tests: added testUTFAndWCharPreallocDest and renamed testLongSimpleTe…

…xt -> testUTFAndWCharNullDest

There were no tests calling WCharToUTF or UTFToWChar with non-NULL dst buffers
(not even implicit calls generated by fbc). That's a big gap, because the
UTF-to-WChar functions all have completely separate implementations for those
two cases.

One of the asserts in the new testcase fails.

Likewise these are no non-NULL dst tests for Char <-> WChar and UTF <-> Char,
although some cases would be implicitly generated by fbc.

tests/wstring/utf_conv.bas

@@ -74,11 +74,12 @@ sub testZstringToNullDest cdecl( )
 	deallocate( utf32 )
 end sub
 
+'' Tests WCharToUTF and UTFToWChar with NULL dest.
 '' The rtlib has UTF encoding routines that can allocate memory for us. If using
 '' that version of them, they pre-allocate some chars (currently typically 8) at
 '' a time. To ensure this works correctly, we have to test with strings longer
 '' than that.
-sub testLongSimpleText cdecl( )
+sub testUTFAndWCharNullDest cdecl( )
 	const TEXT = "testing with a long, but simple 7-bit ASCII string"
 	dim src as wstring * 100 = wstr( TEXT )
 
@@ -143,13 +144,89 @@ sub testLongSimpleText cdecl( )
 	end scope
 end sub
 
+'' Tests WCharToUTF and UTFToWChar with a preallocated destination buffer.
+'' These do not test the cases where the destination buffer is not long enough
+'' to hold the output string (which should work but result in no null
+'' terminators).
+sub testUTFAndWCharPreallocDest cdecl( )
+	const TEXT = "testing with a long, but simple 7-bit ASCII string"
+	dim src as wstring * 100 = wstr( TEXT )
+
+	'' Use buffers shorter than the input buffer, but longer than the input string
+	dim as integer buflen = (len( src ) + 2) * 4
+	dim as ubyte ptr utfbuf = callocate( buflen )
+	dim as ubyte ptr wbuf = callocate( buflen )
+
+	scope
+		'' Convert to UTF8, including null terminator
+		dim as integer utf8bytes
+		dim as ubyte ptr utf8 = WCharToUTF( UTF_ENCOD_UTF8, src, len( src ) + 1, utfbuf, @utf8bytes )
+		CU_ASSERT( utf8 = utfbuf )
+		CU_ASSERT( utf8bytes = (len( TEXT ) + 1) )
+		CU_ASSERT( *cptr( zstring ptr, utf8 ) = TEXT )
+
+		'' Convert back to wstring
+		dim as integer chars = buflen  '' Input buffer length in characters
+		dim as wstring ptr w = UTFToWChar( UTF_ENCOD_UTF8, utf8, wbuf, @chars )
+		CU_ASSERT( w = wbuf )
+		CU_ASSERT( chars = len( TEXT ) )
+		CU_ASSERT( *w = src )
+	end scope
+
+	scope
+		'' Convert to UTF16, including null terminator
+		dim as integer utf16bytes
+		memset( utfbuf, 0, buflen )
+		dim as ushort ptr utf16 = WCharToUTF( UTF_ENCOD_UTF16, src, len( src ) + 1, utfbuf, @utf16bytes )
+		CU_ASSERT( utf16 = cptr( ushort ptr, utfbuf ) )
+		CU_ASSERT( (utf16bytes mod 2) = 0 )
+		CU_ASSERT( (utf16bytes \ 2) = (len( TEXT ) + 1) )
+		for i as integer = 0 to (utf16bytes \ 2) - 1
+			CU_ASSERT( utf16[i] = src[i] )
+		next
+
+		'' Convert back to wstring
+		dim as integer chars = buflen \ 2  '' Input buffer length in characters
+		memset( wbuf, 0, buflen )
+		dim as wstring ptr w = UTFToWChar( UTF_ENCOD_UTF16, utf16, wbuf, @chars )
+		CU_ASSERT( w = wbuf )
+		CU_ASSERT( chars = len( TEXT ) )
+		CU_ASSERT( *w = src )
+	end scope
+
+	scope
+		'' Convert to UTF32, including null terminator
+		dim as integer utf32bytes
+		memset( utfbuf, 0, buflen )
+		dim as ulong ptr utf32 = WCharToUTF( UTF_ENCOD_UTF32, src, len( src ) + 1, utfbuf, @utf32bytes )
+		CU_ASSERT( utf32 = cptr( ulong ptr, utfbuf ) )
+		CU_ASSERT( (utf32bytes mod 4) = 0 )
+		CU_ASSERT( (utf32bytes \ 4) = (len( TEXT ) + 1) )
+		for i as integer = 0 to (utf32bytes \ 4) - 1
+			CU_ASSERT( utf32[i] = src[i] )
+		next
+
+		'' Convert back to wstring
+		dim as integer chars = buflen \ 4  '' Input buffer length in characters
+		memset( wbuf, 0, buflen )
+		dim as wstring ptr w = UTFToWChar( UTF_ENCOD_UTF32, utf32, wbuf, @chars )
+		CU_ASSERT( w = wbuf )
+		CU_ASSERT( chars = len( TEXT ) )
+		CU_ASSERT( *w = src )
+	end scope
+
+	deallocate( utfbuf )
+	deallocate( wbuf )
+end sub
+
 sub ctor( ) constructor
 	fbcu.add_suite( "tests/wstrings/utf_conv" )
 	fbcu.add_test( "test_z", @test_z )
 	fbcu.add_test( "test_w", @test_w )
 	fbcu.add_test( "testWstringToNullDest", @testWstringToNullDest )
 	fbcu.add_test( "testZstringToNullDest", @testZstringToNullDest )
-	fbcu.add_test( "testLongSimpleText", @testLongSimpleText )
+	fbcu.add_test( "testUTFAndWCharNullDest", @testUTFAndWCharNullDest )
+	fbcu.add_test( "testUTFAndWCharPreallocDest", @testUTFAndWCharPreallocDest )
 end sub
 
 end namespace