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use cid::Cid;
use futures::Stream;
use tokio::io::AsyncRead;
use crate::{
error::Error,
header::CarHeader,
util::{ld_read, read_node},
};
/// Reads CAR files that are in a BufReader
pub struct CarReader<R> {
reader: R,
header: CarHeader,
buffer: Vec<u8>,
}
impl<R> CarReader<R>
where
R: AsyncRead + Send + Unpin,
{
/// Creates a new CarReader and parses the CarHeader
pub async fn new(mut reader: R) -> Result<Self, Error> {
let mut buffer = Vec::new();
match ld_read(&mut reader, &mut buffer).await? {
Some(buf) => {
let header = CarHeader::decode(buf)?;
Ok(CarReader {
reader,
header,
buffer,
})
}
None => Err(Error::Parsing(
"failed to parse uvarint for header".to_string(),
)),
}
}
/// Returns the header of this car file.
pub fn header(&self) -> &CarHeader {
&self.header
}
/// Returns the next IPLD Block in the buffer
pub async fn next_block(&mut self) -> Result<Option<(Cid, Vec<u8>)>, Error> {
read_node(&mut self.reader, &mut self.buffer).await
}
pub fn stream(self) -> impl Stream<Item = Result<(Cid, Vec<u8>), Error>> {
futures::stream::try_unfold(self, |mut this| async move {
let maybe_block = read_node(&mut this.reader, &mut this.buffer).await?;
Ok(maybe_block.map(|b| (b, this)))
})
}
}
#[cfg(test)]
mod tests {
use std::io::Cursor;
use cid::Cid;
use futures::TryStreamExt;
use ipld_cbor::DagCborCodec;
use multihash::MultihashDigest;
use crate::{header::CarHeaderV1, writer::CarWriter};
use super::*;
#[tokio::test]
async fn car_write_read() {
let digest_test = multihash::Code::Blake2b256.digest(b"test");
let cid_test = Cid::new_v1(DagCborCodec.into(), digest_test);
let digest_foo = multihash::Code::Blake2b256.digest(b"foo");
let cid_foo = Cid::new_v1(DagCborCodec.into(), digest_foo);
let header = CarHeader::V1(CarHeaderV1::from(vec![cid_foo]));
let mut buffer = Vec::new();
let mut writer = CarWriter::new(header, &mut buffer);
writer.write(cid_test, b"test").await.unwrap();
writer.write(cid_foo, b"foo").await.unwrap();
writer.finish().await.unwrap();
let reader = Cursor::new(&buffer);
let car_reader = CarReader::new(reader).await.unwrap();
let files: Vec<_> = car_reader.stream().try_collect().await.unwrap();
assert_eq!(files.len(), 2);
assert_eq!(files[0].0, cid_test);
assert_eq!(files[0].1, b"test");
assert_eq!(files[1].0, cid_foo);
assert_eq!(files[1].1, b"foo");
}
}
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