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Redis??Zipmap??????????????????????????????ziplist?????????Zipmap????????????????????????????????????????????????????????????????????????????????

Zipmap????????????????????????????????Zipmap???

   
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< len>3
< free>0
< value>"foo"
< len>3
< free>0
< value>"bar"
< len>5
< free>0
< value>"hello"
< len>5
< free>0
< value>"world"

Zipmap??????????

• zmlen?Zipmap???????????????254??????????????254????????Zipmap??????
• len?????????????????????????????
• free?????????????????????

Zipmap??????

Zipmap?????????????????????????????ZipmapSet????????

Zipmap????

Zipmap???????????????????????????????254?????????????????Zipmap?????????

Redis??????

?Redis??Hash???????????????????Zipmap???????Zipmap?????????????????????

????

????????Zipmap?????

unsigned char *zipmapSet(zm, key, klen, val, vlen, update) {
    unsigned int zmlen, offset;
    unsigned int freelen, reqlen = zipmapRequiredLength(klen, vlen);
    unsigned char *p;
    freelen = reqlen;
    if (update) *update = 0;
    p = zipmapLookupRaw(zm, key, klen, &zmlen);
    if (p == NULL) {
        zm = zipmapResize(zm, zmlen + reqlen);
        p = zm + zmlen - 1;
        zmlen += reqlen;
        if (zm[0] < ZIPMAP_BIGLEN) zm[0]++;
    } else {
        if (update) *update = 1;
        freelen = zipmapRawEntryLength(p);
        if (freelen < reqlen) {
            offset = p - zm;
            zm = zipmapResize(zm, zmlen - freelen + reqlen);
            p = zm + offset;
            memmove(p + reqlen, p + freelen, zmlen - (offset + freelen + 1));
            zmlen = zmlen - freelen + reqlen;
            freelen = reqlen;
        }
    }
    empty = freelen - reqlen;
    if (empty >= ZIPMAP_VALUE_MAX_FREE) {
        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;
    }
    p += zipmapEncodeLength(p, klen);
    memcpy(p, key, klen);
    p += klen;
    p += zipmapEncodeLength(p, vlen);
    *p++ = vempty;
    memcpy(p, val, vlen);
    return zm;
}

Zipmap?????

Zipmap?????????????????????????

• ???????????????????????????????????
• ???????????????????????????????????????
• ???????????????????????????

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Zipmap???????????????????????????????????????????Redis??Hash???????????????????????????Zipmap????????????????Redis???????

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