Merge pull request #9 from briandowns/c_client

silly c client

.gitignore

@@ -24,6 +24,7 @@ _testmain.go
 *.test
 *.prof
 
+.vscode
 .idea
 *.iml
 

clients/c/README.md

@@ -0,0 +1,26 @@
+# Sky Island C Client
+
+A feable attempt at writing a client for Sky Island in C.
+
+## Build
+
+```
+cc sky-island.c -lcurl -ljson-c -o sky-func
+```
+
+## Examples
+
+```
+int main(int argc, char* argv[]) {
+  struct client_t* c = malloc(sizeof(struct client_t));
+  c->endpoint = "http://demo.skyisland.io:3281/api/v1/function";
+
+  char* url = "github.com/mmcloughlin/geohash";
+  char* call = "Encode(100.1, 80.9)";
+
+  function(c, url, call);
+  
+  free(c);
+  return (EXIT_SUCCESS);
+}
+```

clients/c/sky-island.c

@@ -0,0 +1,136 @@
+#include <curl/curl.h>
+#include <json-c/json.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct client_t {
+  char* endpoint;
+};
+
+struct response_t {
+  unsigned long timestamp;
+  void* data;
+};
+
+struct curl_fetch_st {
+  char* payload;
+  size_t size;
+};
+
+/* callback for curl fetch */
+size_t curl_callback(void* contents, size_t size, size_t nmemb, void* userp) {
+  size_t realsize = size * nmemb; /* calculate buffer size */
+  struct curl_fetch_st* p =
+      (struct curl_fetch_st*)userp; /* cast pointer to fetch struct */
+
+  /* expand buffer */
+  p->payload = (char*)realloc(p->payload, p->size + realsize + 1);
+
+  if (p->payload == NULL) {
+    fprintf(stderr, "ERROR: Failed to expand buffer in curl_callback");
+    free(p->payload);
+    return -1;
+  }
+
+  /* copy contents to buffer */
+  memcpy(&(p->payload[p->size]), contents, realsize);
+
+  /* set new buffer size */
+  p->size += realsize;
+  p->payload[p->size] = 0;
+
+  return realsize;
+}
+
+/* fetch and return url body via curl */
+CURLcode curl_fetch_url(CURL* ch,
+                        const char* url,
+                        struct curl_fetch_st* fetch) {
+  CURLcode ret_code;
+
+  fetch->payload = (char*)calloc(1, sizeof(fetch->payload));
+
+  if (fetch->payload == NULL) {
+    fprintf(stderr, "ERROR: Failed to allocate payload in curl_fetch_url");
+    return CURLE_FAILED_INIT;
+  }
+
+  fetch->size = 0;
+
+  curl_easy_setopt(ch, CURLOPT_URL, url);
+  curl_easy_setopt(ch, CURLOPT_WRITEFUNCTION, curl_callback);
+  curl_easy_setopt(ch, CURLOPT_WRITEDATA, (void*)fetch);
+  curl_easy_setopt(ch, CURLOPT_USERAGENT, "sky-island-agent/1.0");
+  curl_easy_setopt(ch, CURLOPT_TIMEOUT, 5);
+  curl_easy_setopt(ch, CURLOPT_FOLLOWLOCATION, 0);
+
+  ret_code = curl_easy_perform(ch);
+
+  return ret_code;
+}
+
+static int function(struct client_t* client,
+                    const char* url,
+                    const char* call) {
+  CURL* ch;
+  CURLcode ret_code;
+
+  json_object* json;
+  enum json_tokener_error jerr = json_tokener_success;
+
+  struct curl_fetch_st curl_fetch;
+  struct curl_fetch_st* cf = &curl_fetch;
+  struct curl_slist* headers = NULL;
+
+  if ((ch = curl_easy_init()) == NULL) {
+    fprintf(stderr, "ERROR: Failed to create curl handle in fetch_session");
+    return -1;
+  }
+
+  headers = curl_slist_append(headers, "Accept: application/json");
+  headers = curl_slist_append(headers, "Content-Type: application/json");
+
+  json = json_object_new_object();
+
+  json_object_object_add(json, "url", json_object_new_string(url));
+  json_object_object_add(json, "call", json_object_new_string(call));
+
+  curl_easy_setopt(ch, CURLOPT_CUSTOMREQUEST, "POST");
+  curl_easy_setopt(ch, CURLOPT_HTTPHEADER, headers);
+  curl_easy_setopt(ch, CURLOPT_POSTFIELDS, json_object_to_json_string(json));
+
+  ret_code = curl_fetch_url(ch, client->endpoint, cf);
+  curl_easy_cleanup(ch);
+  curl_slist_free_all(headers);
+
+  json_object_put(json);
+
+  if (ret_code != CURLE_OK || cf->size < 1) {
+    fprintf(stderr, "ERROR: Failed to fetch url (%s) - curl said: %s", url,
+            curl_easy_strerror(ret_code));
+    return -1;
+  }
+
+  if (cf->payload == NULL) {
+    fprintf(stderr, "ERROR: Failed to populate payload");
+    free(cf->payload);
+    return -1;
+  }
+
+  json = json_tokener_parse_verbose(cf->payload, &jerr);
+  free(cf->payload);
+
+  if (jerr != json_tokener_success) {
+    fprintf(stderr, "ERROR: Failed to parse json string");
+    json_object_put(json);
+    return -1;
+  }
+
+  printf("%s\n", json_object_to_json_string(json));
+
+  json_object_put(json);
+
+  return 0;
+}