redict/src/networking.c

#include "redis.h"
#include <sys/uio.h>

void *dupClientReplyValue(void *o) {
    incrRefCount((robj*)o);
    return o;
}

int listMatchObjects(void *a, void *b) {
    return equalStringObjects(a,b);
}

redisClient *createClient(int fd) {
    redisClient *c;

    /* Allocate more space to hold a static write buffer. */
    c = zmalloc(sizeof(redisClient)+REDIS_REPLY_CHUNK_BYTES);
    c->buflen = REDIS_REPLY_CHUNK_BYTES;
    c->bufpos = 0;

    anetNonBlock(NULL,fd);
    anetTcpNoDelay(NULL,fd);
    if (!c) return NULL;
    selectDb(c,0);
    c->fd = fd;
    c->querybuf = sdsempty();
    c->argc = 0;
    c->argv = NULL;
    c->bulklen = -1;
    c->multibulk = 0;
    c->mbargc = 0;
    c->mbargv = NULL;
    c->sentlen = 0;
    c->flags = 0;
    c->lastinteraction = time(NULL);
    c->authenticated = 0;
    c->replstate = REDIS_REPL_NONE;
    c->reply = listCreate();
    listSetFreeMethod(c->reply,decrRefCount);
    listSetDupMethod(c->reply,dupClientReplyValue);
    c->blocking_keys = NULL;
    c->blocking_keys_num = 0;
    c->io_keys = listCreate();
    c->watched_keys = listCreate();
    listSetFreeMethod(c->io_keys,decrRefCount);
    c->pubsub_channels = dictCreate(&setDictType,NULL);
    c->pubsub_patterns = listCreate();
    listSetFreeMethod(c->pubsub_patterns,decrRefCount);
    listSetMatchMethod(c->pubsub_patterns,listMatchObjects);
    if (aeCreateFileEvent(server.el, c->fd, AE_READABLE,
        readQueryFromClient, c) == AE_ERR) {
        freeClient(c);
        return NULL;
    }
    listAddNodeTail(server.clients,c);
    initClientMultiState(c);
    return c;
}

int _ensureFileEvent(redisClient *c) {
    if (c->fd <= 0) return REDIS_ERR;
    if (c->bufpos == 0 && listLength(c->reply) == 0 &&
        (c->replstate == REDIS_REPL_NONE ||
         c->replstate == REDIS_REPL_ONLINE) &&
        aeCreateFileEvent(server.el, c->fd, AE_WRITABLE,
        sendReplyToClient, c) == AE_ERR) return REDIS_ERR;
    return REDIS_OK;
}

/* Create a duplicate of the last object in the reply list when
 * it is not exclusively owned by the reply list. */
robj *dupLastObjectIfNeeded(list *reply) {
    robj *new, *cur;
    listNode *ln;
    redisAssert(listLength(reply) > 0);
    ln = listLast(reply);
    cur = listNodeValue(ln);
    if (cur->refcount > 1) {
        new = dupStringObject(cur);
        decrRefCount(cur);
        listNodeValue(ln) = new;
    }
    return listNodeValue(ln);
}

int _addReplyToBuffer(redisClient *c, char *s, size_t len) {
    size_t available = c->buflen-c->bufpos;

    /* If there already are entries in the reply list, we cannot
     * add anything more to the static buffer. */
    if (listLength(c->reply) > 0) return REDIS_ERR;

    /* Check that the buffer has enough space available for this string. */
    if (len > available) return REDIS_ERR;

    memcpy(c->buf+c->bufpos,s,len);
    c->bufpos+=len;
    return REDIS_OK;
}

void _addReplyObjectToList(redisClient *c, robj *o) {
    robj *tail;
    if (listLength(c->reply) == 0) {
        incrRefCount(o);
        listAddNodeTail(c->reply,o);
    } else {
        tail = listNodeValue(listLast(c->reply));

        /* Append to this object when possible. */
        if (tail->ptr != NULL &&
            sdslen(tail->ptr)+sdslen(o->ptr) <= REDIS_REPLY_CHUNK_BYTES)
        {
            tail = dupLastObjectIfNeeded(c->reply);
            tail->ptr = sdscatlen(tail->ptr,o->ptr,sdslen(o->ptr));
        } else {
            incrRefCount(o);
            listAddNodeTail(c->reply,o);
        }
    }
}

