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use std::{io::Read, mem};
use oval::Buffer;
use snafu::ResultExt;
use crate::{
decode::{
binary_cookies::BinaryCookieFsm,
cookies::CookieFsm,
meta::MetaFsm,
pages::PageFsm,
stream::{State, Values},
DecodeResult,
},
error::{self, Result},
};
#[derive(Clone)]
#[derive(Debug)]
pub struct StreamDecoder<R: Read> {
state: State,
rd: R,
}
impl<R: Read> StreamDecoder<R> {
const BUF_SIZE: usize = 64;
pub fn new(rd: R) -> Self {
Self {
state: State::Bc {
fsm: BinaryCookieFsm {
buffer: Buffer::with_capacity(Self::BUF_SIZE),
},
},
rd,
}
}
pub fn decode(&mut self) -> Result<Values> {
match mem::take(&mut self.state) {
State::Bc { mut fsm } => loop {
let readed = self
.rd
.read(fsm.buffer.space())
.context(error::ReadSnafu)?;
fsm.buffer.fill(readed);
match fsm.process()? {
DecodeResult::Continue(fsm_) => {
fsm = fsm_;
continue;
},
DecodeResult::Done((meta_offset, pages_offset, buffer)) => {
self.state = State::Page {
fsm: PageFsm { buffer },
remaining_page: pages_offset.offset_sizes.len() as u32,
};
return Ok(Values::Bc { meta_offset, pages_offset });
},
}
},
State::Page { mut fsm, remaining_page } => loop {
let readed = self
.rd
.read(fsm.buffer.space())
.context(error::ReadSnafu)?;
fsm.buffer.fill(readed);
match fsm.process()? {
DecodeResult::Continue(fsm_) => {
fsm = fsm_;
continue;
},
DecodeResult::Done((c, buffer)) => {
self.state = State::Cookie {
fsm: CookieFsm { buffer },
remaining_cookie: c.len() as u32,
remaining_page: remaining_page - 1,
};
return Ok(Values::Page(c));
},
}
},
State::Cookie {
remaining_cookie,
remaining_page,
mut fsm,
} => loop {
let readed = self
.rd
.read(fsm.buffer.space())
.context(error::ReadSnafu)?;
fsm.buffer.fill(readed);
match fsm.process()? {
DecodeResult::Continue(fsm_) => {
fsm = fsm_;
continue;
},
DecodeResult::Done((cookie, buffer)) => {
let remaining_cookie = remaining_cookie - 1;
match (remaining_cookie, remaining_page) {
(0, 0) => self.state = State::Meta { fsm: MetaFsm { buffer } },
(0, _) => {
self.state = State::Page {
fsm: PageFsm { buffer },
remaining_page,
};
},
_ => {
self.state = State::Cookie {
fsm: CookieFsm { buffer },
remaining_cookie,
remaining_page,
};
},
}
return Ok(Values::Cookie(cookie));
},
}
},
State::Meta { mut fsm } => loop {
let readed = self
.rd
.read(fsm.buffer.space())
.context(error::ReadSnafu)?;
fsm.buffer.fill(readed);
match fsm.process()? {
DecodeResult::Continue(fsm_) => {
fsm = fsm_;
continue;
},
DecodeResult::Done((checksum, meta)) => {
self.state = State::Finished;
return Ok(Values::Meta { checksum, meta });
},
}
},
State::Finished => Err(error::ParsingCompletedSnafu.build()),
State::Transition => unreachable!(),
}
}
}