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use std::io;
use tonic::async_trait;
use crate::proto::stat_blob_response::ChunkMeta;
use crate::B3Digest;
mod combinator;
mod from_addr;
mod grpc;
mod memory;
mod naive_seeker;
mod simplefs;
mod sled;
#[cfg(test)]
mod tests;
pub use self::combinator::CombinedBlobService;
pub use self::from_addr::from_addr;
pub use self::grpc::GRPCBlobService;
pub use self::memory::MemoryBlobService;
pub use self::simplefs::SimpleFilesystemBlobService;
pub use self::sled::SledBlobService;
/// The base trait all BlobService services need to implement.
/// It provides functions to check whether a given blob exists,
/// a way to read (and seek) a blob, and a method to create a blobwriter handle,
/// which will implement a writer interface, and also provides a close funtion,
/// to finalize a blob and get its digest.
#[async_trait]
pub trait BlobService: Send + Sync {
/// Check if the service has the blob, by its content hash.
/// On implementations returning chunks, this must also work for chunks.
async fn has(&self, digest: &B3Digest) -> io::Result<bool>;
/// Request a blob from the store, by its content hash.
/// On implementations returning chunks, this must also work for chunks.
async fn open_read(&self, digest: &B3Digest) -> io::Result<Option<Box<dyn BlobReader>>>;
/// Insert a new blob into the store. Returns a [BlobWriter], which
/// implements [tokio::io::AsyncWrite] and a [BlobWriter::close] to finalize
/// the blob and get its digest.
async fn open_write(&self) -> Box<dyn BlobWriter>;
/// Return a list of chunks for a given blob.
/// There's a distinction between returning Ok(None) and Ok(Some(vec![])).
/// The former return value is sent in case the blob is not present at all,
/// while the second one is sent in case there's no more granular chunks (or
/// the backend does not support chunking).
/// A default implementation checking for existence and then returning it
/// does not have more granular chunks available is provided.
async fn chunks(&self, digest: &B3Digest) -> io::Result<Option<Vec<ChunkMeta>>> {
if !self.has(digest).await? {
return Ok(None);
} else {
// default implementation, signalling the backend does not have more
// granular chunks available.
return Ok(Some(vec![]));
}
}
}
/// A [tokio::io::AsyncWrite] that the user needs to close() afterwards for persist.
/// On success, it returns the digest of the written blob.
#[async_trait]
pub trait BlobWriter: tokio::io::AsyncWrite + Send + Sync + Unpin + 'static {
/// Signal there's no more data to be written, and return the digest of the
/// contents written.
///
/// Closing a already-closed BlobWriter is a no-op.
async fn close(&mut self) -> io::Result<B3Digest>;
}
/// BlobReader is a [tokio::io::AsyncRead] that also allows seeking.
pub trait BlobReader: tokio::io::AsyncRead + tokio::io::AsyncSeek + Send + Unpin + 'static {}
/// A [`io::Cursor<Vec<u8>>`] can be used as a BlobReader.
impl BlobReader for io::Cursor<Vec<u8>> {}
impl BlobReader for tokio::fs::File {}
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