/* bcal-cfb_bit.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-cfb_bit.h"
#include "bcal-basic.h"

static uint8_t read_bit(void *block, uint32_t index)
{
    uint8_t r;
    r = ((uint8_t*) block)[index / 8];
    r = (r & (0x80 >> (index & 7))) ? 0xff : 0x00;
    return r;
}

static void write_bit(void *block, uint32_t index, uint8_t value)
{
    if (value) {
        /* set bit */
        ((uint8_t*) block)[index / 8] |= 0x80 >> (index & 7);
    } else {
        /* clear bit */
        ((uint8_t*) block)[index / 8] &= ~(0x80 >> (index & 7));
    }
}

uint8_t bcal_cfb_b_init(const bcdesc_t *desc, const void *key,
        uint16_t keysize_b, uint16_t size_b, bcal_cfb_b_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;
    }
    if (size_b > bcal_cipher_getBlocksize_b(desc)) {
        return 0x12;
    }
    ctx->size_b = size_b;
    return bcal_cipher_init(desc, key, keysize_b, &(ctx->cctx));
}

void bcal_cfb_b_free(bcal_cfb_b_ctx_t *ctx)
{
    free(ctx->in_block);
    bcal_cipher_free(&(ctx->cctx));
}

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

void bcal_cfb_b_encNext(void *block, uint8_t offset, bcal_cfb_b_ctx_t *ctx)
{
    uint8_t tmp[ctx->blocksize_B];
    offset &= 7;
    memcpy(tmp, ctx->in_block, ctx->blocksize_B);
    bcal_cipher_enc(tmp, &(ctx->cctx));
    uint16_t i, j;
    uint8_t a;
    for (i = 0; i < ctx->blocksize_B * 8 - ctx->size_b; ++i) {
        a = read_bit(ctx->in_block, i + ctx->size_b);
        write_bit(ctx->in_block, i, a);
    }
    for (j = offset, i = 0; i < ctx->size_b; ++i, ++j) {
        a = read_bit(tmp, i) ^ read_bit(block, j);
        write_bit(ctx->in_block, ctx->blocksize_B * 8 - ctx->size_b + i, a);
        write_bit(block, j, a);
    }
}

void bcal_cfb_b_decNext(void *block, uint8_t offset, bcal_cfb_b_ctx_t *ctx)
{
    uint8_t tmp[ctx->blocksize_B];
    offset &= 7;
    memcpy(tmp, ctx->in_block, ctx->blocksize_B);
    bcal_cipher_enc(tmp, &(ctx->cctx));
    uint16_t i, j;
    uint8_t a, b;
    for (i = 0; i < ctx->blocksize_B * 8 - ctx->size_b; ++i) {
        a = read_bit(ctx->in_block, i + ctx->size_b);
        write_bit(ctx->in_block, i, a);
    }
    for (j = offset, i = 0; i < ctx->size_b; ++i, ++j) {
        a = read_bit(tmp, i);
        b = read_bit(block, j);
        a ^= b;
        write_bit(ctx->in_block, ctx->blocksize_B * 8 - ctx->size_b + i, b);
        write_bit(block, j, a);
    }
}

void bcal_cfb_b_encMsg(const void *iv, void *msg, uint8_t offset,
        uint32_t msg_blocks, bcal_cfb_b_ctx_t *ctx)
{
    bcal_cfb_b_loadIV(iv, ctx);
    uint32_t addr;
    addr = ((uint16_t) msg) * 8 + offset;
    while (msg_blocks--) {
        msg = (void*) ((uint16_t) (addr / 8));
        offset = addr & 7;
        bcal_cfb_b_encNext(msg, offset, ctx);
        addr += ctx->size_b;
    }
}

void bcal_cfb_b_decMsg(const void *iv, void *msg, uint8_t offset,
        uint32_t msg_blocks, bcal_cfb_b_ctx_t *ctx)
{
    bcal_cfb_b_loadIV(iv, ctx);
    uint32_t addr;
    addr = ((uint16_t) msg) * 8 + offset;
    while (msg_blocks--) {
        msg = (void*) ((uint16_t) (addr / 8));
        offset = addr & 7;
        bcal_cfb_b_decNext(msg, offset, ctx);
        addr += ctx->size_b;
    }
}