2019年（2）
分类： Oracle
2019-06-03 14:13:43
同时也再次感受到良好的基础是深入学习的前提。特别强调本文档仅用于学习，并非是要修改redis源码。 建议读者阅读本文档时实际动手敲一下代码，然后翻阅下redis源码，debug下redis
本文档分为三大部分：
环境介绍与效果演示
redis接收命令到返回数据的执行逻辑
代码实现
文档的重点和难点在第三部分，完全阅读本文档需要读者具备基本的c语言和数据结构知识。
redis版本为5.0.3
64 bit
操作系统版本为Ubuntu
18.10 64bit
源码可以用gedit查看
gdb调试
ide
可以用eclipse+CDT
本案例实现了一个链表，对应redis的list数据类型，对链表的操作实现了插入、设置某个节点的值、新建节点、获取一定范围内的节点、获取列表长度等.下面表格列出具体实现的命令与对应的redis原生命令
| 实现命令 | redis原生命令 | 命令含义 |
|---|---|---|
| myrpush | rpush | 从尾部插入链表 |
| mylrange | lrange | 获取范围内值 |
| myrpop | rpop | 从右侧弹出值 |
| myllen | llen | 获取list长度 |
| mylset | lset | 设置某个节点值 |
| myinsert | linsert | 在指定位置插入值 |
| mylindex | lindex | 获取指定位置值 |
实现命令演示：
-
127.0.0.1:6379> myrpush mygjw gjw0(integer) 1127.0.0.1:6379> myrpush mygjw gjw1
-
(integer) 2 127.0.0.1:6379> myrpush mygjw gjw2
-
(integer) 3 127.0.0.1:6379> mylrange 0 -1 (error) ERR wrong number of arguments for 'mylrange' command 127.0.0.1:6379> mylrange mygjw 0 -1
1) "gjw0" 2) "gjw1" 3) "gjw2" 127.0.0.1:6379> myrpop mygjw "gjw2" 127.0.0.1:6379> mylrange mygjw 0 -1
1) "gjw0" 2) "gjw1" 127.0.0.1:6379> myllen mygjw
-
(integer) 2 127.0.0.1:6379> mylset mygjw 0 gjw00 OK127.0.0.1:6379> mylset mygjw 1 gjw01
-
OK127.0.0.1:6379> mylrange mygjw 0 -1
1) "gjw00" 2) "gjw01" 127.0.0.1:6379> mylinsert mygjw 0 gjw0 (integer) 3 127.0.0.1:6379> mylinsert mygjw 1 gjw1
-
(integer) 4 127.0.0.1:6379> mylrange mygjw 0 -1
1) "gjw0" 2) "gjw1" 3) "gjw00" 4) "gjw01" 127.0.0.1:6379> mylindex mygjw 0 "gjw0" 127.0.0.1:6379> mylindex mygjw 1 "gjw1"
此部分只选择与本文档相关部分做简单介绍，实际命令执行涉及到保存文件、主备同步、集群分发等等会复杂很多。下面从server.c文件的processCommand函数开始。
下面以myrpush命令执行的时序图来说明具体调用的函数及其所在的文件，其他命令执行方式都类似.图中方框中字符串是文件名，所有关于list类型的命令处理函数都在文件t_list.c中，其他类型的命令处理函数需要找找对应的源文件，redis命令非常规范，找起来不难。
代码实现与redis源码阅读
1.添加自己的源文件和头文件
mylinkedlist.h、mylinkedlist.h
mylist类型采用双向链表数据结构，数据域采用了哑型指针，方便插入任何类型数据，为了方便代码仅仅实现了char型，node
结构体有个size属性用来存储数据域占用的字节数。
此部分比redis源码实现简单很多，但是如果能看懂这部分代码，也应该可以比较容易的看懂redis源码。redis中list类型数据域是ziplist，默认情况下数据域最大8k字节，ziplist有自己的数据结构，这里列出redis
列表类型处理的相关源文件：quicklist.h、quicklist.c、ziplist.h、ziplist.c
头文件内容如下：
-
/*
-
* mylineklist.h
-
*
-
* Created on: Dec 29, 2018
-
* Author: gjw
-
*/typedef void * ADT; typedef const void * CADT; typedef int (*LIDESTROY) (ADT e); typedef void (*LITRVAVEL) (ADT e); struct NODE; typedef struct NODE * PNODE; typedef struct MylinkedListS MylinkedList; typedef MylinkedList * MYLINKEDLIST; MYLINKEDLIST MyCreateList(); void MyAppend(MYLINKEDLIST list,ADT data,int len); int MyInsert(MYLINKEDLIST list,ADT data,unsigned int pos,int len); void MyDelete(MYLINKEDLIST list,unsigned int pos,LIDESTROY destroy); ADT Myrpop(MYLINKEDLIST list,int * sz); int Mylset(MYLINKEDLIST list, ADT data, unsigned int pos,int len); void MyClear(MYLINKEDLIST list,LIDESTROY destroy); int MyLength(MYLINKEDLIST list); PNODE MyIndex(MYLINKEDLIST list,unsigned int index); void MyTraverse(MYLINKEDLIST list,LITRVAVEL litravel); int MyIsEmpty(MYLINKEDLIST list); PNODE MyNext(PNODE node); void getData(PNODE n,char ** data,int * sz);
在本例中并非所有的声明函数都已实现，仅仅实现了上面演示的几个命令，源文件内容如下：
-
/*
-
* mylinkedlist.c
-
*
-
* Created on: Dec 29, 2018
-
* Author: gjw
-
*/ #include
-
struct NODE {
-
ADT data; int size;
-
PNODE next;
-
PNODE previous;
-
} ;
-
typedef struct NODE NODE;
-
struct MylinkedListS {
-
unsigned int len;
-
PNODE head, tail;
-
};
-
-
MylinkedList* MyCreateList() {
-
MylinkedList* list = (MylinkedList*) malloc(sizeof(MylinkedList));
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PNODE head = (NODE *) malloc(sizeof(NODE));
-
PNODE tail = (NODE *) malloc(sizeof(NODE)); list->head = head; list->tail = tail; list->tail->next=NULL; list->tail->previous=NULL; list->head->next=NULL; list->head->previous=NULL; list->len=0;
-
printf("init a list"); return list;
-
}
-
void MyAppend(MYLINKEDLIST list, ADT data,int len) { if (list->head->next == NULL) {
