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/*
This file is part of jellything (https://codeberg.org/metamuffin/jellything)
which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
Copyright (C) 2025 metamuffin <metamuffin.org>
*/
use crate::{CACHE_GENERATION_BUCKET_COUNT, CONF};
use anyhow::bail;
use base64::{Engine, prelude::BASE64_URL_SAFE};
use sha2::Sha256;
use std::{
fmt::Display,
hash::{Hash, Hasher},
str::FromStr,
};
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct CacheKey(pub [u8; 32]);
impl CacheKey {
pub fn new(ty: CacheContentType, seed: impl Hash) -> Self {
use sha2::Digest;
struct ShaHasher(Sha256);
impl Hasher for ShaHasher {
fn finish(&self) -> u64 {
unreachable!()
}
fn write(&mut self, bytes: &[u8]) {
self.0.update(bytes);
}
}
let mut d = ShaHasher(sha2::Sha256::new());
d.0.update(CONF.secret.as_bytes());
seed.hash(&mut d);
let d = d.0.finalize();
let mut key: [u8; 32] = d.as_slice().try_into().unwrap();
key[0] = ty as u8;
Self(key)
}
pub fn new_json(seed: impl Hash) -> Self {
Self::new(CacheContentType::Json, seed)
}
pub fn new_image(seed: impl Hash) -> Self {
Self::new(CacheContentType::Image, seed)
}
pub fn content_type(&self) -> CacheContentType {
match self.0[0] {
1 => CacheContentType::Image,
2 => CacheContentType::Json,
_ => CacheContentType::Unknown,
}
}
pub(super) fn bucket(&self) -> usize {
(self.0[1] as usize
| ((self.0[2] as usize) << 8)
| ((self.0[3] as usize) << 16)
| ((self.0[4] as usize) << 24))
% CACHE_GENERATION_BUCKET_COUNT
}
}
impl Display for CacheKey {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str(&BASE64_URL_SAFE.encode(self.0))
}
}
impl FromStr for CacheKey {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let mut out = [0; 32];
let size = BASE64_URL_SAFE.decode_slice(s, &mut out)?;
if size != out.len() {
bail!("cache key parse invalid size")
}
Ok(Self(out))
}
}
#[repr(u8)]
pub enum CacheContentType {
Unknown = 0,
Image = 1,
Json = 2,
}
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