/* This method takes responsibility over the sds. When it is no longer
 * needed it will be free'd, otherwise it ends up in a robj. */
void _addReplySdsToList(redisClient *c, sds s) {
    robj *tail;
    if (listLength(c->reply) == 0) {
        listAddNodeTail(c->reply,createObject(REDIS_STRING,s));
    } else {
        tail = listNodeValue(listLast(c->reply));

        /* Append to this object when possible. */
        if (tail->ptr != NULL &&
            sdslen(tail->ptr)+sdslen(s) <= REDIS_REPLY_CHUNK_BYTES)
        {
            tail = dupLastObjectIfNeeded(c->reply);
            tail->ptr = sdscatlen(tail->ptr,s,sdslen(s));
            sdsfree(s);
        } else {
            listAddNodeTail(c->reply,createObject(REDIS_STRING,s));
        }
    }
}

void _addReplyStringToList(redisClient *c, char *s, size_t len) {
    robj *tail;
    if (listLength(c->reply) == 0) {
        listAddNodeTail(c->reply,createStringObject(s,len));
    } else {
        tail = listNodeValue(listLast(c->reply));

        /* Append to this object when possible. */
        if (tail->ptr != NULL &&
            sdslen(tail->ptr)+len <= REDIS_REPLY_CHUNK_BYTES)
        {
            tail = dupLastObjectIfNeeded(c->reply);
            tail->ptr = sdscatlen(tail->ptr,s,len);
        } else {
            listAddNodeTail(c->reply,createStringObject(s,len));
        }
    }
}

void addReply(redisClient *c, robj *obj) {
    if (_ensureFileEvent(c) != REDIS_OK) return;
    if (server.vm_enabled && obj->storage != REDIS_VM_MEMORY) {
        /* Returns a new object with refcount 1 */
        obj = dupStringObject(obj);
    } else {
        /* This increments the refcount. */
        obj = getDecodedObject(obj);
    }
    if (_addReplyToBuffer(c,obj->ptr,sdslen(obj->ptr)) != REDIS_OK)
        _addReplyObjectToList(c,obj);
    decrRefCount(obj);
}

void addReplySds(redisClient *c, sds s) {
    if (_ensureFileEvent(c) != REDIS_OK) {
        /* The caller expects the sds to be free'd. */
        sdsfree(s);
        return;
    }
    if (_addReplyToBuffer(c,s,sdslen(s)) == REDIS_OK) {
        sdsfree(s);
    } else {
        /* This method free's the sds when it is no longer needed. */
        _addReplySdsToList(c,s);
    }
}

void addReplyString(redisClient *c, char *s, size_t len) {
    if (_ensureFileEvent(c) != REDIS_OK) return;
    if (_addReplyToBuffer(c,s,len) != REDIS_OK)
        _addReplyStringToList(c,s,len);
}

void _addReplyError(redisClient *c, char *s, size_t len) {
    addReplyString(c,"-ERR ",5);
    addReplyString(c,s,len);
    addReplyString(c,"\r\n",2);
}

void addReplyError(redisClient *c, char *err) {
    _addReplyError(c,err,strlen(err));
}

void addReplyErrorFormat(redisClient *c, const char *fmt, ...) {
    va_list ap;
    va_start(ap,fmt);
    sds s = sdscatvprintf(sdsempty(),fmt,ap);
    va_end(ap);
    _addReplyError(c,s,sdslen(s));
    sdsfree(s);
}

void _addReplyStatus(redisClient *c, char *s, size_t len) {
    addReplyString(c,"+",1);
    addReplyString(c,s,len);
    addReplyString(c,"\r\n",2);
}

void addReplyStatus(redisClient *c, char *status) {
    _addReplyStatus(c,status,strlen(status));
}

void addReplyStatusFormat(redisClient *c, const char *fmt, ...) {
    va_list ap;
    va_start(ap,fmt);
    sds s = sdscatvprintf(sdsempty(),fmt,ap);
    va_end(ap);
    _addReplyStatus(c,s,sdslen(s));
    sdsfree(s);
}

/* Adds an empty object to the reply list that will contain the multi bulk
 * length, which is not known when this function is called. */
void *addDeferredMultiBulkLength(redisClient *c) {
    if (_ensureFileEvent(c) != REDIS_OK) return NULL;
    listAddNodeTail(c->reply,createObject(REDIS_STRING,NULL));
    return listLast(c->reply);
}