-
MyInsert(list, data, 0,len); return;
-
}
-
printf("->");
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PNODE ctail = (NODE *) malloc(sizeof(NODE));
-
ctail->data=(char *)malloc(len);
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memcpy(ctail->data,data,len);
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ctail->size=len;
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ctail->next=NULL;
-
ctail->previous=list->tail->next; list->tail->next->next = ctail; list->tail->next = ctail; list->len = list->len + 1;
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} int MyInsert(MYLINKEDLIST list, ADT data, unsigned int pos,int len) { if ( pos > list->len) return 0;
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printf("insert success!\n");
-
PNODE node = list->head; for (unsigned int i = 0; i < pos; i++) {
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node = node->next;
-
}
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PNODE newNode = (NODE *) malloc(sizeof(NODE));
-
newNode->data=(char *)malloc(len);
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memcpy(newNode->data,data,len);
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newNode->size=len;
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newNode->next = node->next;
-
newNode->previous=node; if(node->next){
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newNode->next->previous=newNode;
-
}
-
node->next = newNode; list->tail->next=newNode; list->len = list->len + 1; return 1;
-
}
-
-
ADT Myrpop(MYLINKEDLIST list,int * sz){
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PNODE tail=list->tail->next; if(list->len==0){ return NULL;
-
}
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ADT data=tail->data;
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*sz=tail->size; list->tail->next=tail->previous;
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tail->previous->next=NULL; list->len=list->len-1;
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free(tail); return data;
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}int MyLength(MYLINKEDLIST list) { return list->len;
-
} int MyIsEmpty(MYLINKEDLIST list) { return !list->len;
-
}
-
void getData(PNODE n,char ** data,int * sz) {
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*data=n->data;
-
*sz=n->size;
-
}
-
-
PNODE MyNext(PNODE node) { return node->next;
-
}
-
PNODE MyIndex(MYLINKEDLIST list,unsigned int index){
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PNODE n=list->head->next; if(index>=list->len){ return NULL;
-
} for(int i=0;i
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n=n->next;
-
} return n;
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} int Mylset(MYLINKEDLIST list, ADT data, unsigned int pos,int len) {
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PNODE node=list->head->next; if(list->len==0){
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MyInsert(list,data,pos,len); return 1;
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} if(pos>=list->len){ return 0;
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} for(int i=0;i
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node=node->next;
-
}
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realloc(node->data,len);
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node->size=len;
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memcpy(node->data,data,len); return 1;
-
}
2.修改server.h主要是声明自己的类型，添加自定义类型的命令处理函数，加入自定义头文件，添加以下内容
：
server.h #include "mylinkedlist.h" /* mylist ,guojiagnwei add */ #define MYOBJ_LIST 11 /* MYList object. */ void myrpushCommand(client *c); void mylrangeCommand(client *c); void myrpopCommand(client *c); void myllenCommand(client *c); void mylsetCommand(client *c); void mylinsertCommand(client *c); void mylindexCommand(client *c); robj *createMylistObject(void);
