Add `CyanSWF`, the streaming file writer object

server/src/diskstore/cyanswf.rs

@@ -0,0 +1,54 @@
+/*
+ * Created on Sat Sep 19 2020
+ *
+ * This file is a part of TerrabaseDB
+ * Copyright (c) 2020, Sayan Nandan <ohsayan at outlook dot com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+*/
+
+//! # `CyanSWF`
+//! `CyanSWF` short for Cyan "StreamingWriteFile" is a minimal implementation
+//! of a file to which writes are _streamed_.
+//!
+//! What this essentially means — is that,
+//! instead of taking a whole object and then writing it to the disk, like what persistent
+//! storage did till v0.4.2, `CyanSWF` takes a part, encodes into its _kinda binary_
+//! equivalent, and then writes that to disk. It then takes the next part, encodes it, and then writes it to disk.
+//! The advantage of using this method is that the entire object does not need to be encoded at once
+//! which has an additional memory and CPU time overhead.
+//!
+//! TODO: At this moment, this is specific to the core `HashMap`. However, in the future
+//! a more generic implementation is to be made.
+
+use crate::diskstore::TResult;
+use std::fs::File;
+
+/// The magic number that separates every piece of data from the other
+const CYANSWF_MAGIC: u8 = 0xCA;
+
+/// The streaming file writer
+pub struct CyanSWF {
+    /// The file to which data would be streamed into
+    file: File,
+}
+
+impl CyanSWF {
+    /// Create a new `CyanSWF` instance
+    pub fn new(filename_and_path: &str) -> TResult<Self> {
+        let file = File::create(filename_and_path)?;
+        Ok(CyanSWF { file })
+    }
+}

server/src/diskstore/mod.rs

@@ -32,6 +32,7 @@ use std::io::{ErrorKind, Write};
 use std::iter::FromIterator;
 use std::time::Duration;
 use tokio::time;
+mod cyanswf;
 
 type DiskStore = (Vec<String>, Vec<Vec<u8>>);
 

testsuite/src/service.rs

@@ -25,7 +25,7 @@
 use std::path;
 use std::process;
 
-/// A `BackgroundTask` starts `tdb` in a background
+/// A `BackgroundTask` starts `tdb` in a background task
 pub struct BackGroundTask {
     child: process::Child,
 }