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//! A chunk label.
//!
//! De-duplication of backed up data in Obnam relies on cryptographic
//! checksums. They are implemented in this module. Note that Obnam
//! does not aim to make these algorithms configurable, so only a very
//! small number of carefully chosen algorithms are supported here.
use sha2::{Digest, Sha256};
use std::fmt;
/// A checksum of some data.
#[derive(Debug, Clone)]
pub enum Label {
/// An arbitrary, literal string.
Literal(String),
/// A SHA256 checksum.
Sha256(String),
}
impl Label {
/// Construct a literal string.
pub fn literal(s: &str) -> Self {
Self::Literal(s.to_string())
}
/// Compute a SHA256 checksum for a block of data.
pub fn sha256(data: &[u8]) -> Self {
let mut hasher = Sha256::new();
hasher.update(data);
let hash = hasher.finalize();
Self::Sha256(format!("{:x}", hash))
}
/// Create a `Checksum` from a known, previously computed hash.
pub fn sha256_from_str_unchecked(hash: &str) -> Self {
Self::Sha256(hash.to_string())
}
}
impl fmt::Display for Label {
/// Format a checksum for display.
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Literal(s) => write!(f, "{}", s),
Self::Sha256(hash) => write!(f, "{}", hash),
}
}
}
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