/* Populate the length object and try glueing it to the next chunk. */
void setDeferredMultiBulkLength(redisClient *c, void *node, long length) {
    listNode *ln = (listNode*)node;
    robj *len, *next;

    /* Abort when *node is NULL (see addDeferredMultiBulkLength). */
    if (node == NULL) return;

    len = listNodeValue(ln);
    len->ptr = sdscatprintf(sdsempty(),"*%ld\r\n",length);
    if (ln->next != NULL) {
        next = listNodeValue(ln->next);

        /* Only glue when the next node is an sds */
        if (next->ptr != NULL) {
            len->ptr = sdscat(len->ptr,next->ptr);
            listDelNode(c->reply,ln->next);
        }
    }
}

void addReplyDouble(redisClient *c, double d) {
    char dbuf[128], sbuf[128];
    int dlen, slen;
    dlen = snprintf(dbuf,sizeof(dbuf),"%.17g",d);
    slen = snprintf(sbuf,sizeof(sbuf),"$%d\r\n%s\r\n",dlen,dbuf);
    addReplyString(c,sbuf,slen);
}

void _addReplyLongLong(redisClient *c, long long ll, char prefix) {
    char buf[128];
    int len;
    buf[0] = prefix;
    len = ll2string(buf+1,sizeof(buf)-1,ll);
    buf[len+1] = '\r';
    buf[len+2] = '\n';
    addReplyString(c,buf,len+3);
}

void addReplyLongLong(redisClient *c, long long ll) {
    _addReplyLongLong(c,ll,':');
}

void addReplyMultiBulkLen(redisClient *c, long length) {
    _addReplyLongLong(c,length,'*');
}

void addReplyBulkLen(redisClient *c, robj *obj) {
    size_t len;

    if (obj->encoding == REDIS_ENCODING_RAW) {
        len = sdslen(obj->ptr);
    } else {
        long n = (long)obj->ptr;

        /* Compute how many bytes will take this integer as a radix 10 string */
        len = 1;
        if (n < 0) {
            len++;
            n = -n;
        }
        while((n = n/10) != 0) {
            len++;
        }
    }
    _addReplyLongLong(c,len,'$');
}

void addReplyBulk(redisClient *c, robj *obj) {
    addReplyBulkLen(c,obj);
    addReply(c,obj);
    addReply(c,shared.crlf);
}

/* In the CONFIG command we need to add vanilla C string as bulk replies */
void addReplyBulkCString(redisClient *c, char *s) {
    if (s == NULL) {
        addReply(c,shared.nullbulk);
    } else {
        robj *o = createStringObject(s,strlen(s));
        addReplyBulk(c,o);
        decrRefCount(o);
    }
}

void acceptHandler(aeEventLoop *el, int fd, void *privdata, int mask) {
    int cport, cfd;
    char cip[128];
    redisClient *c;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);
    REDIS_NOTUSED(privdata);

    cfd = anetAccept(server.neterr, fd, cip, &cport);
    if (cfd == AE_ERR) {
        redisLog(REDIS_VERBOSE,"Accepting client connection: %s", server.neterr);
        return;
    }
    redisLog(REDIS_VERBOSE,"Accepted %s:%d", cip, cport);
    if ((c = createClient(cfd)) == NULL) {
        redisLog(REDIS_WARNING,"Error allocating resoures for the client");
        close(cfd); /* May be already closed, just ingore errors */
        return;
    }
    /* If maxclient directive is set and this is one client more... close the
     * connection. Note that we create the client instead to check before
     * for this condition, since now the socket is already set in nonblocking
     * mode and we can send an error for free using the Kernel I/O */
    if (server.maxclients && listLength(server.clients) > server.maxclients) {
        char *err = "-ERR max number of clients reached\r\n";

        /* That's a best effort error message, don't check write errors */
        if (write(c->fd,err,strlen(err)) == -1) {
            /* Nothing to do, Just to avoid the warning... */
        }
        freeClient(c);
        return;
    }
    server.stat_numconnections++;
}

static void freeClientArgv(redisClient *c) {
    int j;

    for (j = 0; j < c->argc; j++)
        decrRefCount(c->argv[j]);
    for (j = 0; j < c->mbargc; j++)
        decrRefCount(c->mbargv[j]);
    c->argc = 0;
    c->mbargc = 0;
}

void freeClient(redisClient *c) {
    listNode *ln;

