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Updated: Thursday, June 13, 2019
 
 

CURLMOPT_PUSHFUNCTION (3)

Name

CURLMOPT_PUSHFUNCTION - callback that approves or denies server pushes

Synopsis

#include <curl/curl.h>

char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);

int curl_push_callback(CURL *parent,
CURL *easy,
size_t num_headers,
struct curl_pushheaders *headers,
void *userp);

CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
curl_push_callback func);

Description

CURLMOPT_PUSHFUNCTION(3)   curl_multi_setopt options  CURLMOPT_PUSHFUNCTION(3)



NAME
       CURLMOPT_PUSHFUNCTION - callback that approves or denies server pushes

SYNOPSIS
       #include <curl/curl.h>

       char *curl_pushheader_bynum(struct curl_pushheaders *h, size_t num);
       char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);

       int curl_push_callback(CURL *parent,
                              CURL *easy,
                              size_t num_headers,
                              struct curl_pushheaders *headers,
                              void *userp);

       CURLMcode curl_multi_setopt(CURLM *handle, CURLMOPT_PUSHFUNCTION,
                                   curl_push_callback func);

DESCRIPTION
       This  callback  gets called when a new HTTP/2 stream is being pushed by
       the server (using the PUSH_PROMISE frame). If no push callback is  set,
       all offered pushes will be denied automatically.

CALLBACK DESCRIPTION
       The callback gets its arguments like this:

       parent  is the handle of the stream on which this push arrives. The new
       handle has been duphandle()d from the parent, meaning that it has  got-
       ten  all  its  options  inherited.  It is then up to the application to
       alter any options if desired.

       easy is a newly created handle that represents this upcoming transfer.

       num_headers is the number of name+value pairs that was received and can
       be accessed

       headers  is  a  handle  used  to access push headers using the accessor
       functions  described  below.  This  only  accesses  and  provides   the
       PUSH_PROMISE  headers,  the normal response headers will be provided in
       the header callback as usual.

       userp is the pointer set with CURLMOPT_PUSHDATA(3)

       If the callback returns CURL_PUSH_OK, the 'easy' handle will  be  added
       to the multi handle, the callback must not do that by itself.

       The  callback  can  access PUSH_PROMISE headers with two accessor func-
       tions. These functions can only be used from within this  callback  and
       they  can  only  access  the  PUSH_PROMISE headers. The normal response
       headers will be passed to the header callback for pushed  streams  just
       as for normal streams.

       curl_pushheader_bynum
              Returns  the  header  at  index  'num'  (or  NULL). The returned
              pointer points to a "name:value" string that will be freed  when
              this callback returns.

       curl_pushheader_byname
              Returns the value for the given header name (or NULL). This is a
              shortcut so that the application doesn't have  to  loop  through
              all  headers  to  find  the  one  it  is interested in. The data
              pointed will be freed when this callback returns. If  more  than
              one  header field use the same name, this returns only the first
              one.

CALLBACK RETURN VALUE
       CURL_PUSH_OK (0)
              The application has accepted the stream and  it  can  now  start
              receiving  data, the ownership of the CURL handle has been taken
              over by the application.

       CURL_PUSH_DENY (1)
              The callback denies the stream and no data for this  will  reach
              the application, the easy handle will be destroyed by libcurl.

       *      All other return codes are reserved for future use.

DEFAULT
       NULL, no callback

PROTOCOLS
       HTTP(S) (HTTP/2 only)

EXAMPLE
       /* only allow pushes for file names starting with "push-" */
       int push_callback(CURL *parent,
                         CURL *easy,
                         size_t num_headers,
                         struct curl_pushheaders *headers,
                         void *userp)
       {
         char *headp;
         int *transfers = (int *)userp;
         FILE *out;
         headp = curl_pushheader_byname(headers, ":path");
         if(headp && !strncmp(headp, "/push-", 6)) {
           fprintf(stderr, "The PATH is %s\n", headp);

           /* save the push here */
           out = fopen("pushed-stream", "wb");

           /* write to this file */
           curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);

           (*transfers)++; /* one more */

           return CURL_PUSH_OK;
         }
         return CURL_PUSH_DENY;
       }

       curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_callback);
       curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);

AVAILABILITY
       Added in 7.44.0

RETURN VALUE
       Returns  CURLM_OK  if the option is supported, and CURLM_UNKNOWN_OPTION
       if not.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+------------------+
       |ATTRIBUTE TYPE | ATTRIBUTE VALUE  |
       +---------------+------------------+
       |Availability   | web/curl         |
       +---------------+------------------+
       |Stability      | Uncommitted      |
       +---------------+------------------+
SEE ALSO
       CURLMOPT_PUSHDATA(3),   CURLMOPT_PIPELINING(3),    CURLOPT_PIPEWAIT(3),
       RFC7540



NOTES
       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source    was    downloaded    from    https://github.com/curl/curl/ar-
       chive/curl-7_64_0.zip

       Further information about this software can be found on the open source
       community website at http://curl.haxx.se/.



libcurl 7.44.0                    1 Jun 2015          CURLMOPT_PUSHFUNCTION(3)