progress.h

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/* Copyright (C) 2001-2015 Peter Selinger.
   This file is part of Potrace. It is free software and it is covered
   by the GNU General Public License. See the file COPYING for details. */

/* operations on potrace_progress_t objects, which are defined in
   potracelib.h. Note: the code attempts to minimize runtime overhead
   when no progress monitoring was requested. It also tries to
   minimize excessive progress calculations beneath the "epsilon"
   threshold. */

#ifndef PROGRESS_H
#define PROGRESS_H

/* structure to hold progress bar callback data */
struct progress_s {
  void (*callback)(double progress, void *privdata); /* callback fn */
  void *data;          /* callback function's private data */
  double min, max;     /* desired range of progress, e.g. 0.0 to 1.0 */
  double epsilon;      /* granularity: can skip smaller increments */
  double b;            /* upper limit of subrange in superrange units */
  double d_prev;       /* previous value of d */
};
typedef struct progress_s progress_t;

/* notify given progress object of current progress. Note that d is
   given in the 0.0-1.0 range, which will be scaled and translated to
   the progress object's range. */
static inline void progress_update(double d, progress_t *prog) {
  double d_scaled;

  if (prog != NULL && prog->callback != NULL) {
    d_scaled = prog->min * (1-d) + prog->max * d;
    if (d == 1.0 || d_scaled >= prog->d_prev + prog->epsilon) {
      prog->callback(prog->min * (1-d) + prog->max * d, prog->data);
      prog->d_prev = d_scaled;
    }
  }
}

/* start a subrange of the given progress object. The range is
   narrowed to [a..b], relative to 0.0-1.0 coordinates. If new range
   is below granularity threshold, disable further subdivisions. */
static inline void progress_subrange_start(double a, double b, const progress_t *prog, progress_t *sub) {
  double min, max;

  if (prog == NULL || prog->callback == NULL) {
    sub->callback = NULL;
    return;
  }

  min = prog->min * (1-a) + prog->max * a;
  max = prog->min * (1-b) + prog->max * b;

  if (max - min < prog->epsilon) {
    sub->callback = NULL;    /* no further progress info in subrange */
    sub->b = b;
    return;
  }
  sub->callback = prog->callback;
  sub->data = prog->data;
  sub->epsilon = prog->epsilon;
  sub->min = min;
  sub->max = max;
  sub->d_prev = prog->d_prev;
  return;
}

static inline void progress_subrange_end(progress_t *prog, progress_t *sub) {
  if (prog != NULL && prog->callback != NULL) {
    if (sub->callback == NULL) {
      progress_update(sub->b, prog);
    } else {
      prog->d_prev = sub->d_prev;
    }
  }    
}

#endif /* PROGRESS_H */