Re: [Libmtp-discuss] Implementing Object Copy with Pipe

[James J. <me...@do...>]

Apologies, my code was messed up:

int LIBMTP__Copy_Object(LIBMTP_mtpdevice_t *src_device,
           uint32_t const src_id,
           LIBMTP_mtpdevice_t *dest_device,
           LIBMTP_file_t *dest_file,
           LIBMTP_progressfunc_t const callback,
           void const * const data)
{
   int fildes[2];

   if (pipe(fildes) == -1) {
     add_error_to_errorstack(src_device, LIBMTP_ERROR_GENERAL, 
"_LIBMTP_Copy_Object(): Could not create pipe.");
     return -1;
   }

   if (fork() == 0) {
     uint16_t ret = LIBMTP_Send_File_From_File_Descriptor(dest_device, 
fildes[0], dest_file, callback, data);
     close(fildes[0]);
     if (ret == -1) {
       add_ptp_error_to_errorstack(dest_device, ret, 
"_LIBMTP_Copy_Object(): could not write to destination object.");
       return -1;
     }
   } else {
     uint16_t ret = LIBMTP_Get_File_To_File_Descriptor(src_device, 
src_id, fildes[1], callback, data);
     close(fildes[1]);
     if (ret == -1) {
       add_ptp_error_to_errorstack(src_device, ret, 
"_LIBMTP_Copy_Object(): could not copy object.");
       return -1;
     }
   }

   return 0;
}

On 16/01/2022 21:48, James John wrote:
> Hello,
>
> I am trying to implement object copy into this library using Linux pipes.
>
> Since objects cannot be copied to except downloaded to a file and read 
> back into an MTP file, which will take a lot of time. I played around 
> pipes instead by concurrently writing to pipe and reading from pipe 
> back to another MTP file. But I read that MTP is not multiplexed, so 
> operations cannot be performed concurrently.
>
> I have tried to implement this but I am getting some weird error. 
> Because I assumed each transaction waits for the current to finish. 
> This is what I have:
>
> > int LIBMTP__Copy_Object(LIBMTP_mtpdevice_t *src_device, > uint32_t 
> const src_id, > LIBMTP_mtpdevice_t *dest_device, > LIBMTP_file_t 
> *dest_file, > LIBMTP_progressfunc_t const callback, > void const * 
> const data) > { > int fildes[2]; > > if (pipe(fildes) == -1) { > 
> add_error_to_errorstack(src_device, LIBMTP_ERROR_GENERAL, 
> "_LIBMTP_Copy_Object(): Could not create pipe."); > return -1; > } > > 
> if (fork() == 0) { > uint16_t ret = 
> LIBMTP_Send_File_From_File_Descriptor(dest_device, fildes[0], 
> dest_file, callback, data); > close(fildes[0]); > if (ret == -1) { > 
> add_ptp_error_to_errorstack(dest_device, ret, "_LIBMTP_Copy_Object(): 
> could not write to destination object."); > return -1; > } > } else { 
> > uint16_t ret = LIBMTP_Get_File_To_File_Descriptor(src_device, 
> src_id, fildes[1], callback, data); > close(fildes[1]); > if (ret == 
> -1) { > add_ptp_error_to_errorstack(src_device, ret, 
> "_LIBMTP_Copy_Object(): could not copy object."); > return -1; > } > } 
> > > return 0; > }
>
>
> I need a help in finding why it 
> LIBMTP_Send_File_From_File_Descriptoris not working. Or it can't work 
> because it is not multiplexed?
>
> A bit of a newbie here, still getting familiar with this library and 
> the whole low-level thing. It's for the passion :)
>
>
> Thank you
>
> James
>
>
>
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