with options and tags that are both immutable. 
func (opts DecOptions) DecModeWithTags(tags TagSet) (DecMode, error) {}

// DecModeWithSharedTags returns DecMode with immutable options and mutable shared tags. 
func (opts DecOptions) DecModeWithSharedTags(tags TagSet) (DecMode, error) {}

The empty curly braces prevent a syntax highlighting bug, please ignore them.

API for Using CBOR Tags

TagSet can be used to associate user-defined Go type(s) to tag number(s). It's also used to create EncMode or DecMode. For example, em := EncOptions{...}.EncModeWithTags(ts) or em := EncOptions{...}.EncModeWithSharedTags(ts). This allows every standard API exported by em (like Marshal and NewEncoder) to use the specified tags automatically.

Tag and RawTag can be used to encode/decode a tag number with a Go value, but TagSet is generally recommended.

type TagSet interface {
    // Add adds given tag number(s), content type, and tag options to TagSet.
    Add(opts TagOptions, contentType reflect.Type, num uint64, nestedNum ...uint64) error

    // Remove removes given tag content type from TagSet.
    Remove(contentType reflect.Type)    
}

Tag and RawTag types can also be used to encode/decode tag number with Go value.

type Tag struct {
    Number  uint64
    Content interface{}
}

type RawTag struct {
    Number  uint64
    Content RawMessage
}

See API docs (godoc.org) for more details and more functions. See Usage section for usage and code examples.


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Options

Struct tags, decoding options, and encoding options.

Struct Tags

This library supports both "cbor" and "json" key for some (not all) struct tags. If "cbor" and "json" keys are both present for the same field, then "cbor" key will be used.

Key Format Str Scope Description
cbor or json "myName" field Name of field to use such as "myName", etc. like encoding/json.
cbor or json ",omitempty" field Omit (ignore) this field if value is empty, like encoding/json.
cbor or json "-" field Omit (ignore) this field always, like encoding/json.
cbor ",keyasint" field Treat field as an element of CBOR map with specified int as key.
cbor ",toarray" struct Treat each field as an element of CBOR array. This automatically disables "omitempty" and "keyasint" for all fields in the struct.

The "keyasint" struct tag requires an integer key to be specified:

type myStruct struct {
    MyField     int64    `cbor:"-1,keyasint,omitempty'`
    OurField    string   `cbor:"0,keyasint,omitempty"`
    FooField    Foo      `cbor:"5,keyasint,omitempty"`
    BarField    Bar      `cbor:"hello,omitempty"`
    ...
}

The "toarray" struct tag requires a special field "_" (underscore) to indicate "toarray" applies to the entire struct:

type myStruct struct {
    _           struct{}    `cbor:",toarray"`
    MyField     int64
    OurField    string
    ...
}

Click to expand:

Example Using CBOR Web Tokens

alt text

Decoding Options
DecOptions.TimeTag Description
DecTagIgnored (default) Tag numbers are ignored (if present) for time values.
DecTagOptional Tag numbers are only checked for validity if present for time values.
DecTagRequired Tag numbers must be provided for time values except for CBOR Null and CBOR Undefined.

The following CBOR time values are decoded as Go's "zero time instant":

  • CBOR Null
  • CBOR Undefined
  • CBOR floating-point NaN
  • CBOR floating-point Infinity

Go's time package provides IsZero function, which reports whether t represents "zero time instant"
(January 1, year 1, 00:00:00 UTC).


DecOptions.DupMapKey Description
DupMapKeyQuiet (default) turns off detection of duplicate map keys. It uses a "keep fastest" method by choosing either "keep first" or "keep last" depending on the Go data type.
DupMapKeyEnforcedAPF enforces detection and rejection of duplidate map keys. Decoding stops immediately and returns DupMapKeyError when the first duplicate key is detected. The error includes the duplicate map key and the index number.

DupMapKeyEnforcedAPF uses "Allow Partial Fill" so the destination map or struct can contain some decoded values at the time of error. Users can respond to the DupMapKeyError by discarding the partially filled result if that's required by their protocol.


DecOptions.IntDec Description
IntDecConvertNone (default) When decoding to Go interface{}, CBOR positive int (major type 0) decode to uint64 value, and CBOR negative int (major type 1) decode to int64 value.
IntDecConvertSigned When decoding to Go interface{}, CBOR positive/negative int (major type 0 and 1) decode to int64 value.

If IntDecConvertedSigned is used and value overflows int64, UnmarshalTypeError is returned.


DecOptions.IndefLength Description
IndefLengthAllowed (default) allow indefinite length data
IndefLengthForbidden forbid indefinite length data

DecOptions.TagsMd Description
TagsAllowed (default) allow CBOR tags (major type 6)
TagsForbidden forbid CBOR tags (major type 6)

DecOptions.ExtraReturnErrors Description
ExtraDecErrorNone (default) no extra decoding errors. E.g. ignore unknown fields if encountered.
ExtraDecErrorUnknownField return error if unknown field is encountered

DecOptions.MaxNestedLevels Description
32 (default) allowed setting is [4, 256]

DecOptions.MaxArrayElements Description
131072 (default) allowed setting is [16, 2147483647]

DecOptions.MaxMapPairs Description
131072 (default) allowed setting is [16, 2147483647]
Encoding Options

Integers always encode to the shortest form that preserves value. Encoding of other data types and map key sort order are determined by encoding options.

These functions are provided to create and return a modifiable EncOptions struct with predefined settings.

Predefined EncOptions Description
CanonicalEncOptions() Canonical CBOR (RFC 7049 Section 3.9).
CTAP2EncOptions() CTAP2 Canonical CBOR (FIDO2 CTAP2).
PreferredUnsortedEncOptions() Unsorted, encode float64->float32->float16 when values fit, NaN values encoded as float16 0x7e00.
CoreDetEncOptions() PreferredUnsortedEncOptions() + map keys are sorted bytewise lexicographic.

EncOptions.Sort Description
SortNone (default) No sorting for map keys.
SortLengthFirst Length-first map key ordering.
SortBytewiseLexical Bytewise lexicographic map key ordering (RFC 8949 Section 4.2.1).
SortCanonical (alias) Same as SortLengthFirst (RFC 7049 Section 3.9)
SortCTAP2 (alias) Same as SortBytewiseLexical (CTAP2 Canonical CBOR).
SortCoreDeterministic (alias) Same as SortBytewiseLexical (RFC 8949 Section 4.2.1).

EncOptions.Time Description
TimeUnix (default) (seconds) Encode as integer.
TimeUnixMicro (microseconds) Encode as floating-point. ShortestFloat option determines size.
TimeUnixDynamic (seconds or microseconds) Encode as integer if time doesn't have fractional seconds, otherwise encode as floating-point rounded to microseconds.
TimeRFC3339 (seconds) Encode as RFC 3339 formatted string.
TimeRFC3339Nano (nanoseconds) Encode as RFC3339 formatted string.

EncOptions.TimeTag Description
EncTagNone (default) Tag number will not be encoded for time values.
EncTagRequired Tag number (0 or 1) will be encoded unless time value is undefined/zero-instant.

By default, undefined (zero instant) time values will encode as CBOR Null without tag number for both EncTagNone and EncTagRequired. Although CBOR Undefined might be technically more correct for EncTagRequired, CBOR Undefined might not be supported by other generic decoders and it isn't supported by JSON.

Go's time package provides IsZero function, which reports whether t represents the zero time instant, January 1, year 1, 00:00:00 UTC.


EncOptions.BigIntConvert Description
BigIntConvertShortest (default) Encode big.Int as CBOR integer if value fits.
BigIntConvertNone Encode big.Int as CBOR bignum (tag 2 or 3).

Floating-Point Options

Encoder has 3 types of options for floating-point data: ShortestFloatMode, InfConvertMode, and NaNConvertMode.

EncOptions.ShortestFloat Description
ShortestFloatNone (default) No size conversion. Encode float32 and float64 to CBOR floating-point of same bit-size.
ShortestFloat16 Encode float64 -> float32 -> float16 (IEEE 754 binary16) when values fit.

Conversions for infinity and NaN use InfConvert and NaNConvert settings.

EncOptions.InfConvert Description
InfConvertFloat16 (default) Convert +- infinity to float16 since they always preserve value (recommended)
InfConvertNone Don't convert +- infinity to other representations -- used by CTAP2 Canonical CBOR

EncOptions.NaNConvert Description
NaNConvert7e00 (default) Encode to 0xf97e00 (CBOR float16 = 0x7e00) -- used by RFC 8949 Preferred Encoding, etc.
NaNConvertNone Don't convert NaN to other representations -- used by CTAP2 Canonical CBOR.
NaNConvertQuiet Force quiet bit = 1 and use shortest form that preserves NaN payload.
NaNConvertPreserveSignal Convert to smallest form that preserves value (quit bit unmodified and NaN payload preserved).

EncOptions.IndefLength Description
IndefLengthAllowed (default) allow indefinite length data
IndefLengthForbidden forbid indefinite length data

EncOptions.TagsMd Description
TagsAllowed (default) allow CBOR tags (major type 6)
TagsForbidden forbid CBOR tags (major type 6)
Tag Options

TagOptions specifies how encoder and decoder handle tag number registered with TagSet.

TagOptions.DecTag Description
DecTagIgnored (default) Tag numbers are ignored (if present).
DecTagOptional Tag numbers are only checked for validity if present.
DecTagRequired Tag numbers must be provided except for CBOR Null and CBOR Undefined.

