NAME¶
TclCurl: - get a URL with FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT,
FILE, LDAP, LDAPS, IMAP, IMAPS, POP, POP3, SMTP, SMTPS and gopher syntax.
SYNOPSIS¶
curl::multiinit
multiHandle addhandle
multiHandle removehandle
multiHandle configure
multiHandle perform
multiHandle active
multiHandle getinfo
multihandle cleanup
multihandle auto
curl::multistrerror errorCode
DESCRIPTION¶
TclCurl's multi interface introduces several new abilities that the easy
interface refuses to offer. They are mainly:
- Enable a "pull" interface. The application that uses TclCurl
decides where and when to get/send data.
- Enable multiple simultaneous transfers in the same thread without making
it complicated for the application.
- Keep Tk GUIs 'alive' while transfers are taking place.
-
Blocking¶
A few areas in the code are still using blocking code, even when used from the
multi interface. While we certainly want and intend for these to get fixed in
the future, you should be aware of the following current restrictions:
- Name resolves on non-windows unless c-ares is used.
- GnuTLS SSL connections.
- GnuTLS SSL connections
- Active FTP connections.
- HTTP proxy CONNECT operations.
- SOCKS proxy handshakes
- file:// transfers.
- TELNET transfers
curl::multiinit¶
This procedure must be the first one to call, it returns a
multiHandle
that you need to use to invoke TclCurl procedures. The init MUST have a
corresponding call to
cleanup when the operation is completed.
RETURN VALUE
multiHandle to use.
multiHandle addhandle ?easyHandle?¶
Each single transfer is built up with an 'easy' handle, the kind we have been
using so far with TclCurl, you must create them and setup the appropriate
options for each of them. Then we add them to the 'multi stack' using the
addhandle command.
If the easy handle is not set to use a shared or global DNS cache, it will be
made to use the DNS cache that is shared between all easy handles within the
multi handle.
When an easy handle has been added to a multi stack, you can not and you must
not use
perform on that handle!
multiHandle is the return code from the
curl::multiinit call.
RETURN VALUE The possible return values are:
- -1
- Handle added to the multi stack, please call perform soon
- 0
- Handle added ok.
- 1
- Invalid multi handle.
- 2
- Invalid 'easy' handle. It could mean that it isn't an easy handle at all,
or possibly that the handle already is in used by this or another multi
handle.
- 3
- Out of memory, you should never get this.
- 4
- You found a bug in TclCurl.
multiHandle removehandle ?easyHandle?¶
When a transfer is done or if we want to stop a transfer before it is completed,
we can use the
removehandle command. Once removed from the multi
handle, we can again use other easy interface functions on it.
Please note that when a single transfer is completed, the easy handle is still
left added to the multi stack. You need to remove it and then close or,
possibly, set new options to it and add it again to the multi handle to start
another transfer.
RETURN VALUE The possible return values are:
- 0
- Handle removed ok.
- 1
- Invalid multi handle.
- 2
- Invalid 'easy' handle.
- 3
- Out of memory, you should never get this.
- 4
- You found a bug in TclCurl.
So far the only options are:
- -pipelining
- Pass a 1 to enable or 0 to disable. Enabling pipelining on a multi handle
will make it attempt to perform HTTP Pipelining as far as possible for
transfers using this handle. This means that if you add a second request
that can use an already existing connection, the second request will be
"piped" on the same connection rather than being executed in
parallel.
- -maxconnects
- Pass a number which will be used as the maximum amount of simultaneously
open connections that TclCurl may cache. Default is 10, and TclCurl will
enlarge the size for each added easy handle to make it fit 4 times the
number of added easy handles.
By setting this option, you can prevent the cache size to grow beyond the
limit set by you. When the cache is full, curl closes the oldest one in
the cache to prevent the number of open connections to increase.
This option is for the multi handle's use only, when using the easy
interface you should instead use it's own maxconnects option.
Adding the easy handles to the multi stack does not start any transfer. Remember
that one of the main ideas with this interface is to let your application
drive. You drive the transfers by invoking
perform. TclCurl will then
transfer data if there is anything available to transfer. It'll use the
callbacks and everything else we have setup in the individual easy handles.
It'll transfer data on all current transfers in the multi stack that are ready
to transfer anything. It may be all, it may be none.
When you call
perform and the amount of running handles is changed from
the previous call (or is less than the amount of easy handles you added to the
multi handle), you know that there is one or more transfers less
"running". You can then call
getinfo to get information about
each individual completed transfer. If an added handle fails very quickly, it
may never be counted as a running handle.
RETURN VALUE If everything goes well, it returns the number of running
handles, '0' if all are done. In case of error, it will return the error code.
This function only returns errors etc regarding the whole multi stack. Problems
still might have occurred on individual transfers even when this function
returns ok.
multiHandle active¶
In order to know if any of the easy handles are ready to transfer data before
invoking
perform you can use the
active command, it will return
the number of transfers currently active.
RETURN VALUE The number of active transfers or '-1' in case of error.
multiHandle getinfo¶
This procedure returns very simple information about the transfers, you can get
more detail information using the
getinfo command on each of the easy
handles.
RETURN VALUE A list with the following elements:
- easyHandle about which the info is about.
- state of the transfer, '1' if it is done.
- exit code of the transfer, '0' if there was no error,...
- Number of messages still in the info queue.
- In case there are no messages in the queue it will return {"" 0
0 0}.
-
multiHandle cleanup¶
This procedure must be the last one to call for a multi stack, it is the
opposite of the
curl::multiinit procedure and must be called with the
same
multiHandle as input as the
curl::multiinit call returned.
multiHandle auto ?-command command?¶
Using this command Tcl's event loop will take care of periodically invoking
perform for you, before using it, you must have already added at least
one easy handle to the multi handle.
The
command option allows you to specify a command to invoke after all
the easy handles have finished their transfers, even though I say it is an
option, the truth is you must use this command to cleanup all the handles,
otherwise the transfered files may not be complete.
This support is still in a very experimental state, it may still change without
warning. Any and all comments are welcome.
You can find a couple of examples at
tests/multi.
curl::multistrerror errorCode¶
This procedure returns a string describing the error code passed in the
argument.
SEE ALSO¶
tclcurl, curl.