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comparison mupdf-source/thirdparty/curl/docs/libcurl/opts/CURLMOPT_PUSHFUNCTION.3 @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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23 .TH CURLMOPT_PUSHFUNCTION 3 "1 Jun 2015" "libcurl 7.44.0" "curl_multi_setopt options"
24 .SH NAME
25 CURLMOPT_PUSHFUNCTION \- callback that approves or denies server pushes
26 .SH SYNOPSIS
27 .nf
28 #include <curl/curl.h>
29
30 char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
31 char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);
32
33 int curl_push_callback(CURL *parent,
34 CURL *easy,
35 size_t num_headers,
36 struct curl_pushheaders *headers,
37 void *userp);
38
39 CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
40 curl_push_callback func);
41 .fi
42 .SH DESCRIPTION
43 This callback gets called when a new HTTP/2 stream is being pushed by the
44 server (using the PUSH_PROMISE frame). If no push callback is set, all offered
45 pushes will be denied automatically.
46 .SH CALLBACK DESCRIPTION
47 The callback gets its arguments like this:
48
49 \fIparent\fP is the handle of the stream on which this push arrives. The new
50 handle has been duphandle()d from the parent, meaning that it has gotten all
51 its options inherited. It is then up to the application to alter any options
52 if desired.
53
54 \fIeasy\fP is a newly created handle that represents this upcoming transfer.
55
56 \fInum_headers\fP is the number of name+value pairs that was received and can
57 be accessed
58
59 \fIheaders\fP is a handle used to access push headers using the accessor
60 functions described below. This only accesses and provides the PUSH_PROMISE
61 headers, the normal response headers will be provided in the header callback
62 as usual.
63
64 \fIuserp\fP is the pointer set with \fICURLMOPT_PUSHDATA(3)\fP
65
66 If the callback returns CURL_PUSH_OK, the 'easy' handle will be added to the
67 multi handle, the callback must not do that by itself.
68
69 The callback can access PUSH_PROMISE headers with two accessor
70 functions. These functions can only be used from within this callback and they
71 can only access the PUSH_PROMISE headers. The normal response headers will be
72 passed to the header callback for pushed streams just as for normal streams.
73 .IP curl_pushheader_bynum
74 Returns the header at index 'num' (or NULL). The returned pointer points to a
75 "name:value" string that will be freed when this callback returns.
76 .IP curl_pushheader_byname
77 Returns the value for the given header name (or NULL). This is a shortcut so
78 that the application doesn't have to loop through all headers to find the one
79 it is interested in. The data pointed will be freed when this callback
80 returns. If more than one header field use the same name, this returns only
81 the first one.
82 .SH CALLBACK RETURN VALUE
83 .IP "CURL_PUSH_OK (0)"
84 The application has accepted the stream and it can now start receiving data,
85 the ownership of the CURL handle has been taken over by the application.
86 .IP "CURL_PUSH_DENY (1)"
87 The callback denies the stream and no data for this will reach the
88 application, the easy handle will be destroyed by libcurl.
89 .IP *
90 All other return codes are reserved for future use.
91 .SH DEFAULT
92 NULL, no callback
93 .SH PROTOCOLS
94 HTTP(S) (HTTP/2 only)
95 .SH EXAMPLE
96 .nf
97 /* only allow pushes for file names starting with "push-" */
98 int push_callback(CURL *parent,
99 CURL *easy,
100 size_t num_headers,
101 struct curl_pushheaders *headers,
102 void *userp)
103 {
104 char *headp;
105 int *transfers = (int *)userp;
106 FILE *out;
107 headp = curl_pushheader_byname(headers, ":path");
108 if(headp && !strncmp(headp, "/push-", 6)) {
109 fprintf(stderr, "The PATH is %s\\n", headp);
110
111 /* save the push here */
112 out = fopen("pushed-stream", "wb");
113
114 /* write to this file */
115 curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);
116
117 (*transfers)++; /* one more */
118
119 return CURL_PUSH_OK;
120 }
121 return CURL_PUSH_DENY;
122 }
123
124 curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_callback);
125 curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);
126 .fi
127 .SH AVAILABILITY
128 Added in 7.44.0
129 .SH RETURN VALUE
130 Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
131 .SH "SEE ALSO"
132 .BR CURLMOPT_PUSHDATA "(3), " CURLMOPT_PIPELINING "(3), " CURLOPT_PIPEWAIT "(3), "
133 .BR RFC 7540