🚀 go-pugleaf

Hi all,

How do you put a literal in a string?

Uh, what's wrong with "myline:= 'This is an example';"

Nothing, but now assume that you're doing this many times in a program,
and look at the code generated to make this assignment, you'll see that
it comes to 18 bytes, excluding the string itself.

How do you concatenate a string with a literal?

Uh, what's wrong with "myline:= myline + 'This is an example';"

Nothing, but now assume that you're doing this many times in a program,
and look at the code generated to make this assignment, you'll see that
it comes to 39 bytes, excluding the string itself.

Wouldn't it be nice if you could shorten this? Faced with 20 of such
assignments, and 18 concatenations in a program, I came up with this,
but be warned that it _does not contain any error checking_, in other
words, you have to know what you are doing!

var myline: string; {must be global}

procedure cs_2_line; far; assembler;
asm
  push bp
  mov  bp, sp

  mov  dx, ds
  mov  es, dx
  lds  si, [bp + 2]  {get start of string}
  mov  [bp + 2], cx  {set return address past string}
  mov  al, [si]      {get info byte, $00: fill, $ff: concatenate}
  inc  si
  sub  cx, si        {length of string}
  seges; and  byte ptr myline, al {set length to zero/keep original}
  mov  di, offset myline
  mov  bl, es:[di]   {get current length og myline}
  xor  bh, bh
  add  es:[di], cl   {set new length}
  inc  bx
  add  di, bx        {start position of destination}
  inc  cx            {I know what I'm doing, and}
  shr  cx, 1         {want to move two bytes at a time}
  cld
  rep  movsw

  mov  ds, dx
  pop  bp
end; {cs_2_line}

Moving a literal to myline now becomes:

asm
  mov  cs, offset @1
  call cs_2_line

  db   $00
  db   "This is an example"
@1:
end;

and concatenating something to it is almost the same with:

asm
  mov  cs, offset @1
  call cs_2_line

  db   $ff
  db   "This will be concatenated"
@1:
end;

My savings? 710 bytes...

Decide for yourself if you think it's useful!

Robert

PS: Q: What's the difference between:

myline:= myline + 'this is a veryyyyyyyyyyyyyyyyyyyyyyyyyyy ' +
                  'looooooooooooooooooooooooooooooooooooong '  +
                  'extension to myline';
and

myline:= myline + ('this is a veryyyyyyyyyyyyyyyyyyyyyyyyyyy ' +
                   'looooooooooooooooooooooooooooooooooooong '  +
                   'extension to myline');

A: BP does not fold the constant in the first example at compile time!
--
Robert AH Prins
prino@bigfoot.com


Sent via Deja.com http://www.deja.com/
Before you buy.