Read & parse voltage & current data

[batteryviewer] / batteryviewer.c

#include "chart.h"
#include <ctype.h>
#include <errno.h>
#include <gtk/gtk.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

const char voltage_filename[] = "/sys/class/power_supply/BAT0/voltage_now";
const char current_filename[] = "/sys/class/power_supply/BAT0/current_now";

struct State {
  BVChart *voltage;
  BVChart *current;
};

static float fatof(const char *filename) {
  FILE *f = fopen(filename, "r");
  if (f == NULL) {
    return NAN;
  }

  const int bufsize = 1024;
  char buf[bufsize];
  const int read = fread(buf, sizeof(char), bufsize, f);
  if (read == 0 || read == bufsize || ferror(f)) {
    fclose(f);
    return NAN;
  }
  fclose(f);

  char *end;
  errno = 0;
  float val = strtof(buf, &end);
  int parsed = end - buf;
  gboolean parsed_all = parsed == read;
  gboolean parsed_all_but_space = parsed == read - 1 && isspace(*end);
  gboolean parse_ok = parsed_all || parsed_all_but_space;
  if (errno != 0 || parsed == 0 || !parse_ok) {
    return NAN;
  }
  return val;
}

static gboolean collect_data(struct State *state __attribute__((unused))) {
  fprintf(stderr, "Voltage: %f, current: %f\n", fatof(voltage_filename),
          fatof(current_filename));
  return TRUE;
}

static void activate(GtkApplication *app, gpointer user_data) {

  GtkWidget *window = gtk_application_window_new(app);
  gtk_window_set_title(GTK_WINDOW(window), "BatteryViewer");
  gtk_window_set_default_size(GTK_WINDOW(window), 200, 200);

  GtkWidget *box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 1);
  gtk_container_add(GTK_CONTAINER(window), box);

  struct State *state = (struct State *)user_data;
  state->voltage = BV_CHART(bv_chart_new());
  bv_chart_add_point(state->voltage, 0.0, 0.0);
  bv_chart_add_point(state->voltage, 1.0, 1.0);
  bv_chart_add_point(state->voltage, 3.0, 2.0);
  gboolean expand = TRUE;
  gboolean fill = TRUE;
  guint padding = 0;
  gtk_box_pack_start(GTK_BOX(box), GTK_WIDGET(state->voltage), expand, fill,
                     padding);

  state->current = BV_CHART(bv_chart_new());
  bv_chart_add_point(state->current, 0.0, 1.0);
  bv_chart_add_point(state->current, 1.0, 0.0);
  gtk_box_pack_end(GTK_BOX(box), GTK_WIDGET(state->current), expand, fill,
                   padding);

  gtk_widget_show_all(window);

  g_timeout_add_seconds(1, (GSourceFunc)collect_data, user_data);
}

int main(int argc, char **argv) {
  struct State state;

  GtkApplication *app = gtk_application_new("com.scottworley.batteryviewer",
                                            G_APPLICATION_DEFAULT_FLAGS);
  g_signal_connect(app, "activate", G_CALLBACK(activate), &state);
  int status = g_application_run(G_APPLICATION(app), argc, argv);
  g_object_unref(app);

  return status;
}