Thread: fstream, getch

It's tough to answer what the most efficient way of doing something is when you haven't really said what you are doing.

>Is there a c++ function that can return ALL keys pressed?
It's not about a function that returns ALL keys, it's about how those keys are represented. If your system represents the function keys with multi-value scan codes, you're likely to get the same value for every one if you only read the leading byte. Run this program and see what happens when you hit the F keys:

Code:

#include <stdio.h> 
#include <conio.h> 

int main ( void )
{
  int ch;

  while ( ( ch = getch() ) != 0x1B )
    printf ( "&#37;d\n", ch );

  return 0;
}

You'll probably find something like this:

Code:

F1:  0   59
F2:  0   60
F3:  0   61
F4:  0   62
F5:  0   63
F6:  0   64
F7:  0   65
F8:  0   66
F9:  0   67
F10: 0   68
F11: 224 133
F12: 224 134

Oddly enough, cprog's FAQ tells you about this in the "How do I: Use directional keys in a console application" article. It even offers a handy function that gives you a consistent result for all scan codes:

Code:

int get_code ( void )
{
  int ch = getch();

  if ( ch == 0 || ch == 224 )
    ch = 256 + getch();

  return ch;
}

>Getting 1 key at time and then writing that to the file, or writing a chunk of char data at a time?
It depends on how your implementation handles buffering. If it's done right, there shouldn't be enough of a difference to matter. But it's generally a safer bet to write chunks.

OK, want to make sure I understand this correctly.

So, basically, when using getch(), the F keys just return simple pair of decimal values. If I wanted to check to see if, for example, the F1 key was pressed, I would compare it to that simple int value.

Code:

if (keystroke == 059)
{
// action here
}

After your post, I went ahead and googled "keyboard scan codes" "scan codes". There's also a hex value for the functions keys. If I were to compare using hex values, would it be the same, just reading the keystroke in to a string instead? I hope I haven't completely confused you with my response.

If these are the dec and hex values for the function keys, how would I go about checking for them since they are in pairs?

Code:

F1        (00,59)    (0x00,0x3b)    F2       (00,60)    (0x00,0x3c)
F3        (00,61)    (0x00,0x3d)    F4       (00,62)    (0x00,0x3e)
F5        (00,63)    (0x00,0x3f)    F6       (00,64)    (0x00,0x40)
F7        (00,65)    (0x00,0x41)    F8       (00,66)    (0x00,0x42)
F9        (00,67)    (0x00,0x43)    F10      (00,68)    (0x00,0x44)
F11       (00,133)   (0x00,0x85)    F12      (00,134)   (0x00,0x86)