结合redis设计与实现的redis源码学习-8.2-t_string（字符串键）

#include "server.h"
#include <math.h> /* isnan(), isinf() */
//检查客户端的字符串长度
static int checkStringLength(client *c, long long size) {
if (size > 512*1024*1024) {
addReplyError(c,"string exceeds maximum allowed size (512MB)");//这里说明了一个字符串的的大小不能超过512M
return C_ERR;
}
return C_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.这个函数实现的是Set的不同变体和相关的操作 */
#define OBJ_SET_NO_FLAGS 0
#define OBJ_SET_NX (1<<0)     /* Set if key not exists. */
#define OBJ_SET_XX (1<<1)     /* Set if key exists. */
#define OBJ_SET_EX (1<<2)     /* Set if time in seconds is given */
#define OBJ_SET_PX (1<<3)     /* Set if time in ms in given */
void setGenericCommand(client *c, int flags, robj *key, robj *val, robj *expire, int unit, robj *ok_reply, robj *abort_reply) {
long long milliseconds = 0; /* initialized to avoid any harmness warning */

if (expire) {
if (getLongLongFromObjectOrReply(c, expire, &milliseconds, NULL) != C_OK)
return;
if (milliseconds <= 0) {
addReplyErrorFormat(c,"invalid expire time in %s",c->cmd->name);
return;
}
if (unit == UNIT_SECONDS) milliseconds *= 1000;
}

if ((flags & OBJ_SET_NX && lookupKeyWrite(c->db,key) != NULL) ||
(flags & OBJ_SET_XX && lookupKeyWrite(c->db,key) == NULL))
{
addReply(c, abort_reply ? abort_reply : shared.nullbulk);
return;
}
setKey(c->db,key,val);
server.dirty++;
if (expire) setExpire(c->db,key,mstime()+milliseconds);
notifyKeyspaceEvent(NOTIFY_STRING,"set",key,c->db->id);
if (expire) notifyKeyspaceEvent(NOTIFY_GENERIC,
"expire",key,c->db->id);
addReply(c, ok_reply ? ok_reply : shared.ok);
}

/* SET key value [NX] [XX] [EX <seconds>] [PX <milliseconds>] 根据不同的参数设置不同的参数执行setGenericCommand*/
void setCommand(client *c) {
int j;
robj *expire = NULL;
int unit = UNIT_SECONDS;
int flags = OBJ_SET_NO_FLAGS;

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 & OBJ_SET_XX))
{
flags |= OBJ_SET_NX;
} else if ((a[0] == 'x' || a[0] == 'X') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_NX))
{
flags |= OBJ_SET_XX;
} else if ((a[0] == 'e' || a[0] == 'E') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_PX) && next)
{
flags |= OBJ_SET_EX;
unit = UNIT_SECONDS;
expire = next;
j++;
} else if ((a[0] == 'p' || a[0] == 'P') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_EX) && next)
{
flags |= OBJ_SET_PX;
unit = UNIT_MILLISECONDS;
expire = next;
j++;
} else {
addReply(c,shared.syntaxerr);
return;
}
}

c->argv[2] = tryObjectEncoding(c->argv[2]);
setGenericCommand(c,flags,c->argv[1],c->argv[2],expire,unit,NULL,NULL);
}
//下面是一些针对set特定命令的执行函数，都会调用到setGenericCommand
void setnxCommand(client *c) {
c->argv[2] = tryObjectEncoding(c->argv[2]);
setGenericCommand(c,OBJ_SET_NX,c->argv[1],c->argv[2],NULL,0,shared.cone,shared.czero);
}
void setexCommand(client *c) {
c->argv[3] = tryObjectEncoding(c->argv[3]);
setGenericCommand(c,OBJ_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_SECONDS,NULL,NULL);
}
void psetexCommand(client *c) {
c->argv[3] = tryObjectEncoding(c->argv[3]);
setGenericCommand(c,OBJ_SET_NO_FLAGS,c->argv[1],c->argv[3],c->argv[2],UNIT_MILLISECONDS,NULL,NULL);
}
int getGenericCommand(client *c) {
robj *o;

if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL)
return C_OK;

if (o->type != OBJ_STRING) {
addReply(c,shared.wrongtypeerr);
return C_ERR;
} else {
addReplyBulk(c,o);
return C_OK;
}
}
//获取客户端的命令
void getCommand(client *c) {
getGenericCommand(c);
}

void getsetCommand(client *c) {
if (getGenericCommand(c) == C_ERR) return;
c->argv[2] = tryObjectEncoding(c->argv[2]);
setKey(c->db,c->argv[1],c->argv[2]);
notifyKeyspaceEvent(NOTIFY_STRING,"set",c->argv[1],c->db->id);//通知事件，定义在Notify.c中
server.dirty++;
}
//
void setrangeCommand(client *c) {
robj *o;
long offset;
sds value = c->argv[3]->ptr;

if (getLongFromObjectOrReply(c,c->argv[2],&offset,NULL) != C_OK)
return;

if (offset < 0) {
addReplyError(c,"offset is out of range");
return;
}

o = lookupKeyWrite(c->db,c->argv[1]);//查看key是否过期，然后查询set返回结果，定义在Db.c中
if (o == NULL) {
/* Return 0 when setting nothing on a non-existing string 如果设置的值长度为0，那么直接返回*/
if (sdslen(value) == 0) {
addReply(c,shared.czero);
return;
}

