bacnet_encoding/constructed/
read_access.rs

1//! `BACnetPropertyReference` and `ReadAccessSpecification` (ASHRAE 135-2020
2//! Clause 21), shared by the ReadPropertyMultiple request, the COV and Audit
3//! services and a Group object's List_Of_Group_Members (Clause 12.14.5).
4//!
5//! A property reference is the property identifier in context tag `[0]`,
6//! then an optional Unsigned array index in `[1]`. A specification is the
7//! object identifier in `[0]`, then its references back to back inside an
8//! opening/closing `[1]` pair.
9
10use bacnet_types::constructed::{PropertyReference, ReadAccessSpecification};
11use bacnet_types::enums::PropertyIdentifier;
12use bacnet_types::error::Error;
13use bytes::BytesMut;
14
15use super::tagged::{
16    decode_ctx_object_id, decode_ctx_unsigned, decode_optional_ctx, expect_opening,
17};
18use super::MAX_FRAMED_ITEMS;
19use crate::{primitives, tags};
20
21/// Encode one `BACnetPropertyReference`, appending to `buf`.
22pub fn encode_property_reference(buf: &mut BytesMut, reference: &PropertyReference) {
23    primitives::encode_ctx_unsigned(buf, 0, u64::from(reference.property_identifier.to_raw()));
24    if let Some(index) = reference.property_array_index {
25        primitives::encode_ctx_unsigned(buf, 1, u64::from(index));
26    }
27}
28
29/// Decode one `BACnetPropertyReference` at `offset`; returns it and the
30/// offset just past it. The array index is read only when the next tag is a
31/// primitive context tag `[1]`, so a reference may end the input or be
32/// followed by anything else.
33///
34/// A member whose contents run past the end of `data` fails with
35/// [`Error::BufferTooShort`]; any other malformed input with
36/// [`Error::Decoding`].
37pub fn decode_property_reference(
38    data: &[u8],
39    offset: usize,
40) -> Result<(PropertyReference, usize), Error> {
41    const PROPERTY: &str = "PropertyReference property-id";
42    const INDEX: &str = "PropertyReference array-index";
43    let (property, next) = decode_ctx_unsigned::<u32>(data, offset, 0, PROPERTY)?;
44    let (property_array_index, offset) =
45        decode_optional_ctx(data, next, 1, INDEX, decode_ctx_unsigned::<u32>)?;
46    Ok((
47        PropertyReference {
48            property_identifier: PropertyIdentifier::from_raw(property),
49            property_array_index,
50        },
51        offset,
52    ))
53}
54
55/// Encode one `ReadAccessSpecification`, appending to `buf`. An empty
56/// reference list encodes as the bare `[1]` pair; the ReadPropertyMultiple
57/// request encoder is what refuses one.
58pub fn encode_read_access_specification(buf: &mut BytesMut, spec: &ReadAccessSpecification) {
59    primitives::encode_ctx_object_id(buf, 0, &spec.object_identifier);
60    tags::encode_opening_tag(buf, 1);
61    for reference in &spec.list_of_property_references {
62        encode_property_reference(buf, reference);
63    }
64    tags::encode_closing_tag(buf, 1);
65}
66
67/// Decode one `ReadAccessSpecification` at `offset`; returns it and the
68/// offset just past its closing `[1]` tag, so a sequence of them is walked
69/// by calling this at each element's start. Errors are as for
70/// [`decode_property_reference`].
71pub fn decode_read_access_specification(
72    data: &[u8],
73    offset: usize,
74) -> Result<(ReadAccessSpecification, usize), Error> {
75    const WHAT: &str = "ReadAccessSpecification";
76    let (object_identifier, end) = decode_ctx_object_id(data, offset, 0, WHAT)?;
77    let mut offset = expect_opening(data, end, 1, WHAT)?;
78    let mut list_of_property_references = Vec::new();
79    loop {
80        if offset >= data.len() {
81            return Err(Error::missing(
82                offset,
83                format!("{WHAT} missing closing tag 1"),
84            ));
85        }
86        if list_of_property_references.len() >= MAX_FRAMED_ITEMS {
87            return Err(Error::overflow(
88                offset,
89                format!("{WHAT} property references exceed the item limit"),
90            ));
91        }
92        let (tag, tag_end) = tags::decode_tag(data, offset)?;
93        if tag.is_closing_tag(1) {
94            offset = tag_end;
95            break;
96        }
97        let (reference, next) = decode_property_reference(data, offset)?;
98        list_of_property_references.push(reference);
99        offset = next;
100    }
101    Ok((
102        ReadAccessSpecification {
103            object_identifier,
104            list_of_property_references,
105        },
106        offset,
107    ))
108}
bacnet_encoding/constructed/read_access.rs

bacnet_encoding/constructed/
read_access.rs
