redis源码分析之t_string.c，该文件是处理string类型的源文件，注释略去，具体分析如下：
#include "redis.h" //引入头文件
#include <math.h> /* isnan(), isinf() */ //引入库文件 主要是用到isnan函数和isinf函数 分别是判断是否是数字和是否是无限数字的函数
/*-----------------------------------------------------------------------------
* String Commands
*----------------------------------------------------------------------------*/
//静态函数 用来判断客户端提交的数字是否超过了512MB
static int checkStringLength(redisClient *c, long long size) {
if (size > 512*1024*1024) {
//返回客户端一个错误命令
addReplyError(c,"string exceeds maximum allowed size (512MB)");
//向系统返回一个错误
return REDIS_ERR;
}
return REDIS_OK;
}
/* The setGenericCommand() function implements the SET operation with different
* options and variants. This function is called in order to implement the
* following commands: SET, SETEX, PSETEX, SETNX.
*
* 'flags' changes the behavior of the command (NX or XX, see belove).
*
* 'expire' represents an expire to set in form of a Redis object as passed
* by the user. It is interpreted according to the specified 'unit'.
*
* 'ok_reply' and 'abort_reply' is what the function will reply to the client
* if the operation is performed, or when it is not because of NX or
* XX flags.
*
* If ok_reply is NULL "+OK" is used.
* If abort_reply is NULL, "$-1" is used. */
#define REDIS_SET_NO_FLAGS 0
//移位宏定义
#define REDIS_SET_NX (1<<0) /* Set if key not exists. */
#define REDIS_SET_XX (1<<1) /* Set if key exists. */
//处理客户端发来的SET命令统一处理函数 下面会继续看到SET系列的具体函数。每个SET函数在完成处理之后，统一调用
//setGenericCommand函数
//向客户端返回数据 具体关于addreply的函数介绍见链接：http://www.petermao.com/redis/114.html
addReply(c, abort_reply ? abort_reply : shared.nullbulk);
return;
}
//在数据库中设计key和value值
setKey(c->db,key,val);
//脏数据加1，表示更改了原有数据，需要系统更新到磁盘中去
server.dirty++;
if (expire) setExpire(c->db,key,mstime()+milliseconds);
//事件通知 默认是关闭的 详细见链接 http://www.redisdoc.com/en/latest/topic/notification.html
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"set",key,c->db->id);
if (expire) notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,
"expire",key,c->db->id);
addReply(c, ok_reply ? ok_reply : shared.ok);
}
/* SET key value [NX] [XX] [EX <seconds>] [PX <milliseconds>] */
//据图的SET命令 包括SETNX SETXX SETEX。
void setCommand(redisClient *c) {
int j;
robj *expire = NULL;
int unit = UNIT_SECONDS;
int flags = REDIS_SET_NO_FLAGS;
//以下是解析参数的过程
for (j = 3; j < c->argc; j++) {
char *a = c->argv[j]->ptr;
robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];
if ((a[0] == 'n' || a[0] == 'N') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0') {
flags |= REDIS_SET_NX;
} else if ((a[0] == 'x' || a[0] == 'X') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0') {
flags |= REDIS_SET_XX;
} else if ((a[0] == 'e' || a[0] == 'E') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' && next) {
unit = UNIT_SECONDS;
expire = next;
j++;
} else if ((a[0] == 'p' || a[0] == 'P') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' && next) {
unit = UNIT_MILLISECONDS;
expire = next;
j++;
} else {
//shared是一个共享变量 //Shared objects
addReply(c,shared.syntaxerr);
return;
}
}
c->argv[2] = tryObjectEncoding(c->argv[2]);
//调用setGenericCommand函数
setGenericCommand(c,flags,c->argv[1],c->argv[2],expire,unit,NULL,NULL);
}
//setnxCommand函数
void setnxCommand(redisClient *c) {
c->argv[2] = tryObjectEncoding(c->argv[2]);
setGenericCommand(c,REDIS_SET_NX,c->argv[1],c->argv[2],NULL,0,shared.cone,shared.czero);
}
//setexCommand函数
void setexCommand(redisClient *c) {
c->argv[3] = tryObjectEncoding(c->argv[3]);
setGenericCommand(c,REDIS_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_SECONDS,NULL,NULL);
}
void psetexCommand(redisClient *c) {
c->argv[3] = tryObjectEncoding(c->argv[3]);
setGenericCommand(c,REDIS_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_MILLISECONDS,NULL,NULL);
}
//GET的通用处理函数 http://www.myexception.cn/open-source/1471391.html
int getGenericCommand(redisClient *c) {
