Memcached源码分析之memcached.h

//memcached.h
//返回在item中data字段key的地址，即把指针指向key
#define ITEM_key(item) (((char*)&((item)->data)) \
+ (((item)->it_flags & ITEM_CAS) ? sizeof(uint64_t) : 0))
//返回在item中data字段suffix的地址，即把指针指向suffix
#define ITEM_suffix(item) ((char*) &((item)->data) + (item)->nkey + 1 \
+ (((item)->it_flags & ITEM_CAS) ? sizeof(uint64_t) : 0))
//返回在item中data字段value的地址，即把指针指向value
#define ITEM_data(item) ((char*) &((item)->data) + (item)->nkey + 1 \
+ (item)->nsuffix \
+ (((item)->it_flags & ITEM_CAS) ? sizeof(uint64_t) : 0))
//item总字节数
#define ITEM_ntotal(item) (sizeof(struct _stritem) + (item)->nkey + 1 \
+ (item)->nsuffix + (item)->nbytes \
+ (((item)->it_flags & ITEM_CAS) ? sizeof(uint64_t) : 0))
//conn结构体中state字段的枚举，代表连接状态
enum conn_states {
conn_listening, /**< the socket which listens for connections */
conn_new_cmd, /**< Prepare connection for next command */
conn_waiting, /**< waiting for a readable socket */
conn_read, /**< reading in a command line */
conn_parse_cmd, /**< try to parse a command from the input buffer */
conn_write, /**< writing out a simple response */
conn_nread, /**< reading in a fixed number of bytes */
conn_swallow, /**< swallowing unnecessary bytes w/o storing */
conn_closing, /**< closing this connection */
conn_mwrite, /**< writing out many items sequentially */
conn_closed, /**< connection is closed */
conn_max_state /**< Max state value (used for assertion) */
};
//item保存结果枚举
enum store_item_type {
NOT_STORED=0, STORED, EXISTS, NOT_FOUND
};
//item结构体
typedef struct _stritem {
struct _stritem *next; //链表中下一个，这个链表有可能是slots链表，也有可能是LRU链表，但一个item不可能同时这两个链表中，所以复用一个指针。
struct _stritem *prev; //链表中上一个。
struct _stritem *h_next; //相同hash值中链表的下一个。
rel_time_t time; //最近访问时间
rel_time_t exptime; //过期时间
int nbytes; //value的字节数
unsigned short refcount; //引用计数
uint8_t nsuffix; //后缀长度
uint8_t it_flags; //标记
uint8_t slabs_clsid; //item所在的slabclass的id值
uint8_t nkey; //键长
/* this odd type prevents type-punning issues when we do
* the little shuffle to save space when not using CAS. */
union {
uint64_t cas;
char end;
} data[]; //数据，这个数据不仅仅包括key对应的value，还有key、CAS、后缀等等数据也存在此，所以它有4部分“拼”成：CAS(可选)，KEY，后缀，VALUE。
/* if it_flags & ITEM_CAS we have 8 bytes CAS */
/* then null-terminated key */
/* then " flags length\r\n" (no terminating null) */
/* then data with terminating \r\n (no terminating null; it's binary!) */
} item;
/**
worker线程结构体
*/
typedef struct {
pthread_t thread_id; //线程id
struct event_base *base; //每个线程自己独立的event_base，监听的就是下面的notify_event事件对象
struct event notify_event; //事件对象，fd即为下面的notify_receive_fd
int notify_receive_fd; //管道接收fd
int notify_send_fd; //管道写入fd
struct thread_stats stats; //线程的一些统计
struct conn_queue *new_conn_queue; //连接参数对象CQ_ITEM队列
cache_t *suffix_cache;
uint8_t item_lock_type; //控制线程锁的粒度
} LIBEVENT_THREAD;
/**
主线程结构体
*/
typedef struct {
pthread_t thread_id; //线程id
struct event_base *base; //event_base
} LIBEVENT_DISPATCHER_THREAD;
typedef struct conn conn;
struct conn {
int sfd; //连接的socket fd
sasl_conn_t *sasl_conn;
bool authenticated;
enum conn_states state; //当前的连接状态
