Added TBigInt shift right operator and tests

This commit is contained in:
Stefan Müller 2024-05-23 22:00:45 +02:00
parent 18f432bdfe
commit 4329041353
2 changed files with 128 additions and 1 deletions

View File

@ -99,6 +99,7 @@ type
operator - (const A, B: TBigInt): TBigInt;
operator * (const A, B: TBigInt): TBigInt;
operator shl (const A: TBigInt; const B: Integer): TBigInt;
operator shr (const A: TBigInt; const B: Integer): TBigInt;
operator = (const A, B: TBigInt): Boolean;
operator <> (const A, B: TBigInt): Boolean;
operator < (const A, B: TBigInt): Boolean;
@ -670,6 +671,60 @@ begin
end;
end;
operator shr(const A: TBigInt; const B: Integer): TBigInt;
var
i, j, digitShifts, bitShifts, reverseShift, len, newLength: Integer;
lastDigit: Cardinal;
begin
// Handles shift of zero.
if A = 0 then
begin
Result := TBigInt.Zero;
Exit;
end;
// Determines full digit shifts and bit shifts.
DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
// Handles shift to zero.
if digitShifts >= Length(A.FDigits) then
begin
Result := TBigInt.Zero;
Exit;
end;
if bitShifts > 0 then
begin
reverseShift := CBitsPerDigit - bitShifts;
len := Length(A.FDigits);
lastDigit := A.FDigits[len - 1] >> bitShifts;
newLength := len - digitShifts;
if lastDigit = 0 then
SetLength(Result.FDigits, newLength - 1)
else
SetLength(Result.FDigits, newLength);
// Performs full digit shifts by shifting the access index j for A.FDigits.
j := digitShifts;
for i := 0 to newLength - 2 do
begin
// Performs bit shifts.
Result.FDigits[i] := A.FDigits[j] >> bitShifts;
Inc(j);
Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << reverseShift);
end;
if lastDigit > 0 then
Result.FDigits[newLength - 1] := lastDigit;
end
else
// Performs full digit shifts by copy if there are no bit shifts.
Result.FDigits := Copy(A.FDigits, digitShifts, Length(A.FDigits) - digitShifts);
Result.FIsNegative := A.IsNegative;
end;
operator = (const A, B: TBigInt): Boolean;
begin
Result := A.CompareTo(B) = 0;

View File

@ -55,7 +55,6 @@ type
// TODO: TBigIntConversionTestCase
// TODO: TBigIntIncrementDecrementTestCase
// TODO: TBigIntQuotientTestCase
// TODO: TBigIntShiftRightTestCase
{ TBigIntSignTestCase }
@ -210,6 +209,21 @@ type
procedure TestZero;
end;
{ TBigIntShiftRightTestCase }
TBigIntShiftRightTestCase = class(TTestCase)
private
procedure Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
published
procedure TestShort;
procedure TestShortWithCarry;
procedure TestLongWithCarry;
procedure TestLongWithMultiDigitCarry;
procedure TestWithAlignedDigits;
procedure TestShiftToZero;
procedure TestZero;
end;
{ TBigIntEqualityTestCase }
TBigIntEqualityTestCase = class(TTestCase)
@ -767,6 +781,63 @@ begin
Test('0', 119, '0');
end;
{ TBigIntShiftRightTestCase }
procedure TBigIntShiftRightTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult:
string);
var
a, s: TBigInt;
begin
a := TBigInt.FromHexadecimalString(AHexValueOperand);
s := TBigInt.FromHexadecimalString(AHexValueResult);
AssertTrue('BigInt from hexadecimal string ''' + AHexValueOperand + ''' shifted right by ''' + IntToStr(AShift)
+ ''' was not equal to BigInt from hexadecimal string ''' + AHexValueResult + '''.',
s = (a >> AShift));
end;
procedure TBigIntShiftRightTestCase.TestShort;
begin
// BIN 100110101
// BIN 10011
Test('135', 4, '13');
end;
procedure TBigIntShiftRightTestCase.TestShortWithCarry;
begin
// BIN 1 1101 1010 1110 1001 1000 0111 0000 0000 0000 1111
// BIN 11 1011 0101 1101 0011 0000 1110
Test('1DAE987000F', 15, '3B5D30E');
end;
procedure TBigIntShiftRightTestCase.TestLongWithCarry;
begin
// BIN 10 0110 0001 0110 0100 0111 1100 1001 1001 1111 0010 1010 1000 1000 1010 0010 0010 1101 1101
// BIN 100 1100 0010 1100 1000 1111 1001 0011 0011 1110 0101 0101 0001 0001 0100 0100
Test('261647C99F2A88A22DD', 11, '4C2C8F933E551144');
end;
procedure TBigIntShiftRightTestCase.TestLongWithMultiDigitCarry;
begin
Test('647C99F12A088A22FF6DD02187345A3B839401BFB9272', 104, '647C99F12A088A22FF6');
end;
// Shifts the left operand by a multiple of the length of full TBigInt digits, so the digits will be shifted, but not
// changed.
procedure TBigIntShiftRightTestCase.TestWithAlignedDigits;
begin
Test('C5E10F0F39000AA2000C020000010000000000000F00000007', 32 * 5, 'C5E10F0F39');
end;
procedure TBigIntShiftRightTestCase.TestShiftToZero;
begin
Test('B5D10F0F39882F', 150, '0');
end;
procedure TBigIntShiftRightTestCase.TestZero;
begin
Test('0', 3, '0');
end;
{ TBigIntEqualityTestCase }
procedure TBigIntEqualityTestCase.TestEqual(const AValue: Int64);
@ -954,6 +1025,7 @@ initialization
RegisterTest(TBigIntDifferenceTestCase);
RegisterTest(TBigIntProductTestCase);
RegisterTest(TBigIntShiftLeftTestCase);
RegisterTest(TBigIntShiftRightTestCase);
RegisterTest(TBigIntEqualityTestCase);
RegisterTest(TBigIntComparisonTestCase);
end.