36 lines
854 B
C
36 lines
854 B
C
#include <math.h>
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#include <postgres.h>
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#include <fmgr.h>
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Datum
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maptile_for_point(PG_FUNCTION_ARGS)
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{
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double lat = PG_GETARG_INT64(0) / 10000000.0;
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double lon = PG_GETARG_INT64(1) / 10000000.0;
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int zoom = PG_GETARG_INT32(2);
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double scale = pow(2, zoom);
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double r_per_d = M_PI / 180;
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unsigned int x;
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unsigned int y;
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x = floor((lon + 180.0) * scale / 360.0);
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y = floor((1 - log(tan(lat * r_per_d) + 1.0 / cos(lat * r_per_d)) / M_PI) * scale / 2.0);
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PG_RETURN_INT32((x << zoom) | y);
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}
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PG_FUNCTION_INFO_V1(maptile_for_point);
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/*
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* To bind this into PGSQL, try something like:
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*
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* CREATE FUNCTION maptile_for_point(int8, int8, int4) RETURNS int4
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* AS '/path/to/rails-port/db/functions/libpgosm', 'maptile_for_point'
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* LANGUAGE C STRICT;
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*
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* (without all the *s)
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*/
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#ifdef PG_MODULE_MAGIC
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PG_MODULE_MAGIC;
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#endif
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