如何解决“void *”类型的值不能用于初始化“callback_data *”类型的实体
Severity Code Description Project File Line Suppression State
Error (active) E0144 a value of type "void *" cannot be used to initialize an entity of type "callback_data *"
static size_t write_it(char *buff,size_t size,size_t nmemb,void *cb_data)
{
struct callback_data *data = cb_data; // ERROR
size_t written = 0;
if(data->output)
written = fwrite(buff,size,nmemb,data->output);
else
/* listing output */
written = fwrite(buff,stdout);
return written;
}
我使用的是 VS2019,C++ // 完整代码
#include <curl/curl.h>
#include <stdio.h>
struct callback_data {
FILE *output;
};
static long file_is_coming(struct curl_fileinfo *finfo,struct callback_data *data,int remains);
static long file_is_downloaded(struct callback_data *data);
static size_t write_it(char *buff,void *cb_data);
int main(int argc,char **argv)
{
/* curl easy handle */
CURL *handle;
/* help data */
struct callback_data data = { 0 };
/* global initialization */
int rc = curl_global_init(CURL_GLOBAL_ALL);
if(rc)
return rc;
/* initialization of easy handle */
handle = curl_easy_init();
if(!handle) {
curl_global_cleanup();
return CURLE_OUT_OF_MEMORY;
}
/* turn on wildcard matching */
curl_easy_setopt(handle,CURLOPT_WILDCARDMATCH,1L);
/* callback is called before download of concrete file started */
curl_easy_setopt(handle,CURLOPT_CHUNK_BGN_FUNCTION,file_is_coming);
/* callback is called after data from the file have been transferred */
curl_easy_setopt(handle,CURLOPT_CHUNK_END_FUNCTION,file_is_downloaded);
/* this callback will write contents into files */
curl_easy_setopt(handle,CURLOPT_WRITEFUNCTION,write_it);
/* put transfer data into callbacks */
curl_easy_setopt(handle,CURLOPT_CHUNK_DATA,&data);
curl_easy_setopt(handle,CURLOPT_WRITEDATA,&data);
/* curl_easy_setopt(handle,CURLOPT_VERBOSE,1L); */
/* set an URL containing wildcard pattern (only in the last part) */
if(argc == 2)
curl_easy_setopt(handle,CURLOPT_URL,argv[1]);
else
curl_easy_setopt(handle,"ftp://example.com/test/*");
/* and start transfer! */
rc = curl_easy_perform(handle);
curl_easy_cleanup(handle);
curl_global_cleanup();
return rc;
}
static long file_is_coming(struct curl_fileinfo *finfo,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;
}
static long file_is_downloaded(struct callback_data *data)
{
if(data->output) {
printf("DOWNLOADED\n");
fclose(data->output);
data->output = 0x0;
}
return CURL_CHUNK_END_FUNC_OK;
}
static size_t write_it(char *buff,void *cb_data)
{
struct callback_data *data = cb_data; // ERROR
size_t written = 0;
if(data->output)
written = fwrite(buff,data->output);
else
/* listing output */
written = fwrite(buff,stdout);
return written;
}
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