Manpages - CURLOPT_CHUNK_BGN_FUNCTION.3

CURLOPT_CHUNK_BGN_FUNCTION - callback before a transfer with FTP wildcardmatch

  #include <curl/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);

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.

NULL

FTP

  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);
  }

This was added in 7.21.0

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

*CURLOPT_CHUNK_END_FUNCTION*(3), *CURLOPT_WILDCARDMATCH*(3),