[storage] Add read() to FileWrapper #86 (#87)

* Update file_wrapper.rs

* Update file_wrapper.rs

src/storage/file_wrapper.rs

@@ -1,5 +1,5 @@
 use std::fs::{File, OpenOptions};
-use std::io::{Seek, SeekFrom};
+use std::io::{Read, Seek, SeekFrom};
 
 const ERROR_MESSAGE: &str = "Could not access file";
 
@@ -10,6 +10,15 @@ pub(crate) struct FileWrapper {
     pub(crate) size: u64,
 }
 
+#[allow(dead_code)]
+impl FileWrapper {
+    pub(crate) fn read(&mut self, size: u64) -> Vec<u8> {
+        let mut buffer = vec![0_u8; size as usize];
+        self.file.read_exact(&mut buffer).expect(ERROR_MESSAGE);
+        buffer
+    }
+}
+
 impl From<String> for FileWrapper {
     fn from(filename: String) -> Self {
         let mut file = OpenOptions::new()
@@ -32,8 +41,9 @@ impl From<String> for FileWrapper {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::storage::serialize::Serialize;
     use crate::test_utilities::test_file::TestFile;
-    use std::path::Path;
+    use std::{io::Write, mem::size_of, path::Path};
 
     #[test]
     fn create_new_file() {
@@ -49,6 +59,20 @@ mod tests {
     fn open_existing_file() {
         let test_file = TestFile::from("./file_storage_test02.agdb");
         File::create(test_file.file_name()).unwrap();
-        let _storage = FileWrapper::from(test_file.file_name().clone());
+        let _file = FileWrapper::from(test_file.file_name().clone());
+    }
+
+    #[test]
+    fn read_bytes() {
+        let test_file = TestFile::from("./file_storage_test03.agdb");
+        let mut file = FileWrapper::from(test_file.file_name().clone());
+        let data = 10_i64.serialize();
+
+        file.file.write_all(&data).unwrap();
+        file.file.seek(SeekFrom::Start(0)).unwrap();
+
+        let actual_data = file.read(size_of::<i64>() as u64);
+
+        assert_eq!(data, actual_data);
     }
 }