TagOptions.EncTag Description
EncTagNone (default) Tag number will not be encoded.
EncTagRequired Tag number will be encoded.

Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Usage

🛡️ Use Go's io.LimitReader to limit size when decoding very large or indefinite size data.

Functions with identical signatures to encoding/json include:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, (*Decoder).Decode.

Default Mode

If default options are acceptable, package level functions can be used for encoding and decoding.

b, err := cbor.Marshal(v)        // encode v to []byte b

err := cbor.Unmarshal(b, &v)     // decode []byte b to v

encoder := cbor.NewEncoder(w)    // create encoder with io.Writer w

decoder := cbor.NewDecoder(r)    // create decoder with io.Reader r

Modes

If you need to use options or CBOR tags, then you'll want to create a mode.

"Mode" means defined way of encoding or decoding -- it links the standard API to your CBOR options and CBOR tags. This way, you don't pass around options and the API remains identical to encoding/json.

EncMode and DecMode are interfaces created from EncOptions or DecOptions structs.
For example, em, err := cbor.EncOptions{...}.EncMode() or em, err := cbor.CanonicalEncOptions().EncMode().

EncMode and DecMode use immutable options so their behavior won't accidentally change at runtime. Modes are reusable, safe for concurrent use, and allow fast parallelism.

Creating and Using Encoding Modes

EncMode is an interface (API) created from EncOptions struct. EncMode uses immutable options after being created and is safe for concurrent use. For best performance, EncMode should be reused.

// Create EncOptions using either struct literal or a function.
opts := cbor.CanonicalEncOptions()

// If needed, modify opts. For example: opts.Time = cbor.TimeUnix

// Create reusable EncMode interface with immutable options, safe for concurrent use.
em, err := opts.EncMode()   

// Use EncMode like encoding/json, with same function signatures.
b, err := em.Marshal(v)      // encode v to []byte b

encoder := em.NewEncoder(w)  // create encoder with io.Writer w
err := encoder.Encode(v)     // encode v to io.Writer w

Struct Tags (keyasint, toarray, omitempty)

The keyasint, toarray, and omitempty struct tags make it easy to use compact CBOR message formats. Internet standards often use CBOR arrays and CBOR maps with int keys to save space.


alt text


Decoding CWT (CBOR Web Token) using keyasint and toarray struct tags:

// Signed CWT is defined in RFC 8392
type signedCWT struct {
	_           struct{} `cbor:",toarray"`
	Protected   []byte
	Unprotected coseHeader
	Payload     []byte
	Signature   []byte
}

// Part of COSE header definition
type coseHeader struct {
	Alg int    `cbor:"1,keyasint,omitempty"`
	Kid []byte `cbor:"4,keyasint,omitempty"`
	IV  []byte `cbor:"5,keyasint,omitempty"`
}

// data is []byte containing signed CWT

var v signedCWT
if err := cbor.Unmarshal(data, &v); err != nil {
	return err
}

Encoding CWT (CBOR Web Token) using keyasint and toarray struct tags:

// Use signedCWT struct defined in "Decoding CWT" example.

var v signedCWT
...
if data, err := cbor.Marshal(v); err != nil {
	return err
}

Encoding and Decoding CWT (CBOR Web Token) with CBOR Tags

// Use signedCWT struct defined in "Decoding CWT" example.

// Create TagSet (safe for concurrency).
tags := cbor.NewTagSet()
// Register tag COSE_Sign1 18 with signedCWT type.
tags.Add(	
	cbor.TagOptions{EncTag: cbor.EncTagRequired, DecTag: cbor.DecTagRequired}, 
	reflect.TypeOf(signedCWT{}), 
	18)

// Create DecMode with immutable tags.
dm, _ := cbor.DecOptions{}.DecModeWithTags(tags)

// Unmarshal to signedCWT with tag support.
var v signedCWT
if err := dm.Unmarshal(data, &v); err != nil {
	return err
}

// Create EncMode with immutable tags.
em, _ := cbor.EncOptions{}.EncModeWithTags(tags)

// Marshal signedCWT with tag number.
if data, err := cbor.Marshal(v); err != nil {
	return err
}

For more examples, see examples_test.go.


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Comparisons

Comparisons are between this newer library and a well-known library that had 1,000+ stars before this library was created. Default build settings for each library were used for all comparisons.

This library is safer. Small malicious CBOR messages are rejected quickly before they exhaust system resources.

Decoding 9 or 10 bytes of malformed CBOR data shouldn't exhaust memory. For example,
[]byte{0x9B, 0x00, 0x00, 0x42, 0xFA, 0x42, 0xFA, 0x42, 0xFA, 0x42}

Decode bad 10 bytes to interface{} Decode bad 10 bytes to []byte
fxamacker/cbor
1.0-2.3
49.44 ns/op, 24 B/op, 2 allocs/op* 51.93 ns/op, 32 B/op, 2 allocs/op*
ugorji/go 1.2.6 ⚠️ 45021 ns/op, 262852 B/op, 7 allocs/op 💥 runtime: out of memory: cannot allocate
ugorji/go 1.1.0-1.1.7 💥 runtime: out of memory: cannot allocate 💥 runtime: out of memory: cannot allocate

*Speed and memory are for latest codec version listed in the row (compiled with Go 1.17.5).

fxamacker/cbor CBOR safety settings include: MaxNestedLevels, MaxArrayElements, MaxMapPairs, and IndefLength.

This library is smaller. Programs like senmlCat can be 4 MB smaller by switching to this library. Programs using more complex CBOR data types can be 9.2 MB smaller.

alt text

This library is faster for encoding and decoding CBOR Web Token (CWT). However, speed is only one factor and it can vary depending on data types and sizes. Unlike the other library, this one doesn't use Go's unsafe package or code gen.

alt text

This library uses less memory for encoding and decoding CBOR Web Token (CWT) using test data from RFC 8392 A.1.

fxamacker/cbor 2.3 ugorji/go 1.2.6
Encode CWT 0.18 kB/op         2 allocs/op 1.35 kB/op         4 allocs/op
Decode CWT 160 bytes/op     6 allocs/op 744 bytes/op     6 allocs/op

Running your own benchmarks is highly recommended. Use your most common data structures and data sizes.


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Benchmarks

Go structs are faster than maps with string keys:

  • decoding into struct is >28% faster than decoding into map.
  • encoding struct is >35% faster than encoding map.

Go structs with keyasint struct tag are faster than maps with integer keys:

  • decoding into struct is >28% faster than decoding into map.
  • encoding struct is >34% faster than encoding map.

Go structs with toarray struct tag are faster than slice:

  • decoding into struct is >15% faster than decoding into slice.
  • encoding struct is >12% faster than encoding slice.

Doing your own benchmarks is highly recommended. Use your most common message sizes and data types.

See Benchmarks for fxamacker/cbor.

Fuzzing and Code Coverage

Over 375 tests must pass on 4 architectures before tagging a release. They include all RFC 7049 and RFC 8949 examples, bugs found by fuzzing, maliciously crafted CBOR data, and over 87 tests with malformed data. There's some overlap in the tests but it isn't a high priority to trim tests.

Code coverage must not fall below 95% when tagging a release. Code coverage is above 98% (go test -cover) for cbor v2.3 which is among the highest for libraries (in Go) of this type.

Coverage-guided fuzzing must pass 1+ billion execs using a large corpus before tagging a release. Fuzzing is usually continued after the release is tagged and is manually stopped after reaching 1-3 billion execs. Fuzzing uses a customized version of dvyukov/go-fuzz.

To prevent delays to release schedules, fuzzing is not restarted for a release if changes are limited to ci, docs, and comments.


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Versions and API Changes

This project uses Semantic Versioning, so the API is always backwards compatible unless the major version number changes.

These functions have signatures identical to encoding/json and they will likely never change even after major new releases:
Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, and (*Decoder).Decode.

Newly added API documented as "subject to change" are excluded from SemVer.

Newly added API in the master branch that has never been release tagged are excluded from SemVer.

Code of Conduct

This project has adopted the Contributor Covenant Code of Conduct. Contact faye.github@gmail.com with any questions or comments.

Contributing

Please refer to How to Contribute.

Security Policy

Security fixes are provided for the latest released version of fxamacker/cbor.

For the full text of the Security Policy, see SECURITY.md.

Disclaimers

Phrases like "no crashes", "doesn't crash", and "is secure" mean there are no known crash bugs in the latest version based on results of unit tests and coverage-guided fuzzing. They don't imply the software is 100% bug-free or 100% invulnerable to all known and unknown attacks.

Please read the license for additional disclaimers and terms.

Special Thanks

Making this library better

  • Stefan Tatschner for using this library in sep, being the 1st to discover my CBOR library, requesting time.Time in issue #1, and submitting this library in a PR to cbor.io on Aug 12, 2019.
  • Yawning Angel for using this library to oasis-core, and requesting BinaryMarshaler in issue #5.
  • Jernej Kos for requesting RawMessage in issue #11 and offering feedback on v2.1 API for CBOR tags.
  • ZenGround0 for using this library in go-filecoin, filing "toarray" bug in issue #129, and requesting
    CBOR BSTR <--> Go array in #133.
  • Keith Randall for fixing Go bugs and providing workarounds so we don't have to wait for new versions of Go.

