text: /*
  Copyright (c) 2013 Ben Croston
  
  Permission is hereby granted, free of charge, to any person obtaining a copy of
  this software and associated documentation files (the "Software"), to deal in
  the Software without restriction, including without limitation the rights to
  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
  of the Software, and to permit persons to whom the Software is furnished to do
  so, subject to the following conditions:
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
  */
  
  #include <pthread.h>
  #include <sys/epoll.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <fcntl.h>
  #include <unistd.h>
  #include <string.h>
  #include "event_gpio.h"
  
  const char *stredge[4] = {"none", "rising", "falling", "both"};
  
  // file descriptors
  struct fdx
  {
      int fd;
      unsigned int gpio;
      int initial;
      struct fdx *next;
  };
  struct fdx *fd_list = NULL;
  
  // event callbacks
  struct callback
  {
      unsigned int gpio;
      void (*func)(unsigned int gpio);
      struct callback *next;
  };
  struct callback *callbacks = NULL;
  
  // gpio exports
  struct gpio_exp
  {
      unsigned int gpio;
      struct gpio_exp *next;
  };
  struct gpio_exp *exported_gpios = NULL;
  
  pthread_t threads;
  int event_occurred[54] = { 0 };
  int thread_running = 0;
  int epfd = -1;
  
  int gpio_export(unsigned int gpio)
  {
      int fd, len;
      char str_gpio[3];
      struct gpio_exp *new_gpio, *g;
  
      if ((fd = open("/sys/class/gpio/export", O_WRONLY)) < 0)
      {
          return -1;
      }
      len = snprintf(str_gpio, sizeof(str_gpio), "%d", gpio);
      write(fd, str_gpio, len);
      close(fd);
  
      // add to list
      new_gpio = malloc(sizeof(struct gpio_exp));
      if (new_gpio == 0)
          return -1; // out of memory
  
      new_gpio->gpio = gpio;
      new_gpio->next = NULL;
  
      if (exported_gpios == NULL)
      {
          // create new list
          exported_gpios = new_gpio;
      } else {
          // add to end of existing list
          g = exported_gpios;
          while (g->next != NULL)
              g = g->next;
          g->next = new_gpio;
      }
      return 0;
  }
  
  void close_value_fd(unsigned int gpio)
  {
      struct fdx *f = fd_list;
      struct fdx *temp;
      struct fdx *prev = NULL;
  
      while (f != NULL)
      {
          if (f->gpio == gpio)
          {
              close(f->fd);
              if (prev == NULL)
                  fd_list = f->next;
              else
                  prev->next = f->next;
              temp = f;
              f = f->next;
              free(temp);
          } else {
              prev = f;
              f = f->next;
          }
      }
  }
  
  int gpio_unexport(unsigned int gpio)
  {
      int fd, len;
      char str_gpio[3];
      struct gpio_exp *g, *temp, *prev_g = NULL;
  
      close_value_fd(gpio);
  
      if ((fd = open("/sys/class/gpio/unexport", O_WRONLY)) < 0)
          return -1;
  
      len = snprintf(str_gpio, sizeof(str_gpio), "%d", gpio);
      write(fd, str_gpio, len);
      close(fd);
  
      // remove from list
      g = exported_gpios;
      while (g != NULL)
      {
          if (g->gpio == gpio)
          {
              if (prev_g == NULL)
                  exported_gpios = g->next;
              else
                  prev_g->next = g->next;
              temp = g;
              g = g->next;
              free(temp);
          } else {
              prev_g = g;
              g = g->next;
          }
      }
      return 0;
  }
  
  int gpio_set_direction(unsigned int gpio, unsigned int in_flag)
  {
      int fd;
      char filename[33];
  
      snprintf(filename, sizeof(filename), "/sys/class/gpio/gpio%d/direction", gpio);
      if ((fd = open(filename, O_WRONLY)) < 0)
          return -1;
  
      if (in_flag)
          write(fd, "in", 3);
      else
          write(fd, "out", 4);
  
      close(fd);
      return 0;
  }
  
  int gpio_set_edge(unsigned int gpio, unsigned int edge)
  {
      int fd;
      char filename[28];
  
      snprintf(filename, sizeof(filename), "/sys/class/gpio/gpio%d/edge", gpio);
  
