1 files changed, 83 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..6a1e1d0
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,83 @@
+#[macro_use]
+extern crate log;
+pub mod log_db {
+    use fs2::FileExt;
+    use priority_queue::PriorityQueue;
+    use std::collections::BTreeMap;
+    use std::fs;
+    use std::io;
+    use std::io::Write;
+    use std::path::{Path, PathBuf};
+
+    const ACTIVE_LOG_FILENAME: &str = "db";
+
+    pub trait Record {
+        fn serialize(&self) -> Vec<u8>;
+        fn deserialize(data: Vec<u8>) -> Self;
+    }
+
+    pub struct Config {
+        /// Directory where the database will store its data.
+        pub data_dir: String,
+        /// The maximum size of a segment file in bytes.
+        /// Once a segment file reaches this size, it is closed and a new one is created.
+        /// Closed segment files can be compacted.
+        pub segment_size: u64,
+        /// The maximum size of a single memtable in bytes.
+        /// Note that each secondary index will have its own memtable.
+        pub memtable_size: u64,
+    }
+
+    pub struct DB<T: Record> {
+        data_dir: String,
+        segment_size: u64,
+        memtable_size: u64,
+
+        pub log_path: PathBuf,
+        primary_memtable: BTreeMap<u64, T>,
+    }
+
+    impl<T: Record> DB<T> {
+        pub fn initialize(config: &Config) -> Result<DB<T>, io::Error> {
+            info!("Initializing DB");
+            // If data_dir does not exist, create it
+            if !fs::exists(&config.data_dir)? {
+                fs::create_dir_all(&config.data_dir)?;
+            }
+
+            let log_path = Path::new(&config.data_dir).join(ACTIVE_LOG_FILENAME);
+
+            let db = DB::<T> {
+                data_dir: config.data_dir.clone(),
+                segment_size: config.segment_size,
+                memtable_size: config.memtable_size,
+
+                log_path,
+                primary_memtable: BTreeMap::new(),
+            };
+            Ok(db)
+        }
+
+        pub fn upsert(&self, record: &T) -> Result<(), io::Error> {
+            let mut file = fs::OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(&self.log_path)?;
+
+            // Acquire an exclusive lock for writing
+            file.lock_exclusive()?;
+
+            // Write the record to the log
+            let serialized = record.serialize();
+            file.write_all(&serialized)?;
+
+            // Sync to disk
+            file.flush()?;
+            file.sync_all()?;
+
+            file.unlock()?;
+
+            Ok(())
+        }
+    }
+}