libipld_cbor/
cbor.rs

1//! CBOR helper types for encoding and decoding.
2use std::convert::TryFrom;
3
4use crate::error::UnexpectedCode;
5use libipld_core::ipld::Ipld;
6
7/// Represents a major "byte". This includes both the major bits and the additional info.
8#[repr(transparent)]
9#[derive(Clone, Copy, Eq, PartialEq)]
10pub struct Major(u8);
11
12/// The constant TRUE.
13pub const FALSE: Major = Major::new(MajorKind::Other, 20);
14/// The constant FALSE.
15pub const TRUE: Major = Major::new(MajorKind::Other, 21);
16/// The constant NULL.
17pub const NULL: Major = Major::new(MajorKind::Other, 22);
18/// The major "byte" indicating that a 16 bit float follows.
19pub const F16: Major = Major::new(MajorKind::Other, 25);
20/// The major "byte" indicating that a 32 bit float follows.
21pub const F32: Major = Major::new(MajorKind::Other, 26);
22/// The major "byte" indicating that a 64 bit float follows.
23pub const F64: Major = Major::new(MajorKind::Other, 27);
24
25impl Major {
26    const fn new(kind: MajorKind, info: u8) -> Self {
27        Major(((kind as u8) << 5) | info)
28    }
29
30    /// Returns the major type.
31    #[inline(always)]
32    pub const fn kind(self) -> MajorKind {
33        // This is a 3 bit value, so value 0-7 are covered.
34        unsafe { std::mem::transmute(self.0 >> 5) }
35    }
36
37    /// Returns the additional info.
38    #[inline(always)]
39    pub const fn info(self) -> u8 {
40        self.0 & 0x1f
41    }
42
43    /// Interprets the additioanl info as a number of additional bytes that should be consumed.
44    #[inline(always)]
45    #[allow(clippy::len_without_is_empty)]
46    pub const fn len(self) -> u8 {
47        // All major types follow the same rules for "additioanl bytes".
48        // 24 -> 1, 25 -> 2, 26 -> 4, 27 -> 8
49        match self.info() {
50            info @ 24..=27 => 1 << (info - 24),
51            _ => 0,
52        }
53    }
54}
55
56impl From<Major> for u8 {
57    fn from(m: Major) -> u8 {
58        m.0
59    }
60}
61
62// This is the core of the validation logic. Every major type passes through here giving us a chance
63// to determine if it's something we allow.
64impl TryFrom<u8> for Major {
65    type Error = UnexpectedCode;
66    fn try_from(value: u8) -> Result<Self, Self::Error> {
67        // We don't allow any major types with additional info 28-31 inclusive.
68        // Or the bitmask 0b00011100 = 28.
69        if value & 28 == 28 {
70            return Err(UnexpectedCode::new::<Ipld>(value));
71        } else if (value >> 5) == MajorKind::Other as u8 {
72            match value & 0x1f {
73                // False, True, Null. TODO: Allow undefined?
74                20 | 21 | 22 => (),
75                // Floats. TODO: forbid f16 & f32?
76                25 | 26 | 27 => (),
77                // Everything is forbidden.
78                _ => {
79                    return Err(UnexpectedCode::new::<Ipld>(value));
80                }
81            }
82        }
83        Ok(Major(value))
84    }
85}
86
87/// The type
88#[repr(u8)]
89#[derive(Clone, Copy, Eq, PartialEq)]
90#[allow(dead_code)]
91pub enum MajorKind {
92    /// Non-negative integer (major type 0).
93    UnsignedInt = 0,
94    /// Negative integer (major type 1).
95    NegativeInt = 1,
96    /// Byte string (major type 2).
97    ByteString = 2,
98    /// Unicode text string (major type 3).
99    TextString = 3,
100    /// Array (major type 4).
101    Array = 4,
102    /// Map (major type 5).
103    Map = 5,
104    /// Tag (major type 6).
105    Tag = 6,
106    /// Other (major type 7).
107    Other = 7,
108}
libipld_cbor/cbor.rs

libipld_cbor/
cbor.rs
