NAME

CBOR::Simple - Simple codec for the CBOR serialization format

SYNOPSIS

use CBOR::Simple;

# Encode a Raku value to CBOR, or vice-versa
my $cbor = cbor-encode($value);
my $val1 = cbor-decode($cbor);               # Fails if more data past first decoded value
my $val2 = cbor-decode($cbor, my $pos = 0);  # Updates $pos after decoding first value

# By default, cbor-decode() marks partially corrupt parsed structures with
# Failure nodes at the point of corruption
my $bad  = cbor-decode(buf8.new(0x81 xx 3));  # [[[Failure]]]

# Callers can instead force throwing exceptions on any error
my $*CBOR_SIMPLE_FATAL_ERRORS = True;
my $bad  = cbor-decode(buf8.new(0x81 xx 3));  # BOOM!

# Decode CBOR into diagnostic text, used for checking encodings and complex structures
my $diag = cbor-diagnostic($cbor);

# Force the encoder to tag a value with a particular tag number
my $tagged = CBOR::Simple::Tagged.new(:$tag-number, :$value);
my $cbor   = cbor-encode($tagged);

DESCRIPTION

CBOR::Simple is an easy-to-use implementation of the core functionality of the CBOR serialization format, implementing the standard as of RFC 8949, plus a collection of common tag extensions as described below in TAG IMPLEMENTATION STATUS.

PERFORMANCE

CBOR::Simple is one of the fastest data structure serialization codecs available for Raku. It is comparable in round-trip speed to JSON::Fast for data structures that are the most JSON-friendly. For all other cases tested, CBOR::Simple produces smaller, higher fidelity encodings, faster. For more detail, and comparison with other Raku serialization codecs, see serializer-perf.

NYI

Currently known NOT to work:

• Any tag marked '✘' (valid but not yet supported) or 'D' (deprecated spec) in the ENCODE or DECODE column of the Tag Status Details table below, or any tag not explicitly listed therein, will be treated as an opaque tagged value rather than treated as a native type.

• Packed arrays of 128-bit floats (num128); these are not supported in Rakudo yet.

• Encoding finite 16-bit floats (num16); encoding 16-bit NaN and ±Inf, as well as decoding any num16 all work. This is a performance tradeoff rather than a technical limitation; detecting whether a finite num32 can be shrunk to 16 bits without losing information is costly and rarely results in space savings except in trivial cases (e.g. Nums containing only small integers).

TAG CONTENT STRICTNESS

When encoding, CBOR::Simple makes every attempt to encode tagged content strictly within the tag standards as written, always producing spec-compliant encoded values.

When decoding, CBOR::Simple will often slightly relax the allowed content types in tagged content, especially when later tag proposals made no change other than to extend the allowed content types and allocate a new tag number for that. In the extension case CBOR::Simple is likely to allow both the old and new tag to accept the same content domain when decoding.

For example, when encoding CBOR::Simple will always encode Instant or DateTime as a CBOR epoch-based date/time (tag 1), using standard integer or floating point content data. But when decoding, CBOR::Simple will accept any content that decodes properly as a Raku Real value -- and in particular will handle a CBOR Rational (tag 30) as another valid content type.

DATE, DATETIME, INSTANT

Raku's builtin time handling is richer than the default CBOR data model (though certain tag extensions improve this), so the following mappings apply:

• Encoding

  • Instant and DateTime are both written as tag 1 (epoch-based date/time) with integer (if lossless) or floating point content.

  • Other Dateish are written as tag 100 (RFC 8943 days since 1970-01-01).

• Decoding

  • Tag 0 (date/time string) is parsed as a DateTime.

  • Tag 1 (epoch-based date/time) is parsed via Instant.from-posix(), and handles any Real type in the tag content.

  • Tag 100 (days since 1970-01-01) is parsed via Date.new-from-daycount().

  • Tag 1004 (date string) is parsed as a Date.

