/* File event structure */
typedef struct aeFileEvent {
    int mask; /* one of AE_(READABLE|WRITABLE) */
    aeFileProc *rfileProc;
    aeFileProc *wfileProc;
    void *clientData;
} aeFileEvent;

/* Time event structure */
typedef struct aeTimeEvent {
    long long id; /* time event identifier. */
    long when_sec; /* seconds */
    long when_ms; /* milliseconds */
    aeTimeProc *timeProc;
    aeEventFinalizerProc *finalizerProc;
    void *clientData;
    struct aeTimeEvent *next;
} aeTimeEvent;

/* A fired event */
typedef struct aeFiredEvent {
    int fd;
    int mask;
} aeFiredEvent;

/* State of an event based program */
typedef struct aeEventLoop {
    int maxfd;
    long long timeEventNextId;
    aeFileEvent events[AE_SETSIZE]; /* Registered events */
    aeFiredEvent fired[AE_SETSIZE]; /* Fired events */
    aeTimeEvent *timeEventHead;
    int stop;
    void *apidata; /* This is used for polling API specific data */
    aeBeforeSleepProc *beforesleep;
} aeEventLoop;

/* Process every pending time event, then every pending file event
 * (that may be registered by time event callbacks just processed).
 * Without special flags the function sleeps until some file event
 * fires, or when the next time event occurrs (if any).
 *
 * If flags is 0, the function does nothing and returns.
 * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 * if flags has AE_FILE_EVENTS set, file events are processed.
 * if flags has AE_TIME_EVENTS set, time events are processed.
 * if flags has AE_DONT_WAIT set the function returns ASAP until all
 * the events that's possible to process without to wait are processed.
 *
 * The function returns the number of events processed. */
int aeProcessEvents(aeEventLoop *eventLoop, int flags)
{
    int processed = 0, numevents;

    /* Nothing to do? return ASAP */
    if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS)) return 0;

    /* Note that we want call select() even if there are no
     * file events to process as long as we want to process time
     * events, in order to sleep until the next time event is ready
     * to fire. */
    if (eventLoop->maxfd != -1 ||
        ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
        int j;
        aeTimeEvent *shortest = NULL;
        struct timeval tv, *tvp;

        if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
            shortest = aeSearchNearestTimer(eventLoop);
        if (shortest) {
            long now_sec, now_ms;

            /* Calculate the time missing for the nearest
             * timer to fire. */
            aeGetTime(&now_sec, &now_ms);
            tvp = &tv;
            tvp->tv_sec = shortest->when_sec - now_sec;
            if (shortest->when_ms < now_ms) {
                tvp->tv_usec = ((shortest->when_ms+1000) - now_ms)*1000;
                tvp->tv_sec --;
            } else {
                tvp->tv_usec = (shortest->when_ms - now_ms)*1000;
            }
            if (tvp->tv_sec < 0) tvp->tv_sec = 0;
            if (tvp->tv_usec < 0) tvp->tv_usec = 0;
        } else {
            /* If we have to check for events but need to return
             * ASAP because of AE_DONT_WAIT we need to se the timeout
             * to zero */
            if (flags & AE_DONT_WAIT) {
                tv.tv_sec = tv.tv_usec = 0;
                tvp = &tv;
            } else {
                /* Otherwise we can block */
                tvp = NULL; /* wait forever */
            }
        }

        numevents = aeApiPoll(eventLoop, tvp);
        for (j = 0; j < numevents; j++) {
            aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
            int mask = eventLoop->fired[j].mask;
            int fd = eventLoop->fired[j].fd;
            int rfired = 0;

	    /* note the fe->mask & mask & ... code: maybe an already processed
             * event removed an element that fired and we still didn't
             * processed, so we check if the event is still valid. */
            if (fe->mask & mask & AE_READABLE) {
                rfired = 1;
                fe->rfileProc(eventLoop,fd,fe->clientData,mask);
            }
            if (fe->mask & mask & AE_WRITABLE) {
                if (!rfired || fe->wfileProc != fe->rfileProc)
                    fe->wfileProc(eventLoop,fd,fe->clientData,mask);
            }
            processed++;
        }
    }
    /* Check time events */
    if (flags & AE_TIME_EVENTS)
        processed += processTimeEvents(eventLoop);

    return processed; /* return the number of processed file/time events */
}

int anetTcpServer(char *err, int port, char *bindaddr)
{
    int s, on = 1;
    struct sockaddr_in sa;
    
