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     The code for commands: server.c




     void echoCommand(client *c) {
         addReplyBulk(c,c‐>argv[1]);
     }

addReply* must be nonblocking. (addReplyErrorArity, addReplyBulk,
addReplyBulkCBuffer, ...)


addReply(): networking.c























                               ‐2‐


         if (sdsEncodedObject(obj)) {
             _addReplyToBufferOrList(c,obj‐>ptr,sdslen(obj‐>ptr));
         } else if (obj‐>encoding == OBJ_ENCODING_INT) {
             /* For integer encoded strings we just convert it into a string
              * using our optimized function, and attach the resulting string
              * to the output buffer. */
             char buf[32];
             size_t len = ll2string(buf,sizeof(buf),(long)obj‐>ptr);
             _addReplyToBufferOrList(c,buf,len);
         } else {
             serverPanic("Wrong obj‐>encoding in addReply()");
         }



















































                               ‐3‐


         if (c‐>flags & CLIENT_CLOSE_AFTER_REPLY) return;

     // push message
         if ((c‐>flags & CLIENT_PUSHING) && c == server.current_client &&
             server.executing_client && !cmdHasPushAsReply(server.executing_client‐>cmd))
         {
             _addReplyProtoToList(c,server.pending_push_messages,s,len);
             return;
         }

         if (len > reply_len) _addReplyProtoToList(c,c‐>reply,s+reply_len,len‐reply_len);








         /* Append to tail string when possible. */
         if (tail) {
             /* Copy the part we can fit into the tail, and leave the rest for a
              * new node */
             size_t avail = tail‐>size ‐ tail‐>used;
             size_t copy = avail >= len? len: avail;
             memcpy(tail‐>buf + tail‐>used, s, copy);
             tail‐>used += copy;
             s += copy;
             len ‐= copy;
         }
         if (len) {
             /* Create a new node, make sure it is allocated to at
              * least PROTO_REPLY_CHUNK_BYTES */
             size_t usable_size;
             size_t size = len < PROTO_REPLY_CHUNK_BYTES? PROTO_REPLY_CHUNK_BYTES: len;
             tail = zmalloc_usable(size + sizeof(clientReplyBlock), &usable_size);
             /* take over the allocation’s internal fragmentation */
             tail‐>size = usable_size ‐ sizeof(clientReplyBlock);
             tail‐>used = len;
             memcpy(tail‐>buf, s, len);
             listAddNodeTail(reply_list, tail);
             c‐>reply_bytes += tail‐>size;

             closeClientOnOutputBufferLimitReached(c, 1);
         }