UNDEFINED VALUES

• CBOR's null is translated as Any in Raku.

• CBOR's undefined is translated as Mu in Raku.

• A real Nil in an array (which must be bound, not assigned) is encoded as a CBOR Absent tag (31). Absent values will be recognized on decode as well, but since array contents are assigned into their parent array during decoding, a Nil in an array will be translated to Any by Raku's array assignment semantics.

OTHER SPECIAL CASES

• To mark a substructure for lazy decoding (treating it as an opaque Blob until explicitly decoded), use the tagged value idiom in the SYNOPSIS with :tag-number(24) (encoded CBOR value) or :tag-number(63) (encoded CBOR Sequence).

• CBOR strings claiming to be longer than 2⁶³-1 are treated as malformed.

• Bigfloats and decimal fractions (tags 4, 5, 264, 265) with very large exponents may result in numeric overflow when decoded.

• Keys for Associative types are sorted using Raku's internal sort method rather than the RFC 8949 default sort, because the latter is much slower.

• cbor-diagnostic() always adds encoding indicators for float values.

TAG IMPLEMENTATION STATUS

Note that unrecognized tags will decode to their contents wrapped with a CBOR::Simple::Tagged object that records its tag-number; check marks in the details table indicate conversion to/from an appropriate native Raku type rather than this default behavior.

Tag Status Overview: Native Raku Types

GROUP	SUPPORT	NOTES
Core	Good	Core RFC 8949 CBOR data model and syntax
Collections	Good	Sets, maps with only object or only string keys
Graph	NONE	Cyclic, indirected, and self-referential structures
Numbers	Good	Rational/BigInt/BigFloat support except non-finite triplets
Packed Arrays	Partial	Packed num16/32/64 arrays supported; packed int arrays not
Special Arrays	NONE	Explicit multi-dim/homogenous arrays
Tag Fallbacks	Good	Round tripping of unknown tagged content
Date/Time	Partial	All but tagged time (tags 1001-1003) supported

Tag Status Overview: Specialty Types

GROUP	SUPPORT	NOTES
Encodings	NONE	baseN, MIME, YANG, BER, non-UTF-8 strings
Geo	NONE	Geographic coordinates and shapes
Identifiers	NONE	URI, IRI, UUID, IPLD CID, general identifiers
Networking	NONE	IPv4/IPv6 addresses, subnets, and masks
Security	NONE	COSE and CWT
Specialty	NONE	IoT data, Openswan, PlatformV, DOTS, ERIS, RAINS
String Hints	NONE	JSON conversions, language tags, regex

