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use crate::action::Action;
use crate::core::borrow::BorrowMut;
use crate::core::hash::{BuildHasher, Hasher};
use crate::core::marker::PhantomData;
use crate::core::mem;
use crate::crc32::{BuiltinDigest, IEEE_REVERSE};
use crate::deflate::encoder::Inflater;
use crate::error::CompressionError;
use crate::traits::encoder::Encoder;
struct ScanIterator<I: Iterator, BI: BorrowMut<I>, F: FnMut(&I::Item) -> ()> {
phantom: PhantomData<I>,
inner: BI,
closure: F,
}
impl<I: Iterator, BI: BorrowMut<I>, F: FnMut(&I::Item) -> ()> Iterator
for ScanIterator<I, BI, F>
{
type Item = I::Item;
fn next(&mut self) -> Option<I::Item> {
let ret = self.inner.borrow_mut().next();
if let Some(ref s) = ret {
(self.closure)(s);
}
ret
}
}
impl<I: Iterator, BI: BorrowMut<I>, F: FnMut(&I::Item) -> ()>
ScanIterator<I, BI, F>
{
pub(crate) fn new(inner: BI, closure: F) -> Self {
Self {
inner,
closure,
phantom: PhantomData,
}
}
}
#[derive(Debug)]
pub struct GZipEncoder {
inflater: Inflater,
crc32: Option<BuiltinDigest>,
header_len: u8,
header: [u8; 10],
hash: Option<u32>,
hashlen: u8,
i_size_len: u8,
i_size: u32,
}
impl Default for GZipEncoder {
fn default() -> Self {
Self::new()
}
}
impl GZipEncoder {
pub fn new() -> Self {
Self {
inflater: Inflater::new(),
crc32: Some(IEEE_REVERSE.build_hasher()),
header: [
0x1F, 0x8B, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF,
],
header_len: 10,
hash: None,
hashlen: 3,
i_size: 0,
i_size_len: 4,
}
}
}
impl Encoder for GZipEncoder {
type Error = CompressionError;
type In = u8;
type Out = u8;
fn next<I: Iterator<Item = u8>>(
&mut self,
iter: &mut I,
action: Action,
) -> Option<Result<u8, CompressionError>> {
let hlen = self.header_len;
if hlen > 0 {
let hlen_all = self.header.len();
self.header_len = hlen - 1;
Some(Ok(self.header[hlen_all - hlen as usize]))
} else if let Some(hash) = self.hash {
if self.hashlen == 0 {
if self.i_size_len == 0 {
None
} else {
self.i_size_len -= 1;
let ret = self.i_size as u8;
self.i_size >>= 8;
Some(Ok(ret))
}
} else {
self.hashlen -= 1;
self.hash = Some(hash >> 8);
Some(Ok(hash as u8))
}
} else {
let mut crc32 = mem::replace(&mut self.crc32, None);
let mut i_size = self.i_size;
let ret = self.inflater.next(
&mut ScanIterator::<I, _, _>::new(iter, |x: &u8| {
crc32.as_mut().unwrap().write_u8(*x);
i_size += 1;
}),
action,
);
self.i_size = i_size;
let _ = mem::replace(&mut self.crc32, crc32);
if ret.is_none() {
let hash = self.crc32.as_mut().unwrap().finish() as u32;
let ret = hash as u8;
self.hash = Some(hash >> 8);
Some(Ok(ret))
} else {
ret
}
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::traits::encoder::EncodeExt;
#[cfg(not(feature = "std"))]
#[allow(unused_imports)]
use alloc::vec;
#[cfg(not(feature = "std"))]
use alloc::vec::Vec;
#[test]
fn test_unit() {
let mut encoder = GZipEncoder::new();
let ret = b"a"
.iter()
.cloned()
.encode(&mut encoder, Action::Finish)
.collect::<Result<Vec<_>, _>>();
assert_eq!(
ret,
Ok(vec![
0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF,
0x4b, 0x04, 0x00, 0x43, 0xbe, 0xb7, 0xe8, 0x01, 0x00, 0x00,
0x00,
])
);
}
}