doc: add comments for functions

Add comments for functions:
- encrypt_auth_inplace
- decrypt_auth_inplace

mbedtls/src/cipher/raw/mod.rs

@@ -423,6 +423,25 @@ impl Cipher {
         Ok(plain_len)
     }
 
+    /// The authenticated encryption (AEAD/NIST_KW) function.
+    /// 
+    /// For AEAD modes, the tag will be appended to the ciphertext, as recommended by RFC 5116.
+    /// (NIST_KW doesn't have a separate tag.)
+    /// 
+    /// # Arguments
+    ///
+    /// * `ad` - The additional data to authenticate
+    /// * `data_with_tag` - The data to be encrypted and authenticated, along with space for the tag
+    /// * `tag_len` - The length of the tag to be generated
+    ///
+    /// # Returns
+    ///
+    /// * `Result<usize>` - The length of the encrypted data on success
+    ///
+    /// # Errors
+    ///
+    /// * `Error::CipherBadInputData` - If the size of `data_with_tag` minus `tag_len` is less than
+    ///   or equal to zero
     pub fn encrypt_auth_inplace(
         &mut self,
         ad: &[u8],
@@ -455,6 +474,29 @@ impl Cipher {
         Ok(olen)
     }
 
+
+    /// The authenticated encryption (AEAD/NIST_KW) function.
+    /// 
+    /// If the data is not authentic, then the output buffer is zeroed out to
+    /// prevent the unauthentic plaintext being used, making this interface safer.
+    /// 
+    /// For AEAD modes, the tag must be appended to the ciphertext, as recommended by RFC 5116.
+    /// (NIST_KW doesn't have a separate tag.)
+    /// 
+    /// # Arguments
+    ///
+    /// * `ad` - The additional data to authenticate
+    /// * `data_with_tag` - The data to be encrypted and authenticated, along with space for the tag
+    /// * `tag_len` - The length of the tag to be generated
+    ///
+    /// # Returns
+    ///
+    /// * `Result<usize>` - The length of the decrypted data on success
+    ///
+    /// # Errors
+    ///
+    /// * `Error::CipherBadInputData` - If the size of `data_with_tag` minus `tag_len` is less than
+    ///   or equal to zero
     pub fn decrypt_auth_inplace(
         &mut self,
         ad: &[u8],