3.修改object.c
此文件主要用来操作redis object，添加以下内容
-
robj *createMylistObject(void) {
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MylinkedList* l = MyCreateList(); //quicklist *l = quicklistCreate();
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robj *o = createObject(MYOBJ_LIST,l);
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o->encoding = OBJ_ENCODING_QUICKLIST; return o;
-
}
4.修改
t_list.c文件，实现server.h中声明的命令处理函数
-
//added by guojiangweivoid myrpushCommand(client *c){
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int j, pushed = 0; robj *lobj = lookupKeyWrite(c->db,c->argv[1]); for (j = 2; j < c->argc; j++) { if (!lobj) {
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lobj = createMylistObject(); dbAdd(c->db,c->argv[1],lobj);
-
}
-
MyAppend(lobj->ptr,c->argv[j]->ptr,sdslen(c->argv[j]->ptr));
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pushed++;
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} addReplyLongLong(c, MyLength(lobj->ptr)); if (pushed) {
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char *event = "rpush"; signalModifiedKey(c->db,c->argv[1]); notifyKeyspaceEvent(1,event,c->argv[1],c->db->id);
-
}
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server.dirty += pushed;
-
}
-
void mylrangeCommand(client *c){
-
robj *o;
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long start, end, llen, rangelen;
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char * data;
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int sz; if ((getLongFromObjectOrReply(c, c->argv[2], &start, NULL) != C_OK) ||
-
(getLongFromObjectOrReply(c, c->argv[3], &end, NULL) != C_OK)) return; if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptymultibulk)) == NULL
-
|| checkType(c,o,MYOBJ_LIST)) return; llen = MyLength(o->ptr); /* convert negative indexes */
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if (start < 0) start = llen+start; if (end < 0) end = llen+end; if (start < 0) start = 0; /* Invariant: start >= 0, so this test will be true when end < 0.
-
* The range is empty when start > end or start >= length. */
-
if (start > end || start >= llen) {
-
addReply(c,shared.emptymultibulk);
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return;
-
} if (end >= llen) end = llen-1;
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rangelen = (end-start)+1; /* Return the result in form of a multi-bulk reply */
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addReplyMultiBulkLen(c,rangelen); if (o->encoding == OBJ_ENCODING_QUICKLIST) {
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PNODE n = MyIndex(o->ptr, start); while(rangelen--) {
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getData( n,&data,&sz);
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addReplyBulkCBuffer(c,data,sz);
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n=MyNext(n);
-
}
-
} else {
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serverPanic("List encoding is not QUICKLIST!");
-
}
-
-
}
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void myrpopCommand(client *c){ robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
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int sz; if (o == NULL || checkType(c,o,MYOBJ_LIST)) return; char * data=Myrpop(o->ptr,&sz);
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robj *value = createStringObject(data,sz);
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free(data); if (value == NULL) {
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addReply(c,shared.nullbulk);
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} else {
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char *event = "rpop";
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addReplyBulk(c,value);
