sprintf -> snprintf in bucket code.

[simgear.git] / simgear / bucket / newbucket.cxx

diff --git a/simgear/bucket/newbucket.cxx b/simgear/bucket/newbucket.cxx
index aea0466a862e1246120219fe1586366221581864..0a2e542c3f706290728ee877a7e2a431a3faba31 100644 (file)
--- a/simgear/bucket/newbucket.cxx
+++ b/simgear/bucket/newbucket.cxx
@@ -92,6 +92,11 @@ void SGBucket::set_bucket( double dlon, double dlat ) {
 
     // cout << "diff = " << diff << "  span = " << span << endl;
 
+    /* Calculate the greatest integral longitude less than
+     * or equal to the given longitude (floor(dlon)),
+     * but attribute coordinates near the east border
+     * to the next tile.
+     */
     if ( (dlon >= 0) || (fabs(diff) < SG_EPSILON) ) {
        lon = (int)dlon;
     } else {
@@ -100,22 +105,48 @@ void SGBucket::set_bucket( double dlon, double dlat ) {
 
     // find subdivision or super lon if needed
     if ( span < SG_EPSILON ) {
+        /* sg_bucket_span() never returns 0.0
+         * or anything near it, so this really
+         * should not occur at any time.
+         */
        // polar cap
        lon = 0;
        x = 0;
     } else if ( span <= 1.0 ) {
+        /* We have more than one tile per degree of
+         * longitude, so we need an x offset.
+         */
        x = (int)((dlon - lon) / span);
     } else {
-       if ( dlon >= 0 ) {
-           lon = (int)( (int)(lon / span) * span);
-       } else {
-           // cout << " lon = " << lon 
-           //  << "  tmp = " << (int)((lon-1) / span) << endl;
-           lon = (int)( (int)((lon + 1) / span) * span - span);
-           if ( lon < -180 ) {
-               lon = -180;
-           }
-       }
+        /* We have one or more degrees per tile,
+         * so we need to find the base longitude
+         * of that tile.
+         *
+         * First we calculate the integral base longitude
+         * (e.g. -85.5 => -86) and then find the greatest
+         * multiple of span that is less than or equal to
+         * that longitude.
+         *
+         * That way, the Greenwich Meridian is always
+         * a tile border.
+         *
+         * This gets us into trouble with the polar caps,
+         * which have width 360 and thus either span
+         * the range from 0 to 360 or from -360 to 0
+         * degrees, depending on whether lon is positive
+         * or negative!
+         *
+         * We also get into trouble with the 8 degree tiles
+         * north of 88N and south of 88S, because the west-
+         * and east-most tiles in that range will cover 184W
+         * to 176W and 176E to 184E respectively, with their
+         * center at 180E/W!
+         */
+        lon=(int)floor(floor((lon+SG_EPSILON)/span)*span);
+        /* Correct the polar cap issue */
+        if ( lon < -180 ) {
+            lon = -180;
+        }
        x = 0;
     }
 
@@ -124,11 +155,15 @@ void SGBucket::set_bucket( double dlon, double dlat ) {
     //
     diff = dlat - (double)(int)dlat;
 
+    /* Again, a modified floor() function (see longitude) */
     if ( (dlat >= 0) || (fabs(diff) < SG_EPSILON) ) {
        lat = (int)dlat;
     } else {
        lat = (int)dlat - 1;
     }
+    /* Latitude base and offset are easier, as
+     * tiles always are 1/8 degree of latitude wide.
+     */
     y = (int)((dlat - lat) * 8);
 }
 
@@ -177,7 +212,7 @@ std::string SGBucket::gen_base_path() const {
        main_lat *= -1;
     }
 
-    sprintf(raw_path, "%c%03d%c%02d/%c%03d%c%02d", 
+    snprintf(raw_path, 256, "%c%03d%c%02d/%c%03d%c%02d", 
            hem, top_lon, pole, top_lat, 
            hem, main_lon, pole, main_lat);
 
@@ -213,7 +248,7 @@ double SGBucket::get_width_m() const {
     double local_perimeter = local_radius * SGD_2PI;
     double degree_width = local_perimeter / 360.0;
 
-    return sg_bucket_span( get_center_lat() ) * degree_width;
+    return get_width() * degree_width;
 }
 
 
@@ -310,4 +345,13 @@ void sgBucketDiff( const SGBucket& b1, const SGBucket& b2, int *dx, int *dy ) {
 #endif
 }
 
+void sgGetBuckets( const SGGeod& min, const SGGeod& max, std::vector<SGBucket>& list ) {
+    double lon, lat, span;
 
+    for (lat = min.getLatitudeDeg(); lat <= max.getLatitudeDeg(); lat += SG_BUCKET_SPAN) {
+        span = sg_bucket_span( lat );
+        for (lon = min.getLongitudeDeg(); lon <= max.getLongitudeDeg(); lon += span) {
+            list.push_back( SGBucket(lon , lat) );
+        }
+    }
+}