Merge branch 'master' of https://github.com/szmoore/MCTX3420.git
[matches/MCTX3420.git] / server / sensor.c
index f2c73c5..e429958 100644 (file)
 #include "common.h"
 #include "sensor.h"
 #include "options.h"
+#include "bbb_pin.h"
 #include <math.h>
 
 /** Array of sensors, initialised by Sensor_Init **/
 static Sensor g_sensors[NUMSENSORS]; //global to this file
+
+/** Array of sensor threshold structures defining the safety values of each sensor**/
+const SensorThreshold thresholds[NUMSENSORS]= {
+       //Max Safety, Min safety, Max warning, Min warning
+       {1,-1,1,-1},            // ANALOG_TEST0
+       {500,0,499,0},          // ANALOG_TEST1
+       {5000,0,5000,0},                // ANALOG_REALTEST
+       {5,-5,4,-4},            // ANALOG_FAIL0
+       {1,0,1,0},                      // DIGITAL_TEST0
+       {1,0,1,0},                      // DIGITAL_TEST1
+       {1,0,1,0},                      // DIGITAL_REALTEST
+       {1,0,1,0}                       // DIGITAL_FAIL0
+};
+
+/** Human readable names for the sensors **/
 const char * g_sensor_names[NUMSENSORS] = {    
        "analog_test0", "analog_test1", 
-       "digital_test0", "digital_test1"
+       "analog_realtest", "analog_fail0",
+       "digital_test0", "digital_test1", 
+       "digital_realtest", "digital_fail0"
 };
 
 /**
- * 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
+ * One off initialisation of *all* sensors
  */
-DataPoint * GetData(SensorId sensor_id, DataPoint * d)
+void Sensor_Init()
 {
-       // 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 = TIMEVAL_DIFF(t, g_options.start_time);
-
-       // 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)
+       for (int i = 0; i < NUMSENSORS; ++i)
        {
-               case ANALOG_TEST0:
-               {
-                       //CheckSensor( sensor_id, *sensor value*); 
-               
-                       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
+               g_sensors[i].id = i;
+               Data_Init(&(g_sensors[i].data_file));
+       }
 
-       return d;
+       // Get the ADCs
+       ADC_Export();
+
+       // GPIO1_28 used as a pulse for sampling
+       GPIO_Export(GPIO1_28);
+       // GPIO0_30 toggled during sampling
+       GPIO_Export(GPIO0_30);
 }
 
 /**
- * Checks the sensor data for unsafe or unexpected results 
- * @param sensor_id - The ID of the sensor
- *
-*
-void CheckSensor( SensorId sensor_id)
+ * Sets the sensor to the desired control mode. No checks are
+ * done to see if setting to the desired mode will conflict with
+ * the current mode - the caller must guarantee this itself.
+ * @param s The sensor whose mode is to be changed
+ * @param mode The mode to be changed to
+ * @param arg An argument specific to the mode to be set. 
+ *            e.g for CONTROL_START it represents the experiment name.
+ */
+void Sensor_SetMode(Sensor * s, ControlModes mode, void * arg)
 {
-       switch (sensor_id)
+       switch(mode)
        {
-               case ANALOG_TEST0:
-               {
-                       if( *sensor value* > ANALOG_TEST0_SAFETY)
+               case CONTROL_START:
                        {
-                               LogEx(LOGERR, GetData, Sensor analog_test0 is above the safe value);
-                       //new log function that stops actuators?
+                               // Set filename
+                               char filename[BUFSIZ];
+                               const char *experiment_name = (const char*) arg;
+
+                               if (snprintf(filename, BUFSIZ, "%s_s%d", experiment_name, s->id) >= BUFSIZ)
+                               {
+                                       Fatal("Experiment name \"%s\" too long (>%d)", experiment_name, BUFSIZ);
+                               }
+
+                               Log(LOGDEBUG, "Sensor %d with DataFile \"%s\"", s->id, filename);
+                               // Open DataFile
+                               Data_Open(&(s->data_file), filename);
                        }
-                       //Also include a warning level?
-                       else if( *sensor value* > ANALOG_TEST0_WARN)
+               case CONTROL_RESUME: //Case fallthrough, no break before
                        {
-                               LogEx(LOGWARN, GetData, Sensor analog_test0);   
+                               int ret;
+                               s->activated = true; // Don't forget this!
+
+                               // Create the thread
+                               ret = pthread_create(&(s->thread), NULL, Sensor_Loop, (void*)(s));
+                               if (ret != 0)
+                               {
+                                       Fatal("Failed to create Sensor_Loop for Sensor %d", s->id);
+                               }
+
+                               Log(LOGDEBUG, "Resuming sensor %d", s->id);
                        }
-               }
-       }
+               break;
+
+               case CONTROL_EMERGENCY:
+               case CONTROL_PAUSE:
+                       s->activated = false;
+                       pthread_join(s->thread, NULL);
+                       Log(LOGDEBUG, "Paused sensor %d", s->id);
+               break;
                
