From 2df8266d42dcb2364268ed479d36127e2665383f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20M=C3=BCller?= <stefan.mueller@aksdb.de>
Date: Thu, 23 May 2024 22:01:25 +0200
Subject: [PATCH] Added some improvements for TBigInt shift left operator

---
 UBigInt.pas                | 78 +++++++++++++++++++-------------------
 tests/UBigIntTestCases.pas |  3 +-
 2 files changed, 42 insertions(+), 39 deletions(-)

diff --git a/UBigInt.pas b/UBigInt.pas
index 907ec6b..421368d 100644
--- a/UBigInt.pas
+++ b/UBigInt.pas
@@ -626,49 +626,51 @@ var
 begin
   // Handles shift of zero.
   if A = 0 then
-    Result := TBigInt.Zero
-  else begin
-    // Determines full digit shifts and bit shifts.
-    DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
+  begin
+    Result := TBigInt.Zero;
+    Exit;
+  end;
 
-    if bitShifts > 0 then
+  // Determines full digit shifts and bit shifts.
+  DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
+
+  if bitShifts > 0 then
+  begin
+    reverseShift := CBitsPerDigit - bitShifts;
+    len := Length(A.FDigits);
+    lastDigit := A.FDigits[len - 1] >> reverseShift;
+    newLength := len + digitShifts;
+
+    if lastDigit = 0 then
+      SetLength(Result.FDigits, newLength)
+    else
+      SetLength(Result.FDigits, newLength + 1);
+
+    // Performs full digit shifts by shifting the access index j for A.FDigits.
+    Result.FDigits[digitShifts] := A.FDigits[0] << bitShifts;
+    j := 0;
+    for i := digitShifts + 1 to newLength - 1 do
     begin
-      reverseShift := CBitsPerDigit - bitShifts;
-      len := Length(A.FDigits);
-      lastDigit := A.FDigits[len - 1] >> reverseShift;
-      newLength := len + digitShifts;
-
-      if lastDigit = 0 then
-        SetLength(Result.FDigits, newLength)
-      else
-        SetLength(Result.FDigits, newLength + 1);
-
-      // Performs full digit shifts by shifting the access index j for A.FDigits.
-      Result.FDigits[digitShifts] := A.FDigits[0] << bitShifts;
-      j := 0;
-      for i := digitShifts + 1 to newLength - 1 do
-      begin
-        // Performs bit shifts.
-        Result.FDigits[i] := A.FDigits[j] >> reverseShift;
-        Inc(j);
-        Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << bitShifts);
-      end;
-
-      if Length(Result.FDigits) > newLength then
-        Result.FDigits[newLength] := lastDigit;
-    end
-    else begin
-      // Performs full digit shifts by copy if there are no bit shifts.
-      len := Length(A.FDigits);
-      SetLength(Result.FDigits, len + digitShifts);
-      for i := 0 to digitShifts - 1 do
-        Result.FDigits[i] := 0;
-      for i := 0 to len - 1 do
-        Result.FDigits[i + digitShifts] := A.FDigits[i];
+      // Performs bit shifts.
+      Result.FDigits[i] := A.FDigits[j] >> reverseShift;
+      Inc(j);
+      Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << bitShifts);
     end;
 
-    Result.FIsNegative := A.IsNegative;
+    if lastDigit > 0 then
+      Result.FDigits[newLength] := lastDigit;
+  end
+  else begin
+    // Performs full digit shifts by copy if there are no bit shifts.
+    len := Length(A.FDigits);
+    SetLength(Result.FDigits, len + digitShifts);
+    for i := 0 to digitShifts - 1 do
+      Result.FDigits[i] := 0;
+    for i := 0 to len - 1 do
+      Result.FDigits[i + digitShifts] := A.FDigits[i];
   end;
+
+  Result.FIsNegative := A.IsNegative;
 end;
 
 operator shr(const A: TBigInt; const B: Integer): TBigInt;
diff --git a/tests/UBigIntTestCases.pas b/tests/UBigIntTestCases.pas
index 06019b1..9639ac6 100644
--- a/tests/UBigIntTestCases.pas
+++ b/tests/UBigIntTestCases.pas
@@ -732,7 +732,8 @@ end;
 
 { TBigIntShiftLeftTestCase }
 
-procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
+procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult:
+  string);
 var
   a, s: TBigInt;
 begin