    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        anetSetError(err, "socket: %s\n", strerror(errno));
        return ANET_ERR;
    }
    if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1) {
        anetSetError(err, "setsockopt SO_REUSEADDR: %s\n", strerror(errno));
        close(s);
        return ANET_ERR;
    }
    memset(&sa,0,sizeof(sa));
    sa.sin_family = AF_INET;
    sa.sin_port = htons(port);
    sa.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bindaddr) {
        if (inet_aton(bindaddr, &sa.sin_addr) == 0) {
            anetSetError(err, "Invalid bind address\n");
            close(s);
            return ANET_ERR;
        }
    }
    if (bind(s, (struct sockaddr*)&sa, sizeof(sa)) == -1) {
        anetSetError(err, "bind: %s\n", strerror(errno));
        close(s);
        return ANET_ERR;
    }
    if (listen(s, 511) == -1) { /* the magic 511 constant is from nginx */
        anetSetError(err, "listen: %s\n", strerror(errno));
        close(s);
        return ANET_ERR;
    }
    return s;
}

static int anetTcpGenericConnect(char *err, char *addr, int port, int flags)
{
    int s, on = 1;
    struct sockaddr_in sa;

    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        anetSetError(err, "creating socket: %s\n", strerror(errno));
        return ANET_ERR;
    }
    /* Make sure connection-intensive things like the redis benckmark
     * will be able to close/open sockets a zillion of times */
    setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

    sa.sin_family = AF_INET;
    sa.sin_port = htons(port);
    if (inet_aton(addr, &sa.sin_addr) == 0) {
        struct hostent *he;

        he = gethostbyname(addr);
        if (he == NULL) {
            anetSetError(err, "can't resolve: %s\n", addr);
            close(s);
            return ANET_ERR;
        }
        memcpy(&sa.sin_addr, he->h_addr, sizeof(struct in_addr));
    }
    if (flags & ANET_CONNECT_NONBLOCK) {
        if (anetNonBlock(err,s) != ANET_OK)
            return ANET_ERR;
    }
    if (connect(s, (struct sockaddr*)&sa, sizeof(sa)) == -1) {
        if (errno == EINPROGRESS &&
            flags & ANET_CONNECT_NONBLOCK)
            return s;

        anetSetError(err, "connect: %s\n", strerror(errno));
        close(s);
        return ANET_ERR;
    }
    return s;
}

/* Like read(2) but make sure 'count' is read before to return
 * (unless error or EOF condition is encountered) */
int anetRead(int fd, char *buf, int count)
{
    int nread, totlen = 0;
    while(totlen != count) {
        nread = read(fd,buf,count-totlen);
        if (nread == 0) return totlen;
        if (nread == -1) return -1;
        totlen += nread;
        buf += nread;
    }
    return totlen;
}

/* Like write(2) but make sure 'count' is read before to return
 * (unless error is encountered) */
int anetWrite(int fd, char *buf, int count)
{
    int nwritten, totlen = 0;
    while(totlen != count) {
        nwritten = write(fd,buf,count-totlen);
        if (nwritten == 0) return totlen;
        if (nwritten == -1) return -1;
        totlen += nwritten;
        buf += nwritten;
    }
    return totlen;
}

