Create EncryptionStream struct

src/store/mod.rs

@@ -1,3 +1,5 @@
+use std::io::{Read, Seek, SeekFrom};
+
 pub(crate) mod local;
 pub(crate) mod server;
 
@@ -86,3 +88,61 @@ impl From<u8> for HashType {
         }
     }
 }
+
+struct EncryptionStream {
+    data: Vec<u8>,
+    pos: usize,
+}
+
+impl Read for EncryptionStream {
+    fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
+        let range = self.pos..(self.pos + buf.len()).clamp(0, self.data.len() - buf.len());
+        let size = range.len();
+        buf.copy_from_slice(&self.data[range]);
+        Ok(size)
+    }
+}
+
+impl Seek for EncryptionStream {
+    fn seek(&mut self, pos: std::io::SeekFrom) -> std::io::Result<u64> {
+        let cur = self.pos;
+
+        let newpos = match pos {
+            SeekFrom::Start(x) => {
+                if x > self.data.len() as u64 {
+                    return Err(std::io::Error::new(
+                        std::io::ErrorKind::InvalidInput,
+                        "Seek position out of buffer bounds.",
+                    ));
+                }
+                x
+            }
+            SeekFrom::End(x) => {
+                if x > self.data.len() as i64 {
+                    return Err(std::io::Error::new(
+                        std::io::ErrorKind::InvalidInput,
+                        "Seek position out of buffer bounds.",
+                    ));
+                }
+
+                (self.data.len() as i64 - x) as u64
+            }
+            SeekFrom::Current(x) => {
+                let new = self.pos as i64 + x;
+
+                if new < 0 || new > self.data.len() as i64 {
+                    return Err(std::io::Error::new(
+                        std::io::ErrorKind::InvalidInput,
+                        "Seek position out of buffer bounds.",
+                    ));
+                }
+
+                new as u64
+            }
+        };
+
+        self.pos = newpos as usize;
+
+        Ok(cur as u64)
+    }
+}