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Re: libmachuser vs libmach


From: Thomas Bushnell, BSG
Subject: Re: libmachuser vs libmach
Date: 18 Jun 2002 14:23:04 -0700
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

James Morrison <address@hidden> writes:

> Ok, I'm not too sure what is going on with host_info and
> xxx_host_info, but it seems that xxx_host_info is call to the kernel
> without using mig, but host_info is an interface created by mig.  So
> with host_info the struct is copied to the user process, where in
> xxx_host_info the struct is simply given to the user process.  Am I
> understanding any of this?

No, it's just what I told you.

These are two different interfaces, both MiG.

xxx_host_info uses an old miserable interface, which has a fixed-size
struct.  That's a miserable interface, because any time a new element
needs to be added, you'd need to use a new RPC.

host_info uses a much better interface, in which the user tells the
kernel how many items it wants returned in the struct; as a result,
older users get perfect upward compatibility, provided new items are
always added onto the end.




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