/*
 * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
 * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 *    conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 COPYRIGHT HOLDER OR
 * CONTRIBUTORS 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.
 */

#include "los_random.h"
#include "fcntl.h"
#include "linux/kernel.h"
#include "fs/driver.h"
/*****************************************************************
随机数设备软驱动
	/dev/random在类UNIX系统中是一个特殊的设备文件，可以用作随机数发生器或伪随机数发生器。

*****************************************************************/

static unsigned long g_randomMax =  0x7FFFFFFF; ///< 随机数范围

/// 生成随机数
static long DoRand(unsigned long *value)
{
    long quotient, remainder, t;

    quotient = *value / 127773L;
    remainder = *value % 127773L;
    t = 16807L * remainder - 2836L * quotient;
    if (t <= 0) {
        t += 0x7fffffff;
    }
    return ((*value = t) % (g_randomMax + 1));
}

static unsigned long g_seed = 1;

int RanOpen(struct file *filep)
{
    g_seed = (unsigned long)(LOS_CurrNanosec() & 0xffffffff);//取当前纳秒数
    return 0;//返回成功,目的是为了给g_seed取赋值
}

static int RanClose(struct file *filep)
{
    return 0;
}

int RanIoctl(struct file *filep, int cmd, unsigned long arg)
{
    PRINT_ERR("random ioctl is not supported\n");
    return -ENOTSUP;
}

ssize_t RanRead(struct file *filep, char *buffer, size_t buflen)
{
    ssize_t len = buflen;
    char *buf = buffer;
    unsigned int temp;
    int ret;

    if (len % sizeof(unsigned int)) {
        PRINT_ERR("random size not aligned by 4 bytes\n");
        return -EINVAL;
    }
    while (len > 0) {
        temp = DoRand(&g_seed);
        ret = LOS_CopyFromKernel((void *)buf, sizeof(unsigned int), (void *)&temp, sizeof(unsigned int));
        if (ret) {
            break;
        }
        len -= sizeof(unsigned int);
        buf += sizeof(unsigned int);
    }
    return (buflen - len); /* return a successful len */
}

static ssize_t RanMap(struct file *filep, LosVmMapRegion *region)
{
    PRINTK("%s %d, mmap is not support\n", __FUNCTION__, __LINE__);
    return 0;
}

static const struct file_operations_vfs g_ranDevOps = {
    RanOpen,  /* open */
    RanClose, /* close */
    RanRead,  /* read */
    NULL,      /* write */
    NULL,      /* seek */
    RanIoctl, /* ioctl */
    RanMap,   /* mmap */
#ifndef CONFIG_DISABLE_POLL
    NULL,      /* poll */
#endif
    NULL,      /* unlink */
};
//注册生成随机数驱动
int DevRandomRegister(void)
{
    return register_driver("/dev/random", &g_ranDevOps, 0666, 0); /* 0666: file mode */
}

