TEncoding: fix base convert functions for empty inputs

git-svn-id: trunk@46430 -

rtl/objpas/sysutils/sysencoding.inc

@@ -38,6 +38,9 @@ end;
 
 function TEncoding.GetAnsiBytes(const S: string): TBytes;
 begin
+  if S='' then
+    Result := nil
+  else
     Result := GetAnsiBytes(S, 1, Length(S));
 end;
 
@@ -49,6 +52,9 @@ end;
 
 function TEncoding.GetAnsiString(const Bytes: TBytes): string;
 begin
+  if Length(Bytes)=0 then
+    Result := ''
+  else
     Result := GetAnsiString(Bytes, 0, Length(Bytes));
 end;
 
@@ -294,6 +300,9 @@ end;
 
 function TEncoding.GetByteCount(const Chars: TUnicodeCharArray): Integer;
 begin
+  if Length(Chars)=0 then
+    Result := 0
+  else
     Result := GetByteCount(Chars, 0, Length(Chars));
 end;
 
@@ -309,6 +318,9 @@ end;
 
 function TEncoding.GetByteCount(const S: UnicodeString): Integer;
 begin
+  if S='' then
+    Result := 0
+  else
     Result := GetByteCount(PUnicodeChar(S), Length(S));
 end;
 
@@ -324,6 +336,7 @@ end;
 function TEncoding.GetBytes(const Chars: TUnicodeCharArray): TBytes;
 begin
   SetLength(Result, GetByteCount(Chars));
+  if Length(Result)>0 then
     GetBytes(@Chars[0], Length(Chars), @Result[0], Length(Result));
 end;
 
@@ -358,6 +371,7 @@ end;
 function TEncoding.GetBytes(const S: UnicodeString): TBytes;
 begin
   SetLength(Result, GetByteCount(S));
+  if Length(Result)>0 then
     GetBytes(@S[1], Length(S), @Result[0], Length(Result));
 end;
 
@@ -380,6 +394,9 @@ end;
 
 function TEncoding.GetCharCount(const Bytes: TBytes): Integer;
 begin
+  if Length(Bytes)=0 then
+    Result := 0
+  else
     Result := GetCharCount(@Bytes[0], Length(Bytes));
 end;
 
@@ -394,6 +411,7 @@ end;
 function TEncoding.GetChars(const Bytes: TBytes): TUnicodeCharArray;
 begin
   SetLength(Result, GetCharCount(Bytes));
+  if Length(Result)>0 then
     GetChars(@Bytes[0], Length(Bytes), @Result[0], Length(Result));
 end;
 
@@ -444,8 +462,13 @@ function TEncoding.GetString(const Bytes: TBytes): UnicodeString;
 var
   Chars: TUnicodeCharArray;
 begin
+  if Length(Bytes)=0 then
+    Result := ''
+  else
+  begin
     Chars := GetChars(Bytes);
     SetString(Result, PUnicodeChar(Chars), Length(Chars));
+  end;
 end;
 
 function TEncoding.GetString(const Bytes: TBytes; ByteIndex, ByteCount: Integer): UnicodeString;