gp_camera_file_read vs. gp_camera_file_get

[peterbud]

I was using the sample program sample-capture and sample-trigger-capture, and found the following on my Windows port:

• call to function gp_camera_file_get used in sample-capture WORKS, captures 2 images (both way) without any problem
• call to function gp_camera_file_read used in sample-trigger-capture with the same camera and setting FAILS. As far as I can debug, gp_camera_file_read calls gp_filesystem_read_file, which then calls read_file_func. This one impleneted in ptp2/libary.c, and has a define for folder_to_storage, which expects that the folder paramter should have the name like "/store_xxxxxxxxx/"

Question: is this really a necessary check? Why then the gp_camera_file_get works perfectly?

Sorry if the question is stupid, I have started getting familiar with the library only recently.

[romainreignier]

I have faced the same issue. I wanted to avoid the unnecessary write/delete operation on host filesystem. But I have figured out that the function gp_camera_file_read is never used in the libgphoto2 and gphoto2.

[romainreignier]

In my case, for a Sony PTP camera, the path->folder value is overridden in the capture function here: https://github.com/gphoto/libgphoto2/blob/bc181c8ae3d7eaf175455697678e3b24ae1cdfcd/camlibs/ptp2/library.c#L4215

So the check in folder_to_storage cannot be valid.

[romainreignier]

Removing the folder_to_storage check does not help, the function fail later because the file is not found. Because the gp_camera_file_read is never called I doubt it will work out of the box for ptp camera. @msmeissn what do you think about it?

[msmeissn]

Hmm. The gp_camera_file_read does not cover this case, it should check the filesystem backed cached storage here. This is missing. the _read function is not complete :/

But gp_camera_file_get() does not touch the host filesystem, unless you use gp_file_new_from_fd() or so, so you can still use that.

[romainreignier]

Oh! I've missed the point that I can initialize a CameraFile from memory with gp_file_new() and not gp_file_new_from_fd(). Thanks. Until now, I was creating a temporary file with mkstemp() and then delete it with unlink().