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CURLMOPT_SOCKETFUNCTION.3: clarified
Moved away the callback explanation from curl_multi_socket_action.3 and expanded it somewhat. Closes #4006
This commit is contained in:
Daniel Stenberg
parent
4da5794d81
commit
f0b7b106ff
@ -5,7 +5,7 @@
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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@ -43,15 +43,14 @@ libcurl will test the descriptor internally. It is also permissible to pass
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CURL_SOCKET_TIMEOUT to the \fBsockfd\fP parameter in order to initiate the
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whole process or when a timeout occurs.
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At return, \fBrunning_handles\fP points to the number
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of running easy handles within the multi handle. When this number reaches
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zero, all transfers are complete/done. When you call
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\fIcurl_multi_socket_action(3)\fP on a specific socket and the counter
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decreases by one, it DOES NOT necessarily mean that this exact socket/transfer
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is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out
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which easy handle that completed.
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At return, \fBrunning_handles\fP points to the number of running easy handles
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within the multi handle. When this number reaches zero, all transfers are
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complete/done. When you call \fIcurl_multi_socket_action(3)\fP on a specific
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socket and the counter decreases by one, it DOES NOT necessarily mean that
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this exact socket/transfer is the one that completed. Use
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\fIcurl_multi_info_read(3)\fP to figure out which easy handle that completed.
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The \fIcurl_multi_socket_action(3)\fP functions inform the application about
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The \fIcurl_multi_socket_action(3)\fP function informs the application about
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updates in the socket (file descriptor) status by doing none, one, or multiple
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calls to the socket callback function set with the
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\fICURLMOPT_SOCKETFUNCTION(3)\fP option to \fIcurl_multi_setopt(3)\fP. They
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@ -66,65 +65,6 @@ timeout action: call the \fIcurl_multi_socket_action(3)\fP function with the
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\fIcurl_multi_timeout(3)\fP function to poll the value at any given time, but
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for an event-based system using the callback is far better than relying on
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polling the timeout value.
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.SH "CALLBACK DETAILS"
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The socket \fBcallback\fP function uses a prototype like this
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.nf
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int curl_socket_callback(CURL *easy, /* easy handle */
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curl_socket_t s, /* socket */
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int action, /* see values below */
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void *userp, /* private callback pointer */
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void *socketp); /* private socket pointer,
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\fBNULL\fP if not
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previously assigned with
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\fIcurl_multi_assign(3)\fP */
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.fi
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The callback MUST return 0.
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The \fIeasy\fP argument is a pointer to the easy handle that deals with this
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particular socket. Note that a single handle may work with several sockets
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simultaneously.
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The \fIs\fP argument is the actual socket value as you use it within your
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system.
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The \fIaction\fP argument to the callback has one of five values:
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.RS
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.IP "CURL_POLL_NONE (0)"
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register, not interested in readiness (yet)
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.IP "CURL_POLL_IN (1)"
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register, interested in read readiness
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.IP "CURL_POLL_OUT (2)"
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register, interested in write readiness
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.IP "CURL_POLL_INOUT (3)"
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register, interested in both read and write readiness
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.IP "CURL_POLL_REMOVE (4)"
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unregister
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.RE
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The \fIsocketp\fP argument is a private pointer you have previously set with
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\fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no
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pointer has been set, socketp will be NULL. This argument is of course a
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service to applications that want to keep certain data or structs that are
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strictly associated to the given socket.
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The \fIuserp\fP argument is a private pointer you have previously set with
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\fIcurl_multi_setopt(3)\fP and the \fICURLMOPT_SOCKETDATA(3)\fP option.
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.SH "RETURN VALUE"
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CURLMcode type, general libcurl multi interface error code.
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Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this
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basically means that you should call \fIcurl_multi_socket_action(3)\fP again
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before you wait for more actions on libcurl's sockets. You don't have to do it
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immediately, but the return code means that libcurl may have more data
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available to return or that there may be more data to send off before it is
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"satisfied".
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The return code from this function is for the whole multi stack. Problems
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still might have occurred on individual transfers even when one of these
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functions return OK.
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.SH "TYPICAL USAGE"
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1. Create a multi handle
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@ -5,7 +5,7 @@
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
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.\" *
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.\" * This software is licensed as described in the file COPYING, which
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.\" * you should have received as part of this distribution. The terms
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@ -38,14 +38,24 @@ CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_SOCKETFUNCTION, socket_callb
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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When the \fIcurl_multi_socket_action(3)\fP function runs, it informs the
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When the \fIcurl_multi_socket_action(3)\fP function is called, it informs the
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application about updates in the socket (file descriptor) status by doing
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none, one, or multiple calls to the \fBsocket_callback\fP. The callback gets
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status updates with changes since the previous time the callback was called.
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If the given callback pointer is NULL, no callback will be called. Set the
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callback's \fBuserp\fP argument with \fICURLMOPT_SOCKETDATA(3)\fP. See
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\fIcurl_multi_socket_action(3)\fP for more details on how the callback is used
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and should work.
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none, one, or multiple calls to the \fBsocket_callback\fP. The callback
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function gets status updates with changes since the previous time the callback
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was called. If the given callback pointer is set to NULL, no callback will be
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called.
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.SH "CALLBACK ARGUMENTS"
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\fIeasy\fP identifies the specific transfer for which this update is related.
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\fIs\fP is the specific socket this function invocation concerns. If the
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\fBwhat\fP argument is not CURL_POLL_REMOVE then it holds information about
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what activity on this socket the application is supposed to
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monitor. Subsequent calls to this callback might update the \fBwhat\fP bits
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for a socket that is alredy monitored.
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\fBuserp\fP is set with \fICURLMOPT_SOCKETDATA(3)\fP.
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\fBsocketp\fP is set with \fIcurl_multi_assign(3)\fP or will be NULL.
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The \fBwhat\fP parameter informs the callback on the status of the given
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socket. It can hold one of these values:
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