    /* Note that if the client we are freeing is blocked into a blocking
     * call, we have to set querybuf to NULL *before* to call
     * unblockClientWaitingData() to avoid processInputBuffer() will get
     * called. Also it is important to remove the file events after
     * this, because this call adds the READABLE event. */
    sdsfree(c->querybuf);
    c->querybuf = NULL;
    if (c->flags & REDIS_BLOCKED)
        unblockClientWaitingData(c);

    /* UNWATCH all the keys */
    unwatchAllKeys(c);
    listRelease(c->watched_keys);
    /* Unsubscribe from all the pubsub channels */
    pubsubUnsubscribeAllChannels(c,0);
    pubsubUnsubscribeAllPatterns(c,0);
    dictRelease(c->pubsub_channels);
    listRelease(c->pubsub_patterns);
    /* Obvious cleanup */
    aeDeleteFileEvent(server.el,c->fd,AE_READABLE);
    aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
    listRelease(c->reply);
    freeClientArgv(c);
    close(c->fd);
    /* Remove from the list of clients */
    ln = listSearchKey(server.clients,c);
    redisAssert(ln != NULL);
    listDelNode(server.clients,ln);
    /* Remove from the list of clients waiting for swapped keys, or ready
     * to be restarted, but not yet woken up again. */
    if (c->flags & REDIS_IO_WAIT) {
        redisAssert(server.vm_enabled);
        if (listLength(c->io_keys) == 0) {
            ln = listSearchKey(server.io_ready_clients,c);

            /* When this client is waiting to be woken up (REDIS_IO_WAIT),
             * it should be present in the list io_ready_clients */
            redisAssert(ln != NULL);
            listDelNode(server.io_ready_clients,ln);
        } else {
            while (listLength(c->io_keys)) {
                ln = listFirst(c->io_keys);
                dontWaitForSwappedKey(c,ln->value);
            }
        }
        server.vm_blocked_clients--;
    }
    listRelease(c->io_keys);
    /* Master/slave cleanup.
     * Case 1: we lost the connection with a slave. */
    if (c->flags & REDIS_SLAVE) {
        if (c->replstate == REDIS_REPL_SEND_BULK && c->repldbfd != -1)
            close(c->repldbfd);
        list *l = (c->flags & REDIS_MONITOR) ? server.monitors : server.slaves;
        ln = listSearchKey(l,c);
        redisAssert(ln != NULL);
        listDelNode(l,ln);
    }

    /* Case 2: we lost the connection with the master. */
    if (c->flags & REDIS_MASTER) {
        server.master = NULL;
        server.replstate = REDIS_REPL_CONNECT;
        /* Since we lost the connection with the master, we should also
         * close the connection with all our slaves if we have any, so
         * when we'll resync with the master the other slaves will sync again
         * with us as well. Note that also when the slave is not connected
         * to the master it will keep refusing connections by other slaves. */
        while (listLength(server.slaves)) {
            ln = listFirst(server.slaves);
            freeClient((redisClient*)ln->value);
        }
    }
    /* Release memory */
    zfree(c->argv);
    zfree(c->mbargv);
    freeClientMultiState(c);
    zfree(c);
}

void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask) {
    redisClient *c = privdata;
    int nwritten = 0, totwritten = 0, objlen;
    robj *o;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);

    /* Use writev() if we have enough buffers to send */
    if (!server.glueoutputbuf &&
        listLength(c->reply) > REDIS_WRITEV_THRESHOLD &&
        !(c->flags & REDIS_MASTER))
    {
        sendReplyToClientWritev(el, fd, privdata, mask);
        return;
    }

    while(c->bufpos > 0 || listLength(c->reply)) {
        if (c->bufpos > 0) {
            if (c->flags & REDIS_MASTER) {
                /* Don't reply to a master */
                nwritten = c->bufpos - c->sentlen;
            } else {
                nwritten = write(fd,c->buf+c->sentlen,c->bufpos-c->sentlen);
                if (nwritten <= 0) break;
            }
            c->sentlen += nwritten;
            totwritten += nwritten;

            /* If the buffer was sent, set bufpos to zero to continue with
             * the remainder of the reply. */
            if (c->sentlen == c->bufpos) {
                c->bufpos = 0;
                c->sentlen = 0;
            }
        } else {
            o = listNodeValue(listFirst(c->reply));
            objlen = sdslen(o->ptr);

            if (objlen == 0) {
                listDelNode(c->reply,listFirst(c->reply));
                continue;
            }

            if (c->flags & REDIS_MASTER) {
                /* Don't reply to a master */
                nwritten = objlen - c->sentlen;
            } else {
                nwritten = write(fd, ((char*)o->ptr)+c->sentlen,objlen-c->sentlen);
                if (nwritten <= 0) break;
            }
            c->sentlen += nwritten;
            totwritten += nwritten;

