This commit adds curl_multi_wakeup() which was previously in the TODO
list under the curl_multi_unblock name.
On some platforms and with some configurations this feature might not be
available or can fail, in these cases a new error code
(CURLM_WAKEUP_FAILURE) is returned from curl_multi_wakeup().
Fixes#4418Closes#4608
Repeatedly we see problems where using curl_multi_wait() is difficult or
just awkward because if it has no file descriptor to wait for
internally, it returns immediately and leaves it to the caller to wait
for a small amount of time in order to avoid occasional busy-looping.
This is often missed or misunderstood, leading to underperforming
applications.
This change introduces curl_multi_poll() as a replacement drop-in
function that accepts the exact same set of arguments. This function
works identically to curl_multi_wait() - EXCEPT - for the case when
there's nothing to wait for internally, as then this function will by
itself wait for a "suitable" short time before it returns. This
effectiely avoids all risks of busy-looping and should also make it less
likely that apps "over-wait".
This also changes the curl tool to use this funtion internally when
doing parallel transfers and changes curl_easy_perform() to use it
internally.
Closes#4163
Add functionality so that protocols can do custom keepalive on their
connections, when an external API function is called.
Add docs for the new options in 7.62.0
Closes#1641
Let's add a compile time safe API to select an SSL backend. This
function needs to be called *before* curl_global_init(), and can be
called only once.
Side note: we do not explicitly test that it is called before
curl_global_init(), but we do verify that it is not called multiple times
(even implicitly).
If SSL is used before the function was called, it will use whatever the
CURL_SSL_BACKEND environment variable says (or default to the first
available SSL backend), and if a subsequent call to
curl_global_sslset() disagrees with the previous choice, it will fail
with CURLSSLSET_TOO_LATE.
The function also accepts an "avail" parameter to point to a (read-only)
NULL-terminated list of available backends. This comes in real handy if
an application wants to let the user choose between whatever SSL backends
the currently available libcurl has to offer: simply call
curl_global_sslset(-1, NULL, &avail);
which will return CURLSSLSET_UNKNOWN_BACKEND and populate the avail
variable to point to the relevant information to present to the user.
Just like with the HTTP/2 push functions, we have to add the function
declaration of curl_global_sslset() function to the header file
*multi.h* because VMS and OS/400 require a stable order of functions
declared in include/curl/*.h (where the header files are sorted
alphabetically). This looks a bit funny, but it cannot be helped.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
