Redis源碼分析(二十八)--- object建立和釋放redisObject對象,redisredisobject
今天的學習效率比較高,把Rio分析完了,又順便學習了其中的RedisObject的檔案,只要講的就是RedisObject的一些轉換和建立。裡面的大多數方法都是非常類似的。列出裡面長長的API列表:
/* ------------ API --------------------- */robj *createObject(int type, void *ptr) /* 最初的建立robj對象方法,後面的建立方法與此類似 */robj *createStringObject(char *ptr, size_t len)robj *createStringObjectFromLongLong(long long value)robj *createStringObjectFromLongDouble(long double value)robj *dupStringObject(robj *o)robj *createListObject(void)robj *createZiplistObject(void)robj *createSetObject(void)robj *createIntsetObject(void)robj *createHashObject(void)robj *createZsetObject(void)robj *createZsetZiplistObject(void)void freeStringObject(robj *o) /* free Obj中的特定對象,這裡free的是r->ptr */void freeListObject(robj *o)void freeSetObject(robj *o)void freeZsetObject(robj *o)void freeHashObject(robj *o) /* 釋放hashObject有2種形式,1個是o-ptr的字典對象,還有1個回事壓縮表o->ptr */void incrRefCount(robj *o) /* robj對象增減引用計數,遞增robj中的refcount的值 */void decrRefCount(robj *o) /* 遞減robj中的引用計數,引用到0後,釋放對象 */void decrRefCountVoid(void *o)robj *resetRefCount(robj *obj)int checkType(redisClient *c, robj *o, int type) /* 檢查robj的類型是否為給定的Type類型 */int isObjectRepresentableAsLongLong(robj *o, long long *llval)robj *tryObjectEncoding(robj *o) /* 編碼一個robj中的額字元對象,主要是為了省空間 */robj *getDecodedObject(robj *o) /* 擷取解碼後的robj */int compareStringObjectsWithFlags(robj *a, robj *b, int flags)int compareStringObjects(robj *a, robj *b)int collateStringObjects(robj *a, robj *b)int equalStringObjects(robj *a, robj *b)size_t stringObjectLen(robj *o)int getDoubleFromObject(robj *o, double *target) /* 從robj中擷取double數值 */int getDoubleFromObjectOrReply(redisClient *c, robj *o, double *target, const char *msg)int getLongDoubleFromObject(robj *o, long double *target)int getLongDoubleFromObjectOrReply(redisClient *c, robj *o, long double *target, const char *msg)int getLongLongFromObject(robj *o, long long *target)int getLongLongFromObjectOrReply(redisClient *c, robj *o, long long *target, const char *msg)int getLongFromObjectOrReply(redisClient *c, robj *o, long *target, const char *msg)char *strEncoding(int encoding)unsigned long estimateObjectIdleTime(robj *o)robj *objectCommandLookup(redisClient *c, robj *key) /* obj的尋找命令, */robj *objectCommandLookupOrReply(redisClient *c, robj *key, robj *reply)void objectCommand(redisClient *c)
從前往後看,第一個建立obj:
/* 最初的建立robj對象方法 */robj *createObject(int type, void *ptr) { robj *o = zmalloc(sizeof(*o)); o->type = type; o->encoding = REDIS_ENCODING_RAW; o->ptr = ptr; o->refcount = 1; /* Set the LRU to the current lruclock (minutes resolution). */ o->lru = server.lruclock; return o;}
有建立就必然會有釋放的free方法:
/* free Obj中的特定對象 */void freeStringObject(robj *o) { if (o->encoding == REDIS_ENCODING_RAW) { sdsfree(o->ptr); }}
free方法有很多衍生的方法,看你要釋放哪種類型的空間了,可以,set,dict,ziplist等等。有下面的一些類型:
switch(o->type) { case REDIS_STRING: freeStringObject(o); break; case REDIS_LIST: freeListObject(o); break; case REDIS_SET: freeSetObject(o); break; case REDIS_ZSET: freeZsetObject(o); break; case REDIS_HASH: freeHashObject(o); break; default: redisPanic("Unknown object type"); break; }