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decrRefCount(value); notifyKeyspaceEvent(NOTIFY_LIST,event,c->argv[1],c->db->id); if (listTypeLength(o) == 0) {
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notifyKeyspaceEvent(NOTIFY_GENERIC,"del", c->argv[1],c->db->id); dbDelete(c->db,c->argv[1]);
-
} signalModifiedKey(c->db,c->argv[1]);
-
server.dirty++;
-
}
-
}
-
void myllenCommand(client *c){ robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.czero); if (o == NULL || checkType(c,o,MYOBJ_LIST)) return; addReplyLongLong(c,MyLength(o->ptr));
-
}
-
void mylsetCommand(client *c){ robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr); if (o == NULL || checkType(c,o,MYOBJ_LIST)) return;
-
long index; robj *value = c->argv[3]; if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != C_OK))
-
return; if (o->encoding == OBJ_ENCODING_QUICKLIST) {
-
MYLINKEDLIST ql = o->ptr; int replaced = Mylset(ql,value->ptr, index,sdslen(value->ptr)); if (!replaced) {
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addReply(c,shared.outofrangeerr);
-
} else {
-
addReply(c,shared.ok); signalModifiedKey(c->db,c->argv[1]); notifyKeyspaceEvent(NOTIFY_LIST,"lset",c->argv[1],c->db->id);
-
server.dirty++;
-
}
-
} else {
-
serverPanic("Unknown list encoding");
-
}
-
-
}
-
void mylinsertCommand(client *c){
-
long index;
-
robj *subject;
-
int inserted = 0; if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != C_OK)){
-
addReply(c,shared.syntaxerr);
-
return;
-
} if ((subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
-
checkType(c,subject,MYOBJ_LIST)) return; inserted=MyInsert(subject->ptr,c->argv[3]->ptr,index,sdslen(c->argv[3]->ptr)); if (inserted) { signalModifiedKey(c->db,c->argv[1]);
-
notifyKeyspaceEvent(NOTIFY_LIST,"linsert", c->argv[1],c->db->id);
-
server.dirty++;
-
} else { /* Notify client of a failed insert */
-
addReply(c,shared.cnegone);
-
return;
-
} addReplyLongLong(c,MyLength(subject->ptr));
-
}
-
void mylindexCommand(client *c){
-
long index;
-
int size; robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nokeyerr); if (o == NULL || checkType(c,o,MYOBJ_LIST)) return; if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != C_OK))
-
return;
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PNODE n=MyIndex(o->ptr,index); if(n==NULL){
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addReply(c,shared.nullbulk);
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return;
-
}
-
-
char *data;
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getData( n,&data,&size); if (o->encoding == OBJ_ENCODING_QUICKLIST) { if (data) {
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robj *value=createStringObject(data,size);
-
addReplyBulk(c,value);
-
decrRefCount(value);
-
} else {
-
addReply(c,shared.nullbulk);
-
}
-
} else {
-
serverPanic("Unknown list encoding");
-
}
-
}
5.修改server.c
文件，在变量struct redisCommand redisCommandTable[] 中添加自定义类型命令字符串与命令处理函数映射
-
{"myrpush",myrpushCommand,-3,"wmF",0,NULL,1,1,1,0,0},
-
{"mylrange",mylrangeCommand,4,"wmF",0,NULL,1,1,1,0,0},
-
{"myrpop",myrpopCommand,2,"wmF",0,NULL,1,1,1,0,0},
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{"myllen",myllenCommand,2,"wmF",0,NULL,1,1,1,0,0},
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{"mylset",mylsetCommand,4,"wmF",0,NULL,1,1,1,0,0},
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{"mylinsert",mylinsertCommand,4,"wmF",0,NULL,1,1,1,0,0},
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{"mylindex",mylindexCommand,3,"r",0,NULL,1,1,1,0,0},
另外还需要编辑下make文件，比较简单这里不单独列出。
redis源码阅读
代码实现部分列出了需要修改的文件和修改的内容，redis源码设计的非常好，命名非常规范，如果读者按照文档所列进行了操作，对redis
源码结构和程序逻辑应该有了一个大致的认识，作者本来打算详细写下redis
list类型的源码实现，但是想了想，水平有限，很难做到严谨与通俗，推荐大家看看《redis
设计与实现》这本书吧。个人觉得看源码最主要的是自己修改和不断的debug。
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