漫话Redis源码之七

getrangeCommand这个函数没看的太明白，但大致知道意思：

void getrangeCommand(client *c) {
    robj *o;
    long long start, end;
    char *str, llbuf[32];
    size_t strlen;
 
    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;
 
    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 */
    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. */
    if (start > end || strlen == 0) {
        addReply(c,shared.emptybulk);
    } else {
        addReplyBulkCBuffer(c,(char*)str+start,end-start+1);
    }
}
 
void mgetCommand(client *c) {
    int j;
 
    addReplyArrayLen(c,c->argc-1);
    for (j = 1; j < c->argc; j++) {
        robj *o = lookupKeyRead(c->db,c->argv[j]);
        if (o == NULL) {
            addReplyNull(c);
        } else {
            if (o->type != OBJ_STRING) {
                addReplyNull(c);
            } else {
                addReplyBulk(c,o);
            }
        }
    }
}
 
void msetGenericCommand(client *c, int nx) {
    int j;
 
    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 anything if at least one key already exists. */
    if (nx) {
        for (j = 1; j < c->argc; j += 2) {
            if (lookupKeyWrite(c->db,c->argv[j]) != NULL) {
                addReply(c, shared.czero);
                return;
            }
        }
    }
 
    for (j = 1; j < c->argc; j += 2) {
        c->argv[j+1] = tryObjectEncoding(c->argv[j+1]);
        setKey(c,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);
}
 
void incrDecrCommand(client *c, long long incr) {
    long long value, oldvalue;
    robj *o, *new;
 
    o = lookupKeyWrite(c->db,c->argv[1]);
    if (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 = createStringObjectFromLongLongForValue(value);
        if (o) {
            dbOverwrite(c->db,c->argv[1],new);
        } else {
            dbAdd(c->db,c->argv[1],new);
        }
    }
    signalModifiedKey(c,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);
}