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use std::io::{self, Cursor, Write};
use std::task::Poll;
use std::{
collections::HashMap,
sync::{Arc, RwLock},
};
use tonic::async_trait;
use tracing::instrument;
use super::{BlobReader, BlobService, BlobWriter};
use crate::{B3Digest, Error};
#[derive(Clone, Default)]
pub struct MemoryBlobService {
db: Arc<RwLock<HashMap<B3Digest, Vec<u8>>>>,
}
#[async_trait]
impl BlobService for MemoryBlobService {
/// Constructs a [MemoryBlobService] from the passed [url::Url]:
/// - scheme has to be `memory://`
/// - there may not be a host.
/// - there may not be a path.
fn from_url(url: &url::Url) -> Result<Self, Error> {
if url.scheme() != "memory" {
return Err(crate::Error::StorageError("invalid scheme".to_string()));
}
if url.has_host() || !url.path().is_empty() {
return Err(crate::Error::StorageError("invalid url".to_string()));
}
Ok(Self::default())
}
#[instrument(skip(self, digest), fields(blob.digest=%digest))]
async fn has(&self, digest: &B3Digest) -> Result<bool, Error> {
let db = self.db.read().unwrap();
Ok(db.contains_key(digest))
}
async fn open_read(&self, digest: &B3Digest) -> Result<Option<Box<dyn BlobReader>>, Error> {
let db = self.db.read().unwrap();
match db.get(digest).map(|x| Cursor::new(x.clone())) {
Some(result) => Ok(Some(Box::new(result))),
None => Ok(None),
}
}
#[instrument(skip(self))]
async fn open_write(&self) -> Box<dyn BlobWriter> {
Box::new(MemoryBlobWriter::new(self.db.clone()))
}
}
pub struct MemoryBlobWriter {
db: Arc<RwLock<HashMap<B3Digest, Vec<u8>>>>,
/// Contains the buffer Vec and hasher, or None if already closed
writers: Option<(Vec<u8>, blake3::Hasher)>,
/// The digest that has been returned, if we successfully closed.
digest: Option<B3Digest>,
}
impl MemoryBlobWriter {
fn new(db: Arc<RwLock<HashMap<B3Digest, Vec<u8>>>>) -> Self {
Self {
db,
writers: Some((Vec::new(), blake3::Hasher::new())),
digest: None,
}
}
}
impl tokio::io::AsyncWrite for MemoryBlobWriter {
fn poll_write(
mut self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
b: &[u8],
) -> std::task::Poll<Result<usize, io::Error>> {
Poll::Ready(match &mut self.writers {
None => Err(io::Error::new(
io::ErrorKind::NotConnected,
"already closed",
)),
Some((ref mut buf, ref mut hasher)) => {
let bytes_written = buf.write(b)?;
hasher.write(&b[..bytes_written])
}
})
}
fn poll_flush(
self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Result<(), io::Error>> {
Poll::Ready(match self.writers {
None => Err(io::Error::new(
io::ErrorKind::NotConnected,
"already closed",
)),
Some(_) => Ok(()),
})
}
fn poll_shutdown(
self: std::pin::Pin<&mut Self>,
_cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Result<(), io::Error>> {
// shutdown is "instantaneous", we only write to memory.
Poll::Ready(Ok(()))
}
}
#[async_trait]
impl BlobWriter for MemoryBlobWriter {
async fn close(&mut self) -> Result<B3Digest, Error> {
if self.writers.is_none() {
match &self.digest {
Some(digest) => Ok(digest.clone()),
None => Err(crate::Error::StorageError(
"previously closed with error".to_string(),
)),
}
} else {
let (buf, hasher) = self.writers.take().unwrap();
// We know self.hasher is doing blake3 hashing, so this won't fail.
let digest: B3Digest = hasher.finalize().as_bytes().into();
// Only insert if the blob doesn't already exist.
let db = self.db.read()?;
if !db.contains_key(&digest) {
// drop the read lock, so we can open for writing.
drop(db);
// open the database for writing.
let mut db = self.db.write()?;
// and put buf in there. This will move buf out.
db.insert(digest.clone(), buf);
}
self.digest = Some(digest.clone());
Ok(digest)
}
}
}
#[cfg(test)]
mod tests {
use super::BlobService;
use super::MemoryBlobService;
/// This uses a wrong scheme.
#[test]
fn test_invalid_scheme() {
let url = url::Url::parse("http://foo.example/test").expect("must parse");
assert!(MemoryBlobService::from_url(&url).is_err());
}
/// This correctly sets the scheme, and doesn't set a path.
#[test]
fn test_valid_scheme() {
let url = url::Url::parse("memory://").expect("must parse");
assert!(MemoryBlobService::from_url(&url).is_ok());
}
/// This sets the host to `foo`
#[test]
fn test_invalid_host() {
let url = url::Url::parse("memory://foo").expect("must parse");
assert!(MemoryBlobService::from_url(&url).is_err());
}
/// This has the path "/", which is invalid.
#[test]
fn test_invalid_has_path() {
let url = url::Url::parse("memory:///").expect("must parse");
assert!(MemoryBlobService::from_url(&url).is_err());
}
/// This has the path "/foo", which is invalid.
#[test]
fn test_invalid_path2() {
let url = url::Url::parse("memory:///foo").expect("must parse");
assert!(MemoryBlobService::from_url(&url).is_err());
}
}
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