/*

* OFB Mode

* (C) 1999-2007,2014 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/internal/ofb.h>

#include <botan/exceptn.h>

namespace Botan {

OFB::OFB(std::unique_ptr<BlockCipher> cipher) :

   m_cipher(std::move(cipher)),

   m_buffer(m_cipher->block_size()),

   m_buf_pos(0)

   {

   }

void OFB::clear()

   {

   m_cipher->clear();

   zeroise(m_buffer);

   m_buf_pos = 0;

   }

void OFB::key_schedule(const uint8_t key[], size_t key_len)

   {

   m_cipher->set_key(key, key_len);

   // Set a default all-zeros IV

   set_iv(nullptr, 0);

   }

std::string OFB::name() const

   {

   return "OFB(" + m_cipher->name() + ")";

   }

size_t OFB::default_iv_length() const

   {

   return m_cipher->block_size();

   }

bool OFB::valid_iv_length(size_t iv_len) const

   {

   return (iv_len <= m_cipher->block_size());

   }

Key_Length_Specification OFB::key_spec() const

   {

   return m_cipher->key_spec();

   }

std::unique_ptr<StreamCipher> OFB::new_object() const

   {

   return std::make_unique<OFB>(m_cipher->new_object());

   }

void OFB::cipher(const uint8_t in[], uint8_t out[], size_t length)

   {

   while(length >= m_buffer.size() - m_buf_pos)

      {

      xor_buf(out, in, &m_buffer[m_buf_pos], m_buffer.size() - m_buf_pos);

      length -= (m_buffer.size() - m_buf_pos);

      in += (m_buffer.size() - m_buf_pos);

      out += (m_buffer.size() - m_buf_pos);

      m_cipher->encrypt(m_buffer);

      m_buf_pos = 0;

      }

   xor_buf(out, in, &m_buffer[m_buf_pos], length);

   m_buf_pos += length;

   }

void OFB::set_iv(const uint8_t iv[], size_t iv_len)

   {

   if(!valid_iv_length(iv_len))

      throw Invalid_IV_Length(name(), iv_len);

   zeroise(m_buffer);

   buffer_insert(m_buffer, 0, iv, iv_len);

   m_cipher->encrypt(m_buffer);

   m_buf_pos = 0;

   }

void OFB::seek(uint64_t /*offset*/)

   {

   throw Not_Implemented("OFB does not support seeking");

   }

}