redis源码分析之t_string.c

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
void setGenericCommand(redisClient *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) != REDIS_OK) return; if (milliseconds <= 0) { addReplyError(c,"invalid expire time in SETEX"); return; } if (unit == UNIT_SECONDS)
 milliseconds *= 1000; } if ((flags & REDIS_SET_NX && lookupKeyWrite(c->db,key) != NULL) || (flags & REDIS_SET_XX && lookupKeyWrite(c->db,key) == NULL)) {

//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));
}