Neo4j example in C code

test_neo4j.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <curl/curl.h>

#include <cjson/cJSON.h>


struct MemoryStruct {
  char *memory;
  size_t size;
};
 
static size_t WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
  size_t realsize = size * nmemb;
  struct MemoryStruct *mem = (struct MemoryStruct *)userp;
 
  char *ptr = realloc(mem->memory, mem->size + realsize + 1);
  if(ptr == NULL) {
    /* out of memory! */ 
    printf("not enough memory (realloc returned NULL)\n");
    return 0;
  }
 
  mem->memory = ptr;
  memcpy(&(mem->memory[mem->size]), contents, realsize);
  mem->size += realsize;
  mem->memory[mem->size] = 0;
 
  return realsize;
}

int main(void)
{
    char *url = "http://localhost:7474/db/data/transaction/commit";
    char *neo4j_user  = "neo4j";
    char *neo4j_admin  = "admin";
    char *post_body = "{\"statements\":[{\"statement\":\"match (n) return toString(id(n)) AS txt LIMIT 10\"}]}";
    
    CURL *curl;
    CURLcode res;
    
    struct MemoryStruct chunk;
    chunk.memory = malloc(1);  /* will be grown as needed by the realloc above */ 
    chunk.size = 0;    /* no data at this point */ 
    
    curl_global_init(CURL_GLOBAL_ALL);
    curl = curl_easy_init();                                                                                                                                                                                                                                                           
    if (curl)
    {   
        /* First set the URL that is about to receive our POST. */ 
        curl_easy_setopt(curl, CURLOPT_URL, url);
        
        /* Now specify we want to POST data */ 
        curl_easy_setopt(curl, CURLOPT_POST, 1L);
        
        /* set user name and password for the authentication */ 
        curl_easy_setopt(curl, CURLOPT_USERPWD, "neo4j:admin");
        
        /* The request is a JSON document */ 
        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Accept: application/json");
        headers = curl_slist_append(headers, "Content-Type: application/json");
        headers = curl_slist_append(headers, "charsets: utf-8");
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
        
        /* Send the Cypher query  */ 
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, post_body);

        /* send all data to this function  */ 
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
      
        /* we pass our 'chunk' struct to the callback function */ 
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
        
        /* get verbose debug output please */ 
        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        
        /* Execute the CURL command */
        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 
        {
          printf("Receive => %s\n", chunk.memory);
          
          /* Parsing the response as JSON */
          cJSON *json = cJSON_Parse(chunk.memory);
          if (json == NULL)
          {
            const char *error_ptr = cJSON_GetErrorPtr();
            if (error_ptr != NULL)
            {
                fprintf(stderr, "Error before: %s\n", error_ptr);
            }
          }
          else
          {
            const cJSON *results = NULL;
            const cJSON *result = NULL;
            const cJSON *datas = NULL;
            const cJSON *data = NULL;
            const cJSON *row = NULL;
            const cJSON *value = NULL;
            
            results = cJSON_GetObjectItemCaseSensitive(json, "results");
            cJSON_ArrayForEach(result, results)
            {
                /* For each line in the result */
                datas = cJSON_GetObjectItemCaseSensitive(result, "data");
                cJSON_ArrayForEach(data, datas)
                {
                  /* We take the row */
                  row = cJSON_GetObjectItemCaseSensitive(data, "row");
                  
                  /* For each item in the row result */
                  cJSON_ArrayForEach(value, row)
                  {
                    printf("%s \t", value->valuestring);
                  }
                  printf("\n");
                }
            }
            
            
          }
          cJSON_Delete(json);
        
        }
        
        /* Some cleanups */
        curl_easy_cleanup(curl);
        free(chunk.memory);
        curl_global_cleanup();
    }   
    return 0;
}