CURLOPT_UPLOAD_BUFFERSIZE: set upload buffer size

This is step 3 of #2888.

Fixes #2888
Closes #2896

docs/libcurl/curl_easy_setopt.3

@@ -421,6 +421,8 @@ Size of file to send. \fICURLOPT_INFILESIZE(3)\fP
 Size of file to send. \fICURLOPT_INFILESIZE_LARGE(3)\fP
 .IP CURLOPT_UPLOAD
 Upload data. See \fICURLOPT_UPLOAD(3)\fP
+.IP CURLOPT_UPLOAD_BUFFERSIZE
+Set upload buffer size. See \fICURLOPT_UPLOAD_BUFFERSIZE(3)\fP
 .IP CURLOPT_MIMEPOST
 Post/send MIME data. See \fICURLOPT_MIMEPOST(3)\fP
 .IP CURLOPT_MAXFILESIZE

docs/libcurl/opts/CURLOPT_UPLOAD_BUFFERSIZE.3

@@ -0,0 +1,69 @@
+.\" **************************************************************************
+.\" *                                  _   _ ____  _
+.\" *  Project                     ___| | | |  _ \| |
+.\" *                             / __| | | | |_) | |
+.\" *                            | (__| |_| |  _ <| |___
+.\" *                             \___|\___/|_| \_\_____|
+.\" *
+.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" *
+.\" * This software is licensed as described in the file COPYING, which
+.\" * you should have received as part of this distribution. The terms
+.\" * are also available at https://curl.haxx.se/docs/copyright.html.
+.\" *
+.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+.\" * copies of the Software, and permit persons to whom the Software is
+.\" * furnished to do so, under the terms of the COPYING file.
+.\" *
+.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+.\" * KIND, either express or implied.
+.\" *
+.\" **************************************************************************
+.\"
+.TH CURLOPT_UPLOAD_BUFFERSIZE 3 "18 Aug 2018" "libcurl 7.62.0" "curl_easy_setopt options"
+.SH NAME
+CURLOPT_UPLOAD_BUFFERSIZE \- set preferred upload buffer size
+.SH SYNOPSIS
+#include <curl/curl.h>
+
+CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPLOAD_BUFFERSIZE, long size);
+.SH DESCRIPTION
+Pass a long specifying your preferred \fIsize\fP (in bytes) for the upload
+buffer in libcurl. It makes libcurl uses a larger buffer that gets passed to
+the next layer in the stack to get sent off. In some setups and for some
+protocols, there's a huge performance benefit of having a larger upload
+buffer.
+
+This is just treated as a request, not an order. You cannot be guaranteed to
+actually get the given size.
+
+The upload buffer size is by default 64 kilobytes. The maximum buffer size
+allowed to be set is 2 megabytes. The minimum buffer size allowed to be set is
+16 kilobytes.
+
+Since curl 7.61.1 the upload buffer is allocated on-demand - so if the handle
+isn't used for upload, this buffer will not be allocated at all.
+.SH DEFAULT
+64 kB
+.SH PROTOCOLS
+All
+.SH EXAMPLE
+.nf
+CURL *curl = curl_easy_init();
+if(curl) {
+  curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/foo.bin");
+
+  /* ask libcurl to allocate a larger upload buffer */
+  curl_easy_setopt(curl, CURLOPT_UPLOAD_BUFFERSIZE, 120000L);
+
+  ret = curl_easy_perform(curl);
+
+  curl_easy_cleanup(curl);
+}
+.fi
+.SH AVAILABILITY
+Added in 7.62.0.
+.SH RETURN VALUE
+Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
+.SH "SEE ALSO"
+.BR CURLOPT_BUFFERSIZE "(3), " CURLOPT_READFUNCTION "(3), "

docs/libcurl/opts/Makefile.inc

@@ -327,6 +327,7 @@ man_MANS =                                      \
   CURLOPT_UNIX_SOCKET_PATH.3                    \
   CURLOPT_UNRESTRICTED_AUTH.3                   \
   CURLOPT_UPLOAD.3                              \
+  CURLOPT_UPLOAD_BUFFERSIZE.3                   \
   CURLOPT_URL.3                                 \
   CURLOPT_USERAGENT.3                           \
   CURLOPT_USERNAME.3                            \

docs/libcurl/symbols-in-versions

@@ -616,6 +616,7 @@ CURLOPT_TRANSFER_ENCODING       7.21.6
 CURLOPT_UNIX_SOCKET_PATH        7.40.0
 CURLOPT_UNRESTRICTED_AUTH       7.10.4
 CURLOPT_UPLOAD                  7.1
+CURLOPT_UPLOAD_BUFFERSIZE       7.62.0
 CURLOPT_URL                     7.1
 CURLOPT_USERAGENT               7.1
 CURLOPT_USERNAME                7.19.1