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134 lines
5.1 KiB
Groff
134 lines
5.1 KiB
Groff
.\" **************************************************************************
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.\" * _ _ ____ _
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.\" * Project ___| | | | _ \| |
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.\" * / __| | | | |_) | |
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.\" * | (__| |_| | _ <| |___
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.\" * \___|\___/|_| \_\_____|
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.\" *
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.\" * Copyright (C) 1998 - 2015, 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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.\" * are also available at http://curl.haxx.se/docs/copyright.html.
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.\" *
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.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
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.\" * copies of the Software, and permit persons to whom the Software is
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.\" * furnished to do so, under the terms of the COPYING file.
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.\" *
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.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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.\" * KIND, either express or implied.
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.\" *
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.\" **************************************************************************
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.\"
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.TH CURLMOPT_PUSHFUNCTION 3 "1 Jun 2015" "libcurl 7.44.0" "curl_multi_setopt options"
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.SH NAME
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CURLMOPT_PUSHFUNCTION \- callback that approves or denies server pushes
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.SH SYNOPSIS
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.nf
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#include <curl/curl.h>
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char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
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char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);
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int curl_push_callback(CURL *parent,
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CURL *easy,
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size_t num_headers,
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struct curl_pushheaders *headers,
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void *userp);
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CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
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curl_push_callback func);
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.fi
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.SH DESCRIPTION
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This callback gets called when a new HTTP/2 stream is being pushed by the
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server (using the PUSH_PROMISE frame). If no push callback is set, all offered
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pushes will be denied automatically.
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.SH CALLBACK DESCRIPTION
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The callback gets its arguments like this:
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\fIparent\fP is the handle of the stream on which this push arrives. The new
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handle has been duphandle()d from the parent, meaning that it has gotten all
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its options inherited. It is then up to the application to alter any options
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if desired.
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\fIeasy\fP is a newly created handle that represents this upcoming transfer.
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\fInum_headers\fP is the number of name+value pairs that was received and can
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be accessed
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\fIheaders\fP is a handle used to access push headers using the accessor
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functions described below. This only accesses and provides the PUSH_PROMISE
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headers, the normal response headers will be provided in the header callback
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as usual.
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\fIuserp\fP is the pointer set with \fICURLMOPT_PUSHDATA(3)\fP
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If the callback returns CURL_PUSH_OK, the 'easy' handle will be added to the
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multi handle, the callback must not do that by itself.
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The callback can access PUSH_PROMISE headers with two accessor
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functions. These functions can only be used from within this callback and they
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can only access the PUSH_PROMISE headers. The normal response headers will be
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passed to the header callback for pushed streams just as for normal streams.
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.IP curl_pushheader_bynum
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Returns the header at index 'num' (or NULL). The returned pointer points to a
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"name:value" string that will be freed when this callback returns.
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.IP curl_pushheader_byname
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Returns the value for the given header name (or NULL). This is a shortcut so
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that the application doesn't have to loop through all headers to find the one
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it is interested in. The data pointed will be freed when this callback
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returns. If more than one header field use the same name, this returns only
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the first one.
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.SH CALLBACK RETURN VALUE
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.IP "CURL_PUSH_OK (0)"
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The application has accepted the stream and it can now start receiving data,
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the ownership of the CURL handle has been taken over by the application.
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.IP "CURL_PUSH_DENY (1)"
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The callback denies the stream and no data for this will reach the
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application, the easy handle will be destroyed by libcurl.
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.IP *
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All other return codes are reserved for future use.
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.SH DEFAULT
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NULL, no callback
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.SH PROTOCOLS
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HTTP(S) (HTTP/2 only)
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.SH EXAMPLE
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.nf
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/* only allow pushes for file names starting with "push-" */
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int push_callback(CURL *parent,
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CURL *easy,
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size_t num_headers,
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struct curl_pushheaders *headers,
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void *userp)
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{
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char *headp;
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int *transfers = (int *)userp;
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FILE *out;
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headp = curl_pushheader_byname(headers, ":path");
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if(headp && !strncmp(headp, "/push-", 6)) {
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fprintf(stderr, "The PATH is %s\\n", headp);
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/* save the push here */
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out = fopen("pushed-stream", "wb");
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/* write to this file */
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curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);
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(*transfers)++; /* one more */
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return CURL_PUSH_OK;
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}
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return CURL_PUSH_DENY;
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}
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curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_callback);
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curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);
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.fi
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.SH AVAILABILITY
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Added in 7.44.0
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.SH RETURN VALUE
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Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
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.SH "SEE ALSO"
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.BR CURLMOPT_PUSHDATA "(3), " CURLMOPT_PIPELINING "(3), " CURLOPT_PIPEWAIT "(3), "
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.BR RFC 7540
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