substreams/
hex.rs

1use std::fmt;
2
3/// Hex is a simple wrapper type that you can use to wrap your type so that it
4/// prints in lower hexadecimal format when use as a formatting argument.
5///
6/// # Examples
7///
8/// ```
9/// use substreams::Hex;
10///
11/// println!("Got an hex value {}", Hex(&[0xabu8, 0xcdu8, 0xefu8]));
12/// ```
13///
14/// It can also be used directly to encode your type as a lower hexadecimal
15/// `String`:
16///
17/// # Examples
18///
19/// ```
20/// use substreams::Hex;
21///
22/// let encode = Hex::encode(&[0xabu8, 0xcdu8, 0xefu8]);
23/// ```
24pub struct Hex<T>(pub T);
25
26impl<T: AsRef<[u8]>> Hex<T> {
27    pub fn decode(data: T) -> Result<Vec<u8>, hex::FromHexError> {
28        let data_ref: &[u8] = data.as_ref();
29
30        ::hex::decode(remove_hex_prefix(data_ref))
31    }
32
33    pub fn encode(input: T) -> String {
34        encode_lower_hex(input.as_ref())
35    }
36
37    pub fn to_string(&self) -> String {
38        encode_lower_hex(self.0.as_ref())
39    }
40}
41
42impl<T: AsRef<[u8]>> fmt::Debug for Hex<T> {
43    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
44        write_lower_hex(self.0.as_ref(), f)
45    }
46}
47
48impl<T: AsRef<[u8]>> fmt::Display for Hex<T> {
49    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
50        write_lower_hex(self.0.as_ref(), f)
51    }
52}
53
54impl<T: AsRef<[u8]>> fmt::LowerHex for Hex<T> {
55    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
56        write_lower_hex(self.0.as_ref(), f)
57    }
58}
59
60const LOWER_HEX_BYTES: [&str; 256] = [
61    "00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "0a", "0b", "0c", "0d", "0e", "0f",
62    "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "1a", "1b", "1c", "1d", "1e", "1f",
63    "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "2a", "2b", "2c", "2d", "2e", "2f",
64    "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "3a", "3b", "3c", "3d", "3e", "3f",
65    "40", "41", "42", "43", "44", "45", "46", "47", "48", "49", "4a", "4b", "4c", "4d", "4e", "4f",
66    "50", "51", "52", "53", "54", "55", "56", "57", "58", "59", "5a", "5b", "5c", "5d", "5e", "5f",
67    "60", "61", "62", "63", "64", "65", "66", "67", "68", "69", "6a", "6b", "6c", "6d", "6e", "6f",
68    "70", "71", "72", "73", "74", "75", "76", "77", "78", "79", "7a", "7b", "7c", "7d", "7e", "7f",
69    "80", "81", "82", "83", "84", "85", "86", "87", "88", "89", "8a", "8b", "8c", "8d", "8e", "8f",
70    "90", "91", "92", "93", "94", "95", "96", "97", "98", "99", "9a", "9b", "9c", "9d", "9e", "9f",
71    "a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9", "aa", "ab", "ac", "ad", "ae", "af",
72    "b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8", "b9", "ba", "bb", "bc", "bd", "be", "bf",
73    "c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9", "ca", "cb", "cc", "cd", "ce", "cf",
74    "d0", "d1", "d2", "d3", "d4", "d5", "d6", "d7", "d8", "d9", "da", "db", "dc", "dd", "de", "df",
75    "e0", "e1", "e2", "e3", "e4", "e5", "e6", "e7", "e8", "e9", "ea", "eb", "ec", "ed", "ee", "ef",
76    "f0", "f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8", "f9", "fa", "fb", "fc", "fd", "fe", "ff",
77];
78
79fn remove_hex_prefix(data: &[u8]) -> &[u8] {
80    // Removing 0x prefix. "0" = 48, "x" = 120 (UTF-8)
81    if data[0] == (48 as u8) && data[1] == (120 as u8) {
82        return &data[2..data.len()];
83    }
84
85    return data;
86}
87
88fn write_lower_hex(input: &[u8], mut w: impl std::fmt::Write) -> fmt::Result {
89    for byte in input {
90        w.write_str(LOWER_HEX_BYTES[*byte as usize])?;
91    }
92
93    return Ok(());
94}
95
96fn encode_lower_hex<T: AsRef<[u8]>>(input: T) -> String {
97    let bytes: &[u8] = input.as_ref();
98
99    if bytes.len() == 0 {
100        return String::new();
101    }
102
103    let mut buffer = String::with_capacity(bytes.len());
104    write_lower_hex(bytes, &mut buffer).expect("non-fallible pre-allocated buffer");
105    buffer
106}
107
108#[cfg(test)]
109mod tests {
110    use crate::hex::encode_lower_hex;
111    use crate::Hex;
112
113    #[test]
114    fn it_encode_lower_hex_correctly() {
115        assert_eq!(encode_lower_hex(&[] as &[u8; 0]), "");
116        assert_eq!(encode_lower_hex(&[0x01u8]), "01");
117        assert_eq!(encode_lower_hex(&[0xa1u8, 0xc3u8]), "a1c3");
118    }
119
120    #[test]
121    fn it_decode_remove_hex_prefix_correctly() {
122        let input = "0x6e8b";
123        let expected_result: [u8; 2] = [110, 139];
124
125        let result = Hex::decode(input).unwrap();
126        assert_eq!(result, expected_result.to_vec())
127    }
128
129    #[test]
130    fn it_decode_remove_hex_prefix_string_correctly() {
131        let input = "0x6e8b";
132        let expected_result = "6e8b";
133
134        let result = Hex::decode(input).unwrap();
135        assert_eq!(Hex::encode(result), expected_result)
136    }
137
138    #[test]
139    fn it_decode_without_hex_prefix_correctly() {
140        let input = "6e8b";
141        let expected_result: [u8; 2] = [110, 139];
142
143        let result = Hex::decode(input).unwrap();
144        assert_eq!(result, expected_result.to_vec())
145    }
146
147    #[test]
148    fn it_decode_without_hex_prefix_string_correctly() {
149        let input = "6e8b";
150        let expected_result = "6e8b";
151
152        let result = Hex::decode(input).unwrap();
153        assert_eq!(Hex::encode(result), expected_result)
154    }
155}
substreams/hex.rs

substreams/
hex.rs