Tag Status Details

SPEC	TAGS	ENCODE	DECODE	NOTES
RFC 8949	0	→	✓	DateTime strings → Encoded as tag 1
RFC 8949	1	✓	✓	DateTime/Instant
RFC 8949	2,3	✓	✓	(Big) Int
RFC 8949	4,5	→	✓	Big fractions → Encoded as tag 30
unassigned	6-15
COSE	16-18	✘	✘	MAC/Signatures
unassigned	19-20
RFC 8949	21-23	✘	✘	Expected JSON conversion to baseN
RFC 8949	24	T	✓	Encoded CBOR data item
[Lehmann]	25	✘	✘	String backrefs
[Lehmann]	26,27	✘	✘	General serialized objects
[Lehmann]	28,29	✘	✘	Shareable referenced values
[Occil]	30	✓	✓	Rational numbers
[Vaarala]	31	✓	*	Absent values
RFC 8949	32-34	✘	✘	URIs and base64 encoding
RFC 7094	35	D	D	PCRE/ECMA 262 regex (DEPRECATED)
RFC 8949	36	✘	✘	Text-based MIME message
[Clemente]	37	✘	✘	Binary UUID
[Occil]	38	✘	✘	Language-tagged string
[Clemente]	39	✘	✘	Identifier semantics
RFC 8746	40	✘	✘	Row-major multidim array
RFC 8746	41	✘	✘	Homogenous array
[Mische]	42	✘	✘	IPLD content identifier
[YANG]	43-47	✘	✘	YANG datatypes
unassigned	48-51
draft	52	D	D	IPv4 address/network (DEPRECATED)
unassigned	53
draft	54	D	D	IPv6 address/network (DEPRECATED)
unassigned	55-60
RFC 8392	61	✘	✘	CBOR Web Token (CWT)
unassigned	62
[Bormann]	63	T	✓	Encoded CBOR Sequence
RFC 8746	64-79	✘!	✘!	Packed int arrays
RFC 8746	80-87	✓	✓	Packed num arrays (except 128-bit)
unassigned	88-95
COSE	96-98	✘	✘	Encryption/MAC/Signatures
unassigned	99
RFC 8943	100	✓	✓	Date
unassigned	101-102
[Vidovic]	103	✘	✘	Geo coords
[Clarke]	104	✘	✘	Geo coords ref system WKT/EPSG
unassigned	105-109
RFC 9090	110-112	✘	✘	BER-encoded object ID
unassigned	113-119
[Vidovic]	120	✘	✘	IoT data point
unassigned	121-255
[Lehmann]	256	✘	✘	String backrefs (see tag 25)
[Occil]	257	✘	✘	Binary MIME message
[Napoli]	258	✓	✓	Set
[Holloway]	259	T	✓	Map with object keys
[Raju]	260-261	✘	✘	IPv4/IPv6/MAC address/network
[Raju]	262-263	✘	✘	Embedded JSON/hex strings
[Occil]	264-265	→	*	Extended fractions -> Encoded as tag 30
[Occil]	266-267	✘	✘	IRI/IRI reference
[Occil]	268-270	✘✘	✘✘	Triplet non-finite numerics
RFC 9132	271	✘✘	✘✘	DDoS Open Threat Signaling (DOTS)
[Vaarala]	272-274	✘	✘	Non-UTF-8 strings
[Cormier]	275	T	✓	Map with only string keys
[ERIS]	276	✘	✘	ERIS binary read capability
[Meins]	277-278	✘	✘	Geo area shape/velocity
unassigned	279-1000
[Bormann]	1001-1003	✘	✘	Extended time representations
RFC 8943	1004	→	✓	→ Encoded as tag 100
unassigned	1005-1039
RFC 8746	1040	✘	✘	Column-major multidim array
unassigned	1041-22097
[Lehmann]	22098	✘	✘	Hint for additional indirection
unassigned	22099-25440
[Broadwell]	25441	✓	✓	Capture: reference implementation
unassigned	25442-49999
[Tongzhou]	50000-50011	✘✘	✘✘	PlatformV
unassigned	50012-55798
RFC 8949	55799	✓	✓	Self-described CBOR
[Richardson]	55800	✓	✓	Self-described CBOR Sequence
unassigned	55801-65534
invalid	65535		✓	Invalid tag detected
unassigned	65536-15309735
[Trammell]	15309736	✘✘	✘✘	RAINS message
unassigned	15309737-1330664269
[Hussain]	1330664270	✘✘	✘✘	CBOR-encoded Openswan config file
unassigned	1330664271-4294967294
invalid	4294967295		✓	Invalid tag detected
unassigned	...
invalid	18446744073709551615		✓	Invalid tag detected

Tag Table Symbol Key

SYMBOL	MEANING
✓	Fully supported
*	Supported, but see notes below
T	Encoding supported by explicitly tagging contents
→	Raku values will be encoded using a different tag
D	Deprecated and unsupported tag spec; may eventually be decodable
✘	Not yet implemented
✘!	Not yet implemented, but already requested
✘?	Not yet implemented, but may be easy to add
✘✘	Probably won't be implemented in CBOR::Simple

AUTHOR

Geoffrey Broadwell [email protected]

COPYRIGHT AND LICENSE

Copyright 2021 Geoffrey Broadwell

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.