#include <stdio.h>
#include <algorithm>
#include <windows.h>

int main(int argc, char *argv[])
{
   if (argc < 3)
   {
      printf("FIBSTR <outfile> N(Mb) [O]\n");
      return 0;
   }
   unsigned N, O = 2;
   sscanf(argv[2], "%u", &N);
   N <<= 20;
   if (argc > 3)
   {
       sscanf(argv[3], "%u", &O);
       O = min(26, max(2, O));
   }
   HANDLE fh = CreateFile(
      argv[1],
      GENERIC_READ | GENERIC_WRITE,
      FILE_SHARE_READ,
      0,
      CREATE_ALWAYS,
      FILE_FLAG_SEQUENTIAL_SCAN,
      0);
   HANDLE fmh = CreateFileMapping(fh, 0, PAGE_READWRITE, 0, N, 0);
   char * const beg = static_cast<char*>(
       MapViewOfFile(fmh, FILE_MAP_WRITE, 0, 0, N));
   //
   unsigned len[32];
   for (unsigned i = 0; i != min(N, O); ++i)
   {
      beg[i] = static_cast<char>('a' + i);
      len[i] = 1;
   }
   if (N > O)
   {
      char *cur = beg + O;
      unsigned curLen = 0;
      for (; cur != beg + N; )
      {
         const unsigned len2 = min(
             cur - beg - len[curLen],
             static_cast<unsigned>(beg + N - cur));
         CopyMemory(cur, beg, len2);
         len[curLen++] = cur - beg;
         if (curLen == O)
            curLen = 0;
         cur += len2;
      }
   }
   for (unsigned i = 0; i < N; )
   {
       const unsigned r = rand(), r2 = rand() * rand();
       if (r < 0x6000)
           i += r2 % 0x40;
       else if (r < 0x7000)
           i += r2 % 0x80;
       else if (r < 0x7800)
           i += r2 % 0x100;
       else if (r < 0x7ff8)
           i += r2 % 0x1000;
       else
           i += r2 % (min(0x100000, N / 0x10));
       //
       if (i < N)
           beg[i] = '\n';
   }
   //
   UnmapViewOfFile(beg);
   CloseHandle(fmh);
   CloseHandle(fh);
}