Annotation of embedaddon/curl/docs/libcurl/opts/CURLMOPT_PUSHFUNCTION.3, revision 1.1.1.1
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23: .TH CURLMOPT_PUSHFUNCTION 3 "March 23, 2020" "libcurl 7.70.0" "curl_multi_setopt options"
24:
25: .SH NAME
26: CURLMOPT_PUSHFUNCTION \- callback that approves or denies server pushes
27: .SH SYNOPSIS
28: .nf
29: #include <curl/curl.h>
30:
31: char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
32: char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);
33:
34: int curl_push_callback(CURL *parent,
35: CURL *easy,
36: size_t num_headers,
37: struct curl_pushheaders *headers,
38: void *userp);
39:
40: CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
41: curl_push_callback func);
42: .fi
43: .SH DESCRIPTION
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:
49:
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
53: if desired.
54:
55: \fIeasy\fP is a newly created handle that represents this upcoming transfer.
56:
57: \fInum_headers\fP is the number of name+value pairs that was received and can
58: be accessed
59:
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
63: as usual.
64:
65: \fIuserp\fP is the pointer set with \fICURLMOPT_PUSHDATA(3)\fP
66:
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.
69:
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
82: the first one.
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.
90: .IP *
91: All other return codes are reserved for future use.
92: .SH DEFAULT
93: NULL, no callback
94: .SH PROTOCOLS
95: HTTP(S) (HTTP/2 only)
96: .SH EXAMPLE
97: .nf
98: /* only allow pushes for file names starting with "push-" */
99: int push_callback(CURL *parent,
100: CURL *easy,
101: size_t num_headers,
102: struct curl_pushheaders *headers,
103: void *userp)
104: {
105: char *headp;
106: int *transfers = (int *)userp;
107: FILE *out;
108: headp = curl_pushheader_byname(headers, ":path");
109: if(headp && !strncmp(headp, "/push-", 6)) {
110: fprintf(stderr, "The PATH is %s\\n", headp);
111:
112: /* save the push here */
113: out = fopen("pushed-stream", "wb");
114:
115: /* write to this file */
116: curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);
117:
118: (*transfers)++; /* one more */
119:
120: return CURL_PUSH_OK;
121: }
122: return CURL_PUSH_DENY;
123: }
124:
125: curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_callback);
126: curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);
127: .fi
128: .SH AVAILABILITY
129: Added in 7.44.0
130: .SH RETURN VALUE
131: Returns CURLM_OK if the option is supported, and CURLM_UNKNOWN_OPTION if not.
132: .SH "SEE ALSO"
133: .BR CURLMOPT_PUSHDATA "(3), " CURLMOPT_PIPELINING "(3), " CURLOPT_PIPEWAIT "(3), "
134: .BR RFC 7540
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