feat: store chunks persistently

3 files changed, 49 insertions, 1 deletions

diff --git a/src/chunkmeta.rs b/src/chunkmeta.rs
index 952dc8d..b48b9a3 100644
--- a/src/chunkmeta.rs
+++ b/src/chunkmeta.rs
@@ -92,7 +92,7 @@ impl ChunkMeta {
 impl FromStr for ChunkMeta {
     type Err = serde_json::error::Error;
 
-    /// Parse a JSON representation metdata.
+    /// Parse a JSON representation metadata.
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         serde_json::from_str(s)
     }
diff --git a/src/lib.rs b/src/lib.rs
index 720306d..6955243 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,3 +2,4 @@ pub mod chunk;
 pub mod chunkid;
 pub mod chunkmeta;
 pub mod index;
+pub mod store;
diff --git a/src/store.rs b/src/store.rs
new file mode 100644
index 0000000..0c15f02
--- /dev/null
+++ b/src/store.rs
@@ -0,0 +1,47 @@
+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))
+    }
+}