Documentation
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Overview ¶
Package cbordecode parses CBOR (Concise Binary Object Representation) per RFC 8949. CBOR is the binary JSON-like format used by COSE (signed/encrypted JWT alternative), WebAuthn / CTAP (FIDO2 hardware-token transport), Bluetooth Mesh, CoAP IoT payloads, MQTT-SN attribute encoding, and the "self-describing binary" of choice for any IoT / constrained-device flow since ~2014.
Wrap-vs-native judgement ¶
Native. CBOR is fully published in RFC 8949 with a clean 8-major-type scheme + a small dispatch table for the "additional information" sub-field that encodes either a direct argument value (0-23), a 1/2/4/8-byte argument (24/25/26/27), or an indefinite-length marker (31). Tagged values (major type 6) and simple values (major type 7) round out the model. Pasting a hex blob from a WebAuthn authenticator response, a CTAP request, a CoAP body, or any CBOR-emitting IoT device is enough — no library, no network, no key material.
What this package covers ¶
- **8 major types** per RFC 8949 §3:
- 0 unsigned integer (0..2^64-1).
- 1 negative integer (-1..-2^64).
- 2 byte string (rendered as hex; indefinite chunks concatenated).
- 3 text string (UTF-8; indefinite chunks concatenated).
- 4 array (recursive).
- 5 map (recursive; rendered as ordered list of key/value pairs to preserve duplicate keys + key ordering).
- 6 tagged value (semantic tag + nested value, with a ~30-entry well-known tag-name table).
- 7 simple value / float:
- 20 false / 21 true / 22 null / 23 undefined.
- 24 simple value (1-byte argument).
- 25 IEEE 754 half-precision float.
- 26 IEEE 754 single-precision float.
- 27 IEEE 754 double-precision float.
- 31 "break" stop code (for indefinite-length containers).
- **Argument encoding** (low 5 bits of initial byte): 0..23 direct, 24 = 1-byte uint8 follows, 25 = 2-byte uint16, 26 = 4-byte uint32, 27 = 8-byte uint64, 31 = indefinite-length marker (for byte strings / text strings / arrays / maps).
- **Indefinite-length containers**: byte/text-string chunks concatenated until 0xFF break; arrays / maps walk children until the same break code.
- **Tagged values**: ~30-entry well-known tag table covering the RFC 8949 §3.4 standard tags (0 RFC 3339 date-time string / 1 epoch-time / 2/3 unsigned/negative bignum / 4 decimal fraction / 5 bigfloat / 21/22/23 expected-base64url/base64/base16 / 24 encoded CBOR data / 32 URI / 33 base64url text / 34 base64 text / 35 regex / 36 MIME / 55799 self-describe-CBOR magic), plus the COSE tags (16 Encrypt0 / 17 Mac0 / 18 Sign1 / 96 Encrypt / 97 Mac / 98 Sign) and the WebAuthn CTAP-specific tag 24 (encoded-CBOR-data-item).
- **Floats**: IEEE 754 half precision (16-bit), single (32-bit), and double (64-bit) with NaN / Inf detection.
What this package does NOT cover (deliberately out of scope) ¶
- COSE message body decode beyond the tag — the wrapped COSE_Encrypt0 / COSE_Sign1 / etc. structures are arrays whose contents are themselves CBOR; the outer tag + array is decoded, but COSE-specific semantics (protected header / unprotected header / payload / signature) are not interpreted as named fields.
- WebAuthn / CTAP request-body schema knowledge — the CBOR is decoded as a map, but the field meanings (authData / publicKey / clientDataJSON / etc.) are not annotated.
- Strict mode validation (RFC 8949 §3.1 well-formed + §5.4 deterministic encoding) — we accept any well- formed input even if not minimally encoded; explicit non-conforming inputs (e.g. arg 24 with value < 24) are decoded as-is.
- CDDL (Concise Data Definition Language, RFC 8610) schema validation — pure decode only.
Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type Value ¶
type Value struct {
MajorType int `json:"major_type"`
MajorName string `json:"major_name"`
Uint *uint64 `json:"uint,omitempty"`
Int *int64 `json:"int,omitempty"`
Bytes string `json:"bytes_hex,omitempty"`
Text string `json:"text,omitempty"`
Array []*Value `json:"array,omitempty"`
Map []*MapEntry `json:"map,omitempty"`
Tag *uint64 `json:"tag,omitempty"`
TagName string `json:"tag_name,omitempty"`
TagValue *Value `json:"tag_value,omitempty"`
Simple *uint8 `json:"simple_value,omitempty"`
SimpleName string `json:"simple_name,omitempty"`
Float *float64 `json:"float,omitempty"`
FloatSpec string `json:"float_special,omitempty"`
Indefinite bool `json:"indefinite,omitempty"`
}
Value is the recursive decoded view of one CBOR data item.
Only the fields that match MajorType are populated; the others are zero/nil.
func Decode ¶
Decode parses a hex-encoded CBOR data item. Trailing bytes after the first item are rejected.
func DecodeBytes ¶
DecodeBytes parses a raw CBOR byte buffer into a single data item. Use DecodeStream if multiple items are expected.
func (*Value) AsInt ¶ added in v0.764.0
AsInt returns the value as a signed int64 when it is a CBOR unsigned or negative integer (major types 0 and 1), reporting ok=false otherwise — for a nil value, a non-integer item, or an unsigned value that exceeds math.MaxInt64. It is the common accessor for CBOR maps keyed or valued by integers, such as COSE / CWT label maps. A nil receiver is safe.
Source Files