d08741eab5
are now separate files "postgres.h" and "postgres_fe.h", which are meant to be the primary include files for backend .c files and frontend .c files respectively. By default, only include files meant for frontend use are installed into the installation include directory. There is a new make target 'make install-all-headers' that adds the whole content of the src/include tree to the installed fileset, for use by people who want to develop server-side code without keeping the complete source tree on hand. Cleaned up a whole lot of crufty and inconsistent header inclusions.
73 lines
1.5 KiB
C
73 lines
1.5 KiB
C
#include "postgres.h"
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#include <math.h>
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#include "utils/geo_decls.h" /* for Pt */
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/* Earth's radius is in statute miles. */
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const int EARTH_RADIUS = 3958.747716;
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const int TWO_PI = 2.0 * M_PI;
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double *geo_distance(Point *pt1, Point *pt2);
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/******************************************************
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*
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* degtorad - convert degrees to radians
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*
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* arg: double, angle in degrees
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*
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* returns: double, same angle in radians
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******************************************************/
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static double
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degtorad(double degrees)
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{
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return (degrees / 360.0) * TWO_PI;
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}
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/******************************************************
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*
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* geo_distance - distance between points
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*
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* args:
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* a pair of points - for each point,
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* x-coordinate is longitude in degrees west of Greenwich
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* y-coordinate is latitude in degrees above equator
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*
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* returns: double
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* distance between the points in miles on earth's surface
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******************************************************/
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double *
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geo_distance(Point *pt1, Point *pt2)
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{
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double long1,
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lat1,
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long2,
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lat2;
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double longdiff;
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double *resultp = palloc(sizeof(double));
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/* convert degrees to radians */
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long1 = degtorad(pt1->x);
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lat1 = degtorad(pt1->y);
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long2 = degtorad(pt2->x);
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lat2 = degtorad(pt2->y);
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/* compute difference in longitudes - want < 180 degrees */
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longdiff = fabs(long1 - long2);
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if (longdiff > M_PI)
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longdiff = TWO_PI - longdiff;
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*resultp = EARTH_RADIUS * acos
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(sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(longdiff));
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return resultp;
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}
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