robj *o;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL)
return REDIS_OK;
if (o->type != REDIS_STRING) {
addReply(c,shared.wrongtypeerr);
return REDIS_ERR;
} else {
addReplyBulk(c,o);
return REDIS_OK;
}
}
//get命令 直接调用getGenericCommand函数
void getCommand(redisClient *c) {
getGenericCommand(c);
}
/*
GETSET key value
将给定key的值设为value，并返回旧值。
当key存在但不是字符串类型时，返回一个错误。
*/
void getsetCommand(redisClient *c) {
if (getGenericCommand(c) == REDIS_ERR) return;
c->argv[2] = tryObjectEncoding(c->argv[2]);
//设置值
setKey(c->db,c->argv[1],c->argv[2]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"set",c->argv[1],c->db->id);
server.dirty++;
}
void setrangeCommand(redisClient *c) {
robj *o;
long offset;
sds value = c->argv[3]->ptr;
if (getLongFromObjectOrReply(c,c->argv[2],&offset,NULL) != REDIS_OK)
return;
if (offset < 0) {
addReplyError(c,"offset is out of range");
return;
}
o = lookupKeyWrite(c->db,c->argv[1]);
if (o == NULL) {
/* Return 0 when setting nothing on a non-existing string */
if (sdslen(value) == 0) {
addReply(c,shared.czero);
return;
}
/* Return when the resulting string exceeds allowed size */
if (checkStringLength(c,offset+sdslen(value)) != REDIS_OK)
return;
o = createObject(REDIS_STRING,sdsempty());
dbAdd(c->db,c->argv[1],o);
} else {
size_t olen;
/* Key exists, check type */
if (checkType(c,o,REDIS_STRING))
return;
/* Return existing string length when setting nothing */
olen = stringObjectLen(o);
if (sdslen(value) == 0) {
addReplyLongLong(c,olen);
return;
}
/* Return when the resulting string exceeds allowed size */
if (checkStringLength(c,offset+sdslen(value)) != REDIS_OK)
return;
/* Create a copy when the object is shared or encoded. */
if (o->refcount != 1 || o->encoding != REDIS_ENCODING_RAW) {
robj *decoded = getDecodedObject(o);
o = createStringObject(decoded->ptr, sdslen(decoded->ptr));
decrRefCount(decoded);
dbOverwrite(c->db,c->argv[1],o);
}
}
if (sdslen(value) > 0) {
o->ptr = sdsgrowzero(o->ptr,offset+sdslen(value));
memcpy((char*)o->ptr+offset,value,sdslen(value));
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,
"setrange",c->argv[1],c->db->id);
server.dirty++;
}
addReplyLongLong(c,sdslen(o->ptr));
}
void getrangeCommand(redisClient *c) {
robj *o;
long start, end;
char *str, llbuf[32];
size_t strlen;
if (getLongFromObjectOrReply(c,c->argv[2],&start,NULL) != REDIS_OK)
return;
if (getLongFromObjectOrReply(c,c->argv[3],&end,NULL) != REDIS_OK)
return;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptybulk)) == NULL ||
checkType(c,o,REDIS_STRING)) return;
if (o->encoding == REDIS_ENCODING_INT) {
str = llbuf;
strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
} else {
str = o->ptr;
strlen = sdslen(str);
}
/* Convert negative indexes */
if (start < 0) start = strlen+start;
if (end < 0) end = strlen+end;
if (start < 0) start = 0;
if (end < 0) end = 0;
if ((unsigned)end >= strlen) end = strlen-1;
/* Precondition: end >= 0 && end < strlen, so the only condition where
* nothing can be returned is: start > end. */
if (start > end) {
addReply(c,shared.emptybulk);
} else {
addReplyBulkCBuffer(c,(char*)str+start,end-start+1);
}
}
void mgetCommand(redisClient *c) {
int j;
addReplyMultiBulkLen(c,c->argc-1);
for (j = 1; j < c->argc; j++) {
robj *o = lookupKeyRead(c->db,c->argv[j]);
if (o == NULL) {
addReply(c,shared.nullbulk);
} else {
if (o->type != REDIS_STRING) {
addReply(c,shared.nullbulk);
} else {
addReplyBulk(c,o);
}
}
}
}
void msetGenericCommand(redisClient *c, int nx) {
int j, busykeys = 0;
if ((c->argc % 2) == 0) {
addReplyError(c,"wrong number of arguments for MSET");
return;
}
/* Handle the NX flag. The MSETNX semantic is to return zero and don't
* set nothing at all if at least one already key exists. */
if (nx) {
for (j = 1; j < c->argc; j += 2) {
if (lookupKeyWrite(c->db,c->argv[j]) != NULL) {
busykeys++;
}
}
if (busykeys) {
addReply(c, shared.czero);
return;
}
}
for (j = 1; j < c->argc; j += 2) {