-       
-*/     
+               case CONTROL_STOP:
+                       if (s->activated) //May have been paused before
+                       {
+                               s->activated = false;
+                               pthread_join(s->thread, NULL);
+                       }
 
+                       Data_Close(&(s->data_file)); // Close DataFile
+                       s->newest_data.time_stamp = 0;
+                       s->newest_data.value = 0;
+                       Log(LOGDEBUG, "Stopped sensor %d", s->id);
+               break;
+               default:
+                       Fatal("Unknown control mode: %d", mode);
+       }
+}
 
 /**
- * Destroy a sensor
- * @param s - Sensor to destroy
+ * Sets all sensors to the desired mode. 
+ * @see Sensor_SetMode for more information.
+ * @param mode The mode to be changed to
+ * @param arg An argument specific to the mode to be set.
  */
-void Destroy(Sensor * s)
+void Sensor_SetModeAll(ControlModes mode, void * arg)
 {
-       // Maybe move the binary file into long term file storage?
-       fclose(s->file);
+       for (int i = 0; i < NUMSENSORS; i++)
+               Sensor_SetMode(&g_sensors[i], mode, arg);
 }
 
 
-
 /**
- * Initialise a sensor
- * @param s - Sensor to initialise
+ * Checks the sensor data for unsafe or unexpected results 
+ * @param sensor_id - The ID of the sensor
+ * @param value - The value from the sensor to test
  */
-void Init(Sensor * s, int id)
+void Sensor_CheckData(SensorId id, double value)
 {
-       s->write_index = 0;
-       s->id = id;
-       s->points_written = 0;
-       s->points_read = 0;
-
-       #define FILENAMESIZE 3
-       char filename[FILENAMESIZE];
-       if (s->id >= pow(10, FILENAMESIZE))
+       if( value > thresholds[id].max_error || value < thresholds[id].min_error)
        {
-               Fatal("Too many sensors! FILENAMESIZE is %d; increase it and recompile.", FILENAMESIZE);
+               Log(LOGERR, "Sensor %s is above or below its safety value of %f or %f\n", g_sensor_names[id],thresholds[id].max_error, thresholds[id].min_error);
+               //new function that stops actuators?
+               //Control_SetMode(CONTROL_EMERGENCY, NULL)
+       }
+       else if( value > thresholds[id].max_warn || value < thresholds[id].min_warn)
+       {
+               Log(LOGWARN, "Sensor %s is above or below its warning value of %f or %f\n", g_sensor_names[id],thresholds[id].max_warn, thresholds[id].min_warn);       
        }
-
-       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)
+ * Read a DataPoint from a Sensor; block until value is read
+ * @param id - The ID of the sensor
+ * @param d - DataPoint to set
+ * @returns True if the DataPoint was different from the most recently recorded.
  */
-void * Sensor_Main(void * arg)
+bool Sensor_Read(Sensor * s, DataPoint * d)
 {
-       Sensor * s = (Sensor*)(arg);
+       
+       // Set time stamp
+       struct timeval t;
+       gettimeofday(&t, NULL);
+       d->time_stamp = TIMEVAL_DIFF(t, *Control_GetStartTime());
 
