// random.cpp

/*    Copyright 2012 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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 Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects
 *    for all of the code used other than as permitted herein. If you modify
 *    file(s) with this exception, you may extend this exception to your
 *    version of the file(s), but you are not obligated to do so. If you do not
 *    wish to do so, delete this exception statement from your version. If you
 *    delete this exception statement from all source files in the program,
 *    then also delete it in the license file.
 */

#include "mongo/platform/random.h"

#include <stdio.h>
#include <string.h>

#ifndef _WIN32
#include <errno.h>
#endif

#define _CRT_RAND_S
#include <cstdlib>
#include <iostream>
#include <fstream>

#include "mongo/platform/basic.h"

namespace mongo {

    // ---- PseudoRandom  -----

    int32_t PseudoRandom::nextInt32() {
        int32_t t = _x ^ (_x << 11);
        _x = _y;
        _y = _z;
        _z = _w;
        return _w = _w ^ (_w >> 19) ^ (t ^ (t >> 8));
    }

    namespace {
        const int32_t default_y = 362436069;
        const int32_t default_z = 521288629;
        const int32_t default_w = 88675123;
    }

    PseudoRandom::PseudoRandom( int32_t seed ) {
        _x = seed;
        _y = default_y;
        _z = default_z;
        _w = default_w;
    }


    PseudoRandom::PseudoRandom( uint32_t seed ) {
        _x = static_cast<int32_t>(seed);
        _y = default_y;
        _z = default_z;
        _w = default_w;
    }


    PseudoRandom::PseudoRandom( int64_t seed ) {
        int32_t high = seed >> 32;
        int32_t low = seed & 0xFFFFFFFF;

        _x = high ^ low;
        _y = default_y;
        _z = default_z;
        _w = default_w;
    }

    int64_t PseudoRandom::nextInt64() {
        int64_t a = nextInt32();
        int64_t b = nextInt32();
        return ( a << 32 ) | b;
    }

    // --- SecureRandom ----

    SecureRandom::~SecureRandom() {
    }

#ifdef _WIN32
    class WinSecureRandom : public SecureRandom {
        virtual ~WinSecureRandom(){}
        int64_t nextInt64() {
            uint32_t a, b;
            if ( rand_s(&a) ) {
                abort();
            }
            if ( rand_s(&b) ) {
                abort();
            }
            return ( static_cast<int64_t>(a) << 32 ) | b;
        }
    };

    SecureRandom* SecureRandom::create() {
        return new WinSecureRandom();
    }

#elif defined(__linux__) || defined(__sunos__) || defined(__APPLE__)

    class InputStreamSecureRandom : public SecureRandom {
    public:
        InputStreamSecureRandom( const char* fn ) {
            _in = new std::ifstream( fn, std::ios::binary | std::ios::in );
            if ( !_in->is_open() ) {
                std::cerr << "can't open " << fn << " " << strerror(errno) << std::endl;
                abort();
            }
        }

        ~InputStreamSecureRandom() {
            delete _in;
        }

        int64_t nextInt64() {
            int64_t r;
            _in->read( reinterpret_cast<char*>( &r ), sizeof(r) );
            if ( _in->fail() ) {
                abort();
            }
            return r;
        }

    private:
        std::ifstream* _in;
    };

    SecureRandom* SecureRandom::create() {
        return new InputStreamSecureRandom( "/dev/urandom" );
    }

#else
    class SRandSecureRandom : public SecureRandom {
    public:
        SRandSecureRandom() {
            srandomdev();
        }

        int64_t nextInt64() {
            long a, b;
            a = random();
            b = random();
            return ( static_cast<int64_t>(a) << 32 ) | b;
        }
    };

    SecureRandom* SecureRandom::create() {
        return new SRandSecureRandom();
    }


#endif

}
