Function geohashCommand

app/redis-6.2.6/src/geo.c:871–927

GEOHASH key ele1 ele2 ... eleN * * Returns an array with an 11 characters geohash representation of the * position of the specified elements. */

 * Returns an array with an 11 characters geohash representation of the
 * position of the specified elements. */
void geohashCommand(client *c) {
    char *geoalphabet= "0123456789bcdefghjkmnpqrstuvwxyz";
    int j;

    /* Look up the requested zset */
    robj *zobj = lookupKeyRead(c->db, c->argv[1]);
    if (checkType(c, zobj, OBJ_ZSET)) return;

    /* Geohash elements one after the other, using a null bulk reply for
     * missing elements. */
    addReplyArrayLen(c,c->argc-2);
    for (j = 2; j < c->argc; j++) {
        double score;
        if (!zobj || zsetScore(zobj, c->argv[j]->ptr, &score) == C_ERR) {
            addReplyNull(c);
        } else {
            /* The internal format we use for geocoding is a bit different
             * than the standard, since we use as initial latitude range
             * -85,85, while the normal geohashing algorithm uses -90,90.
             * So we have to decode our position and re-encode using the
             * standard ranges in order to output a valid geohash string. */

            /* Decode... */
            double xy[2];
            if (!decodeGeohash(score,xy)) {
                addReplyNull(c);
                continue;
            }

            /* Re-encode */
            GeoHashRange r[2];
            GeoHashBits hash;
            r[0].min = -180;
            r[0].max = 180;
            r[1].min = -90;
            r[1].max = 90;
            geohashEncode(&r[0],&r[1],xy[0],xy[1],26,&hash);

            char buf[12];
            int i;
            for (i = 0; i < 11; i++) {
                int idx;
                if (i == 10) {
                    /* We have just 52 bits, but the API used to output
                     * an 11 bytes geohash. For compatibility we assume
                     * zero. */
                    idx = 0;
                } else {
                    idx = (hash.bits >> (52-((i+1)*5))) & 0x1f;
                }
                buf[i] = geoalphabet[idx];
            }
            buf[11] = '\0';
            addReplyBulkCBuffer(c,buf,11);
        }
    }
}