/*
 * $Header: /home/gene/library/website/docsrc/test-rpc/src/src/RCS/test0016.c,v 395.1 2008/04/20 17:25:55 gene Exp $
 *
 * Copyright (c) 2006 Gene Michael Stover.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
 * USA
 */
/*
 * Test that we can XDR encode float numbers to a temporary
 * file, then read them again.
 * For this test to be valid, we must already now that XDR
 * decodes float numbers correctly.
 */

#include "this.h"

/*
 */
static char S_pathname[] = "./tmp/test0016.data";

/*
 */
static float S_a[] = { 0.0, -1.1e-1, M_PI, -2.2e2, 3.3e3, 4.4e-4,
                       -5.5e5, 6.6e-6 };
static int S_alen = sizeof S_a / sizeof S_a[0];

/*
 */
static int
S_Write ()
{
  int rc = 0;
  FILE *fp;
  XDR xdr;
  int i;

  fp = fopen (S_pathname, "wb");
  if (fp != NULL) {
    xdrstdio_create (&xdr, fp, XDR_ENCODE);
    for (i = 0; rc == 0 && i < S_alen; ++i) {
      if (xdr_float (&xdr, &S_a[i])) {
        /* good so far */
      } else {
        printf ("\n%s:%d: xdr_float: %s", __FILE__, __LINE__,
                strerror (errno));
        printf ("%s:%d: xdr_float failed for a[%d] = %.3e.",
                __FILE__, __LINE__, i, S_a[i]);
        rc = -26;
      }
    }
    xdr_destroy (&xdr);
    fclose (fp);
  } else {
    printf ("\n%s:%d: fopen: %s", __FILE__, __LINE__, strerror (errno));
    printf ("%s:%d: Could not open \"%s\" for binary output.", __FILE__,
            __LINE__, S_pathname);
    rc = 22;
  }
  return rc;
}

/*
 * Compare a decoded float value with an expected value.
 * Because we are dealing with floating point, we cannot
 * use a simple "=" comparison.  Instead, we check that
 * the numbers are close enough.
 * They are close enough if:
 *
 * 1. They have the same sign,
 * 
 * 2. They have the same magnitude (exponent), &
 *
 * 3. The different in the mantissas is at most the two
 * least significant bits.
 */
static bool_t
S_EqualDouble (double a, double b)
{
  static double mantissa = 23;          /* bits in the mantissa */
  static double forgiven_bits = 2;      /* bits of error we can ignore */
  double maximum_error;
  double error, relative_error;

  /*
   * The maximum error we're willing to accept is the "forgiven_bits"
   * most insignificant bits.  Here, we convert that to a scalar.
   */
  maximum_error = pow (2.0, forgiven_bits - mantissa);

  error = fabs (a - b);
#if 0
  printf ("\n%s:%d: error is %.3e.", __FILE__, __LINE__, error);
#endif
  if (error > 0.0) {
    relative_error = error / b;
  } else {
    /*
     * Absolute error is 0.0.  It has no representation as a
     * relative error.  So we'll treat it as a relative error
     * of zero.
     */
    relative_error = 0.0;
  }
#if 0
  printf ("\n%s:%d: relative error is %.3e.", __FILE__, __LINE__,
          relative_error);
#endif
  /*
   * A & B are equivalent if their error is less than the maximum
   * acceptable error, which was computed from a number of bits.
   */
  return relative_error < maximum_error;
}

/*
 */
static int
S_Read ()
{
  int rc = 0;
  FILE *fp;
  XDR xdr;
  int i;
  float x;

  fp = fopen (S_pathname, "rb");
  if (fp != NULL) {
    xdrstdio_create (&xdr, fp, XDR_DECODE);
    for (i = 0; rc == 0 && i < S_alen; ++i) {
      if (xdr_float (&xdr, &x)) {
        if (S_EqualDouble (x, S_a[i])) {
          /* good so far */
        } else {
          printf ("\n%s:%d: xdr_float decoded %.18e.", __FILE__,
                  __LINE__, x);
          printf ("  Expected a[%d] = %.10e.", i, S_a[i]);
          rc = -47;
        }
      } else {
        printf ("\n%s:%d: xdr_float: %s", __FILE__, __LINE__,
                strerror (errno));
        rc = -46;
      }
    }
    xdr_destroy (&xdr);
    fclose (fp);
  } else {
    printf ("\n%s:%d: fopen: %s", __FILE__, __LINE__, strerror (errno));
    printf ("%s:%d: Could not open \"%s\" for binary input.", __FILE__,
            __LINE__, S_pathname);
    rc = 45;
  }
  return rc;
}

int
main ()
{
  int rc = 0;

  if (S_Write () == 0) {
    if (S_Read () == 0) {
      /* good */
    } else {
      printf ("\n%s:%d: S_Read failed", __FILE__, __LINE__);
      rc = -31;
    }
  } else {
    printf ("\n%s:%d: S_Write failed", __FILE__, __LINE__);
    rc = 31;
  }
  remove (S_pathname);
  return rc == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}

/* --- end of file --- */