GNURLOPT_CHUNK_BGN_FUNCTION(3)

✨ NAME ✨

okay bestie, welcome to the page for GNURLOPT_CHUNK_BGN_FUNCTION(3) — yes, the curl_easy_setopt options manual name is folded right in here. short version: CURLOPT_CHUNK_BGN_FUNCTION is the callback before a transfer with FTP wildcardmatch. 💅

🎀 SYNOPSIS 🎀

#include <gnurl/curl.h>

struct curl_fileinfo {
  char *filename;
  curlfiletype filetype;
  time_t time;   /* always zero! */
  unsigned int perm;
  int uid;
  int gid;
  curl_off_t size;
  long int hardlinks;

  struct {
    /* If some of these fields is not NULL, it is a pointer to b_data. */
    char *time;
    char *perm;
    char *user;
    char *group;
    char *target; /* pointer to the target filename of a symlink */
  } strings;

  unsigned int flags;

  /* used internally */
  char *b_data;
  size_t b_size;
  size_t b_used;
};

long chunk_bgn_callback(const void *transfer_info, void *ptr,
                        int remains);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_CHUNK_BGN_FUNCTION,
                          chunk_bgn_callback);

🌸 DESCRIPTION 🌸

Pass a pointer to your callback function, and it should match the prototype shown above, fr fr. This callback function gets called by libcurl before a part of the stream is going to be transferred — if the transfer supports chunks, that is. 🫶

The transfer_info pointer will point to a struct curl_fileinfo with details about the file that is about to get transferred. yes, all the file lore is in there. ✨

This callback makes sense only when using the CURLOPT_WILDCARDMATCH(3) option for now. no cap.

The target of transfer_info parameter is a "feature depended" structure. For the FTP wildcard download, the target is curl_fileinfo structure (see gnurl/curl.h). The parameter ptr is a pointer given by CURLOPT_CHUNK_DATA(3). The parameter remains contains number of chunks remaining per the transfer. If the feature is not available, the parameter has zero value. 💀

Return one of these, bestie:

• CURL_CHUNK_BGN_FUNC_OK — everything is fine, slay.
• CURL_CHUNK_BGN_FUNC_SKIP — you want to skip the concrete chunk.
• CURL_CHUNK_BGN_FUNC_FAIL — tell libcurl to stop if some error occurred.

💤 DEFAULT 💤

NULL

🌈 PROTOCOLS 🌈

FTP

🧚 EXAMPLE 🧚

this one is a whole little callback moment. it prints stuff, checks filetype, skips files >= 50B, opens output, and wires the callbacks in main. no rewrites, just exact code and vibes:

static long file_is_coming(struct curl_fileinfo *finfo,
                           struct callback_data *data,
                           int remains)
{
  printf("%3d %40s %10luB ", remains, finfo->filename,
         (unsigned long)finfo->size);

  switch(finfo->filetype) {
  case CURLFILETYPE_DIRECTORY:
    printf(" DIR\n");
    break;
  case CURLFILETYPE_FILE:
    printf("FILE ");
    break;
  default:
    printf("OTHER\n");
    break;
  }

  if(finfo->filetype == CURLFILETYPE_FILE) {
    /* do not transfer files >= 50B */
    if(finfo->size > 50) {
      printf("SKIPPED\n");
      return CURL_CHUNK_BGN_FUNC_SKIP;
    }

    data->output = fopen(finfo->filename, "wb");
    if(!data->output) {
      return CURL_CHUNK_BGN_FUNC_FAIL;
    }
  }

  return CURL_CHUNK_BGN_FUNC_OK;
}

int main()
{
  /* data for callback */
  struct callback_data callback_info;

  /* callback is called before download of concrete file started */
  curl_easy_setopt(curl, CURLOPT_CHUNK_BGN_FUNCTION, file_is_coming);
  curl_easy_setopt(curl, CURLOPT_CHUNK_DATA, &callback_info);
}

🦋 AVAILABILITY 🦋

This was added in 7.21.0.

👑 RETURN VALUE 👑

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

🫶 SEE ALSO 🫶

• CURLOPT_CHUNK_END_FUNCTION(3)
• CURLOPT_WILDCARDMATCH(3)

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that's the whole page, bestie — sourced from libcurl 7.37.0, dated 19 Jun 2014, and filed under GNURLOPT_CHUNK_BGN_FUNCTION(3). periodt. 💖