重點介紹裡面的關於引用計數的相關方法,通過robj->refcount的數值進行控制的:
/* robj對象增減引用計數,遞增robj中的refcount的值 */void incrRefCount(robj *o) {//遞增robj中的refcount的值 o->refcount++;}
增加引用計數就一行代碼,但是遞減的話,我們猜也可以猜到,引用計數變為0的時候,說明無人使用了,就可以釋放空間了;
/* 遞減robj中的引用計數,引用到0後,釋放對象 */void decrRefCount(robj *o) {//如果之前的引用計數已經<=0了,說明出現異常情況了 if (o->refcount <= 0) redisPanic("decrRefCount against refcount <= 0"); if (o->refcount == 1) { //如果之前的引用計數為1,再遞減一次,恰好內有被任何對象引用了,所以就可以釋放對象了 switch(o->type) { case REDIS_STRING: freeStringObject(o); break; case REDIS_LIST: freeListObject(o); break; case REDIS_SET: freeSetObject(o); break; case REDIS_ZSET: freeZsetObject(o); break; case REDIS_HASH: freeHashObject(o); break; default: redisPanic("Unknown object type"); break; } zfree(o); } else { //其他對於>1的引用計數的情況,只需要按常規的遞減引用計數即可 o->refcount--; }}
標準的引用計數法控制記憶體的管理,(提醒一下,在JVM中的對象的生命週期管理用的是根搜尋法,不是引用計數),還有一個在robj中的編碼方法的實現也是定義在這個檔案中:
/* Try to encode a string object in order to save space *//* 編碼一個robj中的額字元對象,主要是為了省空間 */robj *tryObjectEncoding(robj *o) { long value; sds s = o->ptr; size_t len; if (o->encoding != REDIS_ENCODING_RAW) //如果robj已經被編碼了,則直接返回 return o; /* Already encoded */ /* It's not safe to encode shared objects: shared objects can be shared * everywhere in the "object space" of Redis. Encoded objects can only * appear as "values" (and not, for instance, as keys) */ /* 如果robj的引用計數超過1個人引用的時候,是不安全的去編碼obj,因為對象是共用的 */ if (o->refcount > 1) return o; /* Currently we try to encode only strings */ redisAssertWithInfo(NULL,o,o->type == REDIS_STRING); /* Check if we can represent this string as a long integer */ len = sdslen(s); if (len > 21 || !string2l(s,len,&value)) { /* We can't encode the object... * * Do the last try, and at least optimize the SDS string inside * the string object to require little space, in case there * is more than 10% of free space at the end of the SDS string. * * We do that for larger strings, using the arbitrary value * of 32 bytes. This code was backported from the unstable branch * where this is performed when the object is too large to be * encoded as EMBSTR. */ if (len > 32 && o->encoding == REDIS_ENCODING_RAW && sdsavail(s) > len/10) { //調用sdsRemoveFreeSpace把0->ptr中的字串中的空格給移除掉 o->ptr = sdsRemoveFreeSpace(o->ptr); } /* Return the original object. */ return o; } .....
就是移除字串中的空格所佔的空間。想對應也存在一個getDecodeObject(),:
/* Get a decoded version of an encoded object (returned as a new object). * If the object is already raw-encoded just increment the ref count. *//* 擷取解碼後的robj */robj *getDecodedObject(robj *o) { robj *dec; if (o->encoding == REDIS_ENCODING_RAW) { //如果沒有編碼方式,則直接增加引用計數,並返回 incrRefCount(o); return o; } if (o->type == REDIS_STRING && o->encoding == REDIS_ENCODING_INT) { char buf[32];//如果是string,Type而且是encoding_int方式的,先做一步轉換 ll2string(buf,32,(long)o->ptr); dec = createStringObject(buf,strlen(buf)); return dec; } else { redisPanic("Unknown encoding type"); }}
以上就是對於對於RedisObject的簡單分析。
在freebsd裡面安裝了個redis,跟著資料庫的開原始碼寫了個程式,想試試用c++串連資料庫伺服器
哦 redis你怎麼裝到系統上的?指定庫是在編譯的時候加上 -lredis 或者類似的參數。
redis源碼的入口函數存在於哪個檔案中
redis.c 太短了? 還得長一點..........................