-       while (Thread_Runstate() == RUNNING) //TODO: Exit condition
+       static bool result = true;
+       
+       
+       // Read value based on Sensor Id
+       switch (s->id)
        {
-               // 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)
+               case ANALOG_REALTEST:
                {
-                       DataPoint * d = &(s->buffer[s->write_index]);
-                       if (GetData(s->id, d) == NULL)
-                       {
-                               Fatal("Error collecting data");
-                       }
-                       s->write_index += 1;
+                       static bool set = false;
+                       
+                       GPIO_Set(GPIO0_30, true);
+                       d->value = (double)ADC_Read(ADC0);      //ADC #0 on the Beaglebone
+                       //Log(LOGDEBUG, "Got value %f from ADC0", d->value);
+                       GPIO_Set(GPIO0_30, false);
+                       set = !set;
+                       GPIO_Set(GPIO1_28, set);
+                       
+                       break;
                }
-
-               //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));
-                       }
-                       s->points_written += amount_written;
-                       //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; 
-}
-
-/**
- * Get position in a binary sensor file with a timestamp using a binary search
- * @param s - Sensor to use
- * @param time_stamp - Timestamp
- * @param count - If not NULL, used to provide number of searches required
- * @param found - If not NULL, set to the closest DataPoint
- * @returns Integer giving the *closest* index in the file
- * TODO: Refactor or replace?
- */
-int FindTime(Sensor * s, double time_stamp, int * count, DataPoint * found)
-{
-       DataPoint d;
-
-       int lower = 0;
-       int upper = s->points_written - 1;
-       int index = 0;
-       if (count != NULL)
-               *count = 0;     
-
-       while (upper - lower > 1)
-       {
-               index = lower + ((upper - lower)/2);
-
-               // Basically anything with fseek is critical; if we don't make it critical the sensor thread may alter data at a random point in the file!
-               // CRITICAL SECTION (May need to rethink how this is done, but I can't see how to do it without fseek :S)
-               // Regarding the suggestion that we have 2 file pointers; one for reading and one for writing:
-               // That seems like it will work... but we will have to be very careful and test it first
-               pthread_mutex_lock(&s->mutex);
-                       fseek(s->file, index*sizeof(DataPoint), SEEK_SET);
-                       int amount_read = fread(&d, sizeof(DataPoint), 1, s->file);
-               pthread_mutex_unlock(&s->mutex);
+               default:
+                       d->value = rand() % 2;
+                       usleep(1000000);
+                       break;
                
-               if (amount_read != 1)
+
+               case ANALOG_TEST0:
                {
-                       Fatal("Couldn't read single data point from sensor %d", s->id);
+                       d->value = (double)(rand() % 100) / 100;
+                       break;
                }
-
-               if (d.time_stamp > time_stamp)
+               case ANALOG_TEST1:
                {
-                       upper = index;
+                       static int count = 0;
+                       count %= 500;
+                       d->value = count++;
+                       break;
                }
-               else if (d.time_stamp < time_stamp)
+
+               case ANALOG_FAIL0:
+                       d->value = 0;
+                       //d->value = (double)(rand() % 6) * -( rand() % 2) / ( rand() % 100 + 1);
+                       //Gives a value between -5 and 5
+                       break;
+               case DIGITAL_TEST0:
+                       d->value = t.tv_sec % 2;
+
+                       break;
+               case DIGITAL_TEST1:
+                       d->value = (t.tv_sec+1)%2;
+                       break;
+               case DIGITAL_REALTEST:
                {
-                       lower = index;
+               // Can pass pin as argument, just using 20 as an example here
+               // Although since pins will be fixed, can just define it here if we need to
+                       //d->value = pinRead(20);       //Pin 20 on the Beaglebone
+                       break;
                }
-               if (count != NULL)
-                       *count += 1;
-       }
+               case DIGITAL_FAIL0:
+                       if( rand() % 100 > 98)
+                               d->value = 2;
+                       d->value = rand() % 2; 
+                       //Gives 0 or 1 or a 2 every 1/100 times
+                       break;
+               //default:
+               //      Fatal("Unknown sensor id: %d", s->id);
+               //      break;
+       }       
+       
 
-       if (found != NULL)
-               *found = d;
+       // Perform sanity check based on Sensor's ID and the DataPoint
+       Sensor_CheckData(s->id, d->value);
 
-       return index;
+       // Update latest DataPoint if necessary
        
+       if (result)
+       {
+               s->newest_data.time_stamp = d->time_stamp;
+               s->newest_data.value = d->value;
+       }
+       return result;
 }
 
