ciborium/value/
canonical.rs

1// SPDX-License-Identifier: Apache-2.0
2
3use crate::value::Value;
4use alloc::vec::Vec;
5use core::cmp::Ordering;
6use serde::{de, ser};
7
8/// Manually serialize values to compare them.
9fn serialized_canonical_cmp(v1: &Value, v2: &Value) -> Ordering {
10    // There is an optimization to be done here, but it would take a lot more code
11    // and using mixing keys, Arrays or Maps as CanonicalValue is probably not the
12    // best use of this type as it is meant mainly to be used as keys.
13
14    let mut bytes1 = Vec::new();
15    let _ = crate::ser::into_writer(v1, &mut bytes1);
16    let mut bytes2 = Vec::new();
17    let _ = crate::ser::into_writer(v2, &mut bytes2);
18
19    match bytes1.len().cmp(&bytes2.len()) {
20        Ordering::Equal => bytes1.cmp(&bytes2),
21        x => x,
22    }
23}
24
25/// Compares two values uses canonical comparison, as defined in both
26/// RFC 7049 Section 3.9 (regarding key sorting) and RFC 8949 4.2.3 (as errata).
27///
28/// In short, the comparison follow the following rules:
29///   - If two keys have different lengths, the shorter one sorts earlier;
30///   - If two keys have the same length, the one with the lower value in
31///     (byte-wise) lexical order sorts earlier.
32///
33/// This specific comparison allows Maps and sorting that respect these two rules.
34pub fn cmp_value(v1: &Value, v2: &Value) -> Ordering {
35    use Value::*;
36
37    match (v1, v2) {
38        (Integer(i), Integer(o)) => {
39            // Because of the first rule above, two numbers might be in a different
40            // order than regular i128 comparison. For example, 10 < -1 in
41            // canonical ordering, since 10 serializes to `0x0a` and -1 to `0x20`,
42            // and -1 < -1000 because of their lengths.
43            i.canonical_cmp(o)
44        }
45        (Text(s), Text(o)) => match s.len().cmp(&o.len()) {
46            Ordering::Equal => s.cmp(o),
47            x => x,
48        },
49        (Bool(s), Bool(o)) => s.cmp(o),
50        (Null, Null) => Ordering::Equal,
51        (Tag(t, v), Tag(ot, ov)) => match Value::from(*t).partial_cmp(&Value::from(*ot)) {
52            Some(Ordering::Equal) | None => match v.partial_cmp(ov) {
53                Some(x) => x,
54                None => serialized_canonical_cmp(v1, v2),
55            },
56            Some(x) => x,
57        },
58        (_, _) => serialized_canonical_cmp(v1, v2),
59    }
60}
61
62/// A CBOR Value that impl Ord and Eq to allow sorting of values as defined in both
63/// RFC 7049 Section 3.9 (regarding key sorting) and RFC 8949 4.2.3 (as errata).
64///
65/// Since a regular [Value] can be
66#[derive(Clone, Debug)]
67pub struct CanonicalValue(Value);
68
69impl PartialEq for CanonicalValue {
70    fn eq(&self, other: &Self) -> bool {
71        self.cmp(other) == Ordering::Equal
72    }
73}
74
75impl Eq for CanonicalValue {}
76
77impl From<Value> for CanonicalValue {
78    fn from(v: Value) -> Self {
79        Self(v)
80    }
81}
82
83impl From<CanonicalValue> for Value {
84    fn from(v: CanonicalValue) -> Self {
85        v.0
86    }
87}
88
89impl ser::Serialize for CanonicalValue {
90    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
91    where
92        S: ser::Serializer,
93    {
94        self.0.serialize(serializer)
95    }
96}
97
98impl<'de> de::Deserialize<'de> for CanonicalValue {
99    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
100    where
101        D: de::Deserializer<'de>,
102    {
103        Value::deserialize(deserializer).map(Into::into)
104    }
105
106    fn deserialize_in_place<D>(deserializer: D, place: &mut Self) -> Result<(), D::Error>
107    where
108        D: de::Deserializer<'de>,
109    {
110        Value::deserialize_in_place(deserializer, &mut place.0)
111    }
112}
113
114impl Ord for CanonicalValue {
115    fn cmp(&self, other: &Self) -> Ordering {
116        cmp_value(&self.0, &other.0)
117    }
118}
119
120impl PartialOrd for CanonicalValue {
121    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
122        Some(cmp_value(&self.0, &other.0))
123    }
124}
ciborium/value/canonical.rs

ciborium/value/
canonical.rs