------------
len|context
------------

void *zmalloc(size_t size) {
    void *ptr = malloc(size+PREFIX_SIZE);

    if (!ptr) zmalloc_oom(size);
#ifdef HAVE_MALLOC_SIZE
    increment_used_memory(redis_malloc_size(ptr));
    return ptr;
#else
    *((size_t*)ptr) = size;
    increment_used_memory(size+PREFIX_SIZE);
    return (char*)ptr+PREFIX_SIZE;
#endif
}

void *zrealloc(void *ptr, size_t size) {
#ifndef HAVE_MALLOC_SIZE
    void *realptr;
#endif
    size_t oldsize;
    void *newptr;

    if (ptr == NULL) return zmalloc(size);
#ifdef HAVE_MALLOC_SIZE
    oldsize = redis_malloc_size(ptr);
    newptr = realloc(ptr,size);
    if (!newptr) zmalloc_oom(size);

    decrement_used_memory(oldsize);
    increment_used_memory(redis_malloc_size(newptr));
    return newptr;
#else
    realptr = (char*)ptr-PREFIX_SIZE;
    oldsize = *((size_t*)realptr);
    newptr = realloc(realptr,size+PREFIX_SIZE);
    if (!newptr) zmalloc_oom(size);

    *((size_t*)newptr) = size;
    decrement_used_memory(oldsize);
    increment_used_memory(size);
    return (char*)newptr+PREFIX_SIZE;
#endif
}

void zfree(void *ptr) {
#ifndef HAVE_MALLOC_SIZE
    void *realptr;
    size_t oldsize;
#endif

    if (ptr == NULL) return;
#ifdef HAVE_MALLOC_SIZE
    decrement_used_memory(redis_malloc_size(ptr));
    free(ptr);
#else
    realptr = (char*)ptr-PREFIX_SIZE;
    oldsize = *((size_t*)realptr);
    decrement_used_memory(oldsize+PREFIX_SIZE);
    free(realptr);
#endif
}

--------------------------------------------------------------------------------------------------------------------------------------------------
cnt |key1.len|key1.context|val1.len|free1.len|val1.context|null1.context|key2.len|key2.context|val2.len|free2.len|val2.context|null2.context|0xFF| 
--------------------------------------------------------------------------------------------------------------------------------------------------

/* Create a new empty zipmap. */
unsigned char *zipmapNew(void) {
    unsigned char *zm = zmalloc(2);

    zm[0] = 0; /* Length */
    zm[1] = ZIPMAP_END;
    return zm;
}

/* Decode the encoded length pointed by 'p' */
static unsigned int zipmapDecodeLength(unsigned char *p) {
    unsigned int len = *p;

    if (len < ZIPMAP_BIGLEN) return len;
    memcpy(&len,p+1,sizeof(unsigned int));
    return len;
}

/* Set key to value, creating the key if it does not already exist.
 * If 'update' is not NULL, *update is set to 1 if the key was
 * already preset, otherwise to 0. */
unsigned char *zipmapSet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char *val, unsigned int vlen, int *update) {
    unsigned int zmlen, offset;
    unsigned int freelen, reqlen = zipmapRequiredLength(klen,vlen);
    unsigned int empty, vempty;
    unsigned char *p;
   
    freelen = reqlen;
    if (update) *update = 0;
    p = zipmapLookupRaw(zm,key,klen,&zmlen);
    if (p == NULL) {
        /* Key not found: enlarge */
        zm = zipmapResize(zm, zmlen+reqlen);
        p = zm+zmlen-1;
        zmlen = zmlen+reqlen;	/* 新的总长 */

        /* Increase zipmap length (this is an insert) */
        if (zm[0] < ZIPMAP_BIGLEN) zm[0]++;
    } else {
        /* Key found. Is there enough space for the new value? */
        /* Compute the total length: */
        if (update) *update = 1;	/* key已存在，则更新key对应的val */
        freelen = zipmapRawEntryLength(p);
        if (freelen < reqlen) {	/* 现存的空间不够用 */
            /* Store the offset of this key within the current zipmap, so
             * it can be resized. Then, move the tail backwards so this
             * pair fits at the current position. */
            offset = p-zm;
            zm = zipmapResize(zm, zmlen-freelen+reqlen);
            p = zm+offset;

