From 1db29a3fa49eca5929ba03346eac7cd49f58e86d Mon Sep 17 00:00:00 2001
From: "Gary E. Miller" <gem@rellim.com>
Date: Fri, 22 Feb 2019 14:59:37 -0800
Subject: deg_to_s(): Add rounding for dd, ddmm, and ddmmss. Update tests.

---
 gpsdclient.c            | 37 +++++++++++++++++++++++---
 tests/test_gpsdclient.c | 70 +++++++++++++++++++++++++++++++------------------
 2 files changed, 77 insertions(+), 30 deletions(-)

diff --git a/gpsdclient.c b/gpsdclient.c
index c34ea06c..3705f6f2 100644
--- a/gpsdclient.c
+++ b/gpsdclient.c
@@ -29,6 +29,7 @@ static struct exportmethod_t exportmethods[] = {
 };
 
 /* convert double degrees to a static string and return a pointer to it
+ * WARNING: not thread safe!
  *
  * deg_str_type:
  *   	deg_dd     : return DD.ddddddd
@@ -38,8 +39,10 @@ static struct exportmethod_t exportmethods[] = {
  * returns 'nan' for 0 > f or 360 < f
  *
  * NOTE: degrees must be positive.
+ *       360.0 is rolled over to 0.0
  *
- * for cm level accuracy we need degrees to 7+ decimal places
+ * for cm level accuracy, at sea level, we need degrees
+ * to 7+ decimal places
  * Ref: https://en.wikipedia.org/wiki/Decimal_degrees
  *
  */
@@ -54,17 +57,43 @@ char *deg_to_str(enum deg_str_type type, double f)
 	return str;
     }
 
-    /* FIXME: s/b rounding */
+    /* add rounding quanta */
+    /* IEEE 754 wants round to nearest even.
+     * We cheat and just round to nearest.
+     * Intel trying to kill off round to nearest even. */
+    switch (type) {
+    default:
+        /* huh? */
+        type = deg_dd;
+        /* FALLTHROUGH */
+    case deg_dd:
+	/* DD.dddddddd */
+	f += 0.5 * 1e-8;              /* round up */
+        break;
+    case deg_ddmm:
+	/* DD MM.mmmmmm */
+	f += (0.5 * 1e-6) / 60;       /* round up */
+        break;
+    case deg_ddmmss:
+	f += (0.5 * 1e-5) / 3600;     /* round up */
+        break;
+    }
     fmin = modf(f, &fdeg);
     deg = (int)fdeg;
+    if (360 == deg) {
+	/* fix round-up roll-over */
+	deg = 0;
+	fmin = 0.0;
+    }
 
     if (deg_dd == type) {
 	/* DD.dddddddd */
+	long frac_deg = (long)(fmin * 100000000.0);
         /* cm level accuracy requires the %08ld */
-	long frac_deg = (long)(fmin * 100000000);
 	(void)snprintf(str, sizeof(str), "%3d.%08ld", deg, frac_deg);
 	return str;
     }
+
     fsec = modf(fmin * 60, &fmin);
     min = (int)fmin;
 
@@ -75,7 +104,7 @@ char *deg_to_str(enum deg_str_type type, double f)
 	return str;
     }
     /* else DD MM SS.sss */
-    fdsec = modf(fsec * 60, &fsec);
+    fdsec = modf(fsec * 60.0, &fsec);
     sec = (int)fsec;
     dsec = (int)(fdsec * 100000.0);
     (void)snprintf(str, sizeof(str), "%3d %02d' %02d.%05d\"", deg, min, sec,
diff --git a/tests/test_gpsdclient.c b/tests/test_gpsdclient.c
index 6f81633f..c65b35f6 100644
--- a/tests/test_gpsdclient.c
+++ b/tests/test_gpsdclient.c
@@ -24,39 +24,57 @@ struct test {
 };
 
 struct test tests[] = {
-    /* 1 degree, 1 arcminute, 1.999 arcsec */
-    {(1.0 + 1.0/60.0 + 1.999/3600.0),
-     "  1.01722194",
-     "  1 01.033316'",
-     "  1 01' 01.99899\""},
-    /* 1 deg, 2 min, 2.0999 sec */
-    {(1.0 + 2.0/60.0 + 2.999/3600.0),
-     "  1.03416638",
-     "  1 02.049983'",
-     "  1 02' 02.99900\""},
-    /* 44.99999994, should not be rounded up */
-    {44.99999994,
-     " 44.99999994",
-     " 44 59.999996'",
-     " 44 59' 59.99978\""},
-    /* 44.99999999999 */
-    /* FIXME: s/b rounded */
-    {44.99999999999,
-     " 44.99999999",
-     " 44 59.999999'",
-     " 44 59' 59.99999\""},
+    /* 1.999999995 sec */
+    {(1.999999995),
+     "  2.00000000",            /* rounded up */
+     "  2 00.000000'",          /* rounded up */
+     "  1 59' 59.99998\""},
+    /* 3.999999999 sec */
+    {(3.999999994),
+     "  3.99999999",            /* not rounded up */
+     "  4 00.000000'",          /* rounded up */
+     "  3 59' 59.99998\""},
+    /* 5 degree, 1.99999960 arcmin */
+    {(5.0 + 1.999999600/60.0),
+     "  5.03333333",
+     "  5 02.000000'",          /* rounded up */
+     "  5 01' 59.99998\""},
+    /* 6 degree, 1.99999940 arcmin */
+    {(6.0 + 1.999999400/60.0),
+     "  6.03333332",
+     "  6 01.999999'",          /* not rounded up */
+     "  6 01' 59.99996\""},
+    /* 7 degree, 59.99999960 arcmin */
+    {(7.0 + 59.999999600/60.0),
+     "  7.99999999",
+     "  8 00.000000'",          /* rounded up */
+     "  7 59' 59.99998\""},
+    /* 9 degree, 59.99999940 arcmin */
+    {(9.0 + 59.999999400/60.0),
+     "  9.99999999",
+     "  9 59.999999'",          /* not rounded up */
+     "  9 59' 59.99996\""},
+    /* 11 degree, 1 arcminute, 1.99999600 arcsec */
+    {(11.0 + 1.0/60.0 + 1.99999600/3600.0),
+     " 11.01722222",
+     " 11 01.033333'",
+     " 11 01' 02.00000\""},     /* rounded up */
+    /* 12 deg, 2 min, 2.99999400 sec */
+    {(12.0 + 2.0/60.0 + 2.99999400/3600.0),
+     " 12.03416667",
+     " 12 02.050000'",
+     " 12 02' 02.99999\""},     /* not rounded up */
     /* -44.99999999999 */
-    /* FIXME: should not be nan? */
+    /* nan because not positive degrees */
     {-44.99999999999,
      "nan",
      "nan",
      "nan"},
     /* 359.99999999999 */
-    /* FIXME: s/b rounded */
     {359.99999999999,
-     "359.99999999",
-     "359 59.999999'",
-     "359 59' 59.99999\""},
+     "  0.00000000",         /* rounded up, and rolled over */
+     "  0 00.000000'",
+     "  0 00' 00.00000\""},
 };
 
 
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