#include <stdio.h>
#include <unistd.h>
#include <sys/sysinfo.h>
#include <stdlib.h>
#include <limits.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <semaphore.h>
#include <sys/stat.h>

typedef double (*function_t)(double);

double* pmap_process(function_t func, const double *in, size_t count);

void pmap_free(double *ptr, size_t count);

double* pmap_process(function_t func, const double *in, size_t count) {
    int processes_num = get_nprocs();

    double* values = (double*) mmap(NULL, sizeof(double)*count, PROT_WRITE|PROT_READ, MAP_SHARED|MAP_ANONYMOUS, -1, 0);

    sem_t* sem = (sem_t*) mmap(NULL, sizeof(sem_t), PROT_WRITE|PROT_READ, MAP_SHARED|MAP_ANONYMOUS, -1, 0);

    for (size_t i = 0; i < count; i++) {
        values[i] = in[i];
    }

    sem_init(sem, 1, processes_num);

    pid_t pids[processes_num];

    for (size_t i = 0; i < processes_num; ++i) {
        pids[i] = fork();

        if (pids[i] == 0) {
            sem_wait(sem);
            size_t from = i*count/processes_num;
            size_t to = (i+1)*count/processes_num - 1;
            if (i == processes_num) {
                to = count - 1;
            }
            for (from; from < to; from++) {
                values[from] = func(values[from]);
            }

            sem_post(sem);
            exit(0);
        }
      }
      int sem_value = 0;
      sem_getvalue(sem, &sem_value);
      while(sem_value != processes_num) {
          sem_getvalue(sem, &sem_value);
      }
      sem_destroy(sem);
      return values;
}

void pmap_free(double *ptr, size_t count) {
    munmap(ptr, sizeof(double)*count);
}