/* Return when the resulting string exceeds allowed size 如果超过最大字节数，直接返回*/
if (checkStringLength(c,offset+sdslen(value)) != C_OK)
return;

o = createObject(OBJ_STRING,sdsnewlen(NULL, offset+sdslen(value)));//创建对象
dbAdd(c->db,c->argv[1],o);//给这个客户端使用的db增加一个对象
} else {
size_t olen;

/* Key exists, check type */
if (checkType(c,o,OBJ_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)) != C_OK)
return;

/* Create a copy when the object is shared or encoded. */
o = dbUnshareStringValue(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(NOTIFY_STRING,
"setrange",c->argv[1],c->db->id);
server.dirty++;
}
addReplyLongLong(c,sdslen(o->ptr));//返回客户端长度
}

void getrangeCommand(client *c) {
robj *o;
long long start, end;
char *str, llbuf[32];
size_t strlen;
//检查第3和第4个参数是否是数字
if (getLongLongFromObjectOrReply(c,c->argv[2],&start,NULL) != C_OK)
return;
if (getLongLongFromObjectOrReply(c,c->argv[3],&end,NULL) != C_OK)
return;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.emptybulk)) == NULL ||
checkType(c,o,OBJ_STRING)) return;//判断类型是否符合要求，返回

if (o->encoding == OBJ_ENCODING_INT) {
str = llbuf;
strlen = ll2string(llbuf,sizeof(llbuf),(long)o->ptr);
} else {
str = o->ptr;
strlen = sdslen(str);
}

/* Convert negative indexes 转化负数的操作*/
if (start < 0 && end < 0 && start > end) {
addReply(c,shared.emptybulk);
return;
}
if (start < 0) start = strlen+start;
if (end < 0) end = strlen+end;
if (start < 0) start = 0;
if (end < 0) end = 0;
if ((unsigned long long)end >= strlen) end = strlen-1;

/* Precondition: end >= 0 && end < strlen, so the only condition where nothing can be returned is: start > end. 判断长度满足条件*/
if (start > end || strlen == 0) {
addReply(c,shared.emptybulk);
} else {
addReplyBulkCBuffer(c,(char*)str+start,end-start+1);
}
}
//获取指定的key的value
void mgetCommand(client *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 != OBJ_STRING) {
addReply(c,shared.nullbulk);
} else {
addReplyBulk(c,o);
}
}
}
}
//mset通用命令
void msetGenericCommand(client *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. 处理NX标志，如果至少存在一个key，那么返回0，且不设置任何内容*/
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(NOTIFY_STRING,"set",c->argv[j],c->db->id);
}
server.dirty += (c->argc-1)/2;
addReply(c, nx ? shared.cone : shared.ok);
}

void msetCommand(client *c) {
msetGenericCommand(c,0);
}

void msetnxCommand(client *c) {
msetGenericCommand(c,1);
}
//是一个value增加incr
void incrDecrCommand(client *c, long long incr) {
long long value, oldvalue;
robj *o, *new;

o = lookupKeyWrite(c->db,c->argv[1]);
if (o != NULL && checkType(c,o,OBJ_STRING)) return;
if (getLongLongFromObjectOrReply(c,o,&value,NULL) != C_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;

if (o && o->refcount == 1 && o->encoding == OBJ_ENCODING_INT &&
(value < 0 || value >= OBJ_SHARED_INTEGERS) &&
value >= LONG_MIN && value <= LONG_MAX)
{
new = o;
o->ptr = (void*)((long)value);
} else {
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(NOTIFY_STRING,"incrby",c->argv[1],c->db->id);
server.dirty++;
addReply(c,shared.colon);
addReply(c,new);
addReply(c,shared.crlf);
}
//+1
void incrCommand(client *c) {
incrDecrCommand(c,1);
}
//-1
void decrCommand(client *c) {
incrDecrCommand(c,-1);
}

//增加命令
void incrbyCommand(client *c) {
long long incr;

if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
incrDecrCommand(c,incr);
}
//减少命令
void decrbyCommand(client *c) {
long long incr;

if (getLongLongFromObjectOrReply(c, c->argv[2], &incr, NULL) != C_OK) return;
incrDecrCommand(c,-incr);
}
//增加浮点数命令
void incrbyfloatCommand(client *c) {
long double incr, value;
robj *o, *new, *aux;

o = lookupKeyWrite(c->db,c->argv[1]);
if (o != NULL && checkType(c,o,OBJ_STRING)) return;
if (getLongDoubleFromObjectOrReply(c,o,&value,NULL) != C_OK ||
getLongDoubleFromObjectOrReply(c,c->argv[2],&incr,NULL) != C_OK)
return;

value += incr;
if (isnan(value) || isinf(value)) {
addReplyError(c,"increment would produce NaN or Infinity");
return;
}
new = createStringObjectFromLongDouble(value,1);
if (o)
dbOverwrite(c->db,c->argv[1],new);
else
dbAdd(c->db,c->argv[1],new);
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(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);
}
//追加命令，不存在创建，是字符类型追加
void appendCommand(client *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,OBJ_STRING))
return;

/* "append" is an argument, so always an sds */
append = c->argv[2];
totlen = stringObjectLen(o)+sdslen(append->ptr);
if (checkStringLength(c,totlen) != C_OK)
return;

/* Append the value */
o = dbUnshareStringValue(c->db,c->argv[1],o);
o->ptr = sdscatlen(o->ptr,append->ptr,sdslen(append->ptr));
totlen = sdslen(o->ptr);
}
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_STRING,"append",c->argv[1],c->db->id);
server.dirty++;
addReplyLongLong(c,totlen);
}
//返回对象长度
void strlenCommand(client *c) {
robj *o;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,o,OBJ_STRING)) return;
addReplyLongLong(c,stringObjectLen(o));
}