Timed User Input C

//imran rana
#include <time.h>
#include <iostream>
#include <conio.h>
#include<stdio.h>

using namespace std;
char* get_timed_input(long timeout_seconds, char* input_buffer,int buffer_size)
{
    time_t start, now;
    int nChars = 0;
    int chr = 0;
    const int VK_RETURN = 13;
    // start timer
    time(&start);
    while( nChars < buffer_size && chr != VK_RETURN)
    {

        time(&now);
        if( (now-start) >= timeout_seconds)
        {
            // timeout
            input_buffer[nChars] ='\0';
            return NULL;
        }
        while( !_kbhit() )
        {
            time(&now);
            if( (now-start) >= timeout_seconds)
            {
                // timeout
                input_buffer[nChars] = '\0';
                return NULL;
            }
        }
        chr = getche();
        input_buffer[nChars++] = chr;
    }

    input_buffer[nChars] = '\0';
    return input_buffer;

}
int main()
{
    char imran[500]= {0};
    get_timed_input(3,imran,500);
    printf("\n:) User Input : %s",imran);
    getch();

}