Cipher_Mode API improvements

The Cipher_Mode::update API is more general than needed to just
support ciphers (this is due to it previously being an API of
Transform which before 8b85b780515 was Cipher_Mode's base class)

Define a less general interface `process` which either processes the
blocks in-place, producing exactly as much output as there was input,
or (SIV/CCM case) saves the entire message for processing in `finish`.
These two uses cover all current or anticipated cipher modes.

Leaves `update` for compatability with existing callers; all that is
needed is an inline function forwarding to `process`.

Removes the return type from `start` - in all cipher implementations,
this always returned an empty vector.

Adds BOTAN_ARG_CHECK macro; right now BOTAN_ASSERT is being used
for argument checking in some places, which is not right at all.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/modes/xts/xts.h b/src/lib/modes/xts/xts.h
index e751b1644..6c4ba8d99 100644
--- a/src/lib/modes/xts/xts.h
+++ b/src/lib/modes/xts/xts.h
@@ -42,7 +42,7 @@ class BOTAN_DLL XTS_Mode : public Cipher_Mode
       void update_tweak(size_t last_used);
 
    private:
-      secure_vector<byte> start_raw(const byte nonce[], size_t nonce_len) override;
+      void start_msg(const byte nonce[], size_t nonce_len) override;
       void key_schedule(const byte key[], size_t length) override;
 
       std::unique_ptr<BlockCipher> m_cipher, m_tweak_cipher;
@@ -57,7 +57,7 @@ class BOTAN_DLL XTS_Encryption final : public XTS_Mode
    public:
       explicit XTS_Encryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
 
-      void update(secure_vector<byte>& blocks, size_t offset = 0) override;
+      size_t process(uint8_t buf[], size_t size) override;
 
       void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
 
@@ -72,7 +72,7 @@ class BOTAN_DLL XTS_Decryption final : public XTS_Mode
    public:
       explicit XTS_Decryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
 
-      void update(secure_vector<byte>& blocks, size_t offset = 0) override;
+      size_t process(uint8_t buf[], size_t size) override;
 
       void finish(secure_vector<byte>& final_block, size_t offset = 0) override;