            /* If we fully sent the object on head go to the next one */
            if (c->sentlen == objlen) {
                listDelNode(c->reply,listFirst(c->reply));
                c->sentlen = 0;
            }
        }
        /* Note that we avoid to send more thank REDIS_MAX_WRITE_PER_EVENT
         * bytes, in a single threaded server it's a good idea to serve
         * other clients as well, even if a very large request comes from
         * super fast link that is always able to accept data (in real world
         * scenario think about 'KEYS *' against the loopback interfae) */
        if (totwritten > REDIS_MAX_WRITE_PER_EVENT) break;
    }
    if (nwritten == -1) {
        if (errno == EAGAIN) {
            nwritten = 0;
        } else {
            redisLog(REDIS_VERBOSE,
                "Error writing to client: %s", strerror(errno));
            freeClient(c);
            return;
        }
    }
    if (totwritten > 0) c->lastinteraction = time(NULL);
    if (listLength(c->reply) == 0) {
        c->sentlen = 0;
        aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
    }
}

void sendReplyToClientWritev(aeEventLoop *el, int fd, void *privdata, int mask)
{
    redisClient *c = privdata;
    int nwritten = 0, totwritten = 0, objlen, willwrite;
    robj *o;
    struct iovec iov[REDIS_WRITEV_IOVEC_COUNT];
    int offset, ion = 0;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);

    listNode *node;
    while (listLength(c->reply)) {
        offset = c->sentlen;
        ion = 0;
        willwrite = 0;

        /* fill-in the iov[] array */
        for(node = listFirst(c->reply); node; node = listNextNode(node)) {
            o = listNodeValue(node);
            objlen = sdslen(o->ptr);

            if (totwritten + objlen - offset > REDIS_MAX_WRITE_PER_EVENT)
                break;

            if(ion == REDIS_WRITEV_IOVEC_COUNT)
                break; /* no more iovecs */

            iov[ion].iov_base = ((char*)o->ptr) + offset;
            iov[ion].iov_len = objlen - offset;
            willwrite += objlen - offset;
            offset = 0; /* just for the first item */
            ion++;
        }

        if(willwrite == 0)
            break;

        /* write all collected blocks at once */
        if((nwritten = writev(fd, iov, ion)) < 0) {
            if (errno != EAGAIN) {
                redisLog(REDIS_VERBOSE,
                         "Error writing to client: %s", strerror(errno));
                freeClient(c);
                return;
            }
            break;
        }

        totwritten += nwritten;
        offset = c->sentlen;

        /* remove written robjs from c->reply */
        while (nwritten && listLength(c->reply)) {
            o = listNodeValue(listFirst(c->reply));
            objlen = sdslen(o->ptr);

            if(nwritten >= objlen - offset) {
                listDelNode(c->reply, listFirst(c->reply));
                nwritten -= objlen - offset;
                c->sentlen = 0;
            } else {
                /* partial write */
                c->sentlen += nwritten;
                break;
            }
            offset = 0;
        }
    }

    if (totwritten > 0)
        c->lastinteraction = time(NULL);

    if (listLength(c->reply) == 0) {
        c->sentlen = 0;
        aeDeleteFileEvent(server.el,c->fd,AE_WRITABLE);
    }
}

/* resetClient prepare the client to process the next command */
void resetClient(redisClient *c) {
    freeClientArgv(c);
    c->bulklen = -1;
    c->multibulk = 0;
}

void closeTimedoutClients(void) {
    redisClient *c;
    listNode *ln;
    time_t now = time(NULL);
    listIter li;

    listRewind(server.clients,&li);
    while ((ln = listNext(&li)) != NULL) {
        c = listNodeValue(ln);
        if (server.maxidletime &&
            !(c->flags & REDIS_SLAVE) &&    /* no timeout for slaves */
            !(c->flags & REDIS_MASTER) &&   /* no timeout for masters */
            !(c->flags & REDIS_BLOCKED) &&  /* no timeout for BLPOP */
            dictSize(c->pubsub_channels) == 0 && /* no timeout for pubsub */
            listLength(c->pubsub_patterns) == 0 &&
            (now - c->lastinteraction > server.maxidletime))
        {
            redisLog(REDIS_VERBOSE,"Closing idle client");
            freeClient(c);
        } else if (c->flags & REDIS_BLOCKED) {
            if (c->blockingto != 0 && c->blockingto < now) {
                addReply(c,shared.nullmultibulk);
                unblockClientWaitingData(c);
            }
        }
    }
}

