我有一个存储250KB数据的char数组。我想使用libcurl将这个char数组上传到S3的存储桶中。我知道如何上传文件，并且可以将所有数据写入文件并将文件发送到S3，但这会增加不必要的额外步骤。
长话短说，如何使用libcurl上传内存的特定部分？
最佳答案
我终于找到了解决方案，并且无需使用中间文件就可以成功上传数据。
如果您未声明读取回调函数，则libcurl将使用fread，它要求您输入文件指针作为输入。我发现克服此指针问题的方法是编写一个读回调函数，然后输入void指针作为READDATA的输入。事不宜迟，这里是工作代码。另一个重要说明是您要上传的框架集的大小。
#include <stdio.h>
#include <curl/curl.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
int framesetSize = 10;
void *frameset = "0123456789";
static size_t my_read_callback(void *ptr, size_t size, size_t nmemb, void *dummy)
{
// we will ignore dummy, and pass frameset as a global parameter, along with framesetSize
size_t retcode = 0;
if (framesetSize == 0)
// we have already finished off all the data
return retcode; // initialized to 0
retcode = ( size * nmemb >= framesetSize) ? framesetSize : size * nmemb;
// set return code as the smaller of max allowed data and remaining data
framesetSize -= retcode; // adjust left amount
memcpy(ptr, frameset, retcode);
frameset += retcode ; // advance frameset pointer
return retcode;
}
int main(void)
{
CURL *curl;
CURLcode res;
double speed_upload, total_time;
curl = curl_easy_init();
if(curl) {
/* upload to this place */
curl_easy_setopt(curl, CURLOPT_READFUNCTION, my_read_callback);
curl_easy_setopt(curl, CURLOPT_URL,
"54.231.19.24/{YOURBUCKETNAME}/furkan-1.txt");
/* tell it to "upload" to the URL */
curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
/* set where to read from (on Windows you need to use READFUNCTION too) */
curl_easy_setopt(curl, CURLOPT_READDATA, &frameset);
/* and give the size of the upload (optional) */
curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, framesetSize);
/* enable verbose for easier tracing */
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK) {
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
}
else {
/* now extract transfer info */
curl_easy_getinfo(curl, CURLINFO_SPEED_UPLOAD, &speed_upload);
curl_easy_getinfo(curl, CURLINFO_TOTAL_TIME, &total_time);
fprintf(stderr, "Speed: %.3f bytes/sec during %.3f seconds\n",
speed_upload, total_time);
}
/* always cleanup */
curl_easy_cleanup(curl);
}
return 0;
}