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use crate::chunk::Chunk;
use crate::chunkid::ChunkId;
use crate::chunkmeta::ChunkMeta;
use std::path::{Path, PathBuf};
/// Store chunks, with metadata, persistently.
///
/// The chunks and their metadata are stored persistently on disk
/// under a directory specified as the Store struct is created. To
/// store or retrieve a chunk its identifier must be used.
pub struct Store {
dir: PathBuf,
}
impl Store {
/// Create a new Store to represent on-disk storage of chunks.x
pub fn new(dir: &Path) -> Self {
Store {
dir: dir.to_path_buf(),
}
}
// Construct name for a file in the store from chunk id and suffix.
fn filename(&self, id: &ChunkId, suffix: &str) -> PathBuf {
self.dir.join(format!("{}.{}", id, suffix))
}
/// Save a chunk into a store.
pub fn save(&self, id: &ChunkId, chunk: &Chunk) -> anyhow::Result<()> {
std::fs::write(&self.filename(id, "meta"), chunk.meta().to_json())?;
std::fs::write(&self.filename(id, "data"), chunk.data())?;
Ok(())
}
/// Load a chunk's metadata from a store.
pub fn load_meta(&self, id: &ChunkId) -> anyhow::Result<ChunkMeta> {
let meta = std::fs::read(&self.filename(id, "meta"))?;
Ok(serde_json::from_slice(&meta)?)
}
/// Load a chunk from a store.
pub fn load(&self, id: &ChunkId) -> anyhow::Result<Chunk> {
let meta = self.load_meta(id)?;
let data = std::fs::read(&self.filename(id, "data"))?;
Ok(Chunk::new(meta, data))
}
}
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