quickjs-tart

quickjs-based runtime for wallet-core logic
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CURLOPT_TRAILERFUNCTION.md (3040B)

      1 ---
      2 c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
      3 SPDX-License-Identifier: curl
      4 Title: CURLOPT_TRAILERFUNCTION
      5 Section: 3
      6 Source: libcurl
      7 See-also:
      8   - CURLOPT_TRAILERDATA (3)
      9   - CURLOPT_WRITEFUNCTION (3)
     10 Protocol:
     11   - HTTP
     12 Added-in: 7.64.0
     13 ---
     14 
     15 # NAME
     16 
     17 CURLOPT_TRAILERFUNCTION - callback for sending trailing headers
     18 
     19 # SYNOPSIS
     20 
     21 ~~~c
     22 #include <curl.h>
     23 
     24 int curl_trailer_callback(struct curl_slist ** list, void *userdata);
     25 
     26 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERFUNCTION,
     27                           curl_trailer_callback *func);
     28 ~~~
     29 
     30 # DESCRIPTION
     31 
     32 Pass a pointer to a callback function.
     33 
     34 This callback function is called once right before sending the final CR LF in
     35 an HTTP chunked transfer to fill a list of trailing headers to be sent before
     36 finishing the HTTP transfer.
     37 
     38 You can set the userdata argument with the CURLOPT_TRAILERDATA(3)
     39 option.
     40 
     41 The trailing headers included in the linked list must not be CRLF-terminated,
     42 because libcurl adds the appropriate line termination characters after each
     43 header item.
     44 
     45 If you use curl_slist_append(3) to add trailing headers to the *curl_slist*
     46 then libcurl duplicates the strings, and frees the *curl_slist* once the
     47 trailers have been sent.
     48 
     49 If one of the trailing header fields is not formatted correctly it is ignored
     50 and an info message is emitted.
     51 
     52 The return value can either be **CURL_TRAILERFUNC_OK** or
     53 **CURL_TRAILERFUNC_ABORT** which would respectively instruct libcurl to
     54 either continue with sending the trailers or to abort the request.
     55 
     56 If you set this option to NULL, then the transfer proceeds as usual
     57 without any interruptions.
     58 
     59 # DEFAULT
     60 
     61 NULL
     62 
     63 # %PROTOCOLS%
     64 
     65 # EXAMPLE
     66 ~~~c
     67 extern size_t read_cb(char *ptr, size_t size,
     68                       size_t nmemb, void *userdata);
     69 
     70 static int trailer_cb(struct curl_slist **tr, void *data)
     71 {
     72   /* libcurl frees the list */
     73   *tr = curl_slist_append(*tr, "My-super-awesome-trailer: trailer-stuff");
     74   return CURL_TRAILERFUNC_OK;
     75 }
     76 
     77 int main(void)
     78 {
     79   CURL *curl = curl_easy_init();
     80   if(curl) {
     81     CURLcode res;
     82 
     83     /* Set the URL of the request */
     84     curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
     85     /* Now set it as a put */
     86     curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
     87 
     88     /* Assuming we have a function that returns the data to be pushed
     89        Let that function be read_cb */
     90     curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_cb);
     91 
     92     struct curl_slist *headers = NULL;
     93     headers = curl_slist_append(headers, "Trailer: My-super-awesome-trailer");
     94     res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
     95 
     96     /* Set the trailers filling callback */
     97     curl_easy_setopt(curl, CURLOPT_TRAILERFUNCTION, trailer_cb);
     98 
     99     /* Perform the transfer */
    100     res = curl_easy_perform(curl);
    101 
    102     curl_easy_cleanup(curl);
    103 
    104     curl_slist_free_all(headers);
    105   }
    106 }
    107 ~~~
    108 
    109 # %AVAILABILITY%
    110 
    111 # RETURN VALUE
    112 
    113 curl_easy_setopt(3) returns a CURLcode indicating success or error.
    114 
    115 CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
    116 libcurl-errors(3).