enum bin_substates substate;
rel_time_t last_cmd_time;
struct event event; // 监听的事件
short ev_flags; //监听的事件类型
short which; /** which events were just triggered */ //刚触发的事件
/**
读buffer会涉及两个方向上的“读”：
一个是从socket读进来到rbuf里面
一个是从rbuf里面把数据读出去解析，读buffer相当于一个中介，从socket读进来最终还是得被别人读出去解析，而
rcurr工作指针与rbytes就是在rbuf数据被读出去解析的时候用到，用来控制可以读出去被解析的数据还剩余多少。
*/
char *rbuf; /** buffer to read commands into */ //读buffer
char *rcurr; /** but if we parsed some already, this is where we stopped */ //读buffer的当前指针
int rsize; /** total allocated size of rbuf */ //读buffer大小
int rbytes; /** how much data, starting from rcur, do we have unparsed */ //剩余buffer字节数
//下面4个属性和上面4个类似
char *wbuf;
char *wcurr;
int wsize;
int wbytes;
/** which state to go into after finishing current write */
enum conn_states write_and_go; //完成当前写操作后，连接状态将会置为此状态
void *write_and_free; /** free this memory after finishing writing */
char *ritem; /** when we read in an item's value, it goes here */ //这个指针指向item结构体中data中的value地址
int rlbytes; //尚未读完item的data的value的字节数
void *item; /* for commands set/add/replace */ //当执行set/add/replace 命令时，此指针用于指向分配的item空间
/* data for the swallow state */
int sbytes; /* how many bytes to swallow */
//下面是往socket写出数据时用的字段
struct iovec *iov; //iovec结构体数组
int iovsize; //*iov数组大小
int iovused; //*iov数组已被使用的元素个数
struct msghdr *msglist; //msghdr结构体数组，表示sendmsg要发送的消息列表
int msgsize; //*msglist数组大小
int msgused; //*msglist数组已使用的元素个数
int msgcurr; //当前要发送的msghdr
int msgbytes; //当前msghdr的字节数
item **ilist; //get key1 key2命令时，要发送给客户端的item列表
int isize; //列表大小
item **icurr; //当前要发送的item
int ileft; //剩余数目
char **suffixlist;
int suffixsize;
char **suffixcurr;
int suffixleft;
enum protocol protocol; /* which protocol this connection speaks */
enum network_transport transport; /* what transport is used by this connection */
//UDP相关的字段
int request_id; /* Incoming UDP request ID, if this is a UDP "connection" */
struct sockaddr_in6 request_addr; /* udp: Who sent the most recent request */
socklen_t request_addr_size;
unsigned char *hdrbuf; /* udp packet headers */
int hdrsize; /* number of headers' worth of space is allocated */
bool noreply; /* True if the reply should not be sent. */
/* current stats command */
struct {
char *buffer;
size_t size;
size_t offset;
} stats;
// 二进制相关的字段
protocol_binary_request_header binary_header;
uint64_t cas; /* the cas to return */
short cmd; /* current command being processed */
int opaque;
int keylen;
conn *next; /* Used for generating a list of conn structures */
LIBEVENT_THREAD *thread; /* Pointer to the thread object serving this connection */
};
//非阻塞方式获取互斥锁
static inline int mutex_lock(pthread_mutex_t *mutex)
{
while (pthread_mutex_trylock(mutex));
return 0;
}
//释放锁
#define mutex_unlock(x) pthread_mutex_unlock(x)
#include "stats.h"
#include "slabs.h"
#include "assoc.h"
#include "items.h"
#include "trace.h"
#include "hash.h"
#include "util.h"

posted @ 2016-09-07 17:01 Beyond it 阅读(562) 评论(0) 编辑收藏举报

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Memcached源码分析之memcached.h

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