      if ((fd = open(filename, O_WRONLY)) < 0)
          return -1;
  
      write(fd, stredge[edge], strlen(stredge[edge]) + 1);
      close(fd);
      return 0;
  }
  
  int add_fd_list(unsigned int gpio, int fd)
  {
      struct fdx *new_fd;
  
      new_fd = malloc(sizeof(struct fdx));
      if (new_fd == 0)
          return -1;  // out of memory
  
      new_fd->fd = fd;
      new_fd->gpio = gpio;
      new_fd->initial = 1;
      if (fd_list == NULL) {
          new_fd->next = NULL;
      } else {
          new_fd->next = fd_list;
      }
      fd_list = new_fd;
      return 0;
  }
  
  unsigned int gpio_lookup(int fd)
  {
      struct fdx *f = fd_list;
      while (f != NULL)
      {
          if (f->fd == fd)
              return f->gpio;
          f = f->next;
      }
      return 0;
  }
  
  int fd_lookup(unsigned int gpio)
  {
      struct fdx *f = fd_list;
      while (f != NULL)
      {
          if (f->gpio == gpio)
              return f->fd;
          f = f->next;
      }
      return 0;
  }
  
  int open_value_file(unsigned int gpio)
  {
      int fd;
      char filename[29];
  
      // create file descriptor of value file
  	snprintf(filename, sizeof(filename), "/sys/class/gpio/gpio%d/value", gpio);
  	if ((fd = open(filename, O_RDONLY | O_NONBLOCK)) < 0)
          return -1;
      add_fd_list(gpio, fd);
      return fd;
  }
  
  void exports_cleanup(void)
  {
      // unexport everything
      while (exported_gpios != NULL)
          gpio_unexport(exported_gpios->gpio);
  }
  
  int add_edge_callback(unsigned int gpio, void (*func)(unsigned int gpio))
  {
      struct callback *cb = callbacks;
      struct callback *new_cb;
  
      new_cb = malloc(sizeof(struct callback));
      if (new_cb == 0)
          return -1;  // out of memory
  
      new_cb->gpio = gpio;
      new_cb->func = func;
      new_cb->next = NULL;
  
      if (callbacks == NULL) {
          // start new list
          callbacks = new_cb;
      } else {
          // add to end of list
          while (cb->next != NULL)
              cb = cb->next;
          cb->next = new_cb;
      }
      return 0;
  }
  
  void run_callbacks(unsigned int gpio)
  {
      struct callback *cb = callbacks;
      while (cb != NULL)
      {
          if (cb->gpio == gpio)
              cb->func(cb->gpio);
          cb = cb->next;
      }
  }
  
  void remove_callbacks(unsigned int gpio)
  {
      struct callback *cb = callbacks;
      struct callback *temp;
      struct callback *prev = NULL;
  
      while (cb != NULL)
      {
          if (cb->gpio == gpio)
          {
              if (prev == NULL)
                  callbacks = cb->next;
              else
                  prev->next = cb->next;
              temp = cb;
              cb = cb->next;
              free(temp);
          } else {
              prev = cb;
              cb = cb->next;
          }
      }
  }
  
  void set_initial_false(unsigned int gpio)
  {
      struct fdx *f = fd_list;
  
      while (f != NULL)
      {
          if (f->gpio == gpio)
              f->initial = 0;
          f = f->next;
      }
  }
  
  int gpio_initial(unsigned int gpio)
  {
      struct fdx *f = fd_list;
  
      while (f != NULL)
      {
          if ((f->gpio == gpio) && f->initial)
              return 1;
          f = f->next;
      }
      return 0;
  }
  
  void *poll_thread(void *threadarg)
  {
      struct epoll_event events;
      char buf;
      unsigned int gpio;
      int n;
  
      thread_running = 1;
      while (thread_running)
      {
          if ((n = epoll_wait(epfd, &events, 1, -1)) == -1)
          {
              thread_running = 0;
              pthread_exit(NULL);
          }
          if (n > 0) {
              lseek(events.data.fd, 0, SEEK_SET);
              if (read(events.data.fd, &buf, 1) != 1)
              {
                  thread_running = 0;
                  pthread_exit(NULL);
              }
              gpio = gpio_lookup(events.data.fd);
              if (gpio_initial(gpio)) {     // ignore first epoll trigger
                  set_initial_false(gpio);
              } else {
                  event_occurred[gpio] = 1;
                  run_callbacks(gpio);
              }
          }
      }
      thread_running = 0;
      pthread_exit(NULL);
  }
  
