//
// VMime library (http://www.vmime.org)
// Copyright (C) 2002 Vincent Richard <vincent@vmime.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, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// Linking this library statically or dynamically with other modules is making
// a combined work based on this library.  Thus, the terms and conditions of
// the GNU General Public License cover the whole combination.
//

#include "vmime/utility/random.hpp"
#include "vmime/platform.hpp"

#include <ctime>


namespace vmime {
namespace utility {


static unsigned int getRandomSeed() {

	unsigned int seed;

	platform::getHandler()->generateRandomBytes(
		reinterpret_cast <unsigned char*>(&seed), sizeof(seed)
	);

	return seed;
}


unsigned int random::getNext() {

	static unsigned int next = getRandomSeed();

	// Park and Miller's minimal standard generator:
	// xn+1 = (a * xn + b) mod c
	// xn+1 = (16807 * xn) mod (2^31 - 1)
	next = static_cast<unsigned int>((16807 * next) % 2147483647ul);
	return next;
}


unsigned int random::getTime() {

	return static_cast <unsigned int>((platform::getHandler()->getUnixTime()));
}


unsigned int random::getProcess() {

	return platform::getHandler()->getProcessId();
}


const string random::getString(const size_t length, const string& randomChars) {

	string res;
	res.resize(length);

	const unsigned int x = static_cast <unsigned int>(randomChars.length());
	size_t c = 0;

	while (c < length) {

		for (unsigned int n = random::getNext() ; n != 0 && c < length ; n /= x) {
			res[c++] = randomChars[n % x];
		}
	}

	return res;
}


} // utility
} // vmime