source: mainline/uspace/lib/c/generic/rndgen.c@ 87337dc5

/*
 * Copyright (c) 2018 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libc
 * @{
 */
/**
 * @file
 * @brief Random number generator.
 *
 * Generate random (as opposed to pseudorandom) numbers. This should be
 * used sparingly (e.g. to seed a pseudorandom number generator).
 */

#include <errno.h>
#include <rndgen.h>
#include <stdint.h>
#include <stdlib.h>
#include <time.h>

/** Create random number generator.
 *
 * @param rrndgen Place to store new random number generator
 * @return EOK on success or error code
 */
errno_t rndgen_create(rndgen_t **rrndgen)
{
        rndgen_t *rndgen;
        struct timeval tv;

        rndgen = calloc(1, sizeof(rndgen_t));
        if (rndgen == NULL)
                return ENOMEM;

        /* XXX This is a rather poor way of generating random numbers */
        gettimeofday(&tv, NULL);
        rndgen->seed = tv.tv_sec ^ tv.tv_usec;

        *rrndgen = rndgen;
        return EOK;
}

/** Destroy random number generator.
 *
 * @param rndgen Random number generator or @c NULL
 */
void rndgen_destroy(rndgen_t *rndgen)
{
        if (rndgen == NULL)
                return;

        free(rndgen);
}

/** Generate random 8-bit integer.
 *
 * @param rndgen Random number generator
 * @param rb Place to store random 8-bit integer
 * @return EOK on success or error code
 */
errno_t rndgen_uint8(rndgen_t *rndgen, uint8_t *rb)
{
        rndgen->seed = (1366 * rndgen->seed + 150889) % 714025;

        *rb = rndgen->seed & 0xff;
        return EOK;
}

/** Generate random 32-bit integer.
 *
 * @param rndgen Random number generator
 * @param rw Place to store random 32-bit integer
 * @return EOK on success or error code
 */
errno_t rndgen_uint32(rndgen_t *rndgen, uint32_t *rw)
{
        int i;
        uint8_t b;
        uint32_t w;
        errno_t rc;

        w = 0;
        for (i = 0; i < 4; i++) {
                rc = rndgen_uint8(rndgen, &b);
                if (rc != EOK)
                        return rc;

                w = (w << 8) | b;
        }

        *rw = w;
        return EOK;
}

/** @}
 */