Contributor: JES R. KLINKE
{
You may use the following unit I have made for an encryption program
of mine. It implements real binary arithmetic, no BCD. But be careful,
there is currently no range checking at all, and overflows may result
in endless loops. If you need 2048 bit integers you have to set
BigNumLength to at least 128, a little more would be safer. Also
notice that the routines cannot handle negative numbers.
I hope you find this one useful.
Jes R Klinke
}
PROGRAM BigNum;
USES
Crt, Dos;
CONST
BigNumLength = 20; {Number of words in value}
TYPE
PBigNum = ^TBigNum;
TBigNum = object
Value : ARRAY [0..BigNumLength - 1] OF WORD;
PROCEDURE ASSIGN (VAR AValue : TBigNum);
PROCEDURE AssignLong (AValue : LONGINT);
PROCEDURE ADD (VAR AValue : TBigNum);
PROCEDURE Subtract (VAR AValue : TBigNum);
PROCEDURE Multiply (VAR AMultiplicator : TBigNum);
FUNCTION Divide (VAR ADivisor : TBigNum) : BOOLEAN;
FUNCTION Modulus (VAR ADivisor : TBigNum) : BOOLEAN;
PROCEDURE SquareRoot;
PROCEDURE Increment (By : WORD);
PROCEDURE Decrement (By : WORD);
PROCEDURE BitwiseOr (VAR AMaske : TBigNum);
FUNCTION Compare (VAR AValue : TBigNum) : INTEGER;
PROCEDURE Mult10;
PROCEDURE Div10;
PROCEDURE Mult2;
PROCEDURE Div2;
FUNCTION STR : STRING;
FUNCTION Str16 : STRING;
PROCEDURE VAL (CONST S : STRING);
FUNCTION AsLong : LONGINT;
END;
PROCEDURE TBigNum.ASSIGN (VAR AValue : TBigNum);
BEGIN
MOVE (AValue.Value, Value, SIZEOF (Value) );;
END;
PROCEDURE TBigNum.AssignLong (AValue : LONGINT);
BEGIN
MOVE (AValue, Value [0], SIZEOF (LONGINT) );;
FILLCHAR (Value [SIZEOF (LONGINT) SHR 1], BigNumLength SHL 1 -
SIZEOF (LONGINT), 0);
END;
PROCEDURE TBigNum.ADD (VAR AValue : TBigNum); assembler;
asm
PUSH DS
LES DI, Self
ADD DI, OFFSET TBigNum.Value
LDS SI, AValue
ADD SI, OFFSET TBigNum.Value
MOV CX, BigNumLength
CLD
CLC
@@0 : LODSW
ADC [ES : DI], AX
INC DI
INC DI
LOOP @@0
POP DS
END;
PROCEDURE TBigNum.Subtract (VAR AValue : TBigNum); assembler;
asm
PUSH DS
LES DI, Self
ADD DI, OFFSET TBigNum.Value
LDS SI, AValue
ADD SI, OFFSET TBigNum.Value
MOV CX, BigNumLength
CLD
CLC
@@0 : LODSW
SBB [ES : DI], AX
INC DI
INC DI
LOOP @@0
POP DS
END;
PROCEDURE TBigNum.Multiply (VAR AMultiplicator : TBigNum); assembler;
VAR
Res : ARRAY [0..BigNumLength] OF WORD;
asm
PUSH DS
PUSH BP
STD
LES DI, AMultiplicator
ADD DI, OFFSET TBigNum.Value
LDS SI, Self
ADD SI, OFFSET TBigNum.Value
PUSH SI
LEA BP, Res
XOR SI, SI
MOV CX, BigNumLength
XOR AX, AX
@@8 : MOV SS : [BP + SI], AX
ADD SI, 2
LOOP @@8
POP SI
XOR BX, BX
@@0 : MOV CX, BX
MOV DX, CX
SHL DX, 1
ADD SI, DX
INC CX
@@1 : LODSW
MOV DX, ES : [DI]
ADD DI, 2
MUL DX
ADD SS : [BP], AX
ADC SS : [BP + 2], DX
JC @@3
@@2 : LOOP @@1
MOV DX, BX
INC DX
