CURLOPT_SEEKFUNCTION.3: also when server closes a connection

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.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.

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This function gets called by libcurl to seek to a certain position in the

input stream and can be used to fast forward a file in a resumed upload

(instead of reading all uploaded bytes with the normal read

function/callback). It is also called to rewind a stream when doing a HTTP PUT

or POST with a multi-pass authentication method. The function shall work like

fseek(3) or lseek(3) and it gets SEEK_SET, SEEK_CUR or SEEK_END as argument

for \fIorigin\fP, although libcurl currently only passes SEEK_SET.

function/callback). It is also called to rewind a stream when data has already

been sent to the server and needs to be sent again. This may happen when doing

a HTTP PUT or POST with a multi-pass authentication method, or when an

existing HTTP connection is reused too late and the server closes the

connection. The function shall work like fseek(3) or lseek(3) and it gets

SEEK_SET, SEEK_CUR or SEEK_END as argument for \fIorigin\fP, although libcurl

currently only passes SEEK_SET.

\fIuserp\fP is the pointer you set with \fICURLOPT_SEEKDATA(3)\fP.