void processInputBuffer(redisClient *c) {
again:
    /* Before to process the input buffer, make sure the client is not
     * waitig for a blocking operation such as BLPOP. Note that the first
     * iteration the client is never blocked, otherwise the processInputBuffer
     * would not be called at all, but after the execution of the first commands
     * in the input buffer the client may be blocked, and the "goto again"
     * will try to reiterate. The following line will make it return asap. */
    if (c->flags & REDIS_BLOCKED || c->flags & REDIS_IO_WAIT) return;
    if (c->bulklen == -1) {
        /* Read the first line of the query */
        char *p = strchr(c->querybuf,'\n');
        size_t querylen;

        if (p) {
            sds query, *argv;
            int argc, j;

            query = c->querybuf;
            c->querybuf = sdsempty();
            querylen = 1+(p-(query));
            if (sdslen(query) > querylen) {
                /* leave data after the first line of the query in the buffer */
                c->querybuf = sdscatlen(c->querybuf,query+querylen,sdslen(query)-querylen);
            }
            *p = '\0'; /* remove "\n" */
            if (*(p-1) == '\r') *(p-1) = '\0'; /* and "\r" if any */
            sdsupdatelen(query);

            /* Now we can split the query in arguments */
            argv = sdssplitlen(query,sdslen(query)," ",1,&argc);
            sdsfree(query);

            if (c->argv) zfree(c->argv);
            c->argv = zmalloc(sizeof(robj*)*argc);

            for (j = 0; j < argc; j++) {
                if (sdslen(argv[j])) {
                    c->argv[c->argc] = createObject(REDIS_STRING,argv[j]);
                    c->argc++;
                } else {
                    sdsfree(argv[j]);
                }
            }
            zfree(argv);
            if (c->argc) {
                /* Execute the command. If the client is still valid
                 * after processCommand() return and there is something
                 * on the query buffer try to process the next command. */
                if (processCommand(c) && sdslen(c->querybuf)) goto again;
            } else {
                /* Nothing to process, argc == 0. Just process the query
                 * buffer if it's not empty or return to the caller */
                if (sdslen(c->querybuf)) goto again;
            }
            return;
        } else if (sdslen(c->querybuf) >= REDIS_REQUEST_MAX_SIZE) {
            redisLog(REDIS_VERBOSE, "Client protocol error");
            freeClient(c);
            return;
        }
    } else {
        /* Bulk read handling. Note that if we are at this point
           the client already sent a command terminated with a newline,
           we are reading the bulk data that is actually the last
           argument of the command. */
        int qbl = sdslen(c->querybuf);

        if (c->bulklen <= qbl) {
            /* Copy everything but the final CRLF as final argument */
            c->argv[c->argc] = createStringObject(c->querybuf,c->bulklen-2);
            c->argc++;
            c->querybuf = sdsrange(c->querybuf,c->bulklen,-1);
            /* Process the command. If the client is still valid after
             * the processing and there is more data in the buffer
             * try to parse it. */
            if (processCommand(c) && sdslen(c->querybuf)) goto again;
            return;
        }
    }
}

void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
    redisClient *c = (redisClient*) privdata;
    char buf[REDIS_IOBUF_LEN];
    int nread;
    REDIS_NOTUSED(el);
    REDIS_NOTUSED(mask);

    nread = read(fd, buf, REDIS_IOBUF_LEN);
    if (nread == -1) {
        if (errno == EAGAIN) {
            nread = 0;
        } else {
            redisLog(REDIS_VERBOSE, "Reading from client: %s",strerror(errno));
            freeClient(c);
            return;
        }
    } else if (nread == 0) {
        redisLog(REDIS_VERBOSE, "Client closed connection");
        freeClient(c);
        return;
    }
    if (nread) {
        c->querybuf = sdscatlen(c->querybuf, buf, nread);
        c->lastinteraction = time(NULL);
    } else {
        return;
    }
    processInputBuffer(c);
}