Add example of REST client

by using libcurl for HTTP connection
and M*LIB for JSON formating.

example/Makefile

@@ -31,7 +31,7 @@ RM=rm -f
 .SUFFIXES: .c .exe
 
 .c.exe:
-	$(CC) $(CFLAGS) $(CPPFLAGS) $< -o $@ `cat config` $(LDFLAGS)
+	$(CC) $(CFLAGS) $(CPPFLAGS) $< -o $@ `cat config` `cat config.curl` $(LDFLAGS)
 
 .c.o:
 	@$(MAKE) config
@@ -53,11 +53,11 @@ config:
 	$(CC) $(CFLAGS) $(CPPFLAGS) -I$(GMP_DIR)/include -L$(GMP_DIR)/lib config-test.c -lgmp -o config-test.exe $(LDFLAGS) 2> /dev/null && echo "-DHAVE_GMP=1 -DHAVE_MPFR=0 -I$(GMP_DIR)/include -L$(GMP_DIR)/lib -lgmp" > config || echo "-DHAVE_GMP=0 -DHAVE_MPFR=0 " > config
 	printf "#include <mpfr.h>\nint main(void){mpfr_t z; mpfr_init(z); return 0;}\n" > config-test.c
 	$(CC) $(CFLAGS) $(CPPFLAGS) -I$(GMP_DIR)/include -I$(MPFR_DIR)/include -L$(GMP_DIR)/lib -L$(MPFR_DIR)/lib config-test.c -lmpfr -lgmp -o config-test.exe $(LDFLAGS) 2> /dev/null && echo "-DHAVE_GMP=1 -DHAVE_MPFR=1  -I$(GMP_DIR)/include -L$(GMP_DIR)/lib -I$(MPFR_DIR)/include -L$(MPFR_DIR)/lib -lmpfr -lgmp" > config || echo "MPFR not available"
+	printf "#include <curl/curl.h>\nint main(void){curl_global_init(CURL_GLOBAL_DEFAULT);}" > config-test.c
+	$(CC) $(CFLAGS) $(CPPFLAGS) config-test.c `curl-config --cflags --libs`  -o config-test.exe 2> /dev/null && echo "-DHAVE_CURL=1 `curl-config --cflags --libs`" > config.curl || echo "-DHAVE_CURL=0 " > config.curl
 	printf "#include <stdio.h>\nint main(void){printf(\"Ok\"); return 0;}\n" > config-test.c
 	$(CC) $(CFLAGS) $(CPPFLAGS) config-test.c -ffunction-sections -fdata-sections -Wl,--gc-sections 2> /dev/null && echo "-ffunction-sections -fdata-sections -Wl,--gc-sections" > config.link || echo "" > config.link
 	$(RM) config-test.c config-test.exe
 
 clean:
-	$(RM) *.exe *.s *~ *.o ./a.dat config config.link
+	$(RM) *.exe *.s *~ *.o ./a.dat config config.link config.curl
-
-