c->argv[j+1] = tryObjectEncoding(c->argv[j+1]);
setKey(c->db,c->argv[j],c->argv[j+1]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"set",c->argv[j],c->db->id);
}
server.dirty += (c->argc-1)/2;
addReply(c, nx ? shared.cone : shared.ok);
}
void msetCommand(redisClient *c) {
msetGenericCommand(c,0);
}
void msetnxCommand(redisClient *c) {
msetGenericCommand(c,1);
}
void incrDecrCommand(redisClient *c, long long incr) {
long long value, oldvalue;
robj *o, *new;
o = lookupKeyWrite(c->db,c->argv[1]);
if (o != NULL && checkType(c,o,REDIS_STRING)) return;
if (getLongLongFromObjectOrReply(c,o,&value,NULL) != REDIS_OK) return;
oldvalue = value;
if ((incr < 0 && oldvalue < 0 && incr < (LLONG_MIN-oldvalue)) ||
(incr > 0 && oldvalue > 0 && incr > (LLONG_MAX-oldvalue))) {
addReplyError(c,"increment or decrement would overflow");
return;
}
value += incr;
new = createStringObjectFromLongLong(value);
if (o)
dbOverwrite(c->db,c->argv[1],new);
else
dbAdd(c->db,c->argv[1],new);
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"incrby",c->argv[1],c->db->id);
server.dirty++;
addReply(c,shared.colon);
addReply(c,new);
addReply(c,shared.crlf);
}
void incrCommand(redisClient *c) {
incrDecrCommand(c,1);
}
void decrCommand(redisClient *c) {
incrDecrCommand(c,-1);
}
void incrbyCommand(redisClient *c) {
long long incr;
if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != REDIS_OK) return;
incrDecrCommand(c,incr);
}
void decrbyCommand(redisClient *c) {
long long incr;
if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != REDIS_OK) return;
incrDecrCommand(c,-incr);
}
void incrbyfloatCommand(redisClient *c) {
long double incr, value;
robj *o, *new, *aux;
o = lookupKeyWrite(c->db,c->argv[1]);
if (o != NULL && checkType(c,o,REDIS_STRING)) return;
if (getLongDoubleFromObjectOrReply(c,o,&value,NULL) != REDIS_OK ||
getLongDoubleFromObjectOrReply(c,c->argv[2],&incr,NULL) != REDIS_OK)
return;
value += incr;
if (isnan(value) || isinf(value)) {
addReplyError(c,"increment would produce NaN or Infinity");
return;
}
new = createStringObjectFromLongDouble(value);
if (o)
dbOverwrite(c->db,c->argv[1],new);
else
dbAdd(c->db,c->argv[1],new);
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"incrbyfloat",c->argv[1],c->db->id);
server.dirty++;
addReplyBulk(c,new);
/* Always replicate INCRBYFLOAT as a SET command with the final value
* in order to make sure that differences in float precision or formatting
* will not create differences in replicas or after an AOF restart. */
aux = createStringObject("SET",3);
rewriteClientCommandArgument(c,0,aux);
decrRefCount(aux);
rewriteClientCommandArgument(c,2,new);
}
void appendCommand(redisClient *c) {
size_t totlen;
robj *o, *append;
o = lookupKeyWrite(c->db,c->argv[1]);
if (o == NULL) {
/* Create the key */
c->argv[2] = tryObjectEncoding(c->argv[2]);
dbAdd(c->db,c->argv[1],c->argv[2]);
incrRefCount(c->argv[2]);
totlen = stringObjectLen(c->argv[2]);
} else {
/* Key exists, check type */
if (checkType(c,o,REDIS_STRING))
return;
/* "append" is an argument, so always an sds */
append = c->argv[2];
totlen = stringObjectLen(o)+sdslen(append->ptr);
if (checkStringLength(c,totlen) != REDIS_OK)
return;
/* If the object is shared or encoded, we have to make a copy */
if (o->refcount != 1 || o->encoding != REDIS_ENCODING_RAW) {
robj *decoded = getDecodedObject(o);
o = createStringObject(decoded->ptr, sdslen(decoded->ptr));
decrRefCount(decoded);
dbOverwrite(c->db,c->argv[1],o);
}
/* Append the value */
o->ptr = sdscatlen(o->ptr,append->ptr,sdslen(append->ptr));
totlen = sdslen(o->ptr);
}
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(REDIS_NOTIFY_STRING,"append",c->argv[1],c->db->id);
server.dirty++;
addReplyLongLong(c,totlen);
}
void strlenCommand(redisClient *c) {
robj *o;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,o,REDIS_STRING)) return;
addReplyLongLong(c,stringObjectLen(o));
}
