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
  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, 0, SEEK_SET);
  36                         rewind(file);
  37                         amount_read = fread(&buffer, sizeof(DataPoint), QUERY_BUFSIZ, file);
  38                         s->read_offset += amount_read;
  39                         Log(LOGDEBUG, "Read %d data points; offset now at %d", amount_read, s->read_offset);
  40
  41                         fclose(file);
  42                 }
  43
  44         pthread_mutex_unlock(&(s->mutex));
  45         //End critical section
  46
  47         // So... we have a buffer
  48         // I guess we'll want to JSON it or something?
  49         // Just print it out for now
  50         for (int i = 0; i < amount_read; ++i)
  51         {
  52                 printf("%f\t%f\n", buffer[i].time, buffer[i].value);
  53         }
  54
  55         // Will want to handle case where there actually wasn't anything new to respond with
  56         // (In case we have a sensor that is slower than the rate of jQuery requests)
  57         if (amount_read == 0)
  58         {
  59                 Log(LOGWARN, "No data points read from sensor%s file");
  60                 printf("# No data\n");
  61         }
  62 }
  63
  64 /**
  65  * Test function to simulate responding to HTTP requests
  66  * @param args - IGNORED (void* required to pass function to pthread_create)
  67  * @returns NULL (void* required to pass function to pthread_create)
  68  */
  69 void * Query_Main(void * args)
  70 {
  71         while (true) //TODO: Exit condition
  72         {
  73
  74                 for (int i = 0; i < NUMSENSORS; ++i)
  75                 {
  76                         printf("# Sensor %d\n", i);
  77                         QuerySensor(i);
  78                         printf("\n");
  79                 }
  80                 usleep(REQUEST_RATE);
  81         }
  82 }