Transfer progress

[kenkit]

Hi, thank you for making this library.
I plan on using it in an app i'm making could not find a way to get transfer progress incase of file download/upload.
Your response will highly appreciated.

[vasild]

Hello,

Monitoring the progress is not possible currently. It would be nice to have such a functionality, but I am afraid I lack the time to implement it.

[kenkit]

Does stringstream store the data after you call client.FilesGet(url, &contents); or does the transfer begin after you begin reading the stream ?
I'd like to try another way to obtain progress information.

[vasild]

Hi,

I am not sure I fully understand your question. The transfer begins when client.FilesGet(url, &contents); is called. As soon as some data is received it will be appended to contents (by calling its write() method). So, contents will be modified (maybe multiple times) during the execution of FilesGet() and when the latter completes, the full response will be available in contents.

If you want to monitor the progress, you have to somehow hook yourself in the cURL callback that appends chunks of data to contents:
https://github.com/vasild/cpp-ipfs-api/blob/e260f39/src/http/transport-curl.cc#L86
Maybe it would be best if FilesGet() is extended to accept a "progress callback" function, pass it down to curl_cb_stream() which would call it with the number of bytes received. Notice that the total size is not available in curl_cb_stream().

[kenkit]

I see, nice explanation also. Thanks for that. I will try implementing this when my app is nearly complete.
Maybe I'll even create a PR if it works well.
EDIT:From your response it seems I will have to redirect output to an fstream since using stringstream may use up alot of ram esp if the file is large. Will see what I can do.

[melroy89]

@kenkit Is this still an issue? Are you missing some functionality? If so, what would your proposal interface?

[kenkit]

I think having a callback through the libcurl progress interface would work.
Maybe just exposing libcurls progress bar interface so the user can set his own callbacks.

[melroy89]

PR's are welcome :)