SHL DX, 1
SUB DI, DX
ADD SI, 2
ADD BP, 2
INC BX
CMP BX, BigNumLength
JNE @@0
CLD
POP BP
LEA SI, Res
PUSH SS
POP DS
LES DI, Self
ADD DI, OFFSET TBigNum.Value
MOV CX, BigNumLength
REP MOVSW
POP DS
JMP @@9
@@3 : PUSH SI
MOV DX, 1
MOV SI, 4
@@4 : ADD [BP + SI], DX
INC SI
INC SI
JC @@4
POP SI
JMP @@2
@@9 :
END;
FUNCTION TBigNum.Divide (VAR ADivisor : TBigNum) : BOOLEAN;
VAR
Bit, Res, Divisor : TBigNum;
WholeResult : BOOLEAN;
BEGIN
Divisor.ASSIGN (ADivisor);
WholeResult := FALSE;
Bit.AssignLong (1);
Res.AssignLong (0);
WHILE Compare (Divisor)>= 0 DO
BEGIN
Bit.Mult2;
Divisor.Mult2;
END;
WHILE (Bit.Value [0] AND 1 = 0) AND NOT WholeResult DO
BEGIN
Bit.Div2;
Divisor.Div2;
CASE Compare (Divisor) OF
1 :
BEGIN
Res.BitwiseOr (Bit);
Subtract (Divisor);
END;
0 :
BEGIN
WholeResult := TRUE;
Res.BitwiseOr (Bit);
Subtract (Divisor);
END;
END;
END;
ASSIGN (Res);
Divide := WholeResult;
END;
FUNCTION TBigNum.Modulus (VAR ADivisor : TBigNum) : BOOLEAN;
VAR
Bit, Res, Divisor : TBigNum;
WholeResult : BOOLEAN;
BEGIN
Divisor.ASSIGN (ADivisor);
WholeResult := FALSE;
Bit.AssignLong (1);
Res.AssignLong (0);
WHILE Compare (Divisor)>= 0 DO
BEGIN
Bit.Mult2;
Divisor.Mult2;
END;
WHILE (Bit.Value [0] AND 1 = 0) AND NOT WholeResult DO
BEGIN
Bit.Div2;
Divisor.Div2;
CASE Compare (Divisor) OF
1 :
BEGIN
Res.BitwiseOr (Bit);
Subtract (Divisor);
END;
0 :
BEGIN
WholeResult := TRUE;
Res.BitwiseOr (Bit);
Subtract (Divisor);
END;
END;
END;
Modulus := WholeResult;
END;
PROCEDURE TBigNum.SquareRoot;
VAR
Guess, NewGuess : TBigNum;
BEGIN
NewGuess.ASSIGN (Self);
NewGuess.Div2;
REPEAT
Guess.ASSIGN (NewGuess);
NewGuess.ASSIGN (Self);
NewGuess.Divide (Guess);
NewGuess.ADD (Guess);
NewGuess.Div2;
UNTIL NewGuess.Compare (Guess) = 0;
ASSIGN (NewGuess);
END;
PROCEDURE TBigNum.Increment (By : WORD); assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
CLD
MOV AX, ES : [DI]
ADD AX, By
STOSW
MOV CX, BigNumLength - 1
@@0 : MOV AX, ES : [DI]
ADC AX, 0
STOSW
LOOP @@0
END;
PROCEDURE TBigNum.Decrement (By : WORD); assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
CLD
MOV AX, ES : [DI]
SUB AX, By
STOSW
MOV CX, BigNumLength - 1
@@0 : MOV AX, ES : [DI]
SBB AX, 0
STOSW
LOOP @@0
END;
PROCEDURE TBigNum.BitwiseOr (VAR AMaske : TBigNum); assembler;
asm
PUSH DS
LES DI, Self
ADD DI, OFFSET TBigNum.Value
LDS SI, AMaske
ADD SI, OFFSET TBigNum.Value
MOV CX, BigNumLength
CLD
@@0 : LODSW
OR AX, ES : [DI]
STOSW
LOOP @@0
POP DS
END;
FUNCTION TBigNum.Compare (VAR AValue : TBigNum) : INTEGER; assembler;
asm
PUSH DS
LES DI, Self
ADD DI, OFFSET TBigNum.Value
LDS SI, AValue
ADD SI, OFFSET TBigNum.Value
MOV CX, BigNumLength
MOV DX, CX
DEC DX
SHL DX, 1
ADD DI, DX
ADD SI, DX
STD
REPZ CMPSW
MOV AX, 0FFFFh