Help clarifying CBOR RFC 7049 or 7049bis (7049bis is the draft of RFC 8949)

  • Carsten Bormann for RFC 7049 (CBOR), adding this library to cbor.io, his fast confirmation to my RFC 7049 errata, approving my pull request to 7049bis, and his patience when I misread a line in 7049bis.
  • Laurence Lundblade for his help on the IETF mailing list for 7049bis and for pointing out on a CBORbis issue that CBOR Undefined might be problematic translating to JSON.
  • Jeffrey Yasskin for his help on the IETF mailing list for 7049bis.

Words of encouragement and support

  • Jakob Borg for his words of encouragement about this library at Go Forum. This is especially appreciated in the early stages when there's a lot of rough edges.

License

Copyright © 2019-2022 Faye Amacker.

fxamacker/cbor is licensed under the MIT License. See LICENSE for the full license text.


Quick StartFeaturesStandardsAPIOptionsUsageFuzzingLicense

Documentation

Overview

Package cbor is a modern CBOR codec (RFC 8949 & RFC 7049) with CBOR tags, Go struct tags (toarray/keyasint/omitempty), Core Deterministic Encoding, CTAP2, Canonical CBOR, float64->32->16, and duplicate map key detection.

Encoding options allow "preferred serialization" by encoding integers and floats to their smallest forms (e.g. float16) when values fit.

Struct tags like "keyasint", "toarray" and "omitempty" make CBOR data smaller and easier to use with structs.

For example, "toarray" tag makes struct fields encode to CBOR array elements. And "keyasint" makes a field encode to an element of CBOR map with specified int key.

Latest docs can be viewed at https://github.com/fxamacker/cbor#cbor-library-in-go

Basics

The Quick Start guide is at https://github.com/fxamacker/cbor#quick-start

Function signatures identical to encoding/json include:

Marshal, Unmarshal, NewEncoder, NewDecoder, (*Encoder).Encode, (*Decoder).Decode.

Standard interfaces include:

BinaryMarshaler, BinaryUnmarshaler, Marshaler, and Unmarshaler.

Custom encoding and decoding is possible by implementing standard interfaces for user-defined Go types.

Codec functions are available at package-level (using defaults options) or by creating modes from options at runtime.

"Mode" in this API means definite way of encoding (EncMode) or decoding (DecMode).

EncMode and DecMode interfaces are created from EncOptions or DecOptions structs.

em := cbor.EncOptions{...}.EncMode()
em := cbor.CanonicalEncOptions().EncMode()
em := cbor.CTAP2EncOptions().EncMode()

Modes use immutable options to avoid side-effects and simplify concurrency. Behavior of modes won't accidentally change at runtime after they're created.

Modes are intended to be reused and are safe for concurrent use.

EncMode and DecMode Interfaces

    // EncMode interface uses immutable options and is safe for concurrent use.
    type EncMode interface {
	Marshal(v interface{}) ([]byte, error)
	NewEncoder(w io.Writer) *Encoder
	EncOptions() EncOptions  // returns copy of options
    }

    // DecMode interface uses immutable options and is safe for concurrent use.
    type DecMode interface {
	Unmarshal(data []byte, v interface{}) error
	NewDecoder(r io.Reader) *Decoder
	DecOptions() DecOptions  // returns copy of options
    }

Using Default Encoding Mode

b, err := cbor.Marshal(v)

encoder := cbor.NewEncoder(w)
err = encoder.Encode(v)

Using Default Decoding Mode

err := cbor.Unmarshal(b, &v)

decoder := cbor.NewDecoder(r)
err = decoder.Decode(&v)

Creating and Using Encoding Modes

// Create EncOptions using either struct literal or a function.
opts := cbor.CanonicalEncOptions()

// If needed, modify encoding options
opts.Time = cbor.TimeUnix

// Create reusable EncMode interface with immutable options, safe for concurrent use.
em, err := opts.EncMode()

// Use EncMode like encoding/json, with same function signatures.
b, err := em.Marshal(v)
// or
encoder := em.NewEncoder(w)
err := encoder.Encode(v)

// NOTE: Both em.Marshal(v) and encoder.Encode(v) use encoding options
// specified during creation of em (encoding mode).

CBOR Options

Predefined Encoding Options: https://github.com/fxamacker/cbor#predefined-encoding-options

Encoding Options: https://github.com/fxamacker/cbor#encoding-options

Decoding Options: https://github.com/fxamacker/cbor#decoding-options

Struct Tags

Struct tags like `cbor:"name,omitempty"` and `json:"name,omitempty"` work as expected. If both struct tags are specified then `cbor` is used.

Struct tags like "keyasint", "toarray", and "omitempty" make it easy to use very compact formats like COSE and CWT (CBOR Web Tokens) with structs.

For example, "toarray" makes struct fields encode to array elements. And "keyasint" makes struct fields encode to elements of CBOR map with int keys.

https://raw.githubusercontent.com/fxamacker/images/master/cbor/v2.0.0/cbor_easy_api.png

Struct tags are listed at https://github.com/fxamacker/cbor#struct-tags-1

Tests and Fuzzing

Over 375 tests are included in this package. Cover-guided fuzzing is handled by fxamacker/cbor-fuzz.

Example (COSE)
// Use "keyasint" struct tag to encode/decode struct to/from CBOR map.
// Use cbor.RawMessage to delay unmarshaling (CrvOrNOrK's data type depends on Kty's value).
type coseKey struct {
	Kty       int             `cbor:"1,keyasint,omitempty"`
	Kid       []byte          `cbor:"2,keyasint,omitempty"`
	Alg       int             `cbor:"3,keyasint,omitempty"`
	KeyOpts   int             `cbor:"4,keyasint,omitempty"`
	IV        []byte          `cbor:"5,keyasint,omitempty"`
	CrvOrNOrK cbor.RawMessage `cbor:"-1,keyasint,omitempty"` // K for symmetric keys, Crv for elliptic curve keys, N for RSA modulus
	XOrE      cbor.RawMessage `cbor:"-2,keyasint,omitempty"` // X for curve x-coordinate, E for RSA public exponent
	Y         cbor.RawMessage `cbor:"-3,keyasint,omitempty"` // Y for curve y-cooridate
	D         []byte          `cbor:"-4,keyasint,omitempty"`
}
// Data from https://tools.ietf.org/html/rfc8392#appendix-A section A.2
// 128-Bit Symmetric Key
cborData, _ := hex.DecodeString("a42050231f4c4d4d3051fdc2ec0a3851d5b3830104024c53796d6d6574726963313238030a")
var v coseKey
if err := cbor.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
if _, err := cbor.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

{Kty:4 Kid:[83 121 109 109 101 116 114 105 99 49 50 56] Alg:10 KeyOpts:0 IV:[] CrvOrNOrK:[80 35 31 76 77 77 48 81 253 194 236 10 56 81 213 179 131] XOrE:[] Y:[] D:[]}
Example (CWT)
// Use "keyasint" struct tag to encode/decode struct to/from CBOR map.
type claims struct {
	Iss string `cbor:"1,keyasint"`
	Sub string `cbor:"2,keyasint"`
	Aud string `cbor:"3,keyasint"`
	Exp int    `cbor:"4,keyasint"`
	Nbf int    `cbor:"5,keyasint"`
	Iat int    `cbor:"6,keyasint"`
	Cti []byte `cbor:"7,keyasint"`
}
// Data from https://tools.ietf.org/html/rfc8392#appendix-A section A.1
cborData, _ := hex.DecodeString("a70175636f61703a2f2f61732e6578616d706c652e636f6d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9f007420b71")
var v claims
if err := cbor.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
if _, err := cbor.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

{Iss:coap://as.example.com Sub:erikw Aud:coap://light.example.com Exp:1444064944 Nbf:1443944944 Iat:1443944944 Cti:[11 113]}
Example (CWTWithDupMapKeyOption)
type claims struct {
	Iss string `cbor:"1,keyasint"`
	Sub string `cbor:"2,keyasint"`
	Aud string `cbor:"3,keyasint"`
	Exp int    `cbor:"4,keyasint"`
	Nbf int    `cbor:"5,keyasint"`
	Iat int    `cbor:"6,keyasint"`
	Cti []byte `cbor:"7,keyasint"`
}

