Re: [Qemu-devel] [PATCH v15 2/9] Add XBZRLE documentation

[Orit Wasserman]

On 07/05/2012 04:24 PM, Eric Blake wrote:
> On 07/05/2012 06:51 AM, Orit Wasserman wrote:
>> Signed-off-by: Orit Wasserman <address@hidden>
>> ---
>>  docs/xbzrle.txt |  136 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 files changed, 136 insertions(+), 0 deletions(-)
>>  create mode 100644 docs/xbzrle.txt
>>
> 
>> +
>> +Example
>> +old buffer:
>> +1001 zeros
>> +05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 00 00 6b 00 6d
>> +3074 zeros
> 
> This _still_ doesn't add up to 4096:
> 
> 1001 + 20 + 3074 = 4095
> 
>> +
>> +new buffer:
>> +1001 zeros
>> +01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 00 67 00 69
>> +3704 zeros
> 
> Still a transposition error.
> 
> Also, this still has the flaw that it is too weak of an example - the
> only unchanged bytes happen to also be zero bytes to begin with; it
> would be much nicer if the example included at least one non-zero byte
> that did not change between old and new.
> 
>> +
>> +encoded buffer:
>> +
>> +encoded length 24
>> +e9 07 0f 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 03 01 67 01 01 69
>                                                          ^^
> That says you have a zrun of 3 bytes, but the example only shows a zrun
> of 2 bytes.
> 
> It feels like I'm pulling teeth to get a good example.  If you will just
> squash in the following (hand-written) diff below, you will then have
> 4096 bytes in both old and new buffers, and your encoded buffer listing
> a zrun of 3 will be correct, plus you will be demonstrating a non-zero
> byte that remained unchanged.
> 
> @@ ???,??? @@
>  Example
>  old buffer:
>  1001 zeros
> -05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 00 00 6b 00 6d
> +05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 68 00 00 6b 00 6d
>  3074 zeros
> 
>  new buffer:
>  1001 zeros
> -01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 00 00 67 00 69
> -3704 zeros
> +01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 68 00 00 67 00 69
> +3074 zeros
> 
>  encoded buffer:
> 
I will use this example ,
thanks,
Orit