/* crc64.c - crc64 function  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2008,2011  Free Software Foundation, Inc.
 *
 *  GRUB 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.
 *
 *  GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/types.h>
#include <grub/crypto.h>

GRUB_MOD_LICENSE("GPLv3+");

static grub_uint64_t crc64_table[256];

/* Helper for init_crc64_table.  */
static grub_uint64_t
reflect(grub_uint64_t ref, int len)
{
	grub_uint64_t result = 0;
	int i;

	for (i = 1; i <= len; i++)
	{
		if (ref & 1)
			result |= 1ULL << (len - i);
		ref >>= 1;
	}

	return result;
}

static void
init_crc64_table(void)
{
	grub_uint64_t polynomial = 0x42f0e1eba9ea3693ULL;
	int i, j;

	for (i = 0; i < 256; i++)
	{
		crc64_table[i] = reflect(i, 8) << 56;
		for (j = 0; j < 8; j++)
		{
			crc64_table[i] = (crc64_table[i] << 1) ^
				(crc64_table[i] & (1ULL << 63) ? polynomial : 0);
		}
		crc64_table[i] = reflect(crc64_table[i], 64);
	}
}

static void
crc64_init(void* context)
{
	if (!crc64_table[1])
		init_crc64_table();
	*(grub_uint64_t*)context = 0;
}

static void
crc64_write(void* context, const void* buf, grub_size_t size)
{
	unsigned i;
	const grub_uint8_t* data = buf;
	grub_uint64_t crc = ~grub_le_to_cpu64(*(grub_uint64_t*)context);

	for (i = 0; i < size; i++)
	{
		crc = (crc >> 8) ^ crc64_table[(crc & 0xFF) ^ *data];
		data++;
	}

	*(grub_uint64_t*)context = grub_cpu_to_le64(~crc);
}

static grub_uint8_t*
crc64_read(void* context)
{
	return context;
}

static void
crc64_final(void* context __attribute__((unused)))
{
}

gcry_md_spec_t _gcry_digest_spec_crc64 =
{
  "CRC64", 0, 0, 0, 8,
  crc64_init, crc64_write, crc64_final, crc64_read,
  sizeof(grub_uint64_t),
  .blocksize = 64
};
