1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164

use std::ops::{BitXor, BitXorAssign};

use massa_serialization::{Deserializer, SerializeError, Serializer};
use nom::{
    error::{context, ContextError, ParseError},
    IResult,
};

use crate::Hash;

/// Extended Hash
#[derive(Clone, Copy, PartialEq, Eq)]
pub struct HashXof<const SIZE: usize>(pub [u8; SIZE]);

impl<const SIZE: usize> HashXof<SIZE> {
    /// From bytes
    pub fn from_bytes(bytes: &[u8; SIZE]) -> Self {
        HashXof(*bytes)
    }

    /// Transform into bytes
    pub fn to_bytes(&self) -> &[u8; SIZE] {
        &self.0
    }

    /// Compute from raw data
    pub fn compute_from(data: &[u8]) -> HashXof<SIZE> {
        let mut hasher = blake3::Hasher::new();
        hasher.update(data);
        let mut hash = [0u8; SIZE];
        let mut output_reader = hasher.finalize_xof();
        output_reader.fill(&mut hash);
        HashXof(hash)
    }

    /// Compute from tuple of byte arrays
    pub fn compute_from_tuple(data: &[&[u8]]) -> Self {
        let mut hasher = blake3::Hasher::new();
        for d in data {
            hasher.update(&(d.len() as u64).to_be_bytes());
            hasher.update(d);
        }
        let mut hash = [0u8; SIZE];
        let mut output_reader = hasher.finalize_xof();
        output_reader.fill(&mut hash);
        HashXof(hash)
    }

    /// Serialize a Hash using `bs58` encoding with checksum.
    /// Motivations for using base58 encoding:
    ///
    /// base58_check is like base64 but-
    /// * fully standardized (no = vs /)
    /// * no weird characters (eg. +) only alphanumeric
    /// * ambiguous letters combined (eg. O vs 0, or l vs 1)
    /// * contains a checksum at the end to detect typing errors
    ///    
    pub fn to_bs58_check(&self) -> String {
        bs58::encode(self.0).with_check().into_string()
    }
}

// To use this xor operator you must ensure that you have all the criteria listed here :
// https://github.com/massalabs/massa/discussions/3852#discussioncomment-6188158
impl<const SIZE: usize> BitXorAssign for HashXof<SIZE> {
    fn bitxor_assign(&mut self, rhs: Self) {
        *self = *self ^ rhs;
    }
}

// To use this xor operator you must ensure that you have all the criteria listed here :
// https://github.com/massalabs/massa/discussions/3852#discussioncomment-6188158
impl<const SIZE: usize> BitXor for HashXof<SIZE> {
    type Output = Self;

    fn bitxor(self, other: Self) -> Self {
        let xored = self
            .0
            .iter()
            .zip(other.0.iter())
            .map(|(a, b)| a ^ b)
            .collect::<Vec<u8>>()
            .try_into()
            .unwrap();
        HashXof(xored)
    }
}

impl<const SIZE: usize> std::fmt::Display for HashXof<SIZE> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}", Hash::compute_from(self.to_bytes()).to_bs58_check())
    }
}

impl<const SIZE: usize> std::fmt::Debug for HashXof<SIZE> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{}", self.to_bs58_check())
    }
}

/// Serializer for `HashXof`
#[derive(Default, Clone)]
pub struct HashXofSerializer;

impl HashXofSerializer {
    /// Creates a serializer for `HashXof`
    pub const fn new() -> Self {
        Self
    }
}

impl<const SIZE: usize> Serializer<HashXof<SIZE>> for HashXofSerializer {
    fn serialize(&self, value: &HashXof<SIZE>, buffer: &mut Vec<u8>) -> Result<(), SerializeError> {
        buffer.extend(value.to_bytes());
        Ok(())
    }
}

/// Deserializer for `HashXof`
#[derive(Default, Clone)]
pub struct HashXofDeserializer;

impl HashXofDeserializer {
    /// Creates a deserializer for `HashXof`
    pub const fn new() -> Self {
        Self
    }
}

impl<const SIZE: usize> Deserializer<HashXof<SIZE>> for HashXofDeserializer {
    /// ## Example
    /// ```rust
    /// use massa_hash::{HashXof, HASH_XOF_SIZE_BYTES, HashXofDeserializer};
    /// use massa_serialization::{Serializer, Deserializer, DeserializeError};
    ///
    /// let hash_deserializer = HashXofDeserializer::new();
    /// let hash: HashXof<HASH_XOF_SIZE_BYTES> = HashXof::compute_from(&"hello world".as_bytes());
    /// let (rest, deserialized) = hash_deserializer.deserialize::<DeserializeError>(hash.to_bytes()).unwrap();
    /// assert_eq!(deserialized, hash);
    /// assert_eq!(rest.len(), 0);
    /// ```
    fn deserialize<'a, E: ParseError<&'a [u8]> + ContextError<&'a [u8]>>(
        &self,
        buffer: &'a [u8],
    ) -> IResult<&'a [u8], HashXof<SIZE>, E> {
        context("Failed hashxof deserialization", |input: &'a [u8]| {
            if buffer.len() < SIZE {
                return Err(nom::Err::Error(ParseError::from_error_kind(
                    input,
                    nom::error::ErrorKind::LengthValue,
                )));
            }
            Ok((
                &buffer[SIZE..],
                HashXof::from_bytes(&buffer[..SIZE].try_into().map_err(|_| {
                    nom::Err::Error(ParseError::from_error_kind(
                        input,
                        nom::error::ErrorKind::Fail,
                    ))
                })?),
            ))
        })(buffer)
    }
}