+/**
+ * @file sensor.c
+ * @brief Implementation of sensor thread
+ * TODO: Finalise implementation
+ */
+
+#include "common.h"
+#include "sensor.h"
+#include "options.h"
+#include <math.h>
+
+/** Array of sensors, initialised by Sensor_Init **/
+static Sensor g_sensors[NUMSENSORS]; //global to this file
+static const char * g_sensor_names[] = {"analog_test0", "analog_test1", "digital_test0", "digital_test1"};
+/**
+ * Read a data value from a sensor; block until value is read
+ * @param sensor_id - The ID of the sensor
+ * @param d - DataPoint to set
+ * @returns NULL for digital sensors when data is unchanged, otherwise d
+ */
+DataPoint * GetData(int sensor_id, DataPoint * d)
+{
+ // switch based on the sensor_id at the moment for testing;
+ // might be able to just directly access ADC from sensor_id?
+ //TODO: Implement for real sensors
+
+
+ //TODO: We should ensure the time is *never* allowed to change on the server if we use gettimeofday
+ // Another way people might think of getting the time is to count CPU cycles with clock()
+ // But this will not work because a) CPU clock speed may change on some devices (RPi?) and b) It counts cycles used by all threads
+
+ struct timeval t;
+ gettimeofday(&t, NULL);
+ d->time_stamp = (t.tv_sec - g_options.start_time.tv_sec) + 1e-6*(t.tv_usec - g_options.start_time.tv_usec);
+
+ // Make time relative
+ //d->time_stamp.tv_sec -= g_options.start_time.tv_sec;
+ //d->time_stamp.tv_usec -= g_options.start_time.tv_usec;
+
+ switch (sensor_id)
+ {
+ case ANALOG_TEST0:
+ {
+ static int count = 0;
+ d->value = count++;
+ break;
+ }
+ case ANALOG_TEST1:
+ d->value = (double)(rand() % 100) / 100;
+ break;
+
+ //TODO: For digital sensors, consider only updating when sensor is actually changed
+ case DIGITAL_TEST0:
+ d->value = t.tv_sec % 2;
+ break;
+ case DIGITAL_TEST1:
+ d->value = (t.tv_sec+1)%2;
+ break;
+ default:
+ Fatal("Unknown sensor id: %d", sensor_id);
+ break;
+ }
+ usleep(100000); // simulate delay in sensor polling
+
+ return d;
+}
+
+
+/**
+ * Destroy a sensor
+ * @param s - Sensor to destroy
+ */
+void Destroy(Sensor * s)
+{
+ // Maybe move the binary file into long term file storage?
+ fclose(s->file);
+}
+
+
+
+/**
+ * Initialise a sensor
+ * @param s - Sensor to initialise
+ */
+void Init(Sensor * s, int id)
+{
+ s->write_index = 0;
+ s->id = id;
+
+ #define FILENAMESIZE 3
+ char filename[FILENAMESIZE];
+ if (s->id >= pow(10, FILENAMESIZE))
+ {
+ Fatal("Too many sensors! FILENAMESIZE is %d; increase it and recompile.", FILENAMESIZE);
+ }
+
+ pthread_mutex_init(&(s->mutex), NULL);
+
+ sprintf(filename, "%d", s->id);
+ unlink(filename); //TODO: Move old files somewhere
+
+ s->file = fopen(filename, "a+b"); // open binary file
+ Log(LOGDEBUG, "Initialised sensor %d; binary file is \"%s\"", id, filename);
+}
+
+
+
+
+
+/**
+ * Run the main sensor polling loop
+ * @param arg - Cast to Sensor* - Sensor that the thread will handle
+ * @returns NULL (void* required to use the function with pthreads)
+ */
+void * Sensor_Main(void * arg)
+{
+ Sensor * s = (Sensor*)(arg);
+
+ while (Thread_Runstate() == RUNNING) //TODO: Exit condition
+ {
+ // The sensor will write data to a buffer until it is full
+ // Then it will open a file and dump the buffer to the end of it.
