patch: reget working again [Re: Reget: bug or feature?]

[Alexander Savelyev]

Pavel Roskin wrote:
> On Tue, 20 Jan 2004, Alexander Savelyev wrote:
> 
> 
>>Arpad Biro wrote:
>>
>>>Hi,
>>>
>>>MC 4.6.1-pre1:
>>>
>>>It seems that when copying files, "reget" means to append the last
>>>s-t bytes of the source file to the target file, where s is the source
>>>size and t is the target size.
>>>
>>>However, when performing "move", "reget" works differently:
>>>the whole source file is appended to the target.
>>>
>>>Is this difference a bug or a feature?
>>
>>It's a bug, below is a patch for this feature. Using global variable the
>>same patch only 6 rows length :)
> 
> 
> "long long" is not portable.

	fixed

> We need a configure check for format
> specification that would work with off_t.  Ideally, conversion to off_t
> should be a separate patch.
> 
> I still don't understand how O_FTPREGET is supposed to work and why it's
> needed.

	It's necessary because FTP protocol supposes use seek (command REST)
only before open (command RETR).
	We from ftpfs_open_data_connection have no access to (FileOpContext)ctx
(ctx->reget) and we should transfer it by a call mc_open from
copy_file_file for vfs_s_open where is called linear_start.

copy_file_file -> mc_open -> vfs_s_open -> linear_start
(ftpfs_linear_start) -> ftpfs_open_data_connection (ftp command "REST
offset")


> It should be documented in a comment before O_FTPREGET.  I
> remember is was discussed already.  There is a comment in vfs.h that
> explains how reget should be implemented:

	I read it.

> /* O_LINEAR is strange beast, be careful. If you open file asserting
>  * O_RDONLY | O_LINEAR, you promise:
>  *
>  *      a) to read file linearly from beginning to the end
>  *      b) not to open another file before you close this one
>  *              (this will likely go away in future)
>  *      as a special gift, you may
>  *      c) lseek() immediately after open(), giving ftpfs chance to
>  *         reget. Be warned that this lseek() can fail, and you _have_
>  *         to handle that gratefully.

	c) is wrong

>  *
>  * O_LINEAR allows filesystems not to create temporary file in some
>  * cases (ftp transfer).                                -- pavel at ucw.cz
>  */
> 
> If lseek() after open() with O_LINEAR cannot be used, I'd like to see this
> comment adjusted.
> 

	adjusted.

	patch below.

-- 
~.

    Alexander

>>> mailto:i at fano.com.ua


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