#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(" 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), "