Added more BigInt features and fixes

- Fixed some uses of Move
- Added Sign, string initializers (hexadecimal and binary), explicit
converter to Int64, comparison operators

UBigInt.pas

@@ -35,6 +35,8 @@ type
     FDigits: TDigits;
     FIsNegative: Boolean;
 
+    function GetSign: Integer;
+
     // Copies consecutive digits from this BigInt to create a new one. The result will be positive. Leading zeros are
     // removed from the result, but AIndex + ACount must not exceed the number of digits of this BigInt.
     // AIndex is the first (least significant) digit to be taken. The digit with this index will become the 0th digit of
@@ -66,11 +68,19 @@ type
     //   Sign * (Abs(a) * Abs(b))
     // where Sign is 1 for ReturnNegative = False and -1 otherwise.
     class function MultiplyAbsoluteValues(constref AA, AB: TBigInt; const AReturnNegative: Boolean): TBigInt; static;
+
+    class function FromHexOrBinString(const AValue: string; const AFromBase: Integer): TBigInt; static;
+    class function ConvertDigitBlock(const AValue: string; var AStartIndex: Integer; const ACharBlockSize, AFromBase:
+      Integer): Cardinal;
   public
     property IsNegative: Boolean read FIsNegative;
+    property Sign: Integer read GetSign;
     class property Zero: TBigInt read GetZero;
     function CompareTo(constref AOther: TBigInt): Integer;
+    function TryToInt64(out AOutput: Int64): Boolean;
     class function FromInt64(const AValue: Int64): TBigInt; static;
+    class function FromHexadecimalString(const AValue: string): TBigInt; static;
+    class function FromBinaryString(const AValue: string): TBigInt; static;
   end;
 
   { Operators }
@@ -83,6 +93,10 @@ type
   operator shl (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;
+  operator <= (const A, B: TBigInt): Boolean;
+  operator > (const A, B: TBigInt): Boolean;
+  operator >= (const A, B: TBigInt): Boolean;
 
 implementation
 
@@ -98,6 +112,16 @@ const
 
 { TBigInt }
 
+function TBigInt.GetSign: Integer;
+begin
+  if FIsNegative then
+    Result := -1
+  else if (Length(FDigits) > 1) or (FDigits[0] <> 0) then
+    Result := 1
+  else
+    Result := 0;
+end;
+
 function TBigInt.GetSegment(const AIndex, ACount: Integer): TBigInt;
 var
   trimmedCount: Integer;
@@ -105,8 +129,7 @@ begin
   trimmedCount := ACount;
   while (trimmedCount > 1) and (FDigits[AIndex + trimmedCount - 1] = 0) do
     Dec(trimmedCount);
-  SetLength(Result.FDigits, trimmedCount);
-  Move(FDigits[AIndex], Result.FDigits[0], CDigitSize * trimmedCount);
+  Result.FDigits := Copy(FDigits, AIndex, trimmedCount);
   Result.FIsNegative := False;
 end;
 
@@ -362,6 +385,65 @@ begin
   end;
 end;
 
+class function TBigInt.FromHexOrBinString(const AValue: string; const AFromBase: Integer): TBigInt;
+var
+  charBlockSize, offset, i, j, k, remainder: Integer;
+  d: Cardinal;
+begin
+  charBlockSize := 64 div AFromBase;
+  if AValue[1] = '-' then
+  begin
+    offset := 2;
+    Result.FIsNegative := True;
+  end
+  else begin
+    offset := 1;
+    Result.FIsNegative := False;
+  end;
+
+  // Calculates the first (most significant) digit d of the result.
+  DivMod(AValue.Length - offset, charBlockSize, i, remainder);
+  k := offset;
+  d := 0;
+  // Checks the first block of chars that is not a full block.
+  if remainder > 0 then
+    d := ConvertDigitBlock(AValue, k, remainder, AFromBase);
+  // Checks full blocks of chars for first digit.
+  while (d = 0) and (i > 0) do
+  begin
+    Dec(i);
+    d := ConvertDigitBlock(AValue, k, charBlockSize, AFromBase);
+  end;
+
+  // Checks for zero.
+  if (d = 0) and (i = 0) then
+    Result := Zero
+  else begin
+    // Initializes the array of digits.
+    SetLength(Result.FDigits, i + 1);
+    Result.FDigits[i] := d;
+
+    // Calculates the other digits.
+    for j := i - 1 downto 0 do
+      Result.FDigits[j] := ConvertDigitBlock(AValue, k, charBlockSize, AFromBase);
+  end;
+end;
+
+class function TBigInt.ConvertDigitBlock(const AValue: string; var AStartIndex: Integer; const ACharBlockSize,
+  AFromBase: Integer): Cardinal;
+var
+  part: string;
+begin
+  part := Copy(AValue, AStartIndex, ACharBlockSize);
+  Inc(AStartIndex, ACharBlockSize);
+  case AFromBase of
+    2: part := '%' + part;
+    8: part := '&' + part;
+    16: part := '$' + part;
+  end;
+  Result := StrToDWord(part);
+end;
+
 function TBigInt.CompareTo(constref AOther: TBigInt): Integer;
 begin
   if FIsNegative = AOther.FIsNegative then
@@ -372,6 +454,35 @@ begin
     Result := -Result;
 end;
 
+function TBigInt.TryToInt64(out AOutput: Int64): Boolean;
+begin
+  AOutput := 0;
+  Result := False;
+  case Length(FDigits) of
+    0: Result := True;
+    1: begin
+      AOutput := FDigits[0];
+      if FIsNegative then
+        AOutput := -AOutput;
+      Result := True;
+    end;
+    2: begin
+      if FDigits[1] <= Integer.MaxValue then
+      begin
+        AOutput := FDigits[1] * CBase + FDigits[0];
+        if FIsNegative then
+          AOutput := -AOutput;
+        Result := True;
+      end
+      else if (FDigits[1] = Integer.MaxValue + 1) and (FDigits[0] = 0) and FIsNegative then
+      begin
+        AOutput := Int64.MinValue;
+        Result := True;
+      end;
+    end;
+  end;
+end;
+
 class function TBigInt.FromInt64(const AValue: Int64): TBigInt;
 var
   absVal: Int64;
@@ -391,6 +502,16 @@ begin
   end;
 end;
 
+class function TBigInt.FromHexadecimalString(const AValue: string): TBigInt;
+begin
+  Result := FromHexOrBinString(AValue, 16);
+end;
+
+class function TBigInt.FromBinaryString(const AValue: string): TBigInt;
+begin
+  Result := FromHexOrBinString(AValue, 2);
+end;
+
 { Operators }
 
 operator := (const A: Int64): TBigInt;
@@ -403,9 +524,13 @@ var
   len: Integer;
 begin
   len := Length(A.FDigits);
-  SetLength(Result.FDigits, len);
-  Move(A.FDigits[0], Result.FDigits[0], len);
+  if (len > 1) or (A.FDigits[0] > 0) then
+  begin
+    Result.FDigits := Copy(A.FDigits, 0, len);
     Result.FIsNegative := not A.FIsNegative;
+  end
+  else
+    Result := TBigInt.Zero;
 end;
 
 operator + (const A, B: TBigInt): TBigInt;
@@ -492,5 +617,25 @@ begin
   Result := A.CompareTo(B) <> 0;
 end;
 
+operator < (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) < 0;
+end;
+
+operator <= (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) <= 0;
+end;
+
+operator > (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) > 0;
+end;
+
+operator >= (const A, B: TBigInt): Boolean;
+begin
+  Result := A.CompareTo(B) >= 0;
+end;
+
 end.