// Data from https://tools.ietf.org/html/rfc8392#appendix-A section A.1
cborData, _ := hex.DecodeString("a70175636f61703a2f2f61732e6578616d706c652e636f6d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9f007420b71")

dm, _ := cbor.DecOptions{DupMapKey: cbor.DupMapKeyEnforcedAPF}.DecMode()

var v claims
if err := dm.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

{Iss:coap://as.example.com Sub:erikw Aud:coap://light.example.com Exp:1444064944 Nbf:1443944944 Iat:1443944944 Cti:[11 113]}
Example (SenML)
// Use "keyasint" struct tag to encode/decode struct to/from CBOR map.
type SenMLRecord struct {
	BaseName    string  `cbor:"-2,keyasint,omitempty"`
	BaseTime    float64 `cbor:"-3,keyasint,omitempty"`
	BaseUnit    string  `cbor:"-4,keyasint,omitempty"`
	BaseValue   float64 `cbor:"-5,keyasint,omitempty"`
	BaseSum     float64 `cbor:"-6,keyasint,omitempty"`
	BaseVersion int     `cbor:"-1,keyasint,omitempty"`
	Name        string  `cbor:"0,keyasint,omitempty"`
	Unit        string  `cbor:"1,keyasint,omitempty"`
	Time        float64 `cbor:"6,keyasint,omitempty"`
	UpdateTime  float64 `cbor:"7,keyasint,omitempty"`
	Value       float64 `cbor:"2,keyasint,omitempty"`
	ValueS      string  `cbor:"3,keyasint,omitempty"`
	ValueB      bool    `cbor:"4,keyasint,omitempty"`
	ValueD      string  `cbor:"8,keyasint,omitempty"`
	Sum         float64 `cbor:"5,keyasint,omitempty"`
}
// Data from https://tools.ietf.org/html/rfc8428#section-6
cborData, _ := hex.DecodeString("87a721781b75726e3a6465763a6f773a3130653230373361303130383030363a22fb41d303a15b00106223614120050067766f6c7461676501615602fb405e066666666666a3006763757272656e74062402fb3ff3333333333333a3006763757272656e74062302fb3ff4cccccccccccda3006763757272656e74062202fb3ff6666666666666a3006763757272656e74062102f93e00a3006763757272656e74062002fb3ff999999999999aa3006763757272656e74060002fb3ffb333333333333")
var v []*SenMLRecord
if err := cbor.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
// Encoder uses ShortestFloat16 option to use float16 as the shortest form that preserves floating-point value.
em, err := cbor.EncOptions{ShortestFloat: cbor.ShortestFloat16}.EncMode()
if err != nil {
	fmt.Println("error:", err)
}
if _, err := em.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
for _, rec := range v {
	fmt.Printf("%+v\n", *rec)
}
Output:

{BaseName:urn:dev:ow:10e2073a0108006: BaseTime:1.276020076001e+09 BaseUnit:A BaseValue:0 BaseSum:0 BaseVersion:5 Name:voltage Unit:V Time:0 UpdateTime:0 Value:120.1 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:-5 UpdateTime:0 Value:1.2 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:-4 UpdateTime:0 Value:1.3 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:-3 UpdateTime:0 Value:1.4 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:-2 UpdateTime:0 Value:1.5 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:-1 UpdateTime:0 Value:1.6 ValueS: ValueB:false ValueD: Sum:0}
{BaseName: BaseTime:0 BaseUnit: BaseValue:0 BaseSum:0 BaseVersion:0 Name:current Unit: Time:0 UpdateTime:0 Value:1.7 ValueS: ValueB:false ValueD: Sum:0}
Example (SignedCWT)
// Use "keyasint" struct tag to encode/decode struct to/from CBOR map.
// Partial COSE header definition
type coseHeader struct {
	Alg int    `cbor:"1,keyasint,omitempty"`
	Kid []byte `cbor:"4,keyasint,omitempty"`
	IV  []byte `cbor:"5,keyasint,omitempty"`
}
// Use "toarray" struct tag to encode/decode struct to/from CBOR array.
type signedCWT struct {
	_           struct{} `cbor:",toarray"`
	Protected   []byte
	Unprotected coseHeader
	Payload     []byte
	Signature   []byte
}
// Data from https://tools.ietf.org/html/rfc8392#appendix-A section A.3
cborData, _ := hex.DecodeString("d28443a10126a104524173796d6d657472696345434453413235365850a70175636f61703a2f2f61732e6578616d706c652e636f6d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9f007420b7158405427c1ff28d23fbad1f29c4c7c6a555e601d6fa29f9179bc3d7438bacaca5acd08c8d4d4f96131680c429a01f85951ecee743a52b9b63632c57209120e1c9e30")
var v signedCWT
if err := cbor.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
if _, err := cbor.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

{_:{} Protected:[161 1 38] Unprotected:{Alg:0 Kid:[65 115 121 109 109 101 116 114 105 99 69 67 68 83 65 50 53 54] IV:[]} Payload:[167 1 117 99 111 97 112 58 47 47 97 115 46 101 120 97 109 112 108 101 46 99 111 109 2 101 101 114 105 107 119 3 120 24 99 111 97 112 58 47 47 108 105 103 104 116 46 101 120 97 109 112 108 101 46 99 111 109 4 26 86 18 174 176 5 26 86 16 217 240 6 26 86 16 217 240 7 66 11 113] Signature:[84 39 193 255 40 210 63 186 209 242 156 76 124 106 85 94 96 29 111 162 159 145 121 188 61 116 56 186 202 202 90 205 8 200 212 212 249 97 49 104 12 66 154 1 248 89 81 236 238 116 58 82 185 182 54 50 197 114 9 18 14 28 158 48]}
Example (SignedCWTWithTag)
// Use "keyasint" struct tag to encode/decode struct to/from CBOR map.
// Partial COSE header definition
type coseHeader struct {
	Alg int    `cbor:"1,keyasint,omitempty"`
	Kid []byte `cbor:"4,keyasint,omitempty"`
	IV  []byte `cbor:"5,keyasint,omitempty"`
}
// Use "toarray" struct tag to encode/decode struct to/from CBOR array.
type signedCWT struct {
	_           struct{} `cbor:",toarray"`
	Protected   []byte
	Unprotected coseHeader
	Payload     []byte
	Signature   []byte
}

// Data from https://tools.ietf.org/html/rfc8392#appendix-A section A.3
cborData, _ := hex.DecodeString("d28443a10126a104524173796d6d657472696345434453413235365850a70175636f61703a2f2f61732e6578616d706c652e636f6d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9f007420b7158405427c1ff28d23fbad1f29c4c7c6a555e601d6fa29f9179bc3d7438bacaca5acd08c8d4d4f96131680c429a01f85951ecee743a52b9b63632c57209120e1c9e30")

// Register tag COSE_Sign1 18 with signedCWT type.
tags := cbor.NewTagSet()
if err := tags.Add(
	cbor.TagOptions{EncTag: cbor.EncTagRequired, DecTag: cbor.DecTagRequired},
	reflect.TypeOf(signedCWT{}),
	18); err != nil {
	fmt.Println("error:", err)
}

dm, _ := cbor.DecOptions{}.DecModeWithTags(tags)
em, _ := cbor.EncOptions{}.EncModeWithTags(tags)

var v signedCWT
if err := dm.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}

if _, err := em.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

{_:{} Protected:[161 1 38] Unprotected:{Alg:0 Kid:[65 115 121 109 109 101 116 114 105 99 69 67 68 83 65 50 53 54] IV:[]} Payload:[167 1 117 99 111 97 112 58 47 47 97 115 46 101 120 97 109 112 108 101 46 99 111 109 2 101 101 114 105 107 119 3 120 24 99 111 97 112 58 47 47 108 105 103 104 116 46 101 120 97 109 112 108 101 46 99 111 109 4 26 86 18 174 176 5 26 86 16 217 240 6 26 86 16 217 240 7 66 11 113] Signature:[84 39 193 255 40 210 63 186 209 242 156 76 124 106 85 94 96 29 111 162 159 145 121 188 61 116 56 186 202 202 90 205 8 200 212 212 249 97 49 104 12 66 154 1 248 89 81 236 238 116 58 82 185 182 54 50 197 114 9 18 14 28 158 48]}
Example (WebAuthn)
// Use cbor.RawMessage to delay unmarshaling (AttStmt's data type depends on Fmt's value).
type attestationObject struct {
	AuthnData []byte          `cbor:"authData"`
	Fmt       string          `cbor:"fmt"`
	AttStmt   cbor.RawMessage `cbor:"attStmt"`
}
cborData, _ := hex.DecodeString("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")
var v attestationObject
if err := cbor.Unmarshal(cborData, &v); err != nil {
	fmt.Println("error:", err)
}
if _, err := cbor.Marshal(v); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", v)
Output:

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func Marshal

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

Marshal returns the CBOR encoding of v using default encoding options. See EncOptions for encoding options.

Marshal uses the following encoding rules:

If value implements the Marshaler interface, Marshal calls its MarshalCBOR method.

If value implements encoding.BinaryMarshaler, Marhsal calls its MarshalBinary method and encode it as CBOR byte string.

Boolean values encode as CBOR booleans (type 7).

Positive integer values encode as CBOR positive integers (type 0).

Negative integer values encode as CBOR negative integers (type 1).

Floating point values encode as CBOR floating points (type 7).

String values encode as CBOR text strings (type 3).

[]byte values encode as CBOR byte strings (type 2).

Array and slice values encode as CBOR arrays (type 4).

Map values encode as CBOR maps (type 5).

Struct values encode as CBOR maps (type 5). Each exported struct field becomes a pair with field name encoded as CBOR text string (type 3) and field value encoded based on its type. See struct tag option "keyasint" to encode field name as CBOR integer (type 0 and 1). Also see struct tag option "toarray" for special field "_" to encode struct values as CBOR array (type 4).

Marshal supports format string stored under the "cbor" key in the struct field's tag. CBOR format string can specify the name of the field, "omitempty" and "keyasint" options, and special case "-" for field omission. If "cbor" key is absent, Marshal uses "json" key.

Struct field name is treated as integer if it has "keyasint" option in its format string. The format string must specify an integer as its field name.

Special struct field "_" is used to specify struct level options, such as "toarray". "toarray" option enables Go struct to be encoded as CBOR array. "omitempty" is disabled by "toarray" to ensure that the same number of elements are encoded every time.

