Start Sketching in replacement for the HAS/SET/-99999 hack we've used for years.

diff --git a/gpsbabel/src/core/optionaldouble.h b/gpsbabel/src/core/optionaldouble.h
new file mode 100644 (file)
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--- /dev/null
+++ b/gpsbabel/src/core/optionaldouble.h
@@ -0,0 +1,64 @@
+/*
+STATUS: experimental
+    For data types we might not know (altitude, heartrate) provide a simple
+    set of getters/setters to them that still exposes whether a member is
+    valid without leaking through 'unknown' values.
+
+    Copyright (C) 2013 Robert Lipe, robertlipe@gpsbabel.org
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU 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 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., 59 Temple Place - Suite 330, Boston, MA 02111 USA
+
+ */
+
+#include <limits>
+
+// As this code began in C, we have several hundred places that set and
+// read creation_time as a time_t.  Provide some operator overloads to make
+// that less painful.
+// Probably all of these should eventually go away and be replaced by 
+// "Better" code in the callers.
+
+// Consider putting in a namespace instead of prefixing 'gb'.
+namespace gpsbabel {
+
+class OptionalDouble {
+public:
+  OptionalDouble() :
+    valid_(false) { }
+
+  inline bool isValid() const {
+    return valid_;
+  }
+
+  double Get() const {
+    if (valid_) {
+      return v_;
+    }
+    // This might be heavy-handed.  Perhaps ctor could declare what "you read
+    // my thing when I told you not to read my thing" value should return.
+    return std::numeric_limits<double>::quiet_NaN();
+  }
+
+  void Set(double v) {
+    valid_ = true;
+    v_ = v;
+  }
+
+ private:
+  double v_;
+  bool valid_;
+};
+
+} // namespace gpsbabel