Merge pull request #3 from skamradt/main

Corrected Integer Overflow decoding an encoded value of $FFFFFFFFFFFF…
sqids · May 24, 2024 · e57db6b · e57db6b
2 parents a3efb87 + 1caa96b
commit e57db6b
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Showing 2 changed files with 16 additions and 1 deletion.
diff --git a/src/sqids.pas b/src/sqids.pas
@@ -185,7 +185,7 @@ function TSqids.ToNumber(AId: string; AAlphabet: string): TNumber;
   L := Length(AAlphabet);
 
   for C in AId do
-    Result := Result * L + TNumber(Pos(C, AAlphabet)) - 1;
+    Result := Result * L + (TNumber(Pos(C, AAlphabet)) - 1);
 end;
 
 function TSqids.IsBlocked(AId: string): Boolean;

diff --git a/tests/delphi/encoding.pas b/tests/delphi/encoding.pas
@@ -22,6 +22,7 @@   TTestEncoding = class(TTestCase)
     procedure IdWithInvalidCharacter;
     // out-of-range test not implemented:
     // compiler enforces that all numbers are within the range of a TNumber
+    procedure ExtremeValue;
   end;
 
 implementation
@@ -180,6 +181,20 @@ procedure TTestEncoding.EmptyString;
   end;
 end;
 
+procedure TTestEncoding.ExtremeValue;
+const
+  Number: TNumber = $FFFFFFFFFFFFFFFF;
+  Id = 'eIkvoXH40Lmd'; // from a previous EncodeSingle
+begin
+  with TSqids.Create do
+  try
+    CheckEquals(EncodeSingle(Number), Id);
+    CheckTrue(DecodeSingle(id)=Number);
+  finally
+    Free;
+  end;
+end;
+
 procedure TTestEncoding.IdWithInvalidCharacter;
 begin
   with TSqids.Create do