server/query.c

   1 /**
   2  * @file query.c
   3  * @purpose Temporary file to run a test thread that will query a sensors thread
   4  * Code will probably be combined with Jeremy's FastCGI API
   5  */
   6
   7
   8
   9 #include "query.h"
  10
  11 #include "sensor.h"
  12 #include "log.h"
  13
  14 static DataPoint buffer[QUERY_BUFSIZ];
  15
  16 /**
  17  * Query sensor with id
  18  * @param id - The index of the sensor in g_sensors
  19  */
  20 void QuerySensor(int id) //TODO: This code will form the SensorHandler FastCGI function (I think?)
  21 {
  22         Sensor * s = g_sensors+id;
  23
  24         int amount_read = 0;
  25         //CRITICAL SECTION (Don't access file while sensor thread is writing to it!)
  26         pthread_mutex_lock(&(s->mutex));
  27
  28                 FILE * file = fopen(s->filename, "rb");
  29                 if (file == NULL)
  30                 {
  31                         Log(LOGWARN, "Couldn't open file \"%s\" mode rb - %s", s->filename, strerror(errno));
  32                 }
  33                 else
  34                 {
  35                         fseek(file, (s->read_offset)*sizeof(DataPoint), SEEK_SET);
  36                         amount_read = fread(&buffer, sizeof(DataPoint), QUERY_BUFSIZ, file);
  37                         s->read_offset += amount_read;
  38                         Log(LOGDEBUG, "Read %d data points; offset now at %d", amount_read, s->read_offset);
  39
  40                         fclose(file);
  41                 }
  42
  43         pthread_mutex_unlock(&(s->mutex));
  44         //End critical section
  45
  46         // So... we have a buffer
  47         // I guess we'll want to JSON it or something?
  48         // Just print it out for now
  49         for (int i = 0; i < amount_read; ++i)
  50         {
  51                 printf("%f\t%f\n", buffer[i].time, buffer[i].value);
  52         }
  53
  54         // Will want to handle case where there actually wasn't anything new to respond with
  55         // (In case we have a sensor that is slower than the rate of jQuery requests)
  56         if (amount_read == 0)
  57         {
  58                 Log(LOGWARN, "No data points read from sensor%s file");
  59                 printf("# No data\n");
  60         }
  61 }
  62
  63 /**
  64  * Test function to simulate responding to HTTP requests
  65  * @param args - IGNORED (void* required to pass function to pthread_create)
  66  * @returns NULL (void* required to pass function to pthread_create)
  67  */
  68 void * Query_Main(void * args)
  69 {
  70         while (true) //TODO: Exit condition
  71         {
  72
  73                 for (int i = 0; i < NUMSENSORS; ++i)
  74                 {
  75                         printf("# Sensor %d\n", i);
  76                         QuerySensor(i);
  77                         printf("\n");
  78                 }
  79                 usleep(REQUEST_RATE);
  80         }
  81 }