+/**
+ * @file sensor.c
+ * @purpose Implementation of sensor thread
+ * TODO: Finalise implementation
+ */
+
+
+#include "common.h"
+#include "sensor.h"
+#include <math.h>
+
+/**
+ * Read a data value from a sensor; block until value is read
+ * @param sensor_id - The ID of the sensor
+ * @returns The current value of the sensor
+ */
+DataPoint GetData(int sensor_id)
+{
+ // 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
+
+ DataPoint d;
+ //TODO: Deal with time stamps properly
+ static int count = 0;
+ d.time = count++;
+ switch (sensor_id)
+ {
+ case SENSOR_TEST0:
+ d.value = count;
+ break;
+ case SENSOR_TEST1:
+ d.value = (float)(rand() % 100) / 100;
+ 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 Sensor_Init(Sensor * s, int id)
+{
+ s->write_index = 0;
+ s->read_offset = 0;
+ s->id = id;
+
+ #define FILENAMESIZE BUFSIZ
+ char filename[FILENAMESIZE];
+ //if (s->id >= pow(10, FILENAMESIZE))
+ if (false)
+ {
+ 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 (true) //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)
+ {
+ s->buffer[s->write_index] = GetData(s->id);
+ 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));
+ 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
+
+ }
+ 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;
+}
+
+/**
+ * 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;
+
+ int sensor_id = SENSOR_NONE;
+
+ while ((params = FCGI_KeyPair(params, &key, &value)) != NULL)
+ {
+ Log(LOGDEBUG, "Got key=%s and value=%s", key, value);
+ if (strcmp(key, "id") == 0)
+ {
+ char *end;
+ if (sensor_id != SENSOR_NONE)
+ {
+ 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;
+ }
+ //TODO: Use human readable sensor identifier string for API?
+ sensor_id = strtol(value, &end, 10);
+ if (*end != '\0')
+ {
+ Log(LOGERR, "Sensor id not an integer; %s", value);
+ status = STATUS_ERROR;
+ break;
+ }
+ }
+ else
+ {
+ Log(LOGERR, "Unknown key \"%s\" (value = %s)", key, value);
+ status = STATUS_ERROR;
+ break;
+ }
+ }
+
+ if (sensor_id == SENSOR_NONE)
+ {
+ Log(LOGERR, "No sensor id specified");
+ status = STATUS_ERROR;
+ }
+ else if (sensor_id >= NUMSENSORS || sensor_id < 0)
+ {
+ Log(LOGERR, "Invalid sensor id %d", sensor_id);
+ 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(&(g_sensors[sensor_id]), 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)
+ {
+ FCGI_JSONValue("[%f, %f]", buffer[i].time, buffer[i].value);
+ if (i+1 < amount_read)
+ FCGI_JSONValue(",");
+ }
+ FCGI_JSONValue("]");
+ //Log(LOGDEBUG, "Done producing JSON response");
+ FCGI_EndJSON();
+ }
+}
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