git.sesse.net Git - nms/blob - sql/get_rate.c

   1 /*
   2    gcc -fPIC -c get_rate.c -I$( pg_config --includedir-server )
   3    gcc -shared -o get_rate.so get_rate.o
   4  */
   5
   6 #include "postgres.h"
   7 #include <string.h>
   8 #include "fmgr.h"
   9 #include "funcapi.h"
  10 #include "catalog/pg_type.h"
  11 #include "utils/lsyscache.h"
  12 #include "utils/array.h"
  13 #include "access/heapam.h"
  14
  15 #ifdef PG_MODULE_MAGIC
  16 PG_MODULE_MAGIC;
  17 #endif
  18
  19 PG_FUNCTION_INFO_V1(get_rate);
  20
  21 Datum
  22 get_rate(PG_FUNCTION_ARGS)
  23 {
  24         float8 bytes_in_1 = PG_GETARG_FLOAT8(0);
  25         float8 bytes_out_1 = PG_GETARG_FLOAT8(1);
  26         float8 time_1 = PG_GETARG_FLOAT8(2);
  27
  28         float8 bytes_in_2 = PG_GETARG_FLOAT8(3);
  29         float8 bytes_out_2 = PG_GETARG_FLOAT8(4);
  30         float8 time_2 = PG_GETARG_FLOAT8(5);
  31
  32         bool no_wrap = PG_GETARG_BOOL(6);
  33
  34         Datum values[2];
  35
  36         int16 elmlen;
  37         bool elmbyval;
  38         char elmalign;
  39
  40         double in_rate, out_rate;
  41
  42         if (bytes_in_2 >= bytes_in_1 && bytes_out_2 >= bytes_out_1) {
  43                 // regular case, no wraparound or reset
  44                 in_rate = (bytes_in_2 - bytes_in_1) / (time_2 - time_1);
  45                 out_rate = (bytes_out_2 - bytes_out_1) / (time_2 - time_1);
  46         } else {
  47                 // is wraparound unlikely?
  48                 if (no_wrap
  49                     || (bytes_in_2 + 4294967296.0 - bytes_in_1) >= 2147483648.0
  50                     || (bytes_out_2 + 4294967296.0 - bytes_out_1) >= 2147483648.0) {
  51                         // assume the switch zeroed in the middle of the poll interval
  52                         in_rate = bytes_in_2 / (2.0 * (time_2 - time_1));
  53                         out_rate = bytes_out_2 / (2.0 * (time_2 - time_1));
  54                 } else {
  55                         // probably wraparound
  56                         if (bytes_in_2 < bytes_in_1)
  57                                 bytes_in_2 += 4294967296.0;
  58                         if (bytes_out_2 < bytes_out_1)
  59                                 bytes_out_2 += 4294967296.0;
  60
  61                         in_rate = (bytes_in_2 - bytes_in_1) / (time_2 - time_1);
  62                         out_rate = (bytes_out_2 - bytes_out_1) / (time_2 - time_1);
  63                 }
  64         }
  65
  66         values[0] = Float8GetDatum(in_rate);
  67         values[1] = Float8GetDatum(out_rate);
  68         get_typlenbyvalalign(FLOAT8OID, &elmlen, &elmbyval, &elmalign);
  69         PG_RETURN_ARRAYTYPE_P(construct_array(values, 2, FLOAT8OID, elmlen, elmbyval, elmalign));
  70 }