Anonymous struct fields are marshaled as if their exported fields were fields in the outer struct. Marshal follows the same struct fields visibility rules used by JSON encoding package.

time.Time values encode as text strings specified in RFC3339 or numerical representation of seconds since January 1, 1970 UTC depending on EncOptions.Time setting. Also See EncOptions.TimeTag to encode time.Time as CBOR tag with tag number 0 or 1.

big.Int values encode as CBOR integers (type 0 and 1) if values fit. Otherwise, big.Int values encode as CBOR bignums (tag 2 and 3). See EncOptions.BigIntConvert to always encode big.Int values as CBOR bignums.

Pointer values encode as the value pointed to.

Interface values encode as the value stored in the interface.

Nil slice/map/pointer/interface values encode as CBOR nulls (type 7).

Values of other types cannot be encoded in CBOR. Attempting to encode such a value causes Marshal to return an UnsupportedTypeError.

Example
type Animal struct {
	Age    int
	Name   string
	Owners []string
	Male   bool
}
animal := Animal{Age: 4, Name: "Candy", Owners: []string{"Mary", "Joe"}}
b, err := cbor.Marshal(animal)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)
Output:

a46341676504644e616d656543616e6479664f776e65727382644d617279634a6f65644d616c65f4
Example (Canonical)

This example uses Marshal to encode struct and map in canonical form.

type Animal struct {
	Age      int
	Name     string
	Contacts map[string]string
	Male     bool
}
animal := Animal{Age: 4, Name: "Candy", Contacts: map[string]string{"Mary": "111-111-1111", "Joe": "222-222-2222"}}
em, err := cbor.CanonicalEncOptions().EncMode()
if err != nil {
	fmt.Println("error:", err)
}
b, err := em.Marshal(animal)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)
Output:

a46341676504644d616c65f4644e616d656543616e647968436f6e7461637473a2634a6f656c3232322d3232322d32323232644d6172796c3131312d3131312d31313131
Example (Keyasint)

This example uses "keyasint" struct tag to encode struct's fiele names as integer. This feautre is very useful in handling COSE, CWT, SenML data.

type Record struct {
	Name        string `cbor:"1,keyasint"`
	Unit        string `cbor:"2,keyasint"`
	Measurement int    `cbor:"3,keyasint"`
}
rec := Record{Name: "current", Unit: "V", Measurement: 1}
b, err := cbor.Marshal(rec)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)
Output:

a3016763757272656e740261560301
Example (Time)
tm, _ := time.Parse(time.RFC3339, "2013-03-21T20:04:00Z")

// Encode time as string in RFC3339 format with second precision.
em, err := cbor.EncOptions{Time: cbor.TimeRFC3339}.EncMode()
if err != nil {
	fmt.Println("error:", err)
}
b, err := em.Marshal(tm)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)

// Encode time as numerical representation of seconds since January 1, 1970 UTC.
em, err = cbor.EncOptions{Time: cbor.TimeUnix}.EncMode()
if err != nil {
	fmt.Println("error:", err)
}
b, err = em.Marshal(tm)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)
Output:

74323031332d30332d32315432303a30343a30305a
1a514b67b0
Example (Toarray)

This example uses "toarray" struct tag to encode struct as CBOR array.

type Record struct {
	_           struct{} `cbor:",toarray"`
	Name        string
	Unit        string
	Measurement int
}
rec := Record{Name: "current", Unit: "V", Measurement: 1}
b, err := cbor.Marshal(rec)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", b)
Output:

836763757272656e74615601

func Unmarshal

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

Unmarshal parses the CBOR-encoded data into the value pointed to by v using default decoding options. If v is nil, not a pointer, or a nil pointer, Unmarshal returns an error.

To unmarshal CBOR into a value implementing the Unmarshaler interface, Unmarshal calls that value's UnmarshalCBOR method with a valid CBOR value.

To unmarshal CBOR byte string into a value implementing the encoding.BinaryUnmarshaler interface, Unmarshal calls that value's UnmarshalBinary method with decoded CBOR byte string.

To unmarshal CBOR into a pointer, Unmarshal sets the pointer to nil if CBOR data is null (0xf6) or undefined (0xf7). Otherwise, Unmarshal unmarshals CBOR into the value pointed to by the pointer. If the pointer is nil, Unmarshal creates a new value for it to point to.

To unmarshal CBOR into an empty interface value, Unmarshal uses the following rules:

CBOR booleans decode to bool.
CBOR positive integers decode to uint64.
CBOR negative integers decode to int64 (big.Int if value overflows).
CBOR floating points decode to float64.
CBOR byte strings decode to []byte.
CBOR text strings decode to string.
CBOR arrays decode to []interface{}.
CBOR maps decode to map[interface{}]interface{}.
CBOR null and undefined values decode to nil.
CBOR times (tag 0 and 1) decode to time.Time.
CBOR bignums (tag 2 and 3) decode to big.Int.

To unmarshal a CBOR array into a slice, Unmarshal allocates a new slice if the CBOR array is empty or slice capacity is less than CBOR array length. Otherwise Unmarshal overwrites existing elements, and sets slice length to CBOR array length.

To unmarshal a CBOR array into a Go array, Unmarshal decodes CBOR array elements into Go array elements. If the Go array is smaller than the CBOR array, the extra CBOR array elements are discarded. If the CBOR array is smaller than the Go array, the extra Go array elements are set to zero values.

To unmarshal a CBOR array into a struct, struct must have a special field "_" with struct tag `cbor:",toarray"`. Go array elements are decoded into struct fields. Any "omitempty" struct field tag option is ignored in this case.

To unmarshal a CBOR map into a map, Unmarshal allocates a new map only if the map is nil. Otherwise Unmarshal reuses the existing map and keeps existing entries. Unmarshal stores key-value pairs from the CBOR map into Go map. See DecOptions.DupMapKey to enable duplicate map key detection.

To unmarshal a CBOR map into a struct, Unmarshal matches CBOR map keys to the keys in the following priority:

  1. "cbor" key in struct field tag,
  2. "json" key in struct field tag,
  3. struct field name.

Unmarshal tries an exact match for field name, then a case-insensitive match. Map key-value pairs without corresponding struct fields are ignored. See DecOptions.ExtraReturnErrors to return error at unknown field.

To unmarshal a CBOR text string into a time.Time value, Unmarshal parses text string formatted in RFC3339. To unmarshal a CBOR integer/float into a time.Time value, Unmarshal creates an unix time with integer/float as seconds and fractional seconds since January 1, 1970 UTC.

To unmarshal CBOR null (0xf6) and undefined (0xf7) values into a slice/map/pointer, Unmarshal sets Go value to nil. Because null is often used to mean "not present", unmarshalling CBOR null and undefined value into any other Go type has no effect and returns no error.

Unmarshal supports CBOR tag 55799 (self-describe CBOR), tag 0 and 1 (time), and tag 2 and 3 (bignum).

Example
type Animal struct {
	Age    int
	Name   string
	Owners []string
	Male   bool
}
cborData, _ := hex.DecodeString("a46341676504644e616d656543616e6479664f776e65727382644d617279634a6f65644d616c65f4")
var animal Animal
err := cbor.Unmarshal(cborData, &animal)
if err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v", animal)
Output:

{Age:4 Name:Candy Owners:[Mary Joe] Male:false}
Example (Time)
cborRFC3339Time, _ := hex.DecodeString("74323031332d30332d32315432303a30343a30305a")
tm := time.Time{}
if err := cbor.Unmarshal(cborRFC3339Time, &tm); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v\n", tm.UTC().Format(time.RFC3339Nano))
cborUnixTime, _ := hex.DecodeString("1a514b67b0")
tm = time.Time{}
if err := cbor.Unmarshal(cborUnixTime, &tm); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%+v\n", tm.UTC().Format(time.RFC3339Nano))
Output:

2013-03-21T20:04:00Z
2013-03-21T20:04:00Z

func Valid added in v2.3.0

func Valid(data []byte) error

Valid checks whether the CBOR data is complete and well-formed.

Types

type BigIntConvertMode added in v2.3.0

type BigIntConvertMode int

BigIntConvertMode specifies how to encode big.Int values.

const (
	// BigIntConvertShortest makes big.Int encode to CBOR integer if value fits.
	// E.g. if big.Int value can be converted to CBOR integer while preserving
	// value, encoder will encode it to CBOR interger (major type 0 or 1).
	BigIntConvertShortest BigIntConvertMode = iota

	// BigIntConvertNone makes big.Int encode to CBOR bignum (tag 2 or 3) without
	// converting it to another CBOR type.
	BigIntConvertNone
)

type DecMode

type DecMode interface {
	// Unmarshal parses the CBOR-encoded data into the value pointed to by v
	// using the decoding mode.  If v is nil, not a pointer, or a nil pointer,
	// Unmarshal returns an error.
	//
	// See the documentation for Unmarshal for details.
	Unmarshal(data []byte, v interface{}) error
	// Valid checks whether the CBOR data is complete and well-formed.
	Valid(data []byte) error
	// NewDecoder returns a new decoder that reads from r using dm DecMode.
	NewDecoder(r io.Reader) *Decoder
	// DecOptions returns user specified options used to create this DecMode.
	DecOptions() DecOptions
}

DecMode is the main interface for CBOR decoding.

type DecOptions

type DecOptions struct {
	// DupMapKey specifies whether to enforce duplicate map key.
	DupMapKey DupMapKeyMode

	// TimeTag specifies whether to check validity of time.Time (e.g. valid tag number and tag content type).
	// For now, valid tag number means 0 or 1 as specified in RFC 7049 if the Go type is time.Time.
	TimeTag DecTagMode