 /**
- * Print sensor data between two indexes in the file, using a given format
- * @param s - Sensor to use
- * @param start - Start index
- * @param end - End index
- * @param output_type - JSON, CSV or TSV output format
+ * Record data from a single Sensor; to be run in a seperate thread
+ * @param arg - Cast to Sensor* - Sensor that the thread will handle
+ * @returns NULL (void* required to use the function with pthreads)
  */
-void PrintData(Sensor * s, int start, int end, OutputType output_type)
+void * Sensor_Loop(void * arg)
 {
-       DataPoint buffer[SENSOR_QUERYBUFSIZ];
-       int index = start;
-
-       if (output_type == JSON)
-       {
-               FCGI_JSONValue("[");
-       }
-
+       Sensor * s = (Sensor*)(arg);
+       Log(LOGDEBUG, "Sensor %d starts", s->id);
 
-       while (index < end)
+       // Until the sensor is stopped, record data points
+       while (s->activated)
        {
-               int to_read = end - index;
-               if (to_read > SENSOR_QUERYBUFSIZ)
-               {
-                       to_read = SENSOR_QUERYBUFSIZ;
-               }
-
-               int amount_read = 0;
-               // CRITICAL SECTION
-               pthread_mutex_lock(&(s->mutex));
-
-                       fseek(s->file, index*sizeof(DataPoint), SEEK_SET);
-                       amount_read = fread(buffer, sizeof(DataPoint), to_read, s->file);
-
-               pthread_mutex_unlock(&(s->mutex));
-               // End critical section
-
-               if (amount_read != to_read)
-               {
-                       Fatal("Failed to read %d DataPoints from sensor %d; read %d instead", to_read, s->id, amount_read);
-               }
-
-               // Print the data
-               for (int i = 0; i < amount_read; ++i)
+               DataPoint d;
+               //Log(LOGDEBUG, "Sensor %d reads data [%f,%f]", s->id, d.time_stamp, d.value);
+               if (Sensor_Read(s, &d)) // If new DataPoint is read:
                {
-                       //TODO: Reformat?
-                       switch (output_type)
-                       {
-                               case JSON:
-                                       FCGI_JSONValue("[%f, %f]", buffer[i].time_stamp, buffer[i].value);
-                                       if (i+1 < amount_read)
-                                               FCGI_JSONValue(",");
-                                       break;
-                               case CSV:
-                                       FCGI_PrintRaw("%f,%f\n", buffer[i].time_stamp, buffer[i].value);
-                                       break;
-                               case TSV:
-                               default:
-                                       FCGI_PrintRaw("%f\t%f\n", buffer[i].time_stamp, buffer[i].value);
-                                       break;
-                       }
+                       //Log(LOGDEBUG, "Sensor %d saves data [%f,%f]", s->id, d.time_stamp, d.value);
+                       Data_Save(&(s->data_file), &d, 1); // Record it
                }
-               index += amount_read;
        }
+       
+       // Needed to keep pthreads happy
 
-       if (output_type == JSON)
-       {
-               FCGI_JSONValue("]");
-       }
-}
-
-/**
- * Fill buffer with most recent sensor data
- * TODO: This may be obselete; remove?
- * @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;
+       Log(LOGDEBUG, "Sensor %d finished", s->id);
+       return NULL;
 }
 
