icydb-core 0.276.0

IcyDB — A schema-first typed query engine and persistence runtime for Internet Computer canisters
Documentation 
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

//! Formatting-free hexadecimal byte encoding shared by values and database surfaces.

/// Encode bytes as lowercase hexadecimal text.
#[must_use]
pub fn encode_hex_lower(bytes: &[u8]) -> String {
    const HEX: &[u8; 16] = b"0123456789abcdef";

    // Keep common hex emission allocation-bounded and formatting-free.
    // Formatting each byte with `"{byte:02x}"` is equivalent on the wire, but
    // it routes through the formatter for every byte on hot cursor/fingerprint
    // display paths.
    let mut out = String::with_capacity(bytes.len().saturating_mul(2));

    for byte in bytes {
        out.push(HEX[(byte >> 4) as usize] as char);
        out.push(HEX[(byte & 0x0f) as usize] as char);
    }

    out
}

#[cfg(test)]
mod tests {
    use super::encode_hex_lower;
    use std::fmt::Write as _;

    #[test]
    fn lowercase_hex_preserves_every_byte_without_a_prefix() {
        let bytes: Vec<_> = (0..=u8::MAX).collect();
        let mut expected = String::new();
        for byte in &bytes {
            write!(expected, "{byte:02x}").unwrap();
        }
        assert_eq!(encode_hex_lower(&bytes), expected);
        assert_eq!(encode_hex_lower(&[]), "");
    }
}