JA @@1
MOV AX, 0000h
JE @@1
MOV AX, 0001h
@@1 : POP DS
END;
PROCEDURE TBigNum.Mult10; assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
XOR BX, BX
MOV CX, BigNumLength
@@0 : MOV AX, [ES : DI]
MOV DX, 10
MUL DX
ADD AX, BX
ADC DX, 0
MOV [ES : DI], AX
INC DI
INC DI
MOV BX, DX
LOOP @@0
END;
PROCEDURE TBigNum.Div10; assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
MOV CX, BigNumLength
MOV DX, CX
DEC DX
SHL DX, 1
ADD DI, DX
XOR DX, DX
@@0 : MOV AX, [ES : DI]
MOV BX, 10
DIV BX
MOV [ES : DI], AX
DEC DI
DEC DI
LOOP @@0
END;
PROCEDURE TBigNum.Mult2; assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
XOR BX, BX
MOV CX, BigNumLength
CLC
CLD
@@0 : MOV AX, [ES : DI]
RCL AX, 1
STOSW
LOOP @@0
END;
PROCEDURE TBigNum.Div2; assembler;
asm
LES DI, Self
ADD DI, OFFSET TBigNum.Value
MOV CX, BigNumLength
MOV DX, CX
DEC DX
SHL DX, 1
ADD DI, DX
XOR DX, DX
CLC
STD
@@0 : MOV AX, [ES : DI]
RCR AX, 1
STOSW
LOOP @@0
END;
FUNCTION TBigNum.STR : STRING;
VAR
M, T : TBigNum;
Res : STRING;
I, Ciffer : INTEGER;
BEGIN
M.ASSIGN (Self);
T.AssignLong (1);
I := 0;
WHILE M.Compare (T)>= 0 DO
BEGIN
T.Mult10;
INC (I);
END;
IF I <= 1 THEN BEGIN STR := CHAR (BYTE ('0') + M.Value [0]); END ELSE BEGIN Res := ''; T.Div10; WHILE I> 0 DO
BEGIN
Ciffer := 0;
WHILE (M.Compare (T)>= 0) DO
BEGIN
M.Subtract (T);
INC (Ciffer);
END;
Res := Res + CHAR (BYTE ('0') + Ciffer);
DEC (I);
T.Div10;
END;
STR := Res;
END;
END;
FUNCTION TBigNum.Str16 : STRING;
CONST
HexCif : ARRAY [0..15] OF CHAR = '0123456789ABCDEF';
VAR
Res : STRING;
I : INTEGER;
ErMed : BOOLEAN;
BEGIN
ErMed := FALSE;
Res := '';
FOR I := BigNumLength - 1 DOWNTO 0 DO
BEGIN
IF ErMed OR (Value [I] 0) THEN
BEGIN
IF ErMed OR (Value [I] SHR 12 AND $F 0) THEN
BEGIN
Res := Res + HexCif [Value [I] SHR 12 AND $F];
ErMed := TRUE;
END;
IF ErMed OR (Value [I] SHR 8 AND $F 0) THEN
BEGIN
Res := Res + HexCif [Value [I] SHR 8 AND $F];
ErMed := TRUE;
END;
IF ErMed OR (Value [I] SHR 4 AND $F 0) THEN
BEGIN
Res := Res + HexCif [Value [I] SHR 4 AND $F];
ErMed := TRUE;
END;
Res := Res + HexCif [Value [I] AND $F];
ErMed := TRUE;
END;
END;
Str16 := Res;
END;
PROCEDURE TBigNum.VAL (CONST S : STRING);
VAR
I : INTEGER;
BEGIN
AssignLong (0);
I := 1;
WHILE I <= LENGTH (S) DO
BEGIN
Mult10;
Increment (BYTE (S [I]) - BYTE ('0') );
INC (I);
END;
END;
FUNCTION TBigNum.AsLong : LONGINT;
VAR
Res : ^LONGINT;
BEGIN
Res := @Value [0];
AsLong := Res^;
END;
VAR
ABigNum : TBigNum;
I : INTEGER;
BEGIN
ABigNum.AssignLong (1);
FOR I := 1 TO 260 DO
BEGIN
WRITELN (ABigNum.STR : 79);
ABigNum.Mult2;
END;
FOR I := 1 TO 260 DO
BEGIN
WRITELN (ABigNum.STR : 79);
ABigNum.Div2;
END;
WRITELN (ABigNum.STR : 79);
WRITE ('Press enter to exit.');
READLN;
END.