+ Log(LOGDEBUG, "Thread for sensor %d exits", s->id);
+ return NULL;
+}
+
+/**
+ * Fill buffer with most recent sensor data
+ * @param s - Sensor to use
+ * @param buffer - Buffer to fill
+ * @param bufsiz - Size of buffer to fill
+ * @returns The number of DataPoints actually read
+ */
+int Sensor_Query(Sensor * s, DataPoint * buffer, int bufsiz)
+{
+ int amount_read = 0;
+ //CRITICAL SECTION (Don't access file while sensor thread is writing to it!)
+ pthread_mutex_lock(&(s->mutex));
+
+ fseek(s->file, -bufsiz*sizeof(DataPoint), SEEK_END);
+ amount_read = fread(buffer, sizeof(DataPoint), bufsiz, s->file);
+ //Log(LOGDEBUG, "Read %d data points", amount_read);
+ pthread_mutex_unlock(&(s->mutex));
+ return amount_read;
+}
+
+/**
+ * Get a Sensor given an ID string
+ * @param id_str ID string
+ * @returns Sensor* identified by the string; NULL on error
+ */
+Sensor * Sensor_Identify(const char * id_str)
+{
+ char * end;
+ // Parse string as integer
+ int id = strtol(id_str, &end, 10);
+ if (*end != '\0')
+ {
+ return NULL;
+ }
+ // Bounds check
+ if (id < 0 || id > NUMSENSORS)
+ return NULL;
+
+ return g_sensors+id;
+}
+
+/**
+ * Handle a request to the sensor module
+ * @param context - The context to work in
+ * @param params - Parameters passed
+ */
+void Sensor_Handler(FCGIContext *context, char * params)
+{
+ DataPoint buffer[SENSOR_QUERYBUFSIZ];
+ StatusCodes status = STATUS_OK;
+ const char * key; const char * value;
+
+ Sensor * sensor = NULL;
+
+ while ((params = FCGI_KeyPair(params, &key, &value)) != NULL)
+ {
+ Log(LOGDEBUG, "Got key=%s and value=%s", key, value);
+ if (strcmp(key, "id") == 0)
+ {
+ if (sensor != NULL)
+ {
+ Log(LOGERR, "Only one sensor id should be specified");
+ status = STATUS_ERROR;
+ break;
+ }
+ if (*value == '\0')
+ {
+ Log(LOGERR, "No id specified.");
+ status = STATUS_ERROR;
+ break;
+ }
+
+ sensor = Sensor_Identify(value);
+ if (sensor == NULL)
+ {
+ Log(LOGERR, "Invalid sensor id: %s", value);
+ status = STATUS_ERROR;
+ break;
+ }
+ }
+ else
+ {
+ Log(LOGERR, "Unknown key \"%s\" (value = %s)", key, value);
+ status = STATUS_ERROR;
+ break;
+ }
+ }
+
+ if (status != STATUS_ERROR && sensor == NULL)
+ {
+ Log(LOGERR, "No valid sensor id given");
+ status = STATUS_ERROR;
+ }
+
+ if (status == STATUS_ERROR)
+ {
+ FCGI_RejectJSON(context);
+ }
+ else
+ {
+
+ FCGI_BeginJSON(context, status);
+ FCGI_JSONPair(key, value); // should spit back sensor ID
+ //Log(LOGDEBUG, "Call Sensor_Query...");
+ int amount_read = Sensor_Query(sensor, buffer, SENSOR_QUERYBUFSIZ);
+ //Log(LOGDEBUG, "Read %d DataPoints", amount_read);
+ //Log(LOGDEBUG, "Produce JSON response");
+ FCGI_JSONKey("data");
+ FCGI_JSONValue("[");
+ for (int i = 0; i < amount_read; ++i)
+ {
+ //TODO: Consider; is it better to give both tv_sec and tv_usec to the client seperately, instead of combining here?
+ //NOTE: Must always use doubles; floats get rounded!
+ double time = buffer[i].time_stamp.tv_sec + 1e-6*(buffer[i].time_stamp.tv_usec);
+ FCGI_JSONValue("[%f, %f]", time, buffer[i].value);
+ if (i+1 < amount_read)
+ FCGI_JSONValue(",");
+ }
+ FCGI_JSONValue("]");
+ //Log(LOGDEBUG, "Done producing JSON response");
+ FCGI_EndJSON();
+ }