example/ex-curl.c

@@ -0,0 +1,160 @@
+#if HAVE_CURL
+
+#include <curl/curl.h>
+#include "m-dict.h"
+#include "m-tuple.h"
+#include "m-string.h"
+#include "m-list.h"
+#include "m-serial-json.h"
+
+/////////////////////////////////////////
+
+// Define container types
+// First a generic map string to string
+DICT_DEF2(map_str, string_t, string_t)
+#define M_OPL_map_str_t() DICT_OPLIST(map_str, STRING_OPLIST, STRING_OPLIST)
+  
+// This structure matches the JSON structure returns by the used WEB server
+// for the GET command.
+// It can be whatever you want provided it matches what is expected by the WEB server
+TUPLE_DEF2(web_data,
+           (args, map_str_t),
+           (headers, map_str_t),
+           (origin, string_t),
+           (url, string_t))
+#define M_OPL_web_data_t() TUPLE_OPLIST(web_data, M_OPL_map_str_t(), M_OPL_map_str_t(), STRING_T, STRING_T)
+
+/////////////////////////////////////////
+
+
+static size_t
+write_data(void *buffer, size_t size, size_t nmemb, void *userp)
+{
+  (void) size; // Parameter not used
+  char *src = buffer;
+  string_ptr str = userp;
+  for(size_t i = 0; i < nmemb; i++) {
+    string_push_back(str, src[i]);
+  }
+  return nmemb;
+}
+
+static bool get_data(web_data_t data, const char url[])
+{
+  m_serial_return_code_t r = M_SERIAL_FAIL;
+  CURLcode res;
+  string_t str;
+  CURL *handle = curl_easy_init();
+  if (handle) {
+      string_init(str);
+      // Perform an http GET request and fill in str with the JSON answer
+      curl_easy_setopt(handle, CURLOPT_URL, url);
+      curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, write_data);
+      curl_easy_setopt(handle, CURLOPT_WRITEDATA, str);
+      res = curl_easy_perform(handle);
+      curl_easy_cleanup(handle);
+      if (res == CURLE_OK) {
+        // Parse the string and fill in the object
+        m_serial_str_json_read_t serial;
+        m_serial_str_json_read_init(serial, string_get_cstr(str));
+        r = web_data_in_serial(data, serial);
+        m_serial_str_json_read_clear(serial);
+      }
+      string_clear(str);
+  }
+  return r == M_SERIAL_OK_DONE;
+}
+
+/////////////////////////////////////////
+
+static size_t
+ignore_data(void *buffer, size_t size, size_t nmemb, void *userp)
+{
+  (void) buffer; // Parameter not used
+  (void) size; // Parameter not used
+  (void) userp; // Parameter not used
+  return nmemb;
+}
+
+static bool post_data(web_data_t data, const char url[], bool display_answer)
+{
+  m_serial_return_code_t r = M_SERIAL_FAIL;
+  CURLcode res = 0;
+  string_t str;
+  CURL *handle = curl_easy_init();
+  if (handle) {
+    string_init(str);
+    // Get a JSON string
+    m_serial_str_json_write_t serial;
+    m_serial_str_json_write_init(serial, str);
+    r = web_data_out_serial(serial, data);
+    m_serial_str_json_write_clear(serial);
+    if (r == M_SERIAL_OK_DONE) {
+      // Post JSON string
+       struct curl_slist *headers=NULL;
+       headers = curl_slist_append(headers, "Content-Type: text/json");
+       if (headers != NULL) {
+         curl_easy_setopt(handle, CURLOPT_POSTFIELDS, string_get_cstr(str));
+         curl_easy_setopt(handle, CURLOPT_URL, url);
+         curl_easy_setopt(handle, CURLOPT_HTTPHEADER, headers);
+         if (display_answer == false) {
+           curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, ignore_data);
+           curl_easy_setopt(handle, CURLOPT_WRITEDATA, NULL);
+         }
+         res = curl_easy_perform(handle);
+         curl_slist_free_all(headers);
+       }
+    }
+    curl_easy_cleanup(handle);
+    string_clear(str);
+  }
+  return (r == M_SERIAL_OK_DONE) && (res == CURLE_OK);
+}
+
+/////////////////////////////////////////
+
+// Remote server URL
+#define URL_GET "https://httpbin.org/get"
+#define URL_POST "https://httpbin.org/post"
+  
+int main(void)
+{
+  CURLcode ret = curl_global_init(CURL_GLOBAL_DEFAULT);
+  if (ret != CURLE_OK) abort();
+
+  web_data_t data;
+  web_data_init(data);
+
+  // Test http GET
+  bool b = get_data(data, URL_GET);
+  if (b) {
+    // We success receiving the JSON object and fill in the C object web_data with it.
+    // Let's display the object content:
+    printf("SUCCESS. Receive data =\n");
+    web_data_out_str(stdout, data);
+    printf("\n");
+  } else {
+    printf("ERROR: Cannot GET data or get data are not in expected format\n");
+  }
+
+  // Test http POST
+  web_data_emplace_origin(data, "This is the origin");
+  web_data_emplace_url(data, "This is the URL");
+  //web_data_set_origin(data, STRING_CTE("This is the origin"));
+  //web_data_set_url(data, STRING_CTE("This is the URL"));
+  b = post_data(data, URL_POST, false);
+  if (b) {
+    printf("SUCCESS: Post\n");
+  } else {
+    printf("ERROR post\n");
+  }
+
+  web_data_clear(data);
+
+  curl_global_cleanup();
+  return 0;
+}
+
+#else
+int main(void) { return 0; }
+#endif