	// MaxNestedLevels specifies the max nested levels allowed for any combination of CBOR array, maps, and tags.
	// Default is 32 levels and it can be set to [4, 256].
	MaxNestedLevels int

	// MaxArrayElements specifies the max number of elements for CBOR arrays.
	// Default is 128*1024=131072 and it can be set to [16, 2147483647]
	MaxArrayElements int

	// MaxMapPairs specifies the max number of key-value pairs for CBOR maps.
	// Default is 128*1024=131072 and it can be set to [16, 2147483647]
	MaxMapPairs int

	// IndefLength specifies whether to allow indefinite length CBOR items.
	IndefLength IndefLengthMode

	// TagsMd specifies whether to allow CBOR tags (major type 6).
	TagsMd TagsMode

	// IntDec specifies which Go integer type (int64 or uint64) to use
	// when decoding CBOR int (major type 0 and 1) to Go interface{}.
	IntDec IntDecMode

	// ExtraReturnErrors specifies extra conditions that should be treated as errors.
	ExtraReturnErrors ExtraDecErrorCond

	// DefaultMapType specifies Go map type to create and decode to
	// when unmarshalling CBOR into an empty interface value.
	// By default, unmarshal uses map[interface{}]interface{}.
	DefaultMapType reflect.Type
}

DecOptions specifies decoding options.

func (DecOptions) DecMode

func (opts DecOptions) DecMode() (DecMode, error)

DecMode returns DecMode with immutable options and no tags (safe for concurrency).

func (DecOptions) DecModeWithSharedTags added in v2.1.0

func (opts DecOptions) DecModeWithSharedTags(tags TagSet) (DecMode, error)

DecModeWithSharedTags returns DecMode with immutable options and mutable shared tags (safe for concurrency).

func (DecOptions) DecModeWithTags added in v2.1.0

func (opts DecOptions) DecModeWithTags(tags TagSet) (DecMode, error)

DecModeWithTags returns DecMode with options and tags that are both immutable (safe for concurrency).

type DecTagMode added in v2.1.0

type DecTagMode int

DecTagMode specifies how decoder handles tag number.

const (
	// DecTagIgnored makes decoder ignore tag number (skips if present).
	DecTagIgnored DecTagMode = iota

	// DecTagOptional makes decoder verify tag number if it's present.
	DecTagOptional

	// DecTagRequired makes decoder verify tag number and tag number must be present.
	DecTagRequired
)

type Decoder

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

Decoder reads and decodes CBOR values from io.Reader.

Example
type Animal struct {
	Age    int
	Name   string
	Owners []string
	Male   bool
}
cborData, _ := hex.DecodeString("a46341676504644d616c65f4644e616d656543616e6479664f776e65727382644d617279634a6f65a46341676506644d616c65f5644e616d656452756479664f776e657273816543696e6479a46341676502644d616c65f5644e616d656444756b65664f776e65727381664e6f72746f6e")
dec := cbor.NewDecoder(bytes.NewReader(cborData))
for {
	var animal Animal
	if err := dec.Decode(&animal); err != nil {
		if err != io.EOF {
			fmt.Println("error:", err)
		}
		break
	}
	fmt.Printf("%+v\n", animal)
}
Output:

{Age:4 Name:Candy Owners:[Mary Joe] Male:false}
{Age:6 Name:Rudy Owners:[Cindy] Male:true}
{Age:2 Name:Duke Owners:[Norton] Male:true}

func NewDecoder

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new decoder that reads and decodes from r using the default decoding options.

func (*Decoder) Decode

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

Decode reads CBOR value and decodes it into the value pointed to by v.

func (*Decoder) NumBytesRead

func (dec *Decoder) NumBytesRead() int

NumBytesRead returns the number of bytes read.

type DupMapKeyError added in v2.1.0

type DupMapKeyError struct {
	Key   interface{}
	Index int
}

DupMapKeyError describes detected duplicate map key in CBOR map.

func (*DupMapKeyError) Error added in v2.1.0

func (e *DupMapKeyError) Error() string

type DupMapKeyMode added in v2.1.0

type DupMapKeyMode int

DupMapKeyMode specifies how to enforce duplicate map key.

const (
	// DupMapKeyQuiet doesn't enforce duplicate map key. Decoder quietly (no error)
	// uses faster of "keep first" or "keep last" depending on Go data type and other factors.
	DupMapKeyQuiet DupMapKeyMode = iota

	// DupMapKeyEnforcedAPF enforces detection and rejection of duplicate map keys.
	// APF means "Allow Partial Fill" and the destination map or struct can be partially filled.
	// If a duplicate map key is detected, DupMapKeyError is returned without further decoding
	// of the map. It's the caller's responsibility to respond to DupMapKeyError by
	// discarding the partially filled result if their protocol requires it.
	// WARNING: using DupMapKeyEnforcedAPF will decrease performance and increase memory use.
	DupMapKeyEnforcedAPF
)

type EncMode

type EncMode interface {
	Marshal(v interface{}) ([]byte, error)
	NewEncoder(w io.Writer) *Encoder
	EncOptions() EncOptions
}

EncMode is the main interface for CBOR encoding.

type EncOptions

type EncOptions struct {
	// Sort specifies sorting order.
	Sort SortMode

	// ShortestFloat specifies the shortest floating-point encoding that preserves
	// the value being encoded.
	ShortestFloat ShortestFloatMode

	// NaNConvert specifies how to encode NaN and it overrides ShortestFloatMode.
	NaNConvert NaNConvertMode

	// InfConvert specifies how to encode Inf and it overrides ShortestFloatMode.
	InfConvert InfConvertMode

	// BigIntConvert specifies how to encode big.Int values.
	BigIntConvert BigIntConvertMode

	// Time specifies how to encode time.Time.
	Time TimeMode

	// TimeTag allows time.Time to be encoded with a tag number.
	// RFC3339 format gets tag number 0, and numeric epoch time tag number 1.
	TimeTag EncTagMode

	// IndefLength specifies whether to allow indefinite length CBOR items.
	IndefLength IndefLengthMode

	// TagsMd specifies whether to allow CBOR tags (major type 6).
	TagsMd TagsMode
}

EncOptions specifies encoding options.

func CTAP2EncOptions

func CTAP2EncOptions() EncOptions

CTAP2EncOptions returns EncOptions for "CTAP2 Canonical CBOR" encoding, defined in CTAP specification, with the following rules:

  1. "Integers must be encoded as small as possible."
  2. "The representations of any floating-point values are not changed."
  3. "The expression of lengths in major types 2 through 5 must be as short as possible."
  4. "Indefinite-length items must be made into definite-length items.""
  5. The keys in every map must be sorted in bytewise lexicographic order. See SortBytewiseLexical for details.
  6. "Tags as defined in Section 2.4 in [RFC7049] MUST NOT be present."

func CanonicalEncOptions

func CanonicalEncOptions() EncOptions

CanonicalEncOptions returns EncOptions for "Canonical CBOR" encoding, defined in RFC 7049 Section 3.9 with the following rules:

  1. "Integers must be as small as possible."
  2. "The expression of lengths in major types 2 through 5 must be as short as possible."
  3. The keys in every map must be sorted in length-first sorting order. See SortLengthFirst for details.
  4. "Indefinite-length items must be made into definite-length items."
  5. "If a protocol allows for IEEE floats, then additional canonicalization rules might need to be added. One example rule might be to have all floats start as a 64-bit float, then do a test conversion to a 32-bit float; if the result is the same numeric value, use the shorter value and repeat the process with a test conversion to a 16-bit float. (This rule selects 16-bit float for positive and negative Infinity as well.) Also, there are many representations for NaN. If NaN is an allowed value, it must always be represented as 0xf97e00."

func CoreDetEncOptions

func CoreDetEncOptions() EncOptions

CoreDetEncOptions returns EncOptions for "Core Deterministic" encoding, defined in RFC 7049bis with the following rules:

  1. "Preferred serialization MUST be used. In particular, this means that arguments (see Section 3) for integers, lengths in major types 2 through 5, and tags MUST be as short as possible" "Floating point values also MUST use the shortest form that preserves the value"
  2. "Indefinite-length items MUST NOT appear."
  3. "The keys in every map MUST be sorted in the bytewise lexicographic order of their deterministic encodings."

func PreferredUnsortedEncOptions

func PreferredUnsortedEncOptions() EncOptions

PreferredUnsortedEncOptions returns EncOptions for "Preferred Serialization" encoding, defined in RFC 7049bis with the following rules:

  1. "The preferred serialization always uses the shortest form of representing the argument (Section 3);"
  2. "it also uses the shortest floating-point encoding that preserves the value being encoded (see Section 5.5)." "The preferred encoding for a floating-point value is the shortest floating-point encoding that preserves its value, e.g., 0xf94580 for the number 5.5, and 0xfa45ad9c00 for the number 5555.5, unless the CBOR-based protocol specifically excludes the use of the shorter floating-point encodings. For NaN values, a shorter encoding is preferred if zero-padding the shorter significand towards the right reconstitutes the original NaN value (for many applications, the single NaN encoding 0xf97e00 will suffice)."
  3. "Definite length encoding is preferred whenever the length is known at the time the serialization of the item starts."

func (EncOptions) EncMode

func (opts EncOptions) EncMode() (EncMode, error)

EncMode returns EncMode with immutable options and no tags (safe for concurrency).

func (EncOptions) EncModeWithSharedTags added in v2.1.0

func (opts EncOptions) EncModeWithSharedTags(tags TagSet) (EncMode, error)

EncModeWithSharedTags returns EncMode with immutable options and mutable shared tags (safe for concurrency).

func (EncOptions) EncModeWithTags added in v2.1.0

func (opts EncOptions) EncModeWithTags(tags TagSet) (EncMode, error)

EncModeWithTags returns EncMode with options and tags that are both immutable (safe for concurrency).

type EncTagMode added in v2.1.0

type EncTagMode int

EncTagMode specifies how encoder handles tag number.

const (
	// EncTagNone makes encoder not encode tag number.
	EncTagNone EncTagMode = iota

	// EncTagRequired makes encoder encode tag number.
	EncTagRequired
)

type Encoder

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

Encoder writes CBOR values to io.Writer.

