Add wallclock time handling

New application and new example.
We use the built-in timer routines and add an offset to get the
wallclock time. The offset can be set by time-changing routines
(currently only settimeofday).
We also maintain an offset for timezone handling but this isn't
currently fully implemented.

apps/time/resource_timestamp.c

@@ -0,0 +1,158 @@
+/**
+ * \file
+ *      Resource for timestamp handling
+ * \author
+ *      Ralf Schlatterbeck <rsc@runtux.com>
+ *
+ * \brief get/put time in seconds since 1970 (UNIX time)
+ * Note: the internal format of the time in seconds is a 64bit number
+ * unfortunately javascript (json) will only support double for which
+ * the mantissa isn't long enough for representing that number. So we're
+ * back to 32 bit and have a year 2038 problem.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "contiki.h"
+#include "time.h"
+#include "time_resource.h"
+#include "jsonparse.h"
+/* Only coap 13 for now */
+#include "er-coap-13.h"
+
+/* Error-handling macro */
+# define BYE(_exp, _tag) \
+   do {                                  \
+     PRINTF("Expect "_exp": %d\n",_tag); \
+     success=0;                          \
+     goto bye;                           \
+   } while(0)
+
+#define DEBUG 1
+#if DEBUG
+#define PRINTF(...) printf(__VA_ARGS__)
+#else
+#define PRINTF(...)
+#endif
+
+RESOURCE \
+    ( timestamp, METHOD_GET | METHOD_PUT
+    , "clock/timestamp"
+    , "title=\"Time\";rt=\"timestamp\""
+    );
+
+void
+timestamp_handler
+    ( void* request
+    , void* response
+    , uint8_t *buffer
+    , uint16_t preferred_size
+    , int32_t *offset
+    )
+{
+  int success = 1;
+
+  int i;
+  char temp[100];
+  int index = 0;
+  int length = 0;
+  int tag = 0;
+  const uint8_t *bytes = NULL;
+  size_t len = 0;
+  struct timeval tv;
+  int n_acc = 0;
+  const uint16_t *accept = NULL;
+  uint16_t a_ctype = REST.type.APPLICATION_JSON;
+  uint16_t c_ctype = REST.get_header_content_type (request);
+
+  /* Seems like accepted type is currently unsupported? */
+  n_acc = REST.get_header_accept (request, &accept);
+  for (i=0; i<n_acc; i++) {
+    if  (  accept [i] == REST.type.TEXT_PLAIN
+        || accept [i] == REST.type.APPLICATION_JSON
+        )
+    {
+      a_ctype = accept [i];
+      break;
+    }
+  }
+
+  switch(REST.get_method_type(request)) {
+    case METHOD_GET:
+      gettimeofday (&tv, NULL);
+      // TEXT format
+      if (a_ctype == REST.type.TEXT_PLAIN) {
+        index += sprintf (temp + index, "%ld\n", (long)tv.tv_sec);
+      } else { // jSON Format
+        // FIXME: Platform doesn't seem to support long long printing
+        // We get empty string
+        index += sprintf
+          ( temp + index
+          ,"{\n \"timestamp\" : \"%ld\"\n}\n"
+          , (long)tv.tv_sec
+          );
+      }
+      length = strlen(temp);
+      memcpy (buffer, temp, length);
+      REST.set_header_content_type (response, a_ctype);
+      REST.set_response_payload (response, buffer, length);
+
+      break;
+    case METHOD_PUT:
+      if ((len = coap_get_payload(request, &bytes))) {
+        if (c_ctype == REST.type.TEXT_PLAIN) {
+          temp [sizeof (temp) - 1] = 0;
+          strncpy (temp, (char *)bytes, MIN (len, sizeof (temp) - 1));
+        } else { // jSON Format
+          struct jsonparse_state state;
+          struct jsonparse_state *parser = &state;
+          PRINTF ("PUT: len: %d, %s\n", len, (char *)bytes);
+          jsonparse_setup (parser, (char *)bytes, len);
+          if ((tag = jsonparse_next (parser)) != JSON_TYPE_OBJECT) {
+            BYE ("OBJECT", tag);
+          }
+          if ((tag = jsonparse_next (parser)) != JSON_TYPE_PAIR_NAME) {
+            BYE ("PAIR_NAME", tag);
+          }
+          while (jsonparse_strcmp_value (parser, "timestamp") != 0) {
+            tag = jsonparse_next (parser);
+            if (tag != JSON_TYPE_PAIR) {
+              BYE ("PAIR", tag);
+            }
+            tag = jsonparse_next (parser);
+            tag = jsonparse_next (parser);
+            if (tag != ',') {
+              BYE (",", tag);
+            }
+            tag = jsonparse_next (parser);
+            if (tag != JSON_TYPE_PAIR_NAME) {
+              BYE ("PAIR_NAME", tag);
+            }
+          }
+          tag = jsonparse_next (parser);
+          if (tag != JSON_TYPE_PAIR) {
+            BYE ("PAIR", tag);
+          }
+          tag = jsonparse_next (parser);
+          if (tag != JSON_TYPE_STRING) {
+            BYE ("STRING", tag);
+          }
+          jsonparse_copy_value (parser, temp, sizeof (temp));
+        }
+        // FIXME: Platform has no strtoll (long long)?
+        tv.tv_sec = strtol (temp, NULL, 10);
+        settimeofday (&tv, NULL);
+        REST.set_response_status(response, REST.status.CHANGED);
+      } else {
+        success = 0;
+      }
+      bye :
+      break;
+    default:
+      success = 0;
+  }
+  if (!success) {
+    REST.set_response_status(response, REST.status.BAD_REQUEST);
+  }
+}