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, 2 insertions, 2 deletions

diff --git a/src/lib/modes/aead/siv/siv.h b/src/lib/modes/aead/siv/siv.h
index d3e4c5270..6acfe515a 100644
--- a/src/lib/modes/aead/siv/siv.h
+++ b/src/lib/modes/aead/siv/siv.h
@@ -21,7 +21,7 @@ namespace Botan {
 class BOTAN_DLL SIV_Mode : public AEAD_Mode
    {
    public:
-      void update(secure_vector<byte>& blocks, size_t offset = 0) override;
+      size_t process(uint8_t buf[], size_t size) override;
 
       void set_associated_data_n(size_t n, const byte ad[], size_t ad_len);
 
@@ -53,7 +53,7 @@ class BOTAN_DLL SIV_Mode : public AEAD_Mode
 
       secure_vector<byte> S2V(const byte text[], size_t text_len);
    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;