From de6287c6c587530a9e0d560f49ef0eb823e040a3 Mon Sep 17 00:00:00 2001
From: femsci <nya@femboy.science>
Date: Thu, 9 Mar 2023 16:11:43 +0100
Subject: [PATCH] Add overflow error handling to WritableDataPage. Add IO
 tests.

---
 src/data/mod.rs          | 29 ++++++++++++++++++++++++++++-
 src/store/local/index.rs |  8 +++++---
 src/store/local/io.rs    | 27 +++++++++++++++++++++++++--
 3 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/src/data/mod.rs b/src/data/mod.rs
index 1cea798..1feeb75 100644
--- a/src/data/mod.rs
+++ b/src/data/mod.rs
@@ -3,7 +3,7 @@ use std::io::{Read, Seek, SeekFrom, Write};
 pub trait DataPager {
     fn get_page(&mut self, offset: usize) -> Result<&mut DataPage, String>;
 
-    fn update_page(&mut self, page: WritableDataPage) -> Result<u64, ()>;
+    fn update_page(&mut self, page: DataPage) -> Result<u64, ()>;
 }
 
 #[derive(PartialEq, Eq, Hash)]
@@ -67,6 +67,16 @@ impl Seek for DataPage {
     }
 }
 
+impl Clone for DataPage {
+    fn clone(&self) -> Self {
+        Self {
+            offset: self.offset,
+            pos: self.pos,
+            data: self.data.clone(),
+        }
+    }
+}
+
 impl DataPage {
     pub(crate) fn load(offset: usize, data: Vec<u8>) -> Self {
         DataPage {
@@ -108,6 +118,13 @@ impl Write for WritableDataPage<'_> {
             return Ok(0);
         }
 
+        if pos + buf.len() > self.page.len() {
+            return Err(std::io::Error::new(
+                std::io::ErrorKind::OutOfMemory,
+                "A write operation would overflow the block.",
+            ));
+        }
+
         self.page.data[pos..pos + len].copy_from_slice(&buf);
 
         Ok(len)
@@ -118,6 +135,12 @@ impl Write for WritableDataPage<'_> {
     }
 }
 
+impl Seek for WritableDataPage<'_> {
+    fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
+        self.page.seek(pos)
+    }
+}
+
 impl WritableDataPage<'_> {
     pub fn data(&self) -> &[u8] {
         self.page.buffer()
@@ -126,6 +149,10 @@ impl WritableDataPage<'_> {
     pub fn offset(&self) -> usize {
         self.page.offset()
     }
+
+    pub fn finish(&self) -> DataPage {
+        self.page.clone()
+    }
 }
 
 #[cfg(test)]
diff --git a/src/store/local/index.rs b/src/store/local/index.rs
index afb7162..1461f33 100644
--- a/src/store/local/index.rs
+++ b/src/store/local/index.rs
@@ -1,7 +1,7 @@
 use std::{
     collections::hash_map::DefaultHasher,
     hash::{Hash, Hasher},
-    io::{Read, Seek, SeekFrom},
+    io::{Read, Seek, SeekFrom, Write},
 };
 
 use crate::data::{DataPage, DataPager};
@@ -179,10 +179,12 @@ impl LocalStore {
 
         node.children.push(entry);
 
+        let mut block = block.mutate();
         block.seek(SeekFrom::Start(position)).unwrap();
-        node.serialize(&self.meta);
+        block.write(&node.serialize(&self.meta)).unwrap();
+        let page = block.finish();
 
-        //todo serialize
+        self.io.update_page(page).unwrap();
 
         todo!()
     }
diff --git a/src/store/local/io.rs b/src/store/local/io.rs
index 740992a..e692034 100644
--- a/src/store/local/io.rs
+++ b/src/store/local/io.rs
@@ -32,9 +32,9 @@ impl DataPager for DataAccessor {
         Ok(self.cache.get_mut(&offset).unwrap())
     }
 
-    fn update_page(&mut self, page: crate::data::WritableDataPage) -> Result<u64, ()> {
+    fn update_page(&mut self, page: crate::data::DataPage) -> Result<u64, ()> {
         self.dirty_pages
-            .push(DataPage::load(page.offset(), page.data().to_vec()));
+            .push(DataPage::load(page.offset(), page.buffer().to_vec()));
         return Ok(1);
     }
 }
@@ -60,3 +60,26 @@ impl DataAccessor {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::io::{Seek, Write};
+
+    use crate::data::DataPage;
+
+    #[test]
+    fn data_page_update() {
+        let data = vec![2, 1, 3, 7, 0, 0, 0];
+        let mut page = DataPage::load(127, data);
+        page.seek(std::io::SeekFrom::Start(2)).unwrap();
+
+        let mut writable = page.mutate();
+
+        writable.write(&[4, 8, 6, 9, 5]).unwrap();
+        let page_mod = writable.finish();
+
+        println!("{:?}", page.buffer());
+        assert!(page.buffer().eq(&[2, 1, 4, 8, 6, 9, 5]));
+        assert!(page_mod.buffer().eq(&[2, 1, 4, 8, 6, 9, 5]));
+    }
+}