#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/resource.h>
#include <linux/types.h>

#include <sys/wait.h>

#define NAME "ANOVIKOV-LAB3.1"

#define START_MEM 1024
#define MAX 100
#define THREADS 8

unsigned int a=0,b=0,c=0,d=0;
unsigned int K;

pid_t *pids;

struct equation {
    unsigned int a;
    unsigned int b;
    unsigned int c;
    unsigned int d;
};

struct equation **result;

typedef unsigned long long uint64;

// for prevent segmentation fault
uint64 result_mem[THREADS];

void print_data(unsigned int a, unsigned int b,
                unsigned int c, unsigned int d,
                int type)
{

    printf("%i %i %i %i", a,b,c,d);
    if (type == 0)
    {
        printf(" a+b+c+d = %i", K);
    }else if(type == 1)
    {
        printf(" a-b+c-d = %i", K);
    }else if(type == 2)
    {
        printf(" a*b-c*d = %i", K);
    }
    printf("\n");

}


struct equation make_equation(unsigned int a, unsigned int b,
                                     unsigned int c, unsigned int d)
{
    struct equation out = {a,b,c,d};
    return out;
}

int main(void)
{
    int i;
    int index;

    int STEP = THREADS;
    K=1024;
    setbuf(stdout, NULL);

    pids = (pid_t*)malloc(sizeof(pid_t) * THREADS);

    result = (struct equation**)malloc(sizeof(struct equation *)*THREADS);

    for (i=0;i<THREADS;i++)
    {
        result[i] = (struct equation*)malloc(sizeof(struct equation) * START_MEM);
        result_mem[i] = START_MEM;
    }

    for(index=0;index<THREADS;index++)
    {
        pid_t p = fork();
        pids[index] = p;

        // variable for current array state
        uint64 arr_i=0;

        switch (p){
            case 0: // child
            {
            STEP = THREADS;
                for(a=0;a<MAX;a++)
                {
                    for(b=0;b<MAX;b++)
                    {
                        for(c=0;c<MAX;c++)
                        {
                            for(d=index;d<MAX;d+=STEP)
                            {

//                                printf("%i %i %i %i\n", a,b,c,d);

                                if (a+b+c+d == K)
                                {
                                    if (result_mem[index] <= arr_i )
                                    {
                                        result[index] = realloc(result[index], sizeof(struct equation)*result_mem[index]*2);
                                        result_mem[index] *= 2;
                                        printf("pid: %i; mem: %lli\n", index, result_mem[index]);
                                        printf("\t%i %i %i %i\n", a,b,c,d);

                                    }
                                    result[index][arr_i++] = make_equation(a,b,c,d);
                                    print_data(a,b,c,d,0);
                                }

                                if (a-b+c-d == K)
                                {
                                    if (result_mem[index] <= arr_i )
                                    {
                                        result[index] = realloc(result[index], sizeof(struct equation)*result_mem[index]*2);
                                        result_mem[index] *= 2;
                                        printf("pid: %i; mem: %lli\n", index, result_mem[index]);
                                        printf("\t%i %i %i %i\n", a,b,c,d);

                                    }
                                    result[index][arr_i++] = make_equation(a,b,c,d);
                                    print_data(a,b,c,d,1);
                                }

                                if (a*b-c*d == K)
                                {
                                    if (result_mem[index] <= arr_i )
                                    {
                                        result[index] = realloc(result[index], sizeof(struct equation)*result_mem[index]*2);
                                        result_mem[index] *= 2;
                                        printf("pid: %i; mem: %lli\n", index, result_mem[index]);
                                        printf("\t%i %i %i %i\n", a,b,c,d);

                                    }
                                    result[index][arr_i++] = make_equation(a,b,c,d);
                                    print_data(a,b,c,d,2);
                                }
                            }
                        }
                    }
                }


                return 0; //similar to _exit(0)
            }
            default: //parent
            {


            }
        }
    }



    wait(NULL);

    return 0;
}