+//
+// interpolater.cxx -- routines to handle linear interpolation from a table of
+// x,y The table must be sorted by "x" in ascending order
+//
+// Written by Curtis Olson, started April 1998.
+//
+// Copyright (C) 1998 Curtis L. Olson - curt@me.umn.edu
+//
+// 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+//
+// $Id$
+// (Log is kept at end of this file)
+
+
+#include <string.h>
+
+#include <Debug/fg_debug.h>
+#include <zlib/zlib.h>
+
+#include "interpolater.hxx"
+
+
+// Constructor -- loads the interpolation table from the specified
+// file
+fgINTERPTABLE::fgINTERPTABLE( char *file ) {
+ char gzfile[256], line[256];
+ gzFile fd;
+
+ fgPrintf( FG_MATH, FG_INFO, "Initializing Interpolator for %s\n", file);
+
+ // First try "file.gz"
+ strcpy(gzfile, file);
+ strcat(gzfile, ".gz");
+ if ( (fd = gzopen(gzfile, "r")) == NULL ) {
+ // Next try "path"
+ if ( (fd = gzopen(file, "r")) == NULL ) {
+ fgPrintf(FG_MATH, FG_ALERT, "Cannot open file: %s\n", file);
+ }
+ }
+
+ size = 0;
+ while ( gzgets(fd, line, 250) != NULL ) {
+ if ( size < MAX_TABLE_SIZE ) {
+ sscanf(line, "%lf %lf\n", &(table[size][0]), &(table[size][1]));
+ size++;
+ } else {
+ fgPrintf( FG_MATH, FG_ALERT,
+ "fgInterpolateInit(): Exceed max table size = %d\n",
+ MAX_TABLE_SIZE );
+ }
+ }
+
+ gzclose(fd);
+}
+
+
+// Given an x value, linearly interpolate the y value from the table
+double fgINTERPTABLE::interpolate(double x) {
+ int i;
+ double y;
+
+ i = 0;
+
+ while ( (x > table[i][0]) && (i < size) ) {
+ i++;
+ }
+
+ printf ("i = %d ", i);
+
+ if ( (i == 0) && (x < table[0][0]) ) {
+ fgPrintf( FG_MATH, FG_ALERT,
+ "fgInterpolateInit(): lookup error, x to small = %.2f\n", x);
+ return(0.0);
+ }
+
+ if ( x > table[i][0] ) {
+ fgPrintf( FG_MATH, FG_ALERT,
+ "fgInterpolateInit(): lookup error, x to big = %.2f\n", x);
+ return(0.0);
+ }
+
+ // y = y1 + (y0 - y1)(x - x1) / (x0 - x1)
+ y = table[i][1] +
+ ( (table[i-1][1] - table[i][1]) *
+ (x - table[i][0]) ) /
+ (table[i-1][0] - table[i][0]);
+
+ return(y);
+}
+
+
+// Destructor
+fgINTERPTABLE::~fgINTERPTABLE( void ) {
+}
+
+
+// $Log$
+// Revision 1.1 1998/04/21 19:14:23 curt
+// Modified Files:
+// Makefile.am Makefile.in
+// Added Files:
+// interpolater.cxx interpolater.hxx
+//
+//