Re: POC: make mxidoff 64 bits

Hi，

I'm currently looking into the `SlruReadSwitchPageSlow` function and have a question regarding the expression `&state->buf.data + bytes_read` —
I suspect the ampersand (&) here might be misused. Would you be able to help me verify this?

```
while (bytes_read < BLCKSZ)
{
ssize_t rc;

rc = pg_pread(state->fd,
&state->buf.data + bytes_read,
BLCKSZ - bytes_read,
offset);
if (rc < 0)
{
if (errno == EINTR)
continue;
pg_fatal("could not read file \"%s\": %m", state->fn);
}
if (rc == 0)
{
/* unexpected EOF */
pg_log(PG_WARNING, "unexpected EOF reading file \"%s\" at offset %u, reading as zeros",
state->fn, (unsigned int) offset);
memset(&state->buf.data + bytes_read, 0, BLCKSZ - bytes_read);
break;
}
bytes_read += rc;
offset += rc;
}
```

```
rc = pg_pread(state->fd,
&state->buf.data + bytes_read,
BLCKSZ - bytes_read,
offset);
memset(&state->buf.data + bytes_read, 0, BLCKSZ - bytes_read);
```

--
Regards,
Man Zeng
www.openhalo.org