//採用CURLOPT_RESUME_FROM_LARGE 實現檔案斷點續傳功能
#include <stdlib.h>
#include <stdio.h>
#include <sys/stat.h>
 
#include <curl/curl.h>
//這個函式為CURLOPT_HEADERFUNCTION引數構造
/* 從http頭部獲取檔案size*/
size_t getcontentlengthfunc(void *ptr, size_t size, size_t nmemb, void *stream) {
       int r;
       long len = 0;
 
       /* _snscanf() is Win32 specific */
       // r = _snscanf(ptr, size * nmemb, "Content-Length: %ld\n", &len);
 r = sscanf(ptr, "Content-Length: %ld\n", &len);
       if (r) /* Microsoft: we don't read the specs */
              *((long *) stream) = len;
 
       return size * nmemb;
}
 
/* 儲存下載檔案 */
size_t wirtefunc(void *ptr, size_t size, size_t nmemb, void *stream)
{
        return fwrite(ptr, size, nmemb, stream);
}
 
/*讀取上傳檔案 */
size_t readfunc(void *ptr, size_t size, size_t nmemb, void *stream)
{
       FILE *f = stream;
       size_t n;
 
       if (ferror(f))
              return CURL_READFUNC_ABORT;
 
       n = fread(ptr, size, nmemb, f) * size;
 
       return n;
}
 
// 下載 或者上傳檔案函式
int download(CURL *curlhandle, const char * remotepath, const char * localpath,
           long timeout, long tries)
{
       FILE *f;
       curl_off_t local_file_len = -1 ;
       long filesize =0 ;
       
       CURLcode r = CURLE_GOT_NOTHING;
       int c;
  struct stat file_info;
  int use_resume = 0;
  /* 得到本地檔案大小 */
  //if(access(localpath,F_OK) ==0)
  
    if(stat(localpath, &file_info) == 0) 
     {
        local_file_len =  file_info.st_size;
        use_resume  = 1;
      }
  //採用追加方式開啟檔案，便於實現檔案斷點續傳工作
       f = fopen(localpath, "ab+"); 
       if (f == NULL) {
              perror(NULL);
              return 0;
       }
 
       //curl_easy_setopt(curlhandle, CURLOPT_UPLOAD, 1L);
 
       curl_easy_setopt(curlhandle, CURLOPT_URL, remotepath);
 
              curl_easy_setopt(curlhandle, CURLOPT_CONNECTTIMEOUT, timeout);  // 設定連線超時，單位秒
       //設定http 頭部處理函式
       curl_easy_setopt(curlhandle, CURLOPT_HEADERFUNCTION, getcontentlengthfunc);
       curl_easy_setopt(curlhandle, CURLOPT_HEADERDATA, &filesize);
 // 設定檔案續傳的位置給libcurl
       curl_easy_setopt(curlhandle, CURLOPT_RESUME_FROM_LARGE, use_resume?local_file_len:0);
 
       curl_easy_setopt(curlhandle, CURLOPT_WRITEDATA, f);
       curl_easy_setopt(curlhandle, CURLOPT_WRITEFUNCTION, wirtefunc);
 
       //curl_easy_setopt(curlhandle, CURLOPT_READFUNCTION, readfunc);
       //curl_easy_setopt(curlhandle, CURLOPT_READDATA, f);
       curl_easy_setopt(curlhandle, CURLOPT_NOPROGRESS, 1L);
       curl_easy_setopt(curlhandle, CURLOPT_VERBOSE, 1L);
  
  
  r = curl_easy_perform(curlhandle);
       
 
       fclose(f);
 
       if (r == CURLE_OK)
              return 1;
       else {
              fprintf(stderr, "%s\n", curl_easy_strerror(r));
              return 0;
       }
}
 
int main(int c, char **argv) {
       CURL *curlhandle = NULL;
 
       curl_global_init(CURL_GLOBAL_ALL);
       curlhandle = curl_easy_init();
 
       //download(curlhandle, "ftp://user:
 
[email protected]/path/file", "C:\\file", 0, 3);
  download(curlhandle , "http://software.sky-union.cn/index.asp","/work/index.asp",1,3);
       curl_easy_cleanup(curlhandle);
       curl_global_cleanup();
 
       return 0;
}