/**
 * @file gmp_helper.c
 * 
 * @brief Implementation of gmp_helper_t.
 * 
 */

/*
 * Copyright (C) 1999, 2000, 2001  Henry Spencer.
 * Copyright (C) 2005 Jan Hutter, Martin Willi
 * Hochschule fuer Technik Rapperswil
 *
 * 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 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 */
 
#include <stdio.h>
 
#include "gmp_helper.h"

#include <utils/allocator.h>
#include <utils/randomizer.h>

/**
 * Number of times the probabilistic primality test is applied.
 */
#define PRIMECHECK_ROUNDS 30


typedef struct private_gmp_helper_t private_gmp_helper_t;

/**
 * Private data of an gmp_helper_t object.
 */
struct private_gmp_helper_t {
	/**
	 * Public gmp_helper_t interface.
	 */
	gmp_helper_t public;
};


/**
 * Implementation of gmp_helper_t.chunk_to_mpz.
 */
static void chunk_to_mpz(private_gmp_helper_t *this, mpz_t *mpz_value, chunk_t data)
{
	size_t i;
	
	mpz_init_set_ui(*(mpz_value), 0);
	
	for (i = 0; i < data.len; i++)
	{
		mpz_mul_ui(*(mpz_value),*(mpz_value), 1 << 8);
		mpz_add_ui(*(mpz_value),*(mpz_value), data.ptr[i]);
	}
}

/**
 * Implementation of gmp_helper_t.mpz_to_chunk.
 */
static void mpz_to_chunk (private_gmp_helper_t *this,mpz_t *mpz_value, chunk_t *data,size_t bytes)
{
	mpz_t temp1, temp2;
	int i;
	chunk_t tmp_chunk;
	
	tmp_chunk.len = bytes;
	tmp_chunk.ptr = allocator_alloc(tmp_chunk.len);
	
	memset(tmp_chunk.ptr,0,tmp_chunk.len);
	
	mpz_init(temp1);
	mpz_init(temp2);
	
	mpz_set(temp1, *mpz_value);
	
	for (i = tmp_chunk.len-1; i >= 0; i--)
	{
		tmp_chunk.ptr[i] = mpz_mdivmod_ui(temp2, NULL, temp1, 1 << 8);
		mpz_set(temp1, temp2);
	}
	
	mpz_clear(temp1);
	mpz_clear(temp2);
	*data = tmp_chunk;
}

/**
 * Implementation of gmp_helper_t.init_prime.
 */
static void init_prime (private_gmp_helper_t *this, mpz_t *prime, int bytes)
{
	randomizer_t *randomizer;
	chunk_t random_bytes;
	randomizer = randomizer_create();
	
	/* TODO change to true random device ? */
	//randomizer->allocate_random_bytes(randomizer,bytes, &random_bytes);
	randomizer->allocate_pseudo_random_bytes(randomizer,bytes, &random_bytes);
	
	/* make sure most significant bit is set */
	random_bytes.ptr[0] = random_bytes.ptr[0] | 0x80;
	
	/* not needed anymore */
	randomizer->destroy(randomizer);
	
	/* convert chunk to mpz value */
	this->public.chunk_to_mpz(&(this->public),prime, random_bytes);
	
	/* chunk is not used anymore */
	allocator_free(random_bytes.ptr);
	random_bytes.ptr = NULL;
	
	/* composites are possible but should never occur */
	mpz_nextprime (*(prime),*(prime));
}

/**
 * Implementation of gmp_helper_t.destroy.
 */
static void destroy(private_gmp_helper_t *this)
{
	allocator_free(this);
}

/*
 * Described in header
 */
gmp_helper_t *gmp_helper_create()
{
	private_gmp_helper_t *this = allocator_alloc_thing(private_gmp_helper_t);
	
	/* public functions */
	this->public.destroy = (void (*)(gmp_helper_t *)) destroy;
	this->public.init_prime = (void (*) (gmp_helper_t *, mpz_t *, int)) init_prime;
	
	/* private functions */
	this->public.chunk_to_mpz = (void (*) (gmp_helper_t *,mpz_t *, chunk_t )) chunk_to_mpz;
	this->public.mpz_to_chunk = (void (*) (gmp_helper_t *,mpz_t *, chunk_t *,size_t )) mpz_to_chunk;
	
	return &(this->public);
}