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23 .TH CURLMOPT_PUSHFUNCTION 3 "February 03, 2016" "libcurl 7.59.0" "curl_multi_setopt options"
26 CURLMOPT_PUSHFUNCTION \- callback that approves or denies server pushes
29 #include <curl/curl.h>
31 char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
32 char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);
34 int curl_push_callback(CURL *parent,
37 struct curl_pushheaders *headers,
40 CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
41 curl_push_callback func);
44 This callback gets called when a new HTTP/2 stream is being pushed by the
45 server (using the PUSH_PROMISE frame). If no push callback is set, all offered
46 pushes will be denied automatically.
47 .SH CALLBACK DESCRIPTION
48 The callback gets its arguments like this:
50 \fIparent\fP is the handle of the stream on which this push arrives. The new
51 handle has been duphandle()d from the parent, meaning that it has gotten all
52 its options inherited. It is then up to the application to alter any options
55 \fIeasy\fP is a newly created handle that represents this upcoming transfer.
57 \fInum_headers\fP is the number of name+value pairs that was received and can
60 \fIheaders\fP is a handle used to access push headers using the accessor
61 functions described below. This only accesses and provides the PUSH_PROMISE
62 headers, the normal response headers will be provided in the header callback
65 \fIuserp\fP is the pointer set with \fICURLMOPT_PUSHDATA(3)\fP
67 If the callback returns CURL_PUSH_OK, the 'easy' handle will be added to the
68 multi handle, the callback must not do that by itself.
70 The callback can access PUSH_PROMISE headers with two accessor
71 functions. These functions can only be used from within this callback and they
72 can only access the PUSH_PROMISE headers. The normal response headers will be
73 passed to the header callback for pushed streams just as for normal streams.
74 .IP curl_pushheader_bynum
75 Returns the header at index 'num' (or NULL). The returned pointer points to a
76 "name:value" string that will be freed when this callback returns.
77 .IP curl_pushheader_byname
78 Returns the value for the given header name (or NULL). This is a shortcut so
79 that the application doesn't have to loop through all headers to find the one
80 it is interested in. The data pointed will be freed when this callback
81 returns. If more than one header field use the same name, this returns only
83 .SH CALLBACK RETURN VALUE
84 .IP "CURL_PUSH_OK (0)"
85 The application has accepted the stream and it can now start receiving data,
86 the ownership of the CURL handle has been taken over by the application.
87 .IP "CURL_PUSH_DENY (1)"
88 The callback denies the stream and no data for this will reach the
89 application, the easy handle will be destroyed by libcurl.
91 All other return codes are reserved for future use.
98 /* only allow pushes for file names starting with "push-" */
99 int push_callback(CURL *parent,
102 struct curl_pushheaders *headers,
106 int *transfers = (int *)userp;
108 headp = curl_pushheader_byname(headers, ":path");
109 if(headp && !strncmp(headp, "/push-", 6)) {
110 fprintf(stderr, "The PATH is %s\\n", headp);
112 /* save the push here */
113 out = fopen("pushed-stream", "wb");
115 /* write to this file */
116 curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);
118 (*transfers)++; /* one more */
122 return CURL_PUSH_DENY;
125 curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_callback);
126 curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);
131 Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
133 .BR CURLMOPT_PUSHDATA "(3), " CURLMOPT_PIPELINING "(3), " CURLOPT_PIPEWAIT "(3), "