Module tags 

BACnet ASN.1 tag encoding and decoding per ASHRAE 135-2020 Clause 20.2.1.

BACnet uses a tag-length-value (TLV) encoding with two tag classes:

• Application tags identify the datatype (Null=0, Boolean=1, …, ObjectIdentifier=12)
• Context tags identify a field within a constructed type (tag number = field index)

Tags also support opening/closing markers for constructed (nested) values.

Modules

app_tag

Application tag numbers.

Structs

Tag

A decoded BACnet tag header.

Enums

TagClass

Tag class: application (datatype) or context (field identifier).

Constants

MAX_CONTEXT_NESTING_DEPTH

Maximum nesting depth for context tags to prevent stack overflow from crafted packets.

Functions

decode_tag

Decode a tag from data starting at offset.

encode_closing_tag

Encode a context-specific closing tag into a growable buffer.

encode_closing_tag_to_sink

Append a context closing marker and return its one- or two-byte length.

encode_opening_tag

Encode a context-specific opening tag into a growable buffer.

encode_opening_tag_to_sink

Append a context opening marker and return its one- or two-byte length.

encode_tag

Encode a tag header into the buffer.

encode_tag_to_sink

Append one tag header and return its byte count.

extract_context_value

Extract raw bytes enclosed by a context opening/closing tag pair.

extract_raw_context

Extract raw bytes enclosed by a context opening/closing tag pair WITHOUT parsing the enclosed content as BACnet tags.