 /**
@@ -363,252 +304,104 @@ Sensor * Sensor_Identify(const char * id_str)
 }
 
 /**
- * Handle a request to the sensor module
- * @param context - The context to work in
- * @param params - Parameters passed
- * TODO: Seriously need to write more helper functions and decrease the size of this function!
+ * Helper: Begin sensor response in a given format
+ * @param context - the FCGIContext
+ * @param id - ID of sensor
+ * @param format - Format
  */
-void Sensor_Handler(FCGIContext *context, char * params)
+void Sensor_BeginResponse(FCGIContext * context, SensorId id, DataFormat format)
 {
-       StatusCodes status = STATUS_OK;
-
-       OutputType output_type = JSON;
-       
-
-
-       const char * key; const char * value;
-
-       Sensor * sensor = NULL;
-
-       struct timeval now;
-       gettimeofday(&now, NULL);
-
-       double start_time = -1;
-       double end_time = -1;
-       double current_time = TIMEVAL_DIFF(now, g_options.start_time)
-       bool seek_time = false;
-       bool points_specified = false;
-       int query_size = SENSOR_QUERYBUFSIZ;
-       int start_index = -1;
-       int end_index = -1;
-
-       /* //Possible use case?
-       FCGIValue values[5] = {
-               {"id", &id, FCGI_REQUIRED(FCGI_INT_T)},
-               {"format", &format, FCGI_STRING_T},
-               {"points", &points, FCGI_STRING_T},
-               {"start_time", &start_time, FCGI_DOUBLE_T},
-               {"end_time", &end_time, FCGI_DOUBLE_T}
-       };
-       if (!FCGI_ParseRequest(context, params, values, 5))
-               return;*/
-
-       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, "format") == 0)
-               {
-                       if (strcmp(value, "json") == 0)
-                               output_type = JSON;
-                       else if (strcmp(value, "csv") == 0)
-                               output_type = CSV;
-                       else if (strcmp(value, "tsv") == 0)
-                               output_type = TSV;                      
-               }
-               else if (strcmp(key, "points") == 0)
-               {
-                       points_specified = true;
-                       if (strcmp(value, "all") == 0)
-                       {
-                               query_size = sensor->points_written;
-                       }
-                       else
-                       {
-                               char * end;
-                               query_size = strtol(value, &end, 10);
-                               if (*end != '\0')
-                               {
-                                       Log(LOGERR, "Require \"all\" or an integer value: %s = %s", key, value);
-                                       status = STATUS_ERROR;
-                                       break;
-                               }
-                       }
-                       
-               }
-               else if (strcmp(key, "start_time") == 0)
-               {
-                       seek_time = true;
-                       char * end;
-                       start_time = strtod(value, &end);
-                       if (*end != '\0')
-                       {
-                               Log(LOGERR, "Require a double: %s = %s", key, value);
-                               status = STATUS_ERROR;
-                               break;
-                       }                       
-
-                       // Treat negative values as being relative to the current time
-                       if (start_time < 0)
-                       {
-                               start_time = current_time + start_time;
-                       }
-                       start_time = floor(start_time);
-               }
-               else if (strcmp(key, "end_time") == 0)
-               {
-                       seek_time = true;
-                       char * end;
-                       end_time = strtod(value, &end);
-                       if (*end != '\0')
-                       {
-                               Log(LOGERR, "Require a double: %s = %s", key, value);
-                               status = STATUS_ERROR;
-                               break;
-                       }       
-
-                       // Treat negative values as being relative to the current time
-                       if (end_time < 0)
-                       {
-                               end_time = current_time + end_time;
-                       }               
-                       end_time = ceil(end_time);
-               }
-               // For backward compatability:
-               else if (strcmp(key, "dump") == 0)
-               {
-                       output_type = TSV;
-                       query_size = sensor->points_written+1;
-               }
-               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, "Invalid input parameters");
-               return;
-       }
-
-
-       if (seek_time)
-       {
-               if (end_time < 0 && !points_specified)
-                       end_index = sensor->points_written;
-               else
-               {
-                       int count = 0; DataPoint d;
-                       end_index = FindTime(sensor, end_time, &count, &d);
-                       Log(LOGDEBUG, "FindTime - Looked for %f; found [%f,%f] after %d iterations; sensor %d, position %d", end_time, d.time_stamp, d.value, count, sensor->id, end_index);
-               }
-               if (start_time < 0)
-                       start_time = 0;
-               else
-               {
-                       int count = 0; DataPoint d;
-                       start_index = FindTime(sensor, start_time, &count, &d);
-                       Log(LOGDEBUG, "FindTime - Looked for %f; found [%f,%f] after %d iterations; sensor %d, position %d", start_time, d.time_stamp, d.value, count, sensor->id, start_index);
-               }
-
-               if (points_specified)
-                       end_index = start_index + query_size;
-       }
-       else
-       {
-               start_index = sensor->points_written - query_size;
-               
-               end_index = sensor->points_written;
-       }
-       
-       if (start_index < 0)
-       {
-               Log(LOGNOTE, "start_index = %d => Clamped to 0", start_index);
-               start_index = 0;
-       }
-       if (end_index > sensor->points_written)
-       {
-               Log(LOGNOTE, "end_index = %d => Clamped to %d", end_index, sensor->points_written);
-               end_index = sensor->points_written;
-       }
-       
-       switch (output_type)
+       // Begin response
+       switch (format)
        {
                case JSON:
-                       FCGI_BeginJSON(context, status);
-                       FCGI_JSONLong("id", sensor->id);
-                       FCGI_JSONKey("data");
-                       PrintData(sensor, start_index, end_index, output_type);
-                       FCGI_EndJSON();
+                       FCGI_BeginJSON(context, STATUS_OK);
+                       FCGI_JSONLong("id", id);
+                       FCGI_JSONPair("name", g_sensor_names[id]);
                        break;
                default:
                        FCGI_PrintRaw("Content-type: text/plain\r\n\r\n");
-                       PrintData(sensor, start_index, end_index, output_type);
-                       //Force download with content-disposition
-                       // Sam: This is cool, but I don't think we should do it
-                       //  - letting the user view it in the browser and then save with their own filename is more flexible
-                       //"Content-disposition: attachment;filename=%d.csv\r\n\r\n", sensor->id);
                        break;
        }
-       
 }
 
