Added TBigInt shift right operator and tests
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UBigInt.pas
55
UBigInt.pas
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@ -99,6 +99,7 @@ type
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operator - (const A, B: TBigInt): TBigInt;
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operator * (const A, B: TBigInt): TBigInt;
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operator shl (const A: TBigInt; const B: Integer): TBigInt;
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operator shr (const A: TBigInt; const B: Integer): TBigInt;
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operator = (const A, B: TBigInt): Boolean;
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operator <> (const A, B: TBigInt): Boolean;
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operator < (const A, B: TBigInt): Boolean;
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@ -670,6 +671,60 @@ begin
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end;
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end;
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operator shr(const A: TBigInt; const B: Integer): TBigInt;
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var
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i, j, digitShifts, bitShifts, reverseShift, len, newLength: Integer;
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lastDigit: Cardinal;
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begin
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// Handles shift of zero.
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if A = 0 then
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begin
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Result := TBigInt.Zero;
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Exit;
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end;
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// Determines full digit shifts and bit shifts.
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DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
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// Handles shift to zero.
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if digitShifts >= Length(A.FDigits) then
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begin
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Result := TBigInt.Zero;
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Exit;
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end;
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if bitShifts > 0 then
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begin
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reverseShift := CBitsPerDigit - bitShifts;
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len := Length(A.FDigits);
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lastDigit := A.FDigits[len - 1] >> bitShifts;
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newLength := len - digitShifts;
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if lastDigit = 0 then
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SetLength(Result.FDigits, newLength - 1)
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else
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SetLength(Result.FDigits, newLength);
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// Performs full digit shifts by shifting the access index j for A.FDigits.
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j := digitShifts;
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for i := 0 to newLength - 2 do
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begin
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// Performs bit shifts.
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Result.FDigits[i] := A.FDigits[j] >> bitShifts;
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Inc(j);
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Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << reverseShift);
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end;
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if lastDigit > 0 then
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Result.FDigits[newLength - 1] := lastDigit;
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end
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else
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// Performs full digit shifts by copy if there are no bit shifts.
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Result.FDigits := Copy(A.FDigits, digitShifts, Length(A.FDigits) - digitShifts);
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Result.FIsNegative := A.IsNegative;
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end;
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operator = (const A, B: TBigInt): Boolean;
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begin
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Result := A.CompareTo(B) = 0;
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@ -55,7 +55,6 @@ type
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// TODO: TBigIntConversionTestCase
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// TODO: TBigIntIncrementDecrementTestCase
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// TODO: TBigIntQuotientTestCase
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// TODO: TBigIntShiftRightTestCase
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{ TBigIntSignTestCase }
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@ -210,6 +209,21 @@ type
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procedure TestZero;
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end;
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{ TBigIntShiftRightTestCase }
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TBigIntShiftRightTestCase = class(TTestCase)
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private
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procedure Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
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published
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procedure TestShort;
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procedure TestShortWithCarry;
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procedure TestLongWithCarry;
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procedure TestLongWithMultiDigitCarry;
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procedure TestWithAlignedDigits;
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procedure TestShiftToZero;
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procedure TestZero;
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end;
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{ TBigIntEqualityTestCase }
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TBigIntEqualityTestCase = class(TTestCase)
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@ -767,6 +781,63 @@ begin
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Test('0', 119, '0');
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end;
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{ TBigIntShiftRightTestCase }
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procedure TBigIntShiftRightTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult:
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string);
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var
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a, s: TBigInt;
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begin
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a := TBigInt.FromHexadecimalString(AHexValueOperand);
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s := TBigInt.FromHexadecimalString(AHexValueResult);
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AssertTrue('BigInt from hexadecimal string ''' + AHexValueOperand + ''' shifted right by ''' + IntToStr(AShift)
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+ ''' was not equal to BigInt from hexadecimal string ''' + AHexValueResult + '''.',
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s = (a >> AShift));
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end;
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procedure TBigIntShiftRightTestCase.TestShort;
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begin
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// BIN 100110101
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// BIN 10011
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Test('135', 4, '13');
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end;
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procedure TBigIntShiftRightTestCase.TestShortWithCarry;
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begin
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// BIN 1 1101 1010 1110 1001 1000 0111 0000 0000 0000 1111
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// BIN 11 1011 0101 1101 0011 0000 1110
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Test('1DAE987000F', 15, '3B5D30E');
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end;
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procedure TBigIntShiftRightTestCase.TestLongWithCarry;
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begin
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// BIN 10 0110 0001 0110 0100 0111 1100 1001 1001 1111 0010 1010 1000 1000 1010 0010 0010 1101 1101
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// BIN 100 1100 0010 1100 1000 1111 1001 0011 0011 1110 0101 0101 0001 0001 0100 0100
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Test('261647C99F2A88A22DD', 11, '4C2C8F933E551144');
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end;
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procedure TBigIntShiftRightTestCase.TestLongWithMultiDigitCarry;
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begin
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Test('647C99F12A088A22FF6DD02187345A3B839401BFB9272', 104, '647C99F12A088A22FF6');
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end;
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// Shifts the left operand by a multiple of the length of full TBigInt digits, so the digits will be shifted, but not
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// changed.
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procedure TBigIntShiftRightTestCase.TestWithAlignedDigits;
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begin
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Test('C5E10F0F39000AA2000C020000010000000000000F00000007', 32 * 5, 'C5E10F0F39');
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end;
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procedure TBigIntShiftRightTestCase.TestShiftToZero;
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begin
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Test('B5D10F0F39882F', 150, '0');
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end;
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procedure TBigIntShiftRightTestCase.TestZero;
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begin
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Test('0', 3, '0');
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end;
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{ TBigIntEqualityTestCase }
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procedure TBigIntEqualityTestCase.TestEqual(const AValue: Int64);
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@ -954,6 +1025,7 @@ initialization
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RegisterTest(TBigIntDifferenceTestCase);
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RegisterTest(TBigIntProductTestCase);
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RegisterTest(TBigIntShiftLeftTestCase);
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RegisterTest(TBigIntShiftRightTestCase);
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RegisterTest(TBigIntEqualityTestCase);
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RegisterTest(TBigIntComparisonTestCase);
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end.
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