Add encrypted file layout table in README

README.md

@@ -154,6 +154,7 @@ let hmac = Hmac::new(
     blake2b, //hash function
 );
 hmac.update(random_salt);
+//integers are encoded in big-endian
 hmac.update(argon2_time_cost);
 hmac.update(argon2_memory_cost);
 hmac.update(argon2_parallelism);
@@ -182,6 +183,41 @@ Once the whole plaintext is encrypted, doby computes and appends the HMAC to the
 output.write(hmac.digest());
 ```
 
+So here is what an encrypted file layout looks like:
+
+<table>
+  <tr>
+    <th align="left">Magic bytes</th>
+    <td>4 bytes</td>
+  </tr>
+  <tr>
+    <th align="left">Salt</th>
+    <td>64 bytes</td>
+  </tr>
+  <tr>
+    <th align="left" rowspan="3">Argon2 parameters</th>
+    <td>Time cost: 4 bytes</td>
+  </tr>
+  <tr>
+    <td>Memory cost: 4 bytes</td>
+  </tr>
+  <tr>
+    <td>Parallelism cost: 1 byte</td>
+  </tr>
+  <tr>
+    <th align="left">Encryption cipher</th>
+    <td>1 byte</td>
+  </tr>
+  <tr>
+    <th align="left">Ciphertext</th>
+    <td>Exact same size as the plaintext</td>
+  </tr>
+  <tr>
+    <th align="left">HMAC</th>
+    <td>64 bytes</td>
+  </tr>
+</table>
+
 ### Decryption
 
 doby reads the public encryption values from the input header to get all parameters needed to re-derive the `master_key` from the password with Argon2.

src/cli.rs

@@ -96,11 +96,11 @@ pub fn parse() -> Option<CliArgs> {
 
     let cipher = app
         .value_of("cipher")
-        .and_then(|s| Some(if s.to_lowercase() == "aes" {
+        .map(|s| if s.to_lowercase() == "aes" {
                 CipherAlgorithm::AesCtr
             } else {
                 CipherAlgorithm::XChaCha20
-            })
+            }
         )
         .unwrap_or_else(|| if aes_ni::get() {
                 CipherAlgorithm::AesCtr

src/lib.rs

@@ -17,7 +17,7 @@ impl Password {
 
 impl From<Option<&str>> for Password {
     fn from(s: Option<&str>) -> Self {
-        Self(s.map(|s| String::from(s)))
+        Self(s.map(String::from))
     }
 }
 
@@ -66,7 +66,7 @@ impl<P: AsRef<Path>> Write for LazyWriter<P> {
     }
 }
 
-pub fn encrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, params: &EncryptionParams, mut cipher: DobyCipher, block_size: usize, already_read: Option<Vec<u8>>) -> io::Result<()> {
+pub fn encrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, params: &EncryptionParams, mut cipher: DobyCipher, block_size: usize, already_read: Option<&[u8]>) -> io::Result<()> {
     writer.write_all(MAGIC_BYTES)?;
     params.write(writer)?;
     let mut buff = vec![0; block_size];
@@ -97,7 +97,7 @@ pub fn decrypt<R: Read, W: Write>(reader: &mut R, writer: &mut W, mut cipher: Do
         if n == 0 {
             break;
         } else {
-           writer.write(&buff[..n])?;
+           writer.write_all(&buff[..n])?;
         }
     }
     Ok(cipher.verify_hmac())

src/main.rs

@@ -16,9 +16,6 @@ fn run() -> bool {
         let mut magic_bytes = vec![0; MAGIC_BYTES.len()];
         match reader.read(&mut magic_bytes) {
             Ok(n) => {
-                if n < magic_bytes.len() {
-                    magic_bytes.truncate(n);
-                }
                 if magic_bytes == MAGIC_BYTES && !cli_args.force_encrypt { //we probably want to decrypt
                     match EncryptionParams::read(&mut reader) {
                         Ok(params) => {
@@ -55,7 +52,7 @@ fn run() -> bool {
                                 &params,
                                 cipher,
                                 cli_args.block_size, 
-                                Some(magic_bytes)
+                                Some(&magic_bytes[..n])
                             ) {
                                 Ok(_) => success = true,
                                 Err(e) => eprintln!("I/O error while encrypting: {}", e)