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// SPDX-FileCopyrightText: edef <edef@unfathomable.blue>
// SPDX-License-Identifier: LGPL-2.1-or-later
use std::mem;
pub struct Chunker<'a> {
state: sys::CaChunker,
buffer: &'a [u8],
}
impl<'a> Chunker<'a> {
pub fn from(buffer: &'a [u8]) -> Self {
Self {
state: sys::CaChunker::new(),
buffer,
}
}
/// SAFETY: `idx` must be an in-bounds index for `self.buffer`
unsafe fn cut(&mut self, idx: usize) -> &'a [u8] {
let ret;
(ret, self.buffer) = (
self.buffer.get_unchecked(..idx),
self.buffer.get_unchecked(idx..),
);
ret
}
}
impl<'a> Iterator for Chunker<'a> {
type Item = &'a [u8];
fn next(&mut self) -> Option<Self::Item> {
if self.buffer.is_empty() {
return None;
}
Some(match self.state.scan(self.buffer) {
Some(n) => unsafe { self.cut(n) },
None => mem::take(&mut self.buffer),
})
}
}
mod sys {
#[repr(C)]
#[derive(Clone)]
pub struct CaChunker {
h: u32,
window_size: usize,
chunk_size: usize,
chunk_size_min: usize,
chunk_size_max: usize,
chunk_size_avg: usize,
discriminator: usize,
window: [u8; 48],
}
impl CaChunker {
pub fn new() -> CaChunker {
unsafe { &ca_chunker_init }.clone()
}
pub fn scan(&mut self, data: &[u8]) -> Option<usize> {
unsafe {
match ca_chunker_scan(self, data.as_ptr(), data.len()) {
usize::MAX => None,
n => Some(n),
}
}
}
}
extern "C" {
static ca_chunker_init: CaChunker;
fn ca_chunker_scan(c: *mut CaChunker, p: *const u8, n: usize) -> usize;
}
}
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