redis_3.0.7_sds.c_sdsIncrLen()

void sdsIncrLen(sds s,int incr)
{
    struct sdshdr *sh = (void*)(s-(sizeof(struct sdshdr)));

    if(incr >= 0)
        assert(sh->free >=(unsigned int)incr);
    else
        assert(sh->len >= (unsigned int)(-incr));
    sh->len += incr;
    sh->free -= incr;
    s[sh->len] = '\0';
}

void assert( int expression );