decode_geohash_bbox()

void decode_geohash_bbox	(	char *	geohash,
		double *	lat,
		double *	lon,
		int	precision
	)

Definition at line 704 of file lwalgorithm.c.

References base32, lwerror(), and precision.

Referenced by parse_geohash(), and test_geohash_bbox().

{
        int i, j, hashlen;
        char c, cd, mask, is_even = 1;
        static char bits[] = {16, 8, 4, 2, 1};

        lat[0] = -90.0;
        lat[1] = 90.0;
        lon[0] = -180.0;
        lon[1] = 180.0;

        hashlen = strlen(geohash);

        if (precision < 0 || precision > hashlen)
        {
                precision = hashlen;
        }

        for (i = 0; i < precision; i++)
        {
                c = tolower(geohash[i]);
                /* Valid characters are all digits and letters except a, i, l and o */
                if (!(((c >= '0') && (c <= '9')) ||
                      ((c >= 'b') && (c <= 'z') && (c != 'i') && (c != 'l') && (c != 'o'))))
                {
                        lwerror("%s: Invalid character '%c'", __func__, geohash[i]);
                        return;
                }
                cd = strchr(base32, c) - base32;

                for (j = 0; j < 5; j++)
                {
                        mask = bits[j];
                        if (is_even)
                        {
                                lon[!(cd & mask)] = (lon[0] + lon[1]) / 2;
                        }
                        else
                        {
                                lat[!(cd & mask)] = (lat[0] + lat[1]) / 2;
                        }
                        is_even = !is_even;
                }
        }
}

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