Contributor: PHIL NICKELL
UNIT MaxMinL;
(*
The source code MaxMinL unit is released to the public domain. No
rights are reserved. Phil Nickell. NSoft Co.
This Turbo Pascal unit implements five highly optimized assembly
language functions that provide MAX() and MIN() for unsigned longword
and signed longintegers, and also a function for an unsigned longword
compare. The word functions treat the passed values as unsigned
values. The integer functions treat the passed values as signed
values. Turbo pascal does not have a LONGWORD data type, but the
MAXLW() and MINLW() functions treat the passed longint types as
unsigned words. Maxlw returns $ffffffff as greater than 0. Minlw
returns 0 as less than $ffffffff.
*)
{$r-,S-}
INTERFACE
FUNCTION MAXLW (a,b:longint) : Longint; { max longword }
FUNCTION MINLW (a,b:Longint) : Longint; { min longword }
FUNCTION MAXLI (a,b:longint) : Longint; { max longint }
function MINLI (a,b:Longint) : Longint; { min longint }
function LWGT (a,b:Longint) : Boolean; { long> unsigned }
IMPLEMENTATION
function maxlw(a,b:longint):longint; Assembler; {long word}
Asm
les ax, a { load longint to es:ax }
mov dx, es { load longint to dx:ax }
cmp dx, word ptr b+2 { cmp high words }
ja @2 { high word> }
jb @1 { high word < } cmp ax, word ptr b { comp low word } jae @2 { low word>= }
@1: les ax, b
mov dx, es { load int to dx:ax }
@2:
End;
function minlw(a,b:longint):longint; Assembler; { longword }
Asm
les ax, a { load longint to es:ax }
mov dx, es { load longint to dx:ax }
cmp dx, word ptr b+2 { cmp high words }
jb @2 { high word < } ja @1 { high word> }
cmp ax, word ptr b { comp low word }
jbe @2 { low word>= }
@1: les ax, b
mov dx, es { load int to dx:ax }
@2:
End;
function maxli(a,b:longint):longint; Assembler;
Asm
les ax, a { load longint to es:ax }
mov dx, es { load longint to dx:ax }
cmp dx, word ptr b+2 { cmp high words }
jg @2 { high word> }
jl @1 { high word < } cmp ax, word ptr b { comp low word } jae @2 { low word>= }
@1: les ax, b
mov dx, es { load int to dx:ax }
@2:
End;
function minli(a,b:longint):longint; Assembler;
Asm
les ax, a { load longint to es:ax }
mov dx, es { load longint to dx:ax }
cmp dx, word ptr b+2 { cmp high words }
jl @2 { high word < } jg @1 { high word> }
cmp ax, word ptr b { comp low word }
jbe @2 { low word>= }
@1: les ax, b
mov dx, es { load int to dx:ax }
@2:
End;
function lwgt(a,b:longint):boolean; Assembler; {unsigned longword greater than
}
Asm
xor cx, cx { cx = 0 = false }
les ax, a { load longint to es:ax }
mov dx, es { load longint to dx:ax }
cmp dx, word ptr b+2 { cmp high words }
jb @2 { high word < } ja @1 { high word> }
cmp ax, word ptr b { comp low word }
jbe @2 { low word <= }
@1: inc cx { cx = 1 = true }
@2: mov ax, cx { load result to ax }
End;
BEGIN {INITIALIZATION}
END.