Example
type Animal struct {
	Age    int
	Name   string
	Owners []string
	Male   bool
}
animals := []Animal{
	{Age: 4, Name: "Candy", Owners: []string{"Mary", "Joe"}, Male: false},
	{Age: 6, Name: "Rudy", Owners: []string{"Cindy"}, Male: true},
	{Age: 2, Name: "Duke", Owners: []string{"Norton"}, Male: true},
}
var buf bytes.Buffer
em, err := cbor.CanonicalEncOptions().EncMode()
if err != nil {
	fmt.Println("error:", err)
}
enc := em.NewEncoder(&buf)
for _, animal := range animals {
	err := enc.Encode(animal)
	if err != nil {
		fmt.Println("error:", err)
	}
}
fmt.Printf("%x\n", buf.Bytes())
Output:

a46341676504644d616c65f4644e616d656543616e6479664f776e65727382644d617279634a6f65a46341676506644d616c65f5644e616d656452756479664f776e657273816543696e6479a46341676502644d616c65f5644e616d656444756b65664f776e65727381664e6f72746f6e
Example (IndefiniteLengthArray)

ExampleEncoder_indefiniteLengthArray encodes a stream of elements as an indefinite length array. Encoder supports nested indefinite length values.

var buf bytes.Buffer
enc := cbor.NewEncoder(&buf)
// Start indefinite length array encoding.
if err := enc.StartIndefiniteArray(); err != nil {
	fmt.Println("error:", err)
}
// Encode array element.
if err := enc.Encode(1); err != nil {
	fmt.Println("error:", err)
}
// Encode array element.
if err := enc.Encode([]int{2, 3}); err != nil {
	fmt.Println("error:", err)
}
// Start a nested indefinite length array as array element.
if err := enc.StartIndefiniteArray(); err != nil {
	fmt.Println("error:", err)
}
// Encode nested array element.
if err := enc.Encode(4); err != nil {
	fmt.Println("error:", err)
}
// Encode nested array element.
if err := enc.Encode(5); err != nil {
	fmt.Println("error:", err)
}
// Close nested indefinite length array.
if err := enc.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
// Close outer indefinite length array.
if err := enc.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", buf.Bytes())
Output:

9f018202039f0405ffff
Example (IndefiniteLengthByteString)

ExampleEncoder_indefiniteLengthByteString encodes a stream of definite length byte string ("chunks") as an indefinite length byte string.

var buf bytes.Buffer
encoder := cbor.NewEncoder(&buf)
// Start indefinite length byte string encoding.
if err := encoder.StartIndefiniteByteString(); err != nil {
	fmt.Println("error:", err)
}
// Encode definite length byte string.
if err := encoder.Encode([]byte{1, 2}); err != nil {
	fmt.Println("error:", err)
}
// Encode definite length byte string.
if err := encoder.Encode([3]byte{3, 4, 5}); err != nil {
	fmt.Println("error:", err)
}
// Close indefinite length byte string.
if err := encoder.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", buf.Bytes())
Output:

5f42010243030405ff
Example (IndefiniteLengthMap)

ExampleEncoder_indefiniteLengthMap encodes a stream of elements as an indefinite length map. Encoder supports nested indefinite length values.

var buf bytes.Buffer
em, err := cbor.EncOptions{Sort: cbor.SortCanonical}.EncMode()
if err != nil {
	fmt.Println("error:", err)
}
enc := em.NewEncoder(&buf)
// Start indefinite length map encoding.
if err := enc.StartIndefiniteMap(); err != nil {
	fmt.Println("error:", err)
}
// Encode map key.
if err := enc.Encode("a"); err != nil {
	fmt.Println("error:", err)
}
// Encode map value.
if err := enc.Encode(1); err != nil {
	fmt.Println("error:", err)
}
// Encode map key.
if err := enc.Encode("b"); err != nil {
	fmt.Println("error:", err)
}
// Start an indefinite length array as map value.
if err := enc.StartIndefiniteArray(); err != nil {
	fmt.Println("error:", err)
}
// Encoded array element.
if err := enc.Encode(2); err != nil {
	fmt.Println("error:", err)
}
// Encoded array element.
if err := enc.Encode(3); err != nil {
	fmt.Println("error:", err)
}
// Close indefinite length array.
if err := enc.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
// Close indefinite length map.
if err := enc.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", buf.Bytes())
Output:

bf61610161629f0203ffff
Example (IndefiniteLengthTextString)

ExampleEncoder_indefiniteLengthTextString encodes a stream of definite length text string ("chunks") as an indefinite length text string.

var buf bytes.Buffer
encoder := cbor.NewEncoder(&buf)
// Start indefinite length text string encoding.
if err := encoder.StartIndefiniteTextString(); err != nil {
	fmt.Println("error:", err)
}
// Encode definite length text string.
if err := encoder.Encode("strea"); err != nil {
	fmt.Println("error:", err)
}
// Encode definite length text string.
if err := encoder.Encode("ming"); err != nil {
	fmt.Println("error:", err)
}
// Close indefinite length text string.
if err := encoder.EndIndefinite(); err != nil {
	fmt.Println("error:", err)
}
fmt.Printf("%x\n", buf.Bytes())
Output:

7f657374726561646d696e67ff

func NewEncoder

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w using the default encoding options.

func (*Encoder) Encode

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

Encode writes the CBOR encoding of v.

func (*Encoder) EndIndefinite

func (enc *Encoder) EndIndefinite() error

EndIndefinite closes last opened indefinite length value.

func (*Encoder) StartIndefiniteArray

func (enc *Encoder) StartIndefiniteArray() error

StartIndefiniteArray starts array encoding of indefinite length. Subsequent calls of (*Encoder).Encode() encodes elements of the array until EndIndefinite is called.

func (*Encoder) StartIndefiniteByteString

func (enc *Encoder) StartIndefiniteByteString() error

StartIndefiniteByteString starts byte string encoding of indefinite length. Subsequent calls of (*Encoder).Encode() encodes definite length byte strings ("chunks") as one continguous string until EndIndefinite is called.

func (*Encoder) StartIndefiniteMap

func (enc *Encoder) StartIndefiniteMap() error

StartIndefiniteMap starts array encoding of indefinite length. Subsequent calls of (*Encoder).Encode() encodes elements of the map until EndIndefinite is called.

func (*Encoder) StartIndefiniteTextString

func (enc *Encoder) StartIndefiniteTextString() error

StartIndefiniteTextString starts text string encoding of indefinite length. Subsequent calls of (*Encoder).Encode() encodes definite length text strings ("chunks") as one continguous string until EndIndefinite is called.

type ExtraDecErrorCond added in v2.3.0

type ExtraDecErrorCond uint

ExtraDecErrorCond specifies extra conditions that should be treated as errors.

const ExtraDecErrorNone ExtraDecErrorCond = 0

ExtraDecErrorNone indicates no extra error condition.

const (
	// ExtraDecErrorUnknownField indicates error condition when destination
	// Go struct doesn't have a field matching a CBOR map key.
	ExtraDecErrorUnknownField ExtraDecErrorCond = 1 << iota
)

type IndefLengthMode added in v2.2.0

type IndefLengthMode int

IndefLengthMode specifies whether to allow indefinite length items.

const (
	// IndefLengthAllowed allows indefinite length items.
	IndefLengthAllowed IndefLengthMode = iota

	// IndefLengthForbidden disallows indefinite length items.
	IndefLengthForbidden
)

type IndefiniteLengthError added in v2.2.0

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

IndefiniteLengthError indicates found disallowed indefinite length items.

func (*IndefiniteLengthError) Error added in v2.2.0

func (e *IndefiniteLengthError) Error() string

type InfConvertMode

type InfConvertMode int

InfConvertMode specifies how to encode Infinity and overrides ShortestFloatMode. ShortestFloatMode is not used for encoding Infinity and NaN values.

const (
	// InfConvertFloat16 always converts Inf to lossless IEEE binary16 (float16).
	InfConvertFloat16 InfConvertMode = iota

	// InfConvertNone never converts (used by CTAP2 Canonical CBOR).
	InfConvertNone
)

type IntDecMode added in v2.3.0

type IntDecMode int

IntDecMode specifies which Go int type (int64 or uint64) should be used when decoding CBOR int (major type 0 and 1) to Go interface{}.

const (
	// IntDecConvertNone affects how CBOR int (major type 0 and 1) decodes to Go interface{}.
	// It makes CBOR positive int (major type 0) decode to uint64 value, and
	// CBOR negative int (major type 1) decode to int64 value.
	IntDecConvertNone IntDecMode = iota