+ // Rinse and repeat
+
+ // The reason I've added the buffer is because locks are expensive
+ // But maybe it's better to just write data straight to the file
+ // I'd like to do some tests by changing SENSOR_DATABUFSIZ
+
+ while (s->write_index < SENSOR_DATABUFSIZ)
+ {
+ DataPoint * d = &(s->buffer[s->write_index]);
+ if (GetData(s->id, d) == NULL)
+ {
+ Fatal("Error collecting data");
+ }
+ s->write_index += 1;
+ }
+
+ //Log(LOGDEBUG, "Filled buffer");
+
+ // CRITICAL SECTION (no threads should be able to read/write the file at the same time)
+ pthread_mutex_lock(&(s->mutex));
+ //TODO: Valgrind complains about this fseek: "Syscall param write(buf) points to uninitialised byte(s)"
+ // Not sure why, but we should find out and fix it.
+ fseek(s->file, 0, SEEK_END);
+ int amount_written = fwrite(s->buffer, sizeof(DataPoint), SENSOR_DATABUFSIZ, s->file);
+ if (amount_written != SENSOR_DATABUFSIZ)
+ {
+ Fatal("Wrote %d data points and expected to write %d to \"%s\" - %s", amount_written, SENSOR_DATABUFSIZ, strerror(errno));
+ }
+ //Log(LOGDEBUG, "Wrote %d data points for sensor %d", amount_written, s->id);
+ pthread_mutex_unlock(&(s->mutex));
+ // End of critical section
+
+ s->write_index = 0; // reset position in buffer
+
+ }
+ 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;
+
+
+ Log(LOGDEBUG, "Sensor \"%s\" identified", g_sensor_names[id]);
+ 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;
+
+ enum {DEFAULT, DUMP} operation = DEFAULT;
+
+ 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 if (strcmp(key, "dump") == 0)
+ {
+ if (operation != DEFAULT)
+ {
+ Log(LOGERR, "Operation already specified!");
+ status = STATUS_ERROR;
+ break;
+ }
+ operation = DUMP;
+ }
+ 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);
+ return;
+ }
+
+ switch (operation)
+ {
+ case DUMP:
+ {
+ FCGI_PrintRaw("Content-type: text/plain\r\n\r\n");
+ //CRITICAL SECTION
+ pthread_mutex_lock(&(sensor->mutex));
+ fseek(sensor->file, 0, SEEK_SET);
+ int amount_read = 0;
+ do
+ {
+ amount_read = fread(buffer, sizeof(DataPoint), SENSOR_QUERYBUFSIZ, sensor->file);
+ for (int i = 0; i < amount_read; ++i)
+ {
+ FCGI_PrintRaw("%f\t%f\n", buffer[i].time_stamp, buffer[i].value);
+ }
+
+ }
+ while (amount_read == SENSOR_QUERYBUFSIZ);
+ pthread_mutex_unlock(&(sensor->mutex));
+ // end critical section
+ break;
+ }
+ default:
+ {
+ 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?
+
+ FCGI_JSONValue("[%f, %f]", buffer[i].time_stamp, buffer[i].value);
+ if (i+1 < amount_read)
+ FCGI_JSONValue(",");
+ }
+ FCGI_JSONValue("]");
+ //Log(LOGDEBUG, "Done producing JSON response");
+ FCGI_EndJSON();
+ break;
+ }
+ }
+}
+
+/**
+ * Setup Sensors, start Sensor polling thread(s)
+ */
+void Sensor_Spawn()
+{
+ // start sensor threads
+ for (int i = 0; i < NUMSENSORS; ++i)
+ {
+ Init(g_sensors+i, i);
+ pthread_create(&(g_sensors[i].thread), NULL, Sensor_Main, (void*)(g_sensors+i));
+ }
+}
+
+/**
+ * Quit Sensor loops
+ */
+void Sensor_Join()
+{
+ if (!Thread_Runstate())
+ {
+ Fatal("This function should not be called before Thread_QuitProgram");
+ }
+ for (int i = 0; i < NUMSENSORS; ++i)
+ {
+ pthread_join(g_sensors[i].thread, NULL);
+ Destroy(g_sensors+i);
+ }
+}
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