Subject: RE: Clarification in torture-tests and impl-guide (Re: [rohc] MULTILOAD operands)

From: "Surtees, Abigail" <[email-masked]>
Date: Mon, 6 Jun 2005 16:22:53 +0100

Hi All,
> 
> > However, the section 2.5 of torture-tests states:
> > 
> >    1.  The MULTILOAD instruction overwrites itself, any of 
> its operands,
> >    or any memory addresses referenced by its operands (in which case
> >    decompression failure should occur).

Pekka, you're right.  This statement is not correct; nor does it reflect
what the test does.  The test itself, is correct.  The above text should
be corrected. 

The text Pekka suggested seems fine; I've left off statement 3 because I
don't think it adds anything:

"  1. The MULTILOAD instruction overwrites itself or any of its
operands,
   in which case decompression failure should occur. 

   2. The memory references of MULTILOAD instruction operands are
   evaluated step-by-step rather than all at once before starting
   to copy data."

> 
> "Decompression failure occurs if the set of 2-byte words set by the
> instruction would overlap the memory locations held by the
> instruction (including its operands) itself, i.e., if the instruction
> would be self-modifying." 
> 
> now reusing a snippet from the code above:
> 
> :initialize_memory 
> MULTILOAD (byte_copy_left, , 
>     circular_buffer, udvm_memory_size, (f_bit|p_bit),
>     $byte_copy_left)
> :end_initialize_memory 
> 
> in my understanding of the rfc the only case when the MULTILOAD above
> would cause a Decompression failure would be when it writes 
> something at
> an address greater than the value of the label initialize_memory and
> lower than end_initialize_memory.
> 
Cristian, your understanding is correct.

Best regards,

Abbie

> > -----Original Message-----
> > From: Cristian CONSTANTIN [mailto:[email-masked]] 
> > Sent: Monday, June 06, 2005 3:02 PM
> > To: Pekka Pessi
> > Cc: West, Mark; Surtees, Abigail; [email-masked]
> > Subject: Re: Clarification in torture-tests and impl-guide 
> > (Re: [rohc] MULTILOAD operands)
> > 
> > 
> > _______________________________________________
> > Rohc mailing list
> > [email-masked]
> > https://www1.ietf.org/mailman/listinfo/rohc
> > 
> 

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