Function lookupStringForBitCommand

app/redis-6.2.6/src/bitops.c:480–493

This is an helper function for commands implementations that need to write * bits to a string object. The command creates or pad with zeroes the string * so that the 'maxbit' bit can be addressed. The object is finally * returned. Otherwise if the key holds a wrong type NULL is returned and * an error is sent to the client. */

 * returned. Otherwise if the key holds a wrong type NULL is returned and
 * an error is sent to the client. */
robj *lookupStringForBitCommand(client *c, uint64_t maxbit) {
    size_t byte = maxbit >> 3;
    robj *o = lookupKeyWrite(c->db,c->argv[1]);
    if (checkType(c,o,OBJ_STRING)) return NULL;

    if (o == NULL) {
        o = createObject(OBJ_STRING,sdsnewlen(NULL, byte+1));
        dbAdd(c->db,c->argv[1],o);
    } else {
        o = dbUnshareStringValue(c->db,c->argv[1],o);
        o->ptr = sdsgrowzero(o->ptr,byte+1);
    }
    return o;
}

/* Return a pointer to the string object content, and stores its length
 * in 'len'. The user is required to pass (likely stack allocated) buffer