	// IntDecConvertSigned affects how CBOR int (major type 0 and 1) decodes to Go interface{}.
	// It makes CBOR positive/negative int (major type 0 and 1) decode to int64 value.
	// If value overflows int64, UnmarshalTypeError is returned.
	IntDecConvertSigned
)

type InvalidUnmarshalError

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

InvalidUnmarshalError describes an invalid argument passed to Unmarshal.

func (*InvalidUnmarshalError) Error

func (e *InvalidUnmarshalError) Error() string

type Marshaler

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

Marshaler is the interface implemented by types that can marshal themselves into valid CBOR.

type MaxArrayElementsError added in v2.2.0

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

MaxArrayElementsError indicates exceeded max number of elements for CBOR arrays.

func (*MaxArrayElementsError) Error added in v2.2.0

func (e *MaxArrayElementsError) Error() string

type MaxMapPairsError added in v2.2.0

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

MaxMapPairsError indicates exceeded max number of key-value pairs for CBOR maps.

func (*MaxMapPairsError) Error added in v2.2.0

func (e *MaxMapPairsError) Error() string

type MaxNestedLevelError added in v2.2.0

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

MaxNestedLevelError indicates exceeded max nested level of any combination of CBOR arrays/maps/tags.

func (*MaxNestedLevelError) Error added in v2.2.0

func (e *MaxNestedLevelError) Error() string

type NaNConvertMode

type NaNConvertMode int

NaNConvertMode specifies how to encode NaN and overrides ShortestFloatMode. ShortestFloatMode is not used for encoding Infinity and NaN values.

const (
	// NaNConvert7e00 always encodes NaN to 0xf97e00 (CBOR float16 = 0x7e00).
	NaNConvert7e00 NaNConvertMode = iota

	// NaNConvertNone never modifies or converts NaN to other representations
	// (float64 NaN stays float64, etc. even if it can use float16 without losing
	// any bits).
	NaNConvertNone

	// NaNConvertPreserveSignal converts NaN to the smallest form that preserves
	// value (quiet bit + payload) as described in RFC 7049bis Draft 12.
	NaNConvertPreserveSignal

	// NaNConvertQuiet always forces quiet bit = 1 and shortest form that preserves
	// NaN payload.
	NaNConvertQuiet
)

type RawMessage

type RawMessage []byte

RawMessage is a raw encoded CBOR value.

func (RawMessage) MarshalCBOR

func (m RawMessage) MarshalCBOR() ([]byte, error)

MarshalCBOR returns m or CBOR nil if m is nil.

func (*RawMessage) UnmarshalCBOR

func (m *RawMessage) UnmarshalCBOR(data []byte) error

UnmarshalCBOR creates a copy of data and saves to *m.

type RawTag added in v2.1.0

type RawTag struct {
	Number  uint64
	Content RawMessage
}

RawTag represents CBOR tag data, including tag number and raw tag content. RawTag implements Unmarshaler and Marshaler interfaces.

func (RawTag) MarshalCBOR added in v2.1.0

func (t RawTag) MarshalCBOR() ([]byte, error)

MarshalCBOR returns CBOR encoding of t.

func (*RawTag) UnmarshalCBOR added in v2.1.0

func (t *RawTag) UnmarshalCBOR(data []byte) error

UnmarshalCBOR sets *t with tag number and raw tag content copied from data.

type SemanticError

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

SemanticError is a description of a CBOR semantic error.

func (*SemanticError) Error

func (e *SemanticError) Error() string

type ShortestFloatMode

type ShortestFloatMode int

ShortestFloatMode specifies which floating-point format should be used as the shortest possible format for CBOR encoding. It is not used for encoding Infinity and NaN values.

const (
	// ShortestFloatNone makes float values encode without any conversion.
	// This is the default for ShortestFloatMode in v1.
	// E.g. a float32 in Go will encode to CBOR float32.  And
	// a float64 in Go will encode to CBOR float64.
	ShortestFloatNone ShortestFloatMode = iota

	// ShortestFloat16 specifies float16 as the shortest form that preserves value.
	// E.g. if float64 can convert to float32 while preserving value, then
	// encoding will also try to convert float32 to float16.  So a float64 might
	// encode as CBOR float64, float32 or float16 depending on the value.
	ShortestFloat16
)

type SortMode

type SortMode int

SortMode identifies supported sorting order.

const (
	// SortNone means no sorting.
	SortNone SortMode = 0

	// SortLengthFirst causes map keys or struct fields to be sorted such that:
	//     - If two keys have different lengths, the shorter one sorts earlier;
	//     - If two keys have the same length, the one with the lower value in
	//       (byte-wise) lexical order sorts earlier.
	// It is used in "Canonical CBOR" encoding in RFC 7049 3.9.
	SortLengthFirst SortMode = 1

	// SortBytewiseLexical causes map keys or struct fields to be sorted in the
	// bytewise lexicographic order of their deterministic CBOR encodings.
	// It is used in "CTAP2 Canonical CBOR" and "Core Deterministic Encoding"
	// in RFC 7049bis.
	SortBytewiseLexical SortMode = 2

	// SortCanonical is used in "Canonical CBOR" encoding in RFC 7049 3.9.
	SortCanonical SortMode = SortLengthFirst

	// SortCTAP2 is used in "CTAP2 Canonical CBOR".
	SortCTAP2 SortMode = SortBytewiseLexical

	// SortCoreDeterministic is used in "Core Deterministic Encoding" in RFC 7049bis.
	SortCoreDeterministic SortMode = SortBytewiseLexical
)

type SyntaxError

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

SyntaxError is a description of a CBOR syntax error.

func (*SyntaxError) Error

func (e *SyntaxError) Error() string

type Tag added in v2.1.0

type Tag struct {
	Number  uint64
	Content interface{}
}

Tag represents CBOR tag data, including tag number and unmarshaled tag content.

type TagOptions added in v2.1.0

type TagOptions struct {
	DecTag DecTagMode
	EncTag EncTagMode
}

TagOptions specifies how encoder and decoder handle tag number.

type TagSet added in v2.1.0

type TagSet interface {
	// Add adds given tag number(s), content type, and tag options to TagSet.
	Add(opts TagOptions, contentType reflect.Type, num uint64, nestedNum ...uint64) error

	// Remove removes given tag content type from TagSet.
	Remove(contentType reflect.Type)
	// contains filtered or unexported methods
}

TagSet is an interface to add and remove tag info. It is used by EncMode and DecMode to provide CBOR tag support.

func NewTagSet added in v2.1.0

func NewTagSet() TagSet

NewTagSet returns TagSet (safe for concurrency).

type TagsMdError added in v2.2.0

type TagsMdError struct {
}

TagsMdError indicates found disallowed CBOR tags.

func (*TagsMdError) Error added in v2.2.0

func (e *TagsMdError) Error() string

type TagsMode added in v2.2.0

type TagsMode int

TagsMode specifies whether to allow CBOR tags.

const (
	// TagsAllowed allows CBOR tags.
	TagsAllowed TagsMode = iota

	// TagsForbidden disallows CBOR tags.
	TagsForbidden
)

type TimeMode

type TimeMode int

TimeMode specifies how to encode time.Time values.

const (
	// TimeUnix causes time.Time to be encoded as epoch time in integer with second precision.
	TimeUnix TimeMode = iota

	// TimeUnixMicro causes time.Time to be encoded as epoch time in float-point rounded to microsecond precision.
	TimeUnixMicro

	// TimeUnixDynamic causes time.Time to be encoded as integer if time.Time doesn't have fractional seconds,
	// otherwise float-point rounded to microsecond precision.
	TimeUnixDynamic

	// TimeRFC3339 causes time.Time to be encoded as RFC3339 formatted string with second precision.
	TimeRFC3339

	// TimeRFC3339Nano causes time.Time to be encoded as RFC3339 formatted string with nanosecond precision.
	TimeRFC3339Nano
)

type UnknownFieldError added in v2.3.0

type UnknownFieldError struct {
	Index int
}

UnknownFieldError describes detected unknown field in CBOR map when decoding to Go struct.

func (*UnknownFieldError) Error added in v2.3.0

func (e *UnknownFieldError) Error() string

type UnmarshalTypeError

type UnmarshalTypeError struct {
	CBORType        string // type of CBOR value
	GoType          string // type of Go value it could not be decoded into
	StructFieldName string // name of the struct field holding the Go value (optional)
	// contains filtered or unexported fields
}

UnmarshalTypeError describes a CBOR value that can't be decoded to a Go type.

func (*UnmarshalTypeError) Error

func (e *UnmarshalTypeError) Error() string

type Unmarshaler

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

Unmarshaler is the interface implemented by types that wish to unmarshal CBOR data themselves. The input is a valid CBOR value. UnmarshalCBOR must copy the CBOR data if it needs to use it after returning.

type UnsupportedTypeError

type UnsupportedTypeError struct {
	Type reflect.Type
}

UnsupportedTypeError is returned by Marshal when attempting to encode value of an unsupported type.

func (*UnsupportedTypeError) Error

func (e *UnsupportedTypeError) Error() string

type WrongTagError added in v2.1.0

type WrongTagError struct {
	RegisteredType   reflect.Type
	RegisteredTagNum []uint64
	TagNum           []uint64
}

WrongTagError describes mismatch between CBOR tag and registered tag.

func (*WrongTagError) Error added in v2.1.0

func (e *WrongTagError) Error() string

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