            /* The +1 in the number of bytes to be moved is caused by the
             * end-of-zipmap byte. Note: the *original* zmlen is used. 
             * void *memmove(void *dest, const void *src, size_t n) */
            memmove(p+reqlen, p+freelen, zmlen-(offset+freelen+1));
            zmlen = zmlen-freelen+reqlen;
            freelen = reqlen;
        }
    }

    /* We now have a suitable block where the key/value entry can
     * be written. If there is too much free space, move the tail
     * of the zipmap a few bytes to the front and shrink the zipmap,
     * as we want zipmaps to be very space efficient. */
    empty = freelen-reqlen;
    if (empty >= ZIPMAP_VALUE_MAX_FREE) {
        /* First, move the tail <empty> bytes to the front, then resize
         * the zipmap to be <empty> bytes smaller. */
        offset = p-zm;
        memmove(p+reqlen, p+freelen, zmlen-(offset+freelen+1));
        zmlen -= empty;
        zm = zipmapResize(zm, zmlen);
        p = zm+offset;
        vempty = 0;
    } else {
        vempty = empty;
    }

    /* Just write the key + value and we are done. */
    /* Key: */
    p += zipmapEncodeLength(p,klen);
    memcpy(p,key,klen);
    p += klen;
    /* Value: */
    p += zipmapEncodeLength(p,vlen);
    *p++ = vempty;
    memcpy(p,val,vlen);
    return zm;
}

/* Remove the specified key. If 'deleted' is not NULL the pointed integer is
 * set to 0 if the key was not found, to 1 if it was found and deleted. */
unsigned char *zipmapDel(unsigned char *zm, unsigned char *key, unsigned int klen, int *deleted) {
    unsigned int zmlen, freelen;
    unsigned char *p = zipmapLookupRaw(zm,key,klen,&zmlen);
    if (p) {
        freelen = zipmapRawEntryLength(p);
        memmove(p, p+freelen, zmlen-((p-zm)+freelen+1));
        zm = zipmapResize(zm, zmlen-freelen);

        /* Decrease zipmap length */
        if (zm[0] < ZIPMAP_BIGLEN) zm[0]--;

        if (deleted) *deleted = 1;
    } else {
        if (deleted) *deleted = 0;
    }
    return zm;
}

/* Search a key and retrieve the pointer and len of the associated value.
 * If the key is found the function returns 1, otherwise 0. */
int zipmapGet(unsigned char *zm, unsigned char *key, unsigned int klen, unsigned char **value, unsigned int *vlen) {
    unsigned char *p;

    if ((p = zipmapLookupRaw(zm,key,klen,NULL)) == NULL) return 0;
    p += zipmapRawKeyLength(p);
    *vlen = zipmapDecodeLength(p);
    *value = p + ZIPMAP_LEN_BYTES(*vlen) + 1;
    return 1;
}

/* Call it before to iterate trought elements via zipmapNext() */
unsigned char *zipmapRewind(unsigned char *zm) {
    return zm+1;
}

/* This function is used to iterate through all the zipmap elements.
 * In the first call the first argument is the pointer to the zipmap + 1.
 * In the next calls what zipmapNext returns is used as first argument.
 * Example:
 *
 * unsigned char *i = zipmapRewind(my_zipmap);
 * while((i = zipmapNext(i,&key,&klen,&value,&vlen)) != NULL) {
 *     printf("%d bytes key at $p\n", klen, key);
 *     printf("%d bytes value at $p\n", vlen, value);
 * }
 */
unsigned char *zipmapNext(unsigned char *zm, unsigned char **key, unsigned int *klen, unsigned char **value, unsigned int *vlen) {
    if (zm[0] == ZIPMAP_END) return NULL;
    if (key) {
        *key = zm;
        *klen = zipmapDecodeLength(zm);
        *key += ZIPMAP_LEN_BYTES(*klen);
    }
    zm += zipmapRawKeyLength(zm);
    if (value) {
        *value = zm+1;	/* +1是free.len.head格式占用的一个字节空间 */
        *vlen = zipmapDecodeLength(zm);
        *value += ZIPMAP_LEN_BYTES(*vlen);
    }
    zm += zipmapRawValueLength(zm);
    return zm;
}