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use crate::{proto, Error};
use std::io::Read;
use tracing::{debug, instrument};
use super::ChunkService;
/// uploads a chunk to a chunk service, and returns its digest (or an error) when done.
#[instrument(skip_all, err)]
pub fn upload_chunk<CS: ChunkService>(
chunk_service: &CS,
chunk_data: Vec<u8>,
) -> Result<[u8; 32], Error> {
let mut hasher = blake3::Hasher::new();
update_hasher(&mut hasher, &chunk_data);
let digest = hasher.finalize();
if chunk_service.has(digest.as_bytes())? {
debug!("already has chunk, skipping");
}
let digest_resp = chunk_service.put(chunk_data)?;
assert_eq!(&digest_resp, digest.as_bytes());
Ok(digest.as_bytes().clone())
}
/// reads through a reader, writes chunks to a [ChunkService] and returns a
/// [proto::BlobMeta] pointing to all the chunks.
#[instrument(skip_all, err)]
pub fn read_all_and_chunk<CS: ChunkService, R: Read>(
chunk_service: &CS,
r: R,
) -> Result<(Vec<u8>, proto::BlobMeta), Error> {
let mut blob_meta = proto::BlobMeta::default();
// hash the file contents, upload chunks if not there yet
let mut blob_hasher = blake3::Hasher::new();
// TODO: play with chunking sizes
let chunker_avg_size = 64 * 1024;
let chunker_min_size = chunker_avg_size / 4;
let chunker_max_size = chunker_avg_size * 4;
let chunker =
fastcdc::v2020::StreamCDC::new(r, chunker_min_size, chunker_avg_size, chunker_max_size);
for chunking_result in chunker {
let chunk = chunking_result.unwrap();
// TODO: convert to error::UnableToRead
let chunk_len = chunk.data.len() as u32;
// update calculate blob hash
update_hasher(&mut blob_hasher, &chunk.data);
let chunk_digest = upload_chunk(chunk_service, chunk.data)?;
blob_meta.chunks.push(proto::blob_meta::ChunkMeta {
digest: chunk_digest.to_vec(),
size: chunk_len,
});
}
Ok((blob_hasher.finalize().as_bytes().to_vec(), blob_meta))
}
/// updates a given hasher with more data. Uses rayon if the data is
/// sufficiently big.
///
/// From the docs:
///
/// To get any performance benefit from multithreading, the input buffer needs
/// to be large. As a rule of thumb on x86_64, update_rayon is slower than
/// update for inputs under 128 KiB. That threshold varies quite a lot across
/// different processors, and it’s important to benchmark your specific use
/// case.
///
/// We didn't benchmark yet, so these numbers might need tweaking.
#[instrument(skip_all)]
pub fn update_hasher(hasher: &mut blake3::Hasher, data: &[u8]) {
if data.len() > 128 * 1024 {
hasher.update_rayon(data);
} else {
hasher.update(data);
}
}
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