PiCloud and REST API with C client

by Amit

I was playing around with PiCloud’s REST API and had a bit of fun writing a C client for it. Now, why C? Well, because one of the reasons they provide a REST API is for your non-Python programs to easily access your Python code on PiCloud.

What I did is simple: I published the square_func using PiCloud’s documentation. Then I used libcurl’s C Interface to replicate the curl statements provided in the documentation. I have
written the client in two parts: client1.c and client2.c. client1.c invokes the published function, hence gets the Job ID. client2.c then uses this jobID to get the result. Here are the source codes:

/*client1.c*/
/* This part of the client invokes the REST API of
   PiCloud and retrieves the Job ID
   http://docs.picloud.com/rest.html#invoking-functions
*/

#include <stdio.h>
#include <curl/curl.h>

int main(void)
{
  CURL *curl;

  /* Make sure you set this appropriately*/
  char *url="https://api.picloud.com/r/3222/square_func/";
  CURLcode res;
  
  curl = curl_easy_init();
  if(curl) {
    /* First set the URL that is about to receive our POST. This URL can
       just as well be a https:// URL if that is what should receive the
       data. */
    curl_easy_setopt(curl, CURLOPT_URL, url);
    /* Specify the user/pass */
    curl_easy_setopt(curl,CURLOPT_USERPWD,"apikey:secretkey");
    
    /* Now specify the POST data */
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "x=5");
    
    /* For HTTPS */
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);

    /* Perform the request, res will get the return code */
    res = curl_easy_perform(curl);
    printf("\nResult of Operation:: %d\n", res);

    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  return 0;
}

/*client2.c*/
/* This part of the client retrieves the result given the
   job ID as the argument*/
#include <stdio.h>
#include <stdlib.h>
#include <curl/curl.h>

int main(int argc, char *argv[])
{
  CURL *curl;
  char url[80];
  CURLcode res;

  if (argc==1)
    {
      printf("Usage: ./client2 <jid>\n");
      exit(0);
    }

  
  strcpy(url,"https://api.picloud.com/job/result/?jid=");
  strcat(url,argv[1]);

  

  curl = curl_easy_init();
  if(curl) {
    /* First set the URL that is about to receive our POST. This URL can
       just as well be a https:// URL if that is what should receive the
       data. */
    curl_easy_setopt(curl, CURLOPT_URL, url);
    
    /* Specify the user/pass */
    curl_easy_setopt(curl,CURLOPT_USERPWD,"apikey:secretkey");
    
    /* for HTTPS */
    curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
    
    /* Perform the request, res will get the return code */
    res = curl_easy_perform(curl);
    printf("\nResult of Operation:: %d\n", res);

    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  return 0;
}

Working

[gene@zion tmp]$ ./client1
{“jid”: 57, “version”: “0.1”}
Result of Operation:: 0

[gene@zion tmp]$ ./client2 57
{“version”: “0.1”, “result”: 25}
Result of Operation:: 0

Hope it works for you. PiCloud is fun!

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