ciborium_ll/
hdr.rs

1use super::*;
2
3use half::f16;
4
5/// A semantic representation of a CBOR item header
6///
7/// This structure represents the valid values of a CBOR item header and is
8/// used extensively when serializing or deserializing CBOR items. Note well
9/// that this structure **DOES NOT** represent the body (i.e. suffix) of the
10/// CBOR item. You must parse the body yourself based on the contents of the
11/// `Header`. However, utility functions are provided for this (see:
12/// `Decoder::bytes()` and `Decoder::text()`).
13#[derive(Copy, Clone, Debug, PartialEq)]
14pub enum Header {
15    /// A positive integer
16    Positive(u64),
17
18    /// A negative integer
19    ///
20    /// Note well that this value has all bits inverted from a normal signed
21    /// integer. For example, to convert the `u64` to a `i128` you would do
22    /// this: `neg as i128 ^ !0`.
23    Negative(u64),
24
25    /// A floating point value
26    Float(f64),
27
28    /// A "simple" value
29    Simple(u8),
30
31    /// A tag
32    Tag(u64),
33
34    /// The "break" value
35    ///
36    /// This value is used to terminate indefinite length arrays and maps,
37    /// as well as segmented byte or text items.
38    Break,
39
40    /// A bytes item
41    ///
42    /// The value contained in this variant indicates the length of the bytes
43    /// which follow or, if `None`, segmented bytes input.
44    ///
45    /// A best practice is to call `Decoder::bytes()` immediately after
46    /// first pulling a bytes item header since this utility function
47    /// encapsulates all the logic needed to handle segmentation.
48    Bytes(Option<usize>),
49
50    /// A text item
51    ///
52    /// The value contained in this variant indicates the length of the text
53    /// which follows (in bytes) or, if `None`, segmented text input.
54    ///
55    /// A best practice is to call `Decoder::text()` immediately after
56    /// first pulling a text item header since this utility function
57    /// encapsulates all the logic needed to handle segmentation.
58    Text(Option<usize>),
59
60    /// An array item
61    ///
62    /// The value contained in this variant indicates the length of the array
63    /// which follows (in items) or, if `None`, an indefinite length array
64    /// terminated by a "break" value.
65    Array(Option<usize>),
66
67    /// An map item
68    ///
69    /// The value contained in this variant indicates the length of the map
70    /// which follows (in item pairs) or, if `None`, an indefinite length map
71    /// terminated by a "break" value.
72    Map(Option<usize>),
73}
74
75impl TryFrom<Title> for Header {
76    type Error = InvalidError;
77
78    fn try_from(title: Title) -> Result<Self, Self::Error> {
79        let opt = |minor| {
80            Some(match minor {
81                Minor::This(x) => x.into(),
82                Minor::Next1(x) => u8::from_be_bytes(x).into(),
83                Minor::Next2(x) => u16::from_be_bytes(x).into(),
84                Minor::Next4(x) => u32::from_be_bytes(x).into(),
85                Minor::Next8(x) => u64::from_be_bytes(x),
86                Minor::More => return None,
87            })
88        };
89
90        let int = |m| opt(m).ok_or(InvalidError(()));
91
92        let len = |m| {
93            opt(m)
94                .map(usize::try_from)
95                .transpose()
96                .or(Err(InvalidError(())))
97        };
98
99        Ok(match title {
100            Title(Major::Positive, minor) => Self::Positive(int(minor)?),
101            Title(Major::Negative, minor) => Self::Negative(int(minor)?),
102            Title(Major::Bytes, minor) => Self::Bytes(len(minor)?),
103            Title(Major::Text, minor) => Self::Text(len(minor)?),
104            Title(Major::Array, minor) => Self::Array(len(minor)?),
105            Title(Major::Map, minor) => Self::Map(len(minor)?),
106            Title(Major::Tag, minor) => Self::Tag(int(minor)?),
107
108            Title(Major::Other, Minor::More) => Self::Break,
109            Title(Major::Other, Minor::This(x)) => Self::Simple(x),
110            Title(Major::Other, Minor::Next1(x)) => Self::Simple(x[0]),
111            Title(Major::Other, Minor::Next2(x)) => Self::Float(f16::from_be_bytes(x).into()),
112            Title(Major::Other, Minor::Next4(x)) => Self::Float(f32::from_be_bytes(x).into()),
113            Title(Major::Other, Minor::Next8(x)) => Self::Float(f64::from_be_bytes(x)),
114        })
115    }
116}
117
118impl From<Header> for Title {
119    fn from(header: Header) -> Self {
120        let int = |i: u64| match i {
121            x if x <= 23 => Minor::This(i as u8),
122            x if x <= core::u8::MAX as u64 => Minor::Next1([i as u8]),
123            x if x <= core::u16::MAX as u64 => Minor::Next2((i as u16).to_be_bytes()),
124            x if x <= core::u32::MAX as u64 => Minor::Next4((i as u32).to_be_bytes()),
125            x => Minor::Next8(x.to_be_bytes()),
126        };
127
128        let len = |l: Option<usize>| l.map(|x| int(x as u64)).unwrap_or(Minor::More);
129
130        match header {
131            Header::Positive(x) => Title(Major::Positive, int(x)),
132            Header::Negative(x) => Title(Major::Negative, int(x)),
133            Header::Bytes(x) => Title(Major::Bytes, len(x)),
134            Header::Text(x) => Title(Major::Text, len(x)),
135            Header::Array(x) => Title(Major::Array, len(x)),
136            Header::Map(x) => Title(Major::Map, len(x)),
137            Header::Tag(x) => Title(Major::Tag, int(x)),
138
139            Header::Break => Title(Major::Other, Minor::More),
140
141            Header::Simple(x) => match x {
142                x @ 0..=23 => Title(Major::Other, Minor::This(x)),
143                x => Title(Major::Other, Minor::Next1([x])),
144            },
145
146            Header::Float(n64) => {
147                let n16 = f16::from_f64(n64);
148                let n32 = n64 as f32;
149
150                Title(
151                    Major::Other,
152                    if f64::from(n16).to_bits() == n64.to_bits() {
153                        Minor::Next2(n16.to_be_bytes())
154                    } else if f64::from(n32).to_bits() == n64.to_bits() {
155                        Minor::Next4(n32.to_be_bytes())
156                    } else {
157                        Minor::Next8(n64.to_be_bytes())
158                    },
159                )
160            }
161        }
162    }
163}
ciborium_ll/hdr.rs

ciborium_ll/
hdr.rs
