if (flag & HIGHFIND)
{
flag=LOWFIND | HIGHFIND;
/* key shall be moved to the current empty position */
gpos=empty;
ptr_to_rec=pos->data;
empty=pos; /* This place is now free */
}
else
{
flag=LOWFIND | LOWUSED; /* key isn't changed */
gpos=pos;
ptr_to_rec=pos->data;
}
}
else
{
if (!(flag & LOWUSED))
{
/* Change link of previous LOW-key */
gpos->data=ptr_to_rec;
gpos->next= (uint) (pos-data);
flag= (flag & HIGHFIND) | (LOWFIND | LOWUSED);
}
gpos=pos;
ptr_to_rec=pos->data;
}
}
else
{ /* key will be moved */
if (!(flag & HIGHFIND))
{
flag= (flag & LOWFIND) | HIGHFIND;
/* key shall be moved to the last (empty) position */
gpos2 = empty; empty=pos;
ptr_to_rec2=pos->data;
}
else
{
if (!(flag & HIGHUSED))
{
/* Change link of previous hash-key and save */
gpos2->data=ptr_to_rec2;
gpos2->next=(uint) (pos-data);
flag= (flag & LOWFIND) | (HIGHFIND | HIGHUSED);
}
gpos2=pos;
ptr_to_rec2=pos->data;
}
}
}
while ((idx=pos->next) != NO_RECORD);
if ((flag & (LOWFIND | LOWUSED)) == LOWFIND)
{
gpos->data=ptr_to_rec;
gpos->next=NO_RECORD;
}
if ((flag & (HIGHFIND | HIGHUSED)) == HIGHFIND)
{
gpos2->data=ptr_to_rec2;
gpos2->next=NO_RECORD;
}
}
/* Check if we are at the empty position */
idx= my_hash_mask(rec_hashnr(info, record), info->blength, info->records + 1);
pos=data+idx;
if (pos == empty)
{
pos->data=(uchar*) record;
pos->next=NO_RECORD;
}
else
{
/* Check if more records in same hash-nr family */
empty[0]=pos[0];
gpos= data + my_hash_rec_mask(info, pos, info->blength, info->records + 1);
if (pos == gpos)
{
pos->data=(uchar*) record;
pos->next=(uint) (empty - data);
}
else
{
pos->data=(uchar*) record;
pos->next=NO_RECORD;
movelink(data,(uint) (pos-data),(uint) (gpos-data),(uint) (empty-data));
}
}
if (++info->records == info->blength)
info->blength+= info->blength;
return(0);
}
同时给出动态hash函数如下：
static uint my_hash_mask(my_hash_value_type hashnr, size_t buffmax,
size_t maxlength)
{
if ((hashnr & (buffmax-1)) < maxlength) return (hashnr & (buffmax-1));
return (hashnr & ((buffmax >> 1) -1));
}
可以看出，hash函数是hash key