On 5/3/2019 11:23 PM, Christopher Head via curl-library wrote: > On Fri, 3 May 2019 17:38:37 -0400 > Ray Satiro via curl-library <curl-library@cool.haxx.se> wrote: > >> I think this will be unclear to the reporter since he basically wants >> to upload arbitrary parts of a file [1]. curl supports resuming an >> upload and sets Content-Range in that case (CURLOPT_RESUME_FROM and >> CURLOPT_INFILESIZE) but does not support CURLOPT_RANGE for arbitrary >> parts, would you agree? > I think the situation is pretty clear to me: I’m doing something > outside what Curl supports, so I should just use CURLOPT_HTTPHEADER to > set Content-Range. I’m fine with this. > > I think I’m now just more confused about why Curl even supports > CURLOPT_RANGE for PUTs at all. I’m honestly not seeing how it’s > possible to use it for *any* purpose, not even for resuming an upload > with intent to complete the whole file: if you set INFILESIZE to the > size of the file then Content-Length is too big, and if you set > INFILESIZE to the size of the residue then the number after the slash > in Content-Range is too small. So RESUME_FROM for PUTs seems to be OK > in the sense that it’s not really standards compliant but does > something vaguely sensible which is useful with some servers, but > CURLOPT_RANGE for PUTs seems to never do anything useful, and yet, > despite that, some effort was put into implementing it. > > So, for my own purposes I have no problem: I’ll just use HTTPHEADER, > given that it seems my desired behaviour wasn’t ever meant to work. But > I’m left wondering about the rest.
I hear you it's confusing to me too which is why I opened the issue to clarify it. I see now that one type of ranged PUT is supported to allow resuming uploading a resource but CURLOPT_RANGE is not used for that. To resume on upload use CURLOPT_INFILESIZE(_LARGE) and CURLOPT_RESUME_FROM(_LARGE), and Content-Range will be derived from both of those, and *not* CURLOPT_RANGE. Maybe that is what Daniel meant by ranged PUTs, or maybe not. As you noted when you tried that the input file will be read until the end. For example: printf "abc" > input curld -v -T input -C 1 http://localhost:8000/destination CURLOPT_UPLOAD is set to 1L for a PUT upload. CURLOPT_READDATA is set to internal struct that contains fd of opened file input. CURLOPT_SEEKDATA is set to same. CURLOPT_READFUNCTION is set to read it. CURLOPT_SEEKFUNCTION is set to seek it. CURLOPT_INFILESIZE_LARGE is set to the size of file input (curl_off_t)3. CURLOPT_RESUME_FROM_LARGE is set to the offset to resume from (curl_off_t)1. CURLOPT_RANGE is set NULL. The server receives: PUT /destination HTTP/1.1 Host: localhost:8000 Content-Range: bytes 1-2/3 User-Agent: curl/7.65.0-DEV Accept: */* Content-Length: 2 Expect: 100-continue bc Also as you noted CURLOPT_RANGE does not work like CURLOPT_RESUME_FROM, in that the former does not have any effect on Content-Length. Content-Length is determined by CURLOPT_INFILESIZE minus CURLOPT_RESUME_FROM. Yet if you specify CURLOPT_RESUME_FROM then CURLOPT_RANGE is ignored, and only CURLOPT_RESUME_FROM changes the starting offset of the file. If you use CURLOPT_RANGE and CURLOPT_INFILESIZE without CURLOPT_RESUME_FROM then libcurl ends up in this block [1]: else { /* Range was selected and then we just pass the incoming range and append total size */ conn->allocptr.rangeline = aprintf("Content-Range: bytes %s/%" CURL_FORMAT_CURL_OFF_T "\r\n", data->state.range, data->state.infilesize); } But I think that will not work correctly since Content-Length is also CURLOPT_INFILESIZE. IIRC it is not good to set the Content-Length header on your own because then internally libcurl doesn't change the length to 0 when it does authentication before the PUT. Therefore I think the best thing to do here is do not use CURLOPT_RANGE (at least until its use is clarified) and set the range header yourself, as I suggested. I will try experimenting with it some later. [1]: https://github.com/curl/curl/blob/curl-7_64_1/lib/http.c#L2485-L2491
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