chrony/tempcomp.c

/*
  chronyd/chronyc - Programs for keeping computer clocks accurate.

 **********************************************************************
 * Copyright (C) Miroslav Lichvar  2011, 2014
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 * 
 **********************************************************************

  =======================================================================

  Routines implementing temperature compensation.

  */

#include "config.h"

#include "array.h"
#include "conf.h"
#include "local.h"
#include "memory.h"
#include "util.h"
#include "logging.h"
#include "sched.h"
#include "tempcomp.h"

/* Sanity limit (in ppm) */
#define MAX_COMP 10.0

static SCH_TimeoutID timeout_id;

static LOG_FileID logfileid;

static char *filename;
static double update_interval;
static double T0, k0, k1, k2;

struct Point {
  double temp;
  double comp;
};

static ARR_Instance points;

static double
get_tempcomp(double temp)
{
  unsigned int i;
  struct Point *p1 = NULL, *p2 = NULL;

  /* If not configured with points, calculate the compensation from the
     specified quadratic function */
  if (!points)
    return k0 + (temp - T0) * k1 + (temp - T0) * (temp - T0) * k2;

  /* Otherwise interpolate/extrapolate between two nearest points */

  for (i = 1; i < ARR_GetSize(points); i++) {
    p2 = (struct Point *)ARR_GetElement(points, i);
    if (p2->temp >= temp)
      break;
  }
  p1 = p2 - 1;

  return (temp - p1->temp) / (p2->temp - p1->temp) *
         (p2->comp - p1->comp) + p1->comp;
}

static void
read_timeout(void *arg)
{
  FILE *f;
  double temp, comp;

  f = UTI_OpenFile(NULL, filename, NULL, 'r', 0);

  if (f && fscanf(f, "%lf", &temp) == 1) {
    comp = get_tempcomp(temp);

    if (fabs(comp) <= MAX_COMP) {
      comp = LCL_SetTempComp(comp);

      DEBUG_LOG("tempcomp updated to %f for %f", comp, temp);

      if (logfileid != -1) {
        struct timespec now;

        LCL_ReadCookedTime(&now, NULL);
        LOG_FileWrite(logfileid, "%s %11.4e %11.4e",
            UTI_TimeToLogForm(now.tv_sec), temp, comp);
      }
    } else {
      LOG(LOGS_WARN, "Temperature compensation of %.3f ppm exceeds sanity limit of %.1f",
          comp, MAX_COMP);
    }
  } else {
    LOG(LOGS_WARN, "Could not read temperature from %s", filename);
  }

  if (f)
    fclose(f);

  timeout_id = SCH_AddTimeoutByDelay(update_interval, read_timeout, NULL);
}

static void
read_points(const char *filename)
{
  FILE *f;
  char line[256];
  struct Point *p;

  f = UTI_OpenFile(NULL, filename, NULL, 'R', 0);

  points = ARR_CreateInstance(sizeof (struct Point));

  while (fgets(line, sizeof (line), f)) {
    p = (struct Point *)ARR_GetNewElement(points);
    if (sscanf(line, "%lf %lf", &p->temp, &p->comp) != 2) {
      LOG_FATAL("Could not read tempcomp point from %s", filename);
      break;
    }
  }

  fclose(f);

  if (ARR_GetSize(points) < 2)
    LOG_FATAL("Not enough points in %s", filename);
}

void
TMC_Initialise(void)
{
  char *point_file;

  CNF_GetTempComp(&filename, &update_interval, &point_file, &T0, &k0, &k1, &k2);

  if (filename == NULL)
    return;

  if (update_interval <= 0.0)
    update_interval = 1.0;

  if (point_file)
    read_points(point_file);

  logfileid = CNF_GetLogTempComp() ? LOG_FileOpen("tempcomp",
      "   Date (UTC) Time        Temp.       Comp.")
    : -1;

  read_timeout(NULL);
}

void
TMC_Finalise(void)
{
  if (filename == NULL)
    return;

  if (points)
    ARR_DestroyInstance(points);

  SCH_RemoveTimeout(timeout_id);
}