Colony

/**

 * @file robot.c

 * @author Colony Project

 * @brief Simulator Robot Management

 *

 * Contains implementations of functions managing robots

 * in the simulator, including process control and memory

 * management.

 **/

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <sys/wait.h>

#include <robot_shared.h>

#include <sys/ipc.h>

#include <sys/types.h>

#include <sys/shm.h>

#include <errno.h>

#include "robot.h"

void sig_chld_handler(int sig);

// global variables

int first_available_id = 0;

// an expanding array of robots

Robot* robots = NULL;

int robots_size = 0;

int robots_initialize(void)

{

        if (signal(SIGCHLD, sig_chld_handler) == SIG_ERR)

                return -1;

        robots_size = 10;

        robots = (Robot*)malloc(sizeof(Robot) * robots_size);

        if (!robots)

                return -1;

        memset(robots, 0, sizeof(Robot) * robots_size);

        return 0;

}

/**

 * Creates a new robot. Returns its id on

 * success, or a negative integer on failure.

 **/

int robot_create(char *execname)

{

        int pid;

        int id = first_available_id;

        Robot* r = &robots[id];

        // do shared memory stuff here

        key_t key = IPC_PRIVATE;

        //Memory accessible only to children with r/w privileges

        r->sharedMemID = shmget(key, sizeof(RobotShared), IPC_CREAT | 0666);

        if(r->sharedMemID < 0)

        {

                fprintf(stderr, "Failed to get shared memory.\n");

                return -1;

        }

        r->shared = (RobotShared*)shmat(r->sharedMemID, NULL, 0);

        if(!(r->shared))

        {

                // TODO: do we have to free the shared memory?

                fprintf(stderr, "Error attaching memory to parent.\n");

                return -1;

        }

        // Initialize robot structure here

        r->shared->motor1 = 0;

        r->shared->motor2 = 0;

        r->id = id;

        if((pid = fork()) < 0)

        {

                // TODO: do we have to free the shared memory?

                r->id = 0;

                fprintf(stderr, "Failed to fork robot process.\n");

                return -1;

        }                                                                                         

        if(!pid)

        {

                char var[21];

                char *envp[] = {var, NULL};

                /* restore default sigchld handler */

                signal(SIGCHLD, SIG_DFL);

                sprintf(var, "memory_id=%d", r->sharedMemID);

                //TODO: keep the other env. stuff around

                execve(execname, NULL, envp);

                fprintf(stderr, "exec failed to run child process.\n");

                exit(-1);

        }

        else

        {

                r->pid = pid;

                do {

                        first_available_id++;

                } while (first_available_id < robots_size &&

                                robots[first_available_id].id != 0);

                // resize the array if necessary

                if (first_available_id >= robots_size)

                {

                        robots_size *= 2;

                        robots = realloc(robots, sizeof(Robot) * robots_size);

                        if (!robots)

                        {

                                fprintf(stderr, "Out of memory.\n");

                                return -1;

                        }

                }

        }

        return id;

}

/**

 * Frees all resources associated with a robot, including

 * killing its process if necessary.

 *

 * @return zero on success, nonzero on failure

 **/

int robot_destroy(int id)

{

        Robot* r;

        if (id < 0 || id >= robots_size)

                return -1;

        r = &robots[id];

        if (r->id == 0)

                return -1;

        if (!shmdt(r->shared))

        {

                fprintf(stderr, "Failed to free shared memory.\n");

                return -1;

        }

        if (!shmctl(r->sharedMemID, IPC_RMID, NULL))

        {

                fprintf(stderr, "Failed to free shared memory.\n");

                return -1;

        }

        memset(r, 0, sizeof(Robot));

        if (id < first_available_id)

                first_available_id = 0;

        return 0;

}

void sig_chld_handler(int sig)

{

        pid_t pid;

        int cstat;

        printf("SIGCHLD: parent waiting\n");

        pid = waitpid(0, &cstat, WUNTRACED);

        printf("got %d from %d\n", cstat, pid);

        kill(pid, SIGCONT);

}