 /**
- * Setup Sensors, start Sensor polling thread(s)
+ * Helper: End sensor response in a given format
+ * @param context - the FCGIContext
+ * @param id - ID of the sensor
+ * @param format - Format
  */
-void Sensor_Spawn()
+void Sensor_EndResponse(FCGIContext * context, SensorId id, DataFormat format)
 {
-       // start sensor threads
-       for (int i = 0; i < NUMSENSORS; ++i)
+       // End response
+       switch (format)
        {
-               Init(g_sensors+i, i);
-               pthread_create(&(g_sensors[i].thread), NULL, Sensor_Main, (void*)(g_sensors+i));
+               case JSON:
+                       FCGI_EndJSON();
+                       break;
+               default:
+                       break;
        }
 }
 
 /**
- * Quit Sensor loops
+ * Handle a request to the sensor module
+ * @param context - The context to work in
+ * @param params - Parameters passed
  */
-void Sensor_Join()
+void Sensor_Handler(FCGIContext *context, char * params)
 {
-       if (!Thread_Runstate())
+       struct timeval now;
+       gettimeofday(&now, NULL);
+       double current_time = TIMEVAL_DIFF(now, *Control_GetStartTime());
+
+       int id = 0;
+       double start_time = 0;
+       double end_time = current_time;
+       const char * fmt_str;
+
+       // key/value pairs
+       FCGIValue values[] = {
+               {"id", &id, FCGI_REQUIRED(FCGI_INT_T)}, 
+               {"format", &fmt_str, FCGI_STRING_T}, 
+               {"start_time", &start_time, FCGI_DOUBLE_T}, 
+               {"end_time", &end_time, FCGI_DOUBLE_T},
+       };
+
+       // enum to avoid the use of magic numbers
+       typedef enum {
+               ID,
+               FORMAT,
+               START_TIME,
+               END_TIME,
+       } SensorParams;
+       
+       // Fill values appropriately
+       if (!FCGI_ParseRequest(context, params, values, sizeof(values)/sizeof(FCGIValue)))
        {
-               Fatal("This function should not be called before Thread_QuitProgram");
+               // Error occured; FCGI_RejectJSON already called
+               return;
        }
-       for (int i = 0; i < NUMSENSORS; ++i)
+
+       // Error checking on sensor id
+       if (id < 0 || id >= NUMSENSORS)
        {
-               pthread_join(g_sensors[i].thread, NULL);
-               Destroy(g_sensors+i);
+               FCGI_RejectJSON(context, "Invalid sensor id");
+               return;
        }
+       Sensor * s = g_sensors+id;
+
+       DataFormat format = Data_GetFormat(&(values[FORMAT]));
+
+       // Begin response
+       Sensor_BeginResponse(context, id, format);
+
+       // Print Data
+       Data_Handler(&(s->data_file), &(values[START_TIME]), &(values[END_TIME]), format, current_time);
+       
+       // Finish response
+       Sensor_EndResponse(context, id, format);
 }
+
+
+

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