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

t_string.c中定义了字符串键的实现过程。

#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setGenericCommandvoid 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valuevoid 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incrvoid 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);}//+1void incrCommand(client *c) {    incrDecrCommand(c,1);}//-1void 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));}