  int gpio_event_added(unsigned int gpio)
  {
      struct fdx *f = fd_list;
      while (f != NULL)
      {
          if (f->gpio == gpio)
              return 1;
          f = f->next;
      }
      return 0;
  }
  
  int add_edge_detect(unsigned int gpio, unsigned int edge)
  // return values:
  // 0 - Success
  // 1 - Edge detection already added
  // 2 - Other error
  {
      int fd;
      pthread_t threads;
      struct epoll_event ev;
      long t = 0;
  
      // check to see if this gpio has been added already
      if (gpio_event_added(gpio) != 0)
          return 1;
  
      // export /sys/class/gpio interface
      gpio_export(gpio);
      gpio_set_direction(gpio, 1); // 1=input
      gpio_set_edge(gpio, edge);
      if ((fd = open_value_file(gpio)) == -1)
          return 2;
      add_fd_list(gpio,fd);
  
      // create epfd if not already open
      if ((epfd == -1) && ((epfd = epoll_create(1)) == -1))
          return 2;
  
      // add to epoll fd
      ev.events = EPOLLIN | EPOLLET | EPOLLPRI;
      ev.data.fd = fd;
      if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev) == -1)
          return 2;
  
      // start poll thread if it is not already running
      if (!thread_running)
      {
          if (pthread_create(&threads, NULL, poll_thread, (void *)t) != 0)
              return 2;
      }
  
      return 0;
  }
  
  void remove_edge_detect(unsigned int gpio)
  {
      struct epoll_event ev;
      int fd = fd_lookup(gpio);
  
      // delete callbacks for gpio
      remove_callbacks(gpio);
  
      // delete epoll of fd
      epoll_ctl(epfd, EPOLL_CTL_DEL, fd, &ev);
  
      // close fd and remove from list
      close_value_fd(gpio);
  
      // set edge to none
      gpio_set_edge(gpio, NO_EDGE);
  
      // unexport gpio
      gpio_unexport(gpio);
  
      // clear detected flag
      event_occurred[gpio] = 0;
  }
  
  int event_detected(unsigned int gpio)
  {
      if (event_occurred[gpio]) {
          event_occurred[gpio] = 0;
          return 1;
      } else {
          return 0;
      }
  }
  
  void event_cleanup(void)
  {
      close(epfd);
      thread_running = 0;
      exports_cleanup();
  }
  
  int blocking_wait_for_edge(unsigned int gpio, unsigned int edge)
  // standalone from all the event functions above
  {
      int epfd, fd, n, i;
      struct epoll_event events, ev;
      char buf;
  
      if ((epfd = epoll_create(1)) == -1)
          return 1;
  
      // check to see if this gpio has been added already
      if (gpio_event_added(gpio) != 0)
          return 2;
  
      // export /sys/class/gpio interface
      gpio_export(gpio);
      gpio_set_direction(gpio, 1); // 1=input
      gpio_set_edge(gpio, edge);
      if ((fd = open_value_file(gpio)) == -1)
          return 3;
  
      // add to epoll fd
      ev.events = EPOLLIN | EPOLLET | EPOLLPRI;
      ev.data.fd = fd;
      if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev) == -1)
      {
          gpio_unexport(gpio);
          close(fd);
          return 4;
      }
  
      // epoll for event
      for (i = 0; i<2; i++) // first time triggers with current state, so ignore
         if ((n = epoll_wait(epfd, &events, 1, -1)) == -1)
         {
             gpio_unexport(gpio);
             close(fd);
             return 5;
         }
  
      if (n > 0)
      {
          lseek(events.data.fd, 0, SEEK_SET);
          if (read(events.data.fd, &buf, 1) != 1)
          {
              gpio_unexport(gpio);
              close(fd);
              return 6;
          }
          if (events.data.fd != fd)
          {
              gpio_unexport(gpio);
              close(fd);
              return 7;
          }
      }
  
      // clean up
      gpio_unexport(gpio);
      close(fd);
      close(epfd);
      return 0;
  }
  