call_eyetracker_manager_posix.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include "tobii_research.h"
#include "tobii_research_eyetracker.h"

typedef enum {
    PD_READ = 0,
    PD_WRITE = 1
} PipeDirection;


static pid_t create_child_process(const char* path, char * const argv[], int* stdout_pipe, int* stderr_pipe) {
    int child_stdout_pipe[2];
    int child_stderr_pipe[2];

    if (pipe(child_stdout_pipe) == -1) {
        perror("child_stdout_pipe");
        exit(EXIT_FAILURE);
    }

    if (pipe(child_stderr_pipe) == -1) {
        perror("child_stderr_pipe");
        exit(EXIT_FAILURE);
    }
    pid_t pid = fork();

    if (pid == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    }

    if (pid == 0) { // Child process
        dup2(child_stdout_pipe[PD_WRITE], STDOUT_FILENO);
        dup2(child_stderr_pipe[PD_WRITE], STDERR_FILENO);
        close(child_stdout_pipe[PD_READ]);
        close(child_stderr_pipe[PD_READ]);

        execvp(path, argv);
        perror(path); // Line reached only if execv fails.
    } else {  // Parent process
        close(child_stdout_pipe[PD_WRITE]);
        close(child_stderr_pipe[PD_WRITE]);
        *stdout_pipe = child_stdout_pipe[PD_READ];
        *stderr_pipe = child_stderr_pipe[PD_READ];
    }
    return pid;
}

static void printf_lines_starting_with(FILE* f, const char* line_start) {
    char *line = NULL;
    size_t len = 0;
    ssize_t read;
    size_t line_start_len = strlen(line_start);
    do {
        read = getline(&line, &len, f);
        if (read != -1 && !strncmp(line, line_start, line_start_len)) {
            printf("%s", line);
        }
    }
    while(read != -1);

    free(line);
}

#if __APPLE__ && __MACH__
    #define ETM_PATH "/Applications/TobiiProEyeTrackerManager.app/Contents/MacOS/TobiiProEyeTrackerManager"
#else
    #define ETM_PATH "TobiiProEyeTrackerManager"
#endif

int main() {
    TobiiResearchEyeTracker* eyetracker;
    char* device_address = NULL;
    char device_address_arg[128];
    int child_stdout_pipe;
    int child_stderr_pipe;
    pid_t pid;
    int wstatus;
    int w;

    TobiiResearchStatus status = tobii_research_get_eyetracker("tobii-ttp://TOBII-IS404-100107417574", &eyetracker);

    if (status != TOBII_RESEARCH_STATUS_OK) {
        printf("ERROR: %d when trying to get eyetracker!\n", status);
        exit(EXIT_FAILURE);
    }

    tobii_research_get_address(eyetracker, &device_address);

    if (status != TOBII_RESEARCH_STATUS_OK) {
        printf("ERROR: %d when trying to get address!\n", status);
        exit(EXIT_FAILURE);
    }
    
    snprintf(device_address_arg, sizeof(device_address_arg)/sizeof(char), "--device-address=%s", device_address);

    tobii_research_free_string(device_address);

    #define MODE    "displayarea"

    char *etm_argv[] = { ETM_PATH,
                         device_address_arg,
                         "--mode=" MODE,
                         NULL};

    pid = create_child_process(ETM_PATH, etm_argv, &child_stdout_pipe, &child_stderr_pipe);

    // Waiting for child process to finish
    w = waitpid(pid, &wstatus, 0);
    if (w == -1) {
        perror("waitpid");
        exit(EXIT_FAILURE);
    }

    if (WEXITSTATUS(wstatus) == 0) {
        printf("Eye Tracker Manager was called successfully!\n");
    } else {
        printf("Eye Tracker Manager call returned the error code: %i\n", WEXITSTATUS(wstatus));

        FILE* child_stderr = fdopen(child_stderr_pipe, "r");
        printf_lines_starting_with(child_stderr, "ETM Error:");
        fclose(child_stderr);
    }
}