在链表模型中，编码基本都是基于quicklist的了，不信？来一段api代码 掌掌眼
void listTypePush(robj *subject, robj *value, int where) {
if (subject->encoding == OBJ_ENCODING_QUICKLIST) {
int pos = (where == LIST_HEAD) ? QUICKLIST_HEAD : QUICKLIST_TAIL;
value = getDecodedObject(value);// 转换成未编码时的sds字符串
size_t len = sdslen(value->ptr);
quicklistPush(subject->ptr, value->ptr, len, pos);
decrRefCount(value);
} else {
serverPanic("Unknown list encoding");
}
}
再比如pop和length函数，也是使用的OBJ_ENCODING_QUICKLIST编码
robj *listTypePop(robj *subject, int where) {
long long vlong;
robj *value = NULL;
int ql_where = where == LIST_HEAD ? QUICKLIST_HEAD : QUICKLIST_TAIL;
if (subject->encoding == OBJ_ENCODING_QUICKLIST) {
if (quicklistPopCustom(subject->ptr, ql_where, (unsigned char **)&value,
NULL, &vlong, listPopSaver)) {
if (!value)
value = createStringObjectFromLongLong(vlong);
}
} else {
serverPanic("Unknown list encoding");
}
return value;
}
unsigned long listTypeLength(const robj *subject) {
if (subject->encoding == OBJ_ENCODING_QUICKLIST) {
return quicklistCount(subject->ptr);
} else {
serverPanic("Unknown list encoding");
}
}
其余对外的api函数均是这样的，底层实现以quicklist为主
list对于数据库的操作代码，逻辑上跟string类型差不多：
1）先在client结构中找到对应的参数；
2）判断参数的合法性；
3）操作list对象，发送事件
这里先给出push的通常实现
void pushGenericCommand(client *c, int where) {
int j, pushed = 0;
robj *lobj = lookupKeyWrite(c->db,c->argv[1]);
if (lobj && lobj->type != OBJ_LIST) {
addReply(c,shared.wrongtypeerr);
return;
}
for (j = 2; j < c->argc; j++) {
if (!lobj) {
lobj = createQuicklistObject();
quicklistSetOptions(lobj->ptr, server.list_max_ziplist_size,
server.list_compress_depth);
dbAdd(c->db,c->argv[1],lobj);
}
listTypePush(lobj,c->argv[j],where);
pushed++;
}
addReplyLongLong(c, (lobj ? listTypeLength(lobj) : 0));
if (pushed) {
char *event = (where == LIST_HEAD) ? "lpush" : "rpush";
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_LIST,event,c->argv[1],c->db->id);
}
server.dirty += pushed;
}
对于x类的命令，它的逻辑在判断为空或者编码非OBJ_LIST时直接返回，并不往下再走了，代码就不贴出来了~
之后有点意思的代码就是rpoplpush了，它不是直接pop，然后push，而是保存pop的值，增加引用计数，push成功后，减引用计数，这属于历史遗留问题了，之前的版本需要保护客户端的命令参数向量~
void rpoplpushCommand(client *c) {
robj *sobj, *value;
if ((sobj = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
checkType(c,sobj,OBJ_LIST)) return;
if (listTypeLength(sobj) == 0) {
/* This may only happen after loading very old RDB files. Recent
* versions of Redis delete keys of empty lists. */
addReply(c,shared.nullbulk);
} else {
robj *dobj = lookupKeyWrite(c->db,c->argv[2]);
robj *touchedkey = c->argv[1];
if (dobj && checkType(c,dobj,OBJ_LIST)) return;
value = listTypePop(sobj,LIST_TAIL);
/* We saved touched key, and protect it, since rpoplpushHandlePush
* may change the client command argument vector (it does not
* currently). */
incrRefCount(touchedkey);
rpoplpushHandlePush(c,c->argv[2],dobj,value);
/* listTypePop returns an object with its refcount incremented */
decrRefCount(value);
/* Delete the source list when it is empty */
notifyKeyspaceEvent(NOTIFY_LIST,"rpop",touchedkey,c->db->id);
if (listTypeLength(sobj) == 0) {
dbDelete(c->db,touchedkey);
notifyKeyspaceEvent(NOTIFY_GENERIC,"del",
touchedkey,c->db->id);
}
signalModifiedKey(c->db,touchedkey);
decrRefCount(touchedkey);
server.dirty++;
}
}
再之后就是BLPOP等阻塞操作也需要说一下：
1）如果链表存在且不为空，则正常pop
2）如果链表不存在或者为空，需要先将请求的客户端挂起，不进行服务，并将所有阻塞在某个key的客户端放进一个链表里，直到进来新的数据，会依次被serve，代码如下：
void blockForKeys(client *c, robj **keys, int numkeys, mstime_t timeout, robj *target) {
dictEntry *de;
list *l;
int j;
c->bpop.timeout = timeout;
c->bpop.target = target;
if (target != NULL) incrRefCount(target);
for (j = 0; j < numkeys; j++) {
/* If the key already exists in the dict ignore it. */
if (dictAdd(c->bpop.keys,keys[j],NULL) != DICT_OK) continue;
incrRefCount(keys[j]);
/* And in the other "side", to map keys -> clients */
de = dictFind(c->db->blocking_keys,keys[j]);
if (de == NULL) {
int retval;
/* For every key we take a list of clients blocked for it */
l = listCreate();
retval = dictAdd(c->db->blocking_keys,keys[j],l);
incrRefCount(keys[j]);
serverAssertWithInfo(c,keys[j],retval == DICT_OK);
} else {
l = dictGetVal(de);
}
listAddNodeTail(l,c);
}
blockClient(c,BLOCKED_LIST);
}
解除阻塞操作如下：
void unblockClientWaitingData(client *c) {
dictEntry *de;
dictIterator *di;
list *l;
serverAssertWithInfo(c,NULL,dictSize(c->bpop.keys) != 0);
di = dictGetIterator(c->bpop.keys);
/* The client may wait for multiple keys, so unblock it for every key. */
while((de = dictNext(di)) != NULL) {
robj *key = dictGetKey(de);
/* Remove this client from the list of clients waiting for this key. */
l = dictFetchValue(c->db->blocking_keys,key);
serverAssertWithInfo(c,key,l != NULL);
listDelNode(l,listSearchKey(l,c));
/* If the list is empty we need to remove it to avoid wasting memory */
if (listLength(l) == 0)
dictDelete(c->db->blocking_keys,key);
}
dictReleaseIterator(di);
/* Cleanup the client structure */
dictEmpty(c->bpop.keys,NULL);
if (c->bpop.target) {
decrRefCount(c->bpop.target);
c->bpop.target = NULL;
}
}
发送ready信息代码如下：
void signalListAsReady(redisDb *db, robj *key) {
readyList *rl;
/* No clients blocking for this key? No need to queue it. */
if (dictFind(db->blocking_keys,key) == NULL) return;
/* Key was already signaled? No need to queue it again. */
if (dictFind(db->ready_keys,key) != NULL) return;
/* Ok, we need to queue this key into server.ready_keys. */
rl = zmalloc(sizeof(*rl));
rl->key = key;
rl->db = db;
incrRefCount(key);
listAddNodeTail(server.ready_keys,rl);
/* We also add the key in the db->ready_keys dictionary in order
* to avoid adding it multiple times into a list with a simple O(1)
* check. */
incrRefCount(key);
serverAssert(dictAdd(db->ready_keys,key,NULL) == DICT_OK);
}
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转载请注明原文链接：redis源码阅读之链表对象模型
转载请注明原文链接：redis源码阅读之链表对象模型
