decode_geohash_bbox()

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

Definition at line 721 of file lwalgorithm.c.

{
        bool is_even = 1;
 
        lat[0] = -90.0;
        lat[1] = 90.0;
        lon[0] = -180.0;
        lon[1] = 180.0;
 
        size_t hashlen = strlen(geohash);
        if (precision < 0 || (size_t)precision > hashlen)
        {
                precision = (int)hashlen;
        }
 
        for (int i = 0; i < precision; i++)
        {
                char c = tolower(geohash[i]);
 
                /* Valid characters are all digits in base32 */
                char *base32_pos = strchr(base32, c);
                if (!base32_pos)
                {
                        lwerror("%s: Invalid character '%c'", __func__, geohash[i]);
                        return;
                }
                char cd = base32_pos - base32;
 
                for (size_t j = 0; j < 5; j++)
                {
                        const char bits[] = {16, 8, 4, 2, 1};
                        char 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;
                }
        }
}

References base32, lwerror(), and precision.

Referenced by parse_geohash(), and test_geohash_bbox().

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