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User space data

I want to be able to share a dynamic binary tree which is part of a user process in the kernel space. The tree will be used as shared data between user space process and kernel thread. Is this something that can be accomplished using the mmap() facility? Is there better alternative to achieve this? The pointers used in the data structure will be a issue for sure.

The other option would be to add some messages between the user process and the kernel and sync up the trees. I am trying to avoid this to avoid synchronization issues.

Thanks, Shobha.

Reply to
Shobha
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The "Unix way" would be to make it a file and/or a directory structure from user view, doing a driver that offers "open" "read", etc.

-Michael

Reply to
Michael Schnell

Michael,

Are you referring to writing the binary tree to a file? Can you elaborate?

Thanks, Shobha.

Michael Schnell wrote:

Reply to
Shobha

Why not ?

The user program can do (e.g.) seek() and read()/write(). These calls are transferred 1:1 to the driver. So (AFAIK) a seek to n+1 and read a byte does not necessary need to offer the same byte as the second byte of two bytes read after seeking to n. Moreover the result of a read can change dynamically with any instance.

So a seek could provide a "tree address" of some kind (e.g. each bit a path though the binary tree) and a read could return the leaf data (maybe including some kind of linked list data (next/previous leaf) if useful).

Overwriting a leaf would be similar as reading, creating a new leaf might use seek(,,end).

Moreover there are ioctl() calls that can be used for configuration or other special purposes.

-Michael

Reply to
Michael Schnell

Not quite the same thing, but SNOBOL (a very early string processing language, which pioneered what had become regular expressions) had user-definable, arbitrary data structures. Binary trees were easily doable...

In the above scenario, all you really need to provide is a direction to the next node/leaf. So a seek for a binary tree has 3 directions: parent, left child, right child, for a ternary tree it has 4 directions, and for an arbitrary n tree it has up to n+1 directions... Although that can be simplified to 4 by using parent, left sibling, right sibling, and child.

There is considerable prior art in implementing these kinds of data structures... So a bit of research might yield good results...

--Yan

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Captain Dondo

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