CURLOPT_CHUNK_BGN_FUNCTION man page

CURLOPT_CHUNK_BGN_FUNCTION — callback before a transfer with FTP wildcardmatch

Synopsis

#include <curl/curl.h>

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, which should match the prototype shown above.

This callback function gets called by libcurl before a part of the stream is going to be transferred (if the transfer supports chunks).

The transfer_info pointer will point to a struct curl_fileinfo with details about the file that is about to get transferred.

This callback makes sense only when using the CURLOPT_WILDCARDMATCH(3) option for now.

The target of transfer_info parameter is a "feature depended" structure. For the FTP wildcard download, the target is curl_fileinfo structure (see curl/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 CURL_CHUNK_BGN_FUNC_OK if everything is fine, CURL_CHUNK_BGN_FUNC_SKIP if you want to skip the concrete chunk or CURL_CHUNK_BGN_FUNC_FAIL to tell libcurl to stop if some error occurred.

Default

NULL

Protocols

FTP

Example

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(" DIR0);
    break;
  case CURLFILETYPE_FILE:
    printf("FILE ");
    break;
  default:
    printf("OTHER0);
    break;
  }

  if(finfo->filetype == CURLFILETYPE_FILE) {
    /* do not transfer files >= 50B */
    if(finfo->size > 50) {
      printf("SKIPPED0);
      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),

Referenced By

curl_easy_setopt(3), CURLOPT_CHUNK_DATA(3), CURLOPT_CHUNK_END_FUNCTION(3).

May 31, 2017 libcurl 7.57.0 curl_easy_setopt options