From: Sam Moore <matches@ucc.asn.au>
Date: Sun, 18 Aug 2013 13:11:37 +0000 (+0800)
Subject: Change sensor data transfer
X-Git-Url: https://git.ucc.asn.au/?a=commitdiff_plain;h=97d3625dcb84e6371d2464c93ae9bef8a3d4b466;p=matches%2FMCTX3420.git

Change sensor data transfer

 - Keep binary file always open (mode "a+b"); don't need to reopen each time it is accessed
 - Fill query buffer with most recent datapoints (as opposed to trying to transfer datapoints in sequential order)
   - Better because it keeps client as up to date as possible
   - Rather than client getting increasingly outdated data

TODO:
 - Test to see if buffers in front of writing to file worth it
   - Probably will be; saves from having to unlock mutex on every single data point
 - Merge Query and FCGI stuff
---

diff --git a/server/query.c b/server/query.c
index 8499e37..86696bb 100644
--- a/server/query.c
+++ b/server/query.c
@@ -25,21 +25,10 @@ void QuerySensor(int id) //TODO: This code will form the SensorHandler FastCGI f
 	//CRITICAL SECTION (Don't access file while sensor thread is writing to it!)
 	pthread_mutex_lock(&(s->mutex));
 
-		FILE * file = fopen(s->filename, "rb");
-		if (file == NULL)
-		{
-			Log(LOGWARN, "Couldn't open file \"%s\" mode rb - %s", s->filename, strerror(errno));			
-		}
-		else
-		{
-			fseek(file, (s->read_offset)*sizeof(DataPoint), SEEK_SET);
-			amount_read = fread(&buffer, sizeof(DataPoint), QUERY_BUFSIZ, file);
-			s->read_offset += amount_read;
-			Log(LOGDEBUG, "Read %d data points; offset now at %d", amount_read, s->read_offset);
-			
-			fclose(file);
-		}
-
+		fseek(s->file, -QUERY_BUFSIZ*sizeof(DataPoint), SEEK_END);
+		amount_read = fread(&buffer, sizeof(DataPoint), QUERY_BUFSIZ, s->file);
+		Log(LOGDEBUG, "Read %d data points", amount_read);
+		
 	pthread_mutex_unlock(&(s->mutex));
 	//End critical section
 
diff --git a/server/sensor.c b/server/sensor.c
index a3d3f0b..b746134 100644
--- a/server/sensor.c
+++ b/server/sensor.c
@@ -48,8 +48,8 @@ DataPoint GetData(int sensor_id)
  */
 void Destroy(Sensor * s)
 {
-	//TODO: Surely we'll need to do something here?
 	// Maybe move the binary file into long term file storage?
+	fclose(s->file);
 }
 
 
@@ -64,14 +64,18 @@ void Sensor_Init(Sensor * s, int id)
 	s->read_offset = 0;
 	s->id = id;
 
+	#define FILENAMESIZE 4
+	char filename[FILENAMESIZE];
 	if (s->id >= pow(10, FILENAMESIZE))
 	{
 		Fatal("Too many sensors! FILENAMESIZE is %d; increase it and recompile.", FILENAMESIZE);
 	}
-	sprintf(s->filename, "%d", s->id);
-	unlink(s->filename); //TODO: Move old files somewhere
+		
+	sprintf(filename, "%d", s->id);
+	unlink(filename); //TODO: Move old files somewhere
 
-	Log(LOGDEBUG, "Initialised sensor %d; binary file is \"%s\"", id, s->filename);
+	s->file = fopen(filename, "a+b"); // open binary file
+	Log(LOGDEBUG, "Initialised sensor %d; binary file is \"%s\"", id, filename);
 }
 
 
@@ -104,23 +108,13 @@ void * Sensor_Main(void * arg)
 
 		// CRITICAL SECTION (no threads should be able to read/write the file at the same time)
 		pthread_mutex_lock(&(s->mutex));
-
-			// Open binary file in append mode and dump buffer into it
-			FILE * file = fopen(s->filename, "ab");
-			if (file == NULL)
-			{
-				Fatal("Couldn't open file \"%s\" mode ab - %s", s->filename, strerror(errno));
-			}
-			int amount_written = fwrite(s->buffer, sizeof(DataPoint), SENSOR_DATABUFSIZ, file);
+			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);
-
-			fclose(file);
-
 		pthread_mutex_unlock(&(s->mutex));
 		// End of critical section
 
diff --git a/server/sensor.h b/server/sensor.h
index e51ab0c..ae17ce3 100644
--- a/server/sensor.h
+++ b/server/sensor.h
@@ -14,11 +14,10 @@
 /** Number of data points to keep in sensor buffers **/
 #define SENSOR_DATABUFSIZ 10
 
+
 /** Number of sensors **/
 #define NUMSENSORS 1
 
-#define FILENAMESIZE 10
-
 /** Structure to represent data recorded by a sensor at an instant in time **/
 typedef struct
 {
@@ -40,7 +39,7 @@ typedef struct
 	/** Offset position in binary file for query thread to read from**/
 	int read_offset;
 	/** File to write data into when buffer is full **/
-	char filename[FILENAMESIZE];
+	FILE * file;
 	/** Thread running the sensor **/
 	pthread_t thread;
 	/** Mutex to protect access to stuff **/