Re: [Libguestfs] [PREVIEW ONLY] Refactor data transfer code
On 22/09/10 09:50, Richard W.M. Jones wrote:
On Wed, Sep 22, 2010 at 09:36:41AM +0100, Matthew Booth wrote:
> On 21/09/10 20:12, Richard W.M. Jones wrote:
>>
>> This patch is not using hread/hwrite?
>
> No. That will be required for changing formats, but not for a straight copy.
>
>> Anyway I'd be interested in whether you can do all you wanted from
>> hread/hwrite/hseek/etc using the proposed upload-offset API that I
>> posted here:
>>
>> http://www.redhat.com/archives/libguestfs/2010-September/msg00026.html
>> http://www.redhat.com/archives/libguestfs/2010-September/msg00027.html
>
> No, because the API requires passing in a file, which I don't have.
This is not true. You can write from anything that you can get into a
file descriptor, by specifying "/dev/fd/NN" as the filename.
However the API does require that the source of the data comes from a
separate thread or process, which is not how virt-v2v works at the
moment.
I suspect you need to just use pwrite. AFAICT it already does
everything you need.
Except read and write from a block device, although that could be fixed
with new APIs.
Also, as I said before, I think the handle-based API is a good
alternative for large data-transfer. I don't think your hexedit
experience was a good example. For example, I would expect using hread
to be less code than using pread for reading the contents of a file into
memory in chunks.
Matt
--
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team
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