/* bcal-ofb.c */
/*
 This file is part of the AVR-Crypto-Lib.
 Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdint.h>
#include <string.h>
#include "bcal-ofb.h"
#include "bcal-basic.h"
#include "memxor.h"

uint8_t bcal_ofb_init(const bcdesc_t *desc, const void *key, uint16_t keysize_b,
        bcal_ofb_ctx_t *ctx)
{
    ctx->desc = (bcdesc_t*) desc;
    ctx->blocksize_B = (bcal_cipher_getBlocksize_b(desc) + 7) / 8;
    ctx->in_block = malloc(ctx->blocksize_B);
    if (ctx->in_block == NULL) {
        return 0x11;
    }
    return bcal_cipher_init(desc, key, keysize_b, &(ctx->cctx));
}

void bcal_ofb_free(bcal_ofb_ctx_t *ctx)
{
    free(ctx->in_block);
    bcal_cipher_free(&(ctx->cctx));
}

void bcal_ofb_loadIV(const void *iv, bcal_ofb_ctx_t *ctx)
{
    if (iv) {
        memcpy(ctx->in_block, iv, ctx->blocksize_B);
    }
}

void bcal_ofb_encNext(void *block, bcal_ofb_ctx_t *ctx)
{
    bcal_cipher_enc(ctx->in_block, &(ctx->cctx));
    memxor(block, ctx->in_block, ctx->blocksize_B);
}

void bcal_ofb_decNext(void *block, bcal_ofb_ctx_t *ctx)
{
    bcal_cipher_enc(ctx->in_block, &(ctx->cctx));
    memxor(block, ctx->in_block, ctx->blocksize_B);
}

void bcal_ofb_encMsg(const void *iv, void *msg, uint32_t msg_len_b,
        bcal_ofb_ctx_t *ctx)
{
    uint16_t block_len_b;
    block_len_b = ctx->blocksize_B * 8;
    bcal_ofb_loadIV(iv, ctx);
    while (msg_len_b > block_len_b) {
        bcal_ofb_encNext(msg, ctx);
        msg_len_b -= block_len_b;
        msg = (uint8_t*) msg + ctx->blocksize_B;
    }
    bcal_cipher_enc(ctx->in_block, &(ctx->cctx));
    ctx->in_block[msg_len_b / 8] = 0xff00 >> (msg_len_b & 7);
    memxor(msg, ctx->in_block, (msg_len_b + 7) / 8);
}

void bcal_ofb_decMsg(const void *iv, void *msg, uint32_t msg_len_b,
        bcal_ofb_ctx_t *ctx)
{
    bcal_ofb_encMsg(iv, msg, msg_len_b, ctx);
}