Fix StartWritingUnicodeText

Its comment in include/tools/stream.hxx tells:
Switch to no endian swapping and write 0xfeff

It was introduced in commit 3c2105e07d29b2069349e1a54e08463d359f988f
Author Eike Rathke <er@openoffice.org>
Date   Fri Dec 22 00:19:05 2000 +0000
new: read/write Unicode or Bytecode

and included a call to SetEndianSwap( FALSE ). That call was dropped
in commit 8130714148d58dd2bf1ef12dcc6dd6d5838be0d1
Author Noel Grandin <noel@peralex.com>
Date   Mon Jan 05 08:47:31 2015 +0200
fdo#84938: replace NUMBERFORMAT_INT_ constants with 'enum class'

(likely by accident).

To simplify the fix, drop redundant m_nEndian: m_isSwap is enough.

Change-Id: Ia9a0fe2d55563e7ba21bd4cf17c4ca999c6feaf7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141521
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Signed-off-by: Xisco Fauli <xiscofauli@libreoffice.org>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141777

4 files changed, 55 insertions, 6 deletions

diff --git a/include/tools/stream.hxx b/include/tools/stream.hxx
index 897af71d5021..39e8dc52f65a 100644
--- a/include/tools/stream.hxx
+++ b/include/tools/stream.hxx
@@ -161,7 +161,6 @@ private:
     bool            m_isSwap;
     bool            m_isEof;
     ErrCode         m_nError;
-    SvStreamEndian  m_nEndian;
     SvStreamCompressFlags m_nCompressMode;
     LineEnd         m_eLineDelimiter;
     rtl_TextEncoding m_eStreamCharSet;
@@ -207,7 +206,7 @@ public:
     virtual void    ResetError();
 
     void            SetEndian( SvStreamEndian SvStreamEndian );
-    SvStreamEndian  GetEndian() const { return m_nEndian; }
+    SvStreamEndian  GetEndian() const;
     /// returns status of endian swap flag
     bool            IsEndianSwap() const { return m_isSwap; }
 
diff --git a/tools/CppunitTest_tools_test.mk b/tools/CppunitTest_tools_test.mk
index c36af07547c2..c9e49a4fa5cf 100644
--- a/tools/CppunitTest_tools_test.mk
+++ b/tools/CppunitTest_tools_test.mk
@@ -61,6 +61,7 @@ $(eval $(call gb_CppunitTest_use_libraries,tools_test, \
     tl \
     test \
     unotest \
+    utl \
 ))
 
 $(eval $(call gb_CppunitTest_use_static_libraries,tools_test, \
diff --git a/tools/qa/cppunit/test_stream.cxx b/tools/qa/cppunit/test_stream.cxx
index 4672af6c70c9..02fe22343130 100644
--- a/tools/qa/cppunit/test_stream.cxx
+++ b/tools/qa/cppunit/test_stream.cxx
@@ -12,6 +12,7 @@
 #include <cppunit/TestFixture.h>
 #include <cppunit/extensions/HelperMacros.h>
 #include <tools/stream.hxx>
+#include <unotools/tempfile.hxx>
 #include <sstream>
 
 //Tests for eofbit/badbit/goodbit/failbit
@@ -27,6 +28,7 @@ namespace
         void test_read_cstring();
         void test_read_pstring();
         void test_readline();
+        void test_write_unicode();
 
         CPPUNIT_TEST_SUITE(Test);
         CPPUNIT_TEST(test_stdstream);
@@ -34,6 +36,7 @@ namespace
         CPPUNIT_TEST(test_read_cstring);
         CPPUNIT_TEST(test_read_pstring);
         CPPUNIT_TEST(test_readline);
+        CPPUNIT_TEST(test_write_unicode);
         CPPUNIT_TEST_SUITE_END();
     };
 
@@ -275,6 +278,43 @@ namespace
         CPPUNIT_ASSERT(issB.eof());         //<-- diff A
     }
 
