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[Xen-devel] XenBus watches and values with null bytes

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] XenBus watches and values with null bytes
From: ramsdell@xxxxxxxxx (John D. Ramsdell)
Date: 10 May 2006 08:20:17 -0400
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I'm trying to understand the XenBus interface in
linux-2.6-xen-sparse/include/xen/xenbus.h.  I found the relevant page
on the Xen Wiki, but it does not answer my questions.  

1. I notice that xenbus_write has a prototype of 

int xenbus_write(xenbus_transaction_t t,
                 const char *dir, const char *node, 
                 const char *string);

   How does one associate a value with a key when the value contains
   the null byte?  Is zero the only character forbidden from being
   part of a value?  For example, does a value have to be a UTF-8
   encoded string?

2. A watch includes a callback that provides an array of
   null terminated character strings.  I assume these are the paths to
   the keys at or below the node being watched, but I saw no comment
   describing what a callback provides.  Please fill me in.

3. Is there a better source for XenBus/XenStore developer
   documentation?  I Google'd, but came up empty handed.


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