X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=simgear%2Fmath%2Finterpolater.cxx;h=1bbbadc801d2a427ccd91cb8ac66cb3ef18d7f6e;hb=11479cd8c386d8bf7e1fee7bed60ab4abefc5fad;hp=ccb71d6be5b783e5aea6e06750040e5e106ba306;hpb=e4bbc5c50b079ff2c6f00c6e2e650502f2ae95f8;p=simgear.git

diff --git a/simgear/math/interpolater.cxx b/simgear/math/interpolater.cxx
index ccb71d6b..1bbbadc8 100644
--- a/simgear/math/interpolater.cxx
+++ b/simgear/math/interpolater.cxx
@@ -4,7 +4,7 @@
 //
 // Written by Curtis Olson, started April 1998.
 //
-// Copyright (C) 1998  Curtis L. Olson  - curt@me.umn.edu
+// Copyright (C) 1998  Curtis L. Olson  - http://www.flightgear.org/~curt
 //
 // This library is free software; you can redistribute it and/or
 // modify it under the terms of the GNU Library General Public
@@ -16,46 +16,55 @@
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 // Library General Public License for more details.
 //
-// You should have received a copy of the GNU Library General Public
-// License along with this library; if not, write to the
-// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-// Boston, MA  02111-1307, USA.
+// 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.
 //
 // $Id$
 
+#ifdef HAVE_CONFIG_H
+#  include <simgear_config.h>
+#endif
 
 #include <simgear/compiler.h>
 
-#include <stdlib.h> // for exit()
+#include <string>
 
-#include STL_STRING
-
-// depricated - #include <simgear/sg_zlib.h>
 #include <simgear/debug/logstream.hxx>
 #include <simgear/misc/sgstream.hxx>
+#include <simgear/props/props.hxx>
 
 #include "interpolater.hxx"
 
-SG_USING_STD(string);
+#include <simgear/math/SGMath.hxx>
+
+using std::string;
 
 // Constructor -- starts with an empty table.
 SGInterpTable::SGInterpTable()
-    : size(0)
 {
 }
 
+SGInterpTable::SGInterpTable(const SGPropertyNode* interpolation) 
+{
+    if (!interpolation)
+        return;
+    std::vector<SGPropertyNode_ptr> entries = interpolation->getChildren("entry");
+    for (unsigned i = 0; i < entries.size(); ++i)
+        addEntry(entries[i]->getDoubleValue("ind", 0.0),
+                 entries[i]->getDoubleValue("dep", 0.0));
+}
 
 // Constructor -- loads the interpolation table from the specified
 // file
 SGInterpTable::SGInterpTable( const string& file ) 
-  : size(0)
 {
     SG_LOG( SG_MATH, SG_INFO, "Initializing Interpolator for " << file );
 
     sg_gzifstream in( file );
     if ( !in.is_open() ) {
         SG_LOG( SG_GENERAL, SG_ALERT, "Cannot open file: " << file );
-	exit(-1);
+        return;
     }
 
     in >> skipcomment;
@@ -63,8 +72,7 @@ SGInterpTable::SGInterpTable( const string& file )
       double ind, dep;
       in >> ind >> dep;
       in >> skipws;
-      table.push_back(Entry(ind, dep));
-      size++;
+      _table[ind] = dep;
     }
 }
 
@@ -72,51 +80,42 @@ SGInterpTable::SGInterpTable( const string& file )
 // Add an entry to the table.
 void SGInterpTable::addEntry (double ind, double dep)
 {
-  table.push_back(Entry(ind,dep));
-  size++;
+  _table[ind] = dep;
 }
 
-
 // Given an x value, linearly interpolate the y value from the table
 double SGInterpTable::interpolate(double x) const
 {
-    int i;
-    double y;
-
-    if (size == 0.0) {
-      return 0.0;
-    }
-
-    i = 0;
-
-    while ( (i < size) && (x > table[i].ind) ) {
-	// cout << "  i = " << i << " table[i].ind = " << table[i].ind << endl;
-	// cout << "  size = " << size << endl;
-	i++;
-    }
-
-    // printf ("i = %d ", i);
-
-    if ( i <= 0 ) {
-	SG_LOG( SG_MATH, SG_DEBUG, 
-		"interpolate(): lookup error, x to small = " << x );
-	return table[0].dep;
-    }
-
-    // cout << " table[size-1].ind = " << table[size-1].ind << endl;
-    if ( i >= size ) {
-	SG_LOG( SG_MATH, SG_DEBUG, 
-		"interpolate(): lookup error, x to big = " << x );
-	return table[size-1].dep;
-    }
-
-    // y = y1 + (y0 - y1)(x - x1) / (x0 - x1)
-    y = table[i].dep + 
-	( (table[i-1].dep - table[i].dep) * 
-	  (x - table[i].ind) ) /
-	(table[i-1].ind - table[i].ind);
-
-    return(y);
+  // Empty table??
+  if (_table.empty())
+    return 0;
+  
+  // Find the table bounds for the requested input.
+  Table::const_iterator upBoundIt = _table.upper_bound(x);
+  // points to a value outside the map. That is we are out of range.
+  // use the last entry
+  if (upBoundIt == _table.end())
+    return _table.rbegin()->second;
+  
+  // points to the first key must be lower
+  // use the first entry
+  if (upBoundIt == _table.begin())
+    return upBoundIt->second;
+  
+  // we know that we do not stand at the beginning, so it is safe to do so
+  Table::const_iterator loBoundIt = upBoundIt;
+  --loBoundIt;
+  
+  // Just do linear interpolation.
+  double loBound = loBoundIt->first;
+  double upBound = upBoundIt->first;
+  double loVal = loBoundIt->second;
+  double upVal = upBoundIt->second;
+  
+  // division by zero should not happen since the std::map
+  // has sorted out duplicate entries before. Also since we have a
+  // map, we know that we get different first values for different iterators
+  return loVal + (upVal - loVal)*(x - loBound)/(upBound - loBound);
 }