+    void Test::test_write_unicode()
+    {
+        const OUString write("abc");
+        utl::TempFile aTempFile(u"test_write_unicode");
+        aTempFile.EnableKillingFile();
+        {
+            SvStream& s = *aTempFile.GetStream(StreamMode::WRITE);
+            s.SetEndian(SvStreamEndian::BIG);
+            if (!s.IsEndianSwap())
+                s.SetEndian(SvStreamEndian::LITTLE);
+            CPPUNIT_ASSERT(s.IsEndianSwap());
+            // StartWritingUnicodeText must switch to no endian swapping and write 0xfeff
+            s.StartWritingUnicodeText();
+            // Without the fix in place, this would fail
+            CPPUNIT_ASSERT(!s.IsEndianSwap());
+            s.WriteUnicodeOrByteText(write, RTL_TEXTENCODING_UNICODE);
+            aTempFile.CloseStream();
+        }
+        {
+            SvStream& s = *aTempFile.GetStream(StreamMode::READ);
+            s.SetEndian(SvStreamEndian::BIG);
+            if (!s.IsEndianSwap())
+                s.SetEndian(SvStreamEndian::LITTLE);
+            CPPUNIT_ASSERT(s.IsEndianSwap());
+            s.StartReadingUnicodeText(RTL_TEXTENCODING_DONTKNOW);
+            CPPUNIT_ASSERT(!s.IsEndianSwap());
+            CPPUNIT_ASSERT_EQUAL(sal_uInt64(2), s.Tell()); // after BOM
+            OUString read;
+            CPPUNIT_ASSERT(s.ReadUniOrByteStringLine(read, RTL_TEXTENCODING_UNICODE));
+            // Without the fix in place, this would fail with
+            // - Expected: abc
+            // - Actual  : 愀戀挀
+            CPPUNIT_ASSERT_EQUAL(write, read);
+            aTempFile.CloseStream();
+        }
+    }
+
     CPPUNIT_TEST_SUITE_REGISTRATION(Test);
 }
 
diff --git a/tools/source/stream/stream.cxx b/tools/source/stream/stream.cxx
index a4579d1f81db..a5dfacb3895a 100644
--- a/tools/source/stream/stream.cxx
+++ b/tools/source/stream/stream.cxx
@@ -361,11 +361,19 @@ void SvStream::SetError( ErrCode nErrorCode )
 
 void SvStream::SetEndian( SvStreamEndian nNewFormat )
 {
-    m_nEndian = nNewFormat;
 #ifdef OSL_BIGENDIAN
-    m_isSwap = m_nEndian == SvStreamEndian::LITTLE;
+    m_isSwap = nNewFormat == SvStreamEndian::LITTLE;
 #else
-    m_isSwap = m_nEndian == SvStreamEndian::BIG;
+    m_isSwap = nNewFormat == SvStreamEndian::BIG;
+#endif
+}
+
+SvStreamEndian SvStream::GetEndian() const
+{
+#ifdef OSL_BIGENDIAN
+    return m_isSwap ? SvStreamEndian::LITTLE : SvStreamEndian::BIG;
+#else
+    return m_isSwap ? SvStreamEndian::BIG : SvStreamEndian::LITTLE;
 #endif
 }
 
@@ -709,10 +717,11 @@ bool SvStream::WriteUniOrByteChar( sal_Unicode ch, rtl_TextEncoding eDestCharSet
 
 void SvStream::StartWritingUnicodeText()
 {
+    m_isSwap = false; // Switch to no endian swapping
     // BOM, Byte Order Mark, U+FEFF, see
     // http://www.unicode.org/faq/utf_bom.html#BOM
     // Upon read: 0xfeff(-257) => no swap; 0xfffe(-2) => swap
-    writeNumberWithoutSwap(sal_uInt16(0xfeff)); // write native format
+    WriteUInt16(0xfeff);
 }
 
 void SvStream::StartReadingUnicodeText( rtl_TextEncoding eReadBomCharSet )