Title: Using Big Integers (32, 64, 128, 256... bit)
Question: How can I use very large (32 bit or more) integers?
Answer:
Check out the Big Integer units:
http://home.student.utwente.nl/e.j.molendijk/index.html
I will not list the source here, since it is way to big.
But a few of the included functions:
procedure BIntAdd(Var Dest : TBInt; Src : TBInt); overload;
procedure BIntAdd(Var Dest : TBInt; Const Src : Cardinal=1); overload;
{================================================================
BIntSub: Dest := Dest - Src;
1. BIntSub makes sure that Dest and Src have the same memory size
2. If the result is negative. A Two's Complement notation is returned.
3. Src can also be an unsigned integer, optimezed routines will be used
in this case.
Calling BIntAdd without the Src parameter results in Dest := Dest - 1
You can/should call BSub or BDec directly when you are sure that the
conditions specified at step 1 are met.
}
procedure BIntSub(Var Dest : TBInt; Src : TBInt); overload;
procedure BIntSub(Var Dest : TBInt; Src : Cardinal=1); overload;
{================================================================
BIntMul: Dest := Src1 * Src2;
1. BIntAdd makes sure that Dest can is big enough to hold the result;
And that Dest, Src1 and Src2 are all 32 bit alligned.
2. Dest will never overflow
You can/should call BMul directly when you are sure that the
conditions specified at step 1 are met.
}
procedure BIntMul(Var Dest : TBInt; Src1, Src2 : TBInt); overload;
procedure BIntMul(Var Dest : TBInt; Src1 : TBInt; Src2 : Cardinal); overload;
procedure BIntDivMod(x,y : TBInt; Var q,r : TBInt);
{================================================================
BIntAbs: A := Abs(A);
Returns the absolute value of A
}
Procedure BIntAbs(Var A : TBInt);
{================================================================
BIntCmp: Compare Src1 and Src2. return: Equal, Smaller or Greater.
1. BIntCmp makes sure that Src1 and Src2 are of same size and both 32 bit
alligned.
You can/should call BCmp directly when you are sure that the
conditions specified at step 1 are met.
}
Function BIntCmp(Src1, Src2 : TBInt) : TBIntEq; overload;
Function BIntCmp(Src1 : TBInt; Src2 : Integer) : TBIntEq; overload;
{================================================================
BIntCopy: Dest := Src;
1. Makes sure Dest is big enough to hold Src
}
procedure BIntCopy(Var Dst : TBInt; Const Src : TBInt);
{================================================================
BIntSetBit: Dest := Dest or (1 shl b);
or
BIntGetBit: Result := Bit at position b in A.
Sets bit at position b to a one.
Bit position b must be withing the memory size of Dest, otherwise it will
not be set.
0 }
procedure BIntSetBit(Var a : TBInt; b : Integer);
Function BIntGetBit(Var a : TBInt; b : Integer) : Integer;
{================================================================
See comment in implementation for more details about the following internal routines
}
procedure BIntReduce(Var A : TBInt);
Procedure BIntBurn(Var A : TBInt);
procedure BIntChk(Var A, B : TBInt);
Procedure BIntChkIncOverflow(Var A : TBInt);
Procedure BIntChkSumOverflow(Var A,B : TBInt);
Procedure BIntChkMulOverflow(Var A,B,C : TBInt);
Function BIntGetBitLength(BInt : TBInt) : Integer;
Procedure BIntSetBitLength(Var BInt : TBInt; Bits : Integer);
Function BIntNegative(Const A : TBInt) : Boolean;