On Thu, 9 Aug 2012, Florian Pritz wrote:
When using curl to upload files to a pastebin, I noticed that `curl -v -F
"file=@/proc/cpuinfo" http://...` will send an http request stating that the
file is empty, but it reads the contents anyway and the server (apache in my
case) returns "400 Bad Request" because it didn't expect the content.
Yes. I took a decision many years ago (introduced in libcurl 7.12.1 in August
2004) that I would let libcurl stat() the file first to figure out the file
size (and use that in the request headers) and then read the file contents
later in a streaming manner when providing thr request body. That is necessary
to avoid having to read the entire thing into memory before sending it off -
which libcurl used to do before that.
The downside is that it doesn't handle growing or shrinking files properly.
Right now I'm using this code[1] to work around the problem. Basically I
just load the file into memory in case st_size is 0 and pass it as
CURLFORM_BUFFER{,PTR} instead of CURLFORM_FILE.
Sounds like a decent work-around. Another version could copy the file to a
temporary one and you'd then upload that. It would use less memory but require
temp file management in your app.
I hope this is enough for someone with more knowledge about libcurl
internals to fix this properly.
Sorry, but what exactly would a "proper" fix be to this problem you think?
I can think of one fix if we assume that the server is a HTTP/1.1, as then we
could send the whole request using chunked encoding - but libcurl can't
blindly assume 1.1 and some server won't like getting such posted in a chunked
manner.
--
/ daniel.haxx.se
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