// 使用近似 LRU 算法，计算出给定对象的闲置时长
unsigned long long estimateObjectIdleTime(robj *o) {
unsigned long long lruclock = LRU_CLOCK();
if (lruclock >= o->lru) {
return (lruclock - o->lru) * REDIS_LRU_CLOCK_RESOLUTION;
} else {
return (lruclock + (REDIS_LRU_CLOCK_MAX - o->lru)) *
REDIS_LRU_CLOCK_RESOLUTION;
}
}
/// 返回obj的限制时间
unsigned long long estimateObjectIdleTime(robj *o) {
unsigned long long lruclock = LRU_CLOCK();
if (lruclock >= o->lru) {
return (lruclock - o->lru) * REDIS_LRU_CLOCK_RESOLUTION;
} else { /// 因为LRU_CLOCK最大为0xFFFFFF,时间戳大大超过这个值,所以会rollback
return (lruclock + (REDIS_LRU_CLOCK_MAX - o->lru)) *
REDIS_LRU_CLOCK_RESOLUTION;
}
}
robj *createObject(int type, void *ptr) {
robj *o = zmalloc(sizeof(*o));
o->type = type;
o->encoding = OBJ_ENCODING_RAW;
o->ptr = ptr;
o->refcount = 1;
/* Set the LRU to the current lruclock (minutes resolution). */
o->lru = LRU_CLOCK();
return o;
}
robj *createObject(int type, void *ptr) { //创建一个默认的对象
robj *o = zmalloc(sizeof(*o)); //分配空间
o->type = type; //设置对象类型
o->encoding = OBJ_ENCODING_RAW; //设置默认的编码方式
o->ptr = ptr; //设置
o->refcount = 1; //引用计数为1
/* Set the LRU to the current lruclock (minutes resolution). */
o->lru = LRU_CLOCK(); //计算设置当前LRU时间
return o;
}
robj *lookupKey(redisDb *db, robj *key) {
dictEntry *de = dictFind(db->dict,key->ptr);
if (de) {
robj *val = dictGetVal(de);
/* Update the access time for the ageing algorithm.
* Don't do it if we have a saving child, as this will trigger
* a copy on write madness. */
if (server.rdb_child_pid == -1 && server.aof_child_pid == -1)
val->lru = LRU_CLOCK();
return val;
} else {
return NULL;
}
}
// 创建一个 REDIS_ENCODING_EMBSTR 编码的字符对象
// 这个字符串对象中的 sds 会和字符串对象的 redisObject 结构一起分配
// 因此这个字符也是不可修改的
robj *createEmbeddedStringObject(char *ptr, size_t len) {
robj *o = zmalloc(sizeof(robj)+sizeof(struct sdshdr)+len+1);
struct sdshdr *sh = (void*)(o+1);
o->type = REDIS_STRING;
o->encoding = REDIS_ENCODING_EMBSTR;
o->ptr = sh+1;
o->refcount = 1;
o->lru = LRU_CLOCK();
sh->len = len;
sh->free = 0;
if (ptr) {
memcpy(sh->buf,ptr,len);
sh->buf[len] = '\0';
} else {
memset(sh->buf,0,len+1);
}
return o;
}
//创建一个embstr编码的字符串对象
robj *createEmbeddedStringObject(const char *ptr, size_t len) {
robj *o = zmalloc(sizeof(robj)+sizeof(struct sdshdr8)+len+1); //分配空间
struct sdshdr8 *sh = (void*)(o+1); //o+1刚好就是struct sdshdr8的地址
o->type = OBJ_STRING; //类型为字符串对象
o->encoding = OBJ_ENCODING_EMBSTR; //设置编码类型OBJ_ENCODING_EMBSTR
o->ptr = sh+1; //指向分配的sds对象，分配的len+1的空间首地址
o->refcount = 1; //设置引用计数
o->lru = LRU_CLOCK(); //计算设置当前LRU时间
sh->len = len; //设置字符串长度
sh->alloc = len; //设置最大容量
sh->flags = SDS_TYPE_8; //设置sds的类型
if (ptr) { //如果传了字符串参数
memcpy(sh->buf,ptr,len); //将传进来的ptr保存到对象中
sh->buf[len] = '\0'; //结束符标志
} else {
memset(sh->buf,0,len+1); //否则将对象的空间初始化为0
}
return o;
}