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/**
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* @file robot.c
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* @author Colony Project
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* @brief Simulator Robot Management
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*
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* Contains implementations of functions managing robots
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* in the simulator, including process control and memory
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* management.
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**/
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#include <stdlib.h> |
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#include <stdio.h> |
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#include <string.h> |
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#include <unistd.h> |
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#include <signal.h> |
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#include <sys/wait.h> |
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#include <robot_shared.h> |
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#include <sys/ipc.h> |
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#include <sys/types.h> |
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#include <sys/shm.h> |
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#include <errno.h> |
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#include "robot.h" |
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void sig_chld_handler(int sig); |
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// global variables
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int first_available_id = 0; |
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// an expanding array of robots
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Robot* robots = NULL;
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int robots_size = 0; |
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int robots_initialize(void) |
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{ |
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if (signal(SIGCHLD, sig_chld_handler) == SIG_ERR)
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return -1; |
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robots_size = 10;
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robots = (Robot*)malloc(sizeof(Robot) * robots_size);
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if (!robots)
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return -1; |
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memset(robots, 0, sizeof(Robot) * robots_size); |
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return 0; |
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} |
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/**
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* Creates a new robot. Returns its id on
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* success, or a negative integer on failure.
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**/
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int robot_create(char *execname) |
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{ |
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int pid;
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int id = first_available_id;
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Robot* r = &robots[id]; |
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// do shared memory stuff here
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key_t key = IPC_PRIVATE; |
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//Memory accessible only to children with r/w privileges
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r->sharedMemID = shmget(key, sizeof(RobotShared), IPC_CREAT | 0666); |
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if(r->sharedMemID < 0) |
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{ |
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fprintf(stderr, "Failed to get shared memory.\n");
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return -1; |
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} |
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r->shared = (RobotShared*)shmat(r->sharedMemID, NULL, 0); |
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if(!(r->shared))
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{ |
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//Free shared memory region
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if (!shmctl(r->sharedMemID, IPC_RMID, NULL)) |
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fprintf(stderr, "Failed to free shared memory.\n");
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fprintf(stderr, "Error attaching memory to parent.\n");
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return -1; |
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} |
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// Initialize robot structure here
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r->shared->motor1 = 0;
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r->shared->motor2 = 0;
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r->id = id; |
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if((pid = fork()) < 0) |
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{ |
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//Free Shared Memory Region
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if (!shmdt(r->shared))
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fprintf(stderr, "Failed to free shared memory.\n");
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if (!shmctl(r->sharedMemID, IPC_RMID, NULL)) |
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fprintf(stderr, "Failed to free shared memory.\n");
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r->id = 0;
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fprintf(stderr, "Failed to fork robot process.\n");
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return -1; |
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} |
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if(!pid)
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{ |
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char var[21]; |
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/* restore default sigchld handler */
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signal(SIGCHLD, SIG_DFL); |
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sprintf(var, "memory_id=%d", r->sharedMemID);
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putenv(var); |
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//TODO: keep the other env. stuff around
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execv(execname, NULL);
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fprintf(stderr, "exec failed to run child process.\n");
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exit(-1);
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} |
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else
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{ |
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r->pid = pid; |
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do {
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first_available_id++; |
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} while (first_available_id < robots_size &&
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robots[first_available_id].id != 0);
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// resize the array if necessary
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if (first_available_id >= robots_size)
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{ |
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robots_size *= 2;
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robots = realloc(robots, sizeof(Robot) * robots_size);
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if (!robots)
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{ |
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fprintf(stderr, "Out of memory.\n");
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return -1; |
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} |
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} |
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} |
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return id;
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} |
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/**
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* Frees all resources associated with a robot, including
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* killing its process if necessary.
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*
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* @return zero on success, nonzero on failure
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**/
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int robot_destroy(int id) |
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{ |
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Robot* r; |
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if (id < 0 || id >= robots_size) |
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return -1; |
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r = &robots[id]; |
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if (r->id == 0) |
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return -1; |
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if (!shmdt(r->shared))
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{ |
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fprintf(stderr, "Failed to free shared memory.\n");
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return -1; |
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} |
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if (!shmctl(r->sharedMemID, IPC_RMID, NULL)) |
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{ |
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fprintf(stderr, "Failed to free shared memory.\n");
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return -1; |
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} |
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memset(r, 0, sizeof(Robot)); |
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if (id < first_available_id)
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first_available_id = 0;
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return 0; |
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} |
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void sig_chld_handler(int sig) |
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{ |
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pid_t pid; |
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int cstat;
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printf("SIGCHLD: parent waiting\n");
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pid = waitpid(0, &cstat, WUNTRACED);
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printf("got %d from %d\n", cstat, pid);
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kill(pid, SIGCONT); |
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} |
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