#include <iostream>
#include <fstream>

using namespace std;

typedef unsigned char byte;
typedef signed char sbyte;

struct observation
{ short int year;
  byte      month, day;
  short int mint, avgt, maxt;
  sbyte     snow, rain;
  byte      wind; };

const int szob = sizeof(observation);

int main()
{ if (szob != 14)
  { cerr << "Look out! sizeof(observation) is " << szob << ", not 14\n";
    exit(1); }
  cout << "OK so far\n";

  fstream bf("data.dat", ios::in | ios::binary);
  if (bf.fail())
  { cerr << "Can't read data.dat\n";
    exit(1); }

  bf.seekg(0, ios::end);
  int filelen = bf.tellg();
  cout << filelen << " bytes = " << filelen/szob << " records\n";
  if (filelen % szob != 0)
  { cout << filelen % szob << " bytes left over\n";
    exit(1); }

  int wanty = 2003, wantm = 10, wantd = 30;

  int first = 0, last = filelen / szob - 1;
  while (first <= last)
  { int mid = (first + last) / 2;

    observation ob;
    bf.seekg(mid * szob, ios::beg);
    bf.read((char *) & ob, szob);

    cout << "looking at " << ob.year << " " << (int)ob.month << " " << (int)ob.day << "\n";

    char side;
    if (ob.year < wanty)
      side = '<';
    else if (ob.year > wanty)
      side = '>';
    else if (ob.month < wantm)
      side = '<';
    else if (ob.month > wantm)
      side = '>';
    else if (ob.day < wantd)
      side = '<';
    else if (ob.day > wantd)
      side = '>';
    else
      side = '=';

    if (side == '<')
      first = mid + 1;
    else if (side == '>')
      last = mid - 1;
    else
    { cout << "found what I wanted\n";
      break; } }

  bf.close(); }