Libcurl Image Upload Post from memory - c++

Question

I am writing a program that pulls an image from a restful server that is delivered in JSON, parsed, processed and sent back to the server. I am having issues on sending the image back. Currently I have it stored in a string and am trying to use CURLFORM_BUFFER to send it back. I have confirmed that the image is in the string by writing it to file. No problems there. My current code is below. I am currently experiencing a seg fault 11 on the post. My code is below.
#include <stdio.h>
#include <curl/curl.h>
#include <string.h>
#include <stdlib.h>
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "dist/jsoncpp.cpp"
#include "dist/json/json.h"
using namespace std;
static size_t write_data(void *contents, size_t size, size_t nmemb,
void *userp)
{
((std::string*)userp)->append((char*)contents, size * nmemb);
return size * nmemb;
}
void uploadImage(std::string readBuffer){
CURL *curl;
CURLcode res;
struct curl_httppost *formpost=NULL;
struct curl_httppost *lastptr=NULL;
struct curl_slist *headerlist=NULL;
static const char buf[] = "Expect:";
curl_global_init(CURL_GLOBAL_ALL);
printf("Image length: %d\n\n", readBuffer.length());
CURLFORMcode code = curl_formadd(&formpost,
&lastptr,
CURLFORM_COPYNAME, "processedImage",
CURLFORM_BUFFER, "image.jpg",
CURLFORM_BUFFERPTR, readBuffer,
//CURLFORM_BUFFERLENGTH, readBuffer.length(),
CURLFORM_END);
if(code != 0){
printf("Something went wrong in formadd.\n");
}
curl = curl_easy_init();
/* initialize custom header list (stating that Expect: 100-continue is not
wanted */
headerlist = curl_slist_append(headerlist, buf);
if(curl) {
/* what URL that receives this POST */
curl_easy_setopt(curl, CURLOPT_URL, "uploadProcessedImageURL");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);
curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
//curl_easy_setopt(curl, CURLOPT_POSTFIELDS, formpost);
/* Perform the request, res will get the return code */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* always cleanup */
curl_easy_cleanup(curl);
/* then cleanup the formpost chain */
curl_formfree(formpost);
/* free slist */
curl_slist_free_all (headerlist);
}
}
int main(void)
{
CURL *curl;
CURLcode res;
const cv::_InputArray data;
std::string readBuffer;
char *url = "requestImageFileURL";
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &readBuffer);
readBuffer.clear();
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
//printf("%s\n\n", readBuffer.c_str());
printf("Image retrieved.\n");
Json::Value values;
Json::Reader reader;
reader.parse(readBuffer, values);
Json::Value imageArray = values.get("userUploadedImage","default
value");
Json::Value idNumber = values.get("id","default value");
Json::FastWriter fastWriter;
std::string output = fastWriter.write(imageArray);
//cout << output << endl;
std::vector<char> vectordata(output.begin(), output.end());
//for (auto i = vectordata.begin(); i != vectordata.end(); ++i)
//std::cout << *i;
cv::Mat data_mat(vectordata,true);
cv::Mat image(cv::imdecode(data_mat, 1));
std::cout<<"Height: " << image.rows <<" Width: "<<image.cols<<endl;
//cv::namedWindow( "Display Image", CV_WINDOW_AUTOSIZE );
//cv::imshow( "Display Image",image);
//cv::waitKey(0);
uploadImage(readBuffer);
return 0;
}