1 /*

     2 * Copyright (c) 2007-2009 Nokia Corporation and/or its subsidiary(-ies).

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

     5 * under the terms of the License "Eclipse Public License v1.0"

     6 * which accompanies this distribution, and is available

     7 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description: 

    15 *

    16 */

    17 

    18 

    19 /**

    20  @file

    21  @publishedPartner

    22  @released

    23 */

    24 

    25 #ifndef __ROMLIT_H__

    26 #define __ROMLIT_H__

    27 #include <e32def.h>

    28 #include <u32std.h>

    29 /**

    30    Special ROM friendly _LIT16 replacement.

    31 

    32    The existing _LIT16 macro/template successfully creates descriptors

    33    which will be put into ROM, but it is IMPOSSIBLE to initialize

    34    another "romable" variable with the address of one....

    35 

    36    What happens is that the compiler thinks it needs to call the

    37    TLitC16 operator& function call (even though it is a cast which

    38    will be optimized out of existence) to take the address of the

    39    object created by _LIT16.

    40 

    41    The result is that the DESTINATION variable gets moved from ROM to

    42    an initialized data area so that the return value of the TLitC16

    43    operator& function can be written to it at run time.

    44 

    45    The net result is that your code will not be legal in a target DLL

    46    (unless you enable thread initialized data, which is not

    47    recommended).

    48 

    49    A solution is to use this macro/class which creates TRomLitC16

    50    objects which have an identical layout to TPtrC16 objects and can

    51    generally be used just like all the other descriptor types.

    52 

    53    You use the _ROMLIT16 macro to create a TRomLitC16 object, then

    54    take its address and store that in a TRomLitC16 ptr. Attempting to

    55    store its address into other ptr types will compile but encounter

    56    the same problem as trying to use _LIT16.

    57    

    58    In most cases you can just dereference a TRomLitC16 ptr and pass it

    59    to any functions which can handle a _LIT16 (due to the out cast

    60    operators). If it doesn't automatically work, apply the function

    61    operator to the TRomLitC16 which will return a TDescC16 reference

    62    (for example ((*ptrToTRomLitC16)()') which is 100% compatible.

    63 */

    64 

    65 #ifndef __TText_defined

    66 #define __TText_defined

    67 #ifdef __GCC32__

    68 typedef wchar_t __TText;

    69 #else

    70 typedef TUint16 __TText;

    71 #endif

    72 #endif

    73 

    74 // All L"" strings are correctly aligned to an even boundary so can be

    75 // placed directly into the ptr field of a TPtr object.

    76 //

    77 // Note that the RVCT assembler listings are confusing because a

    78 // standalone ALIGN directive's argument is the requested alignment,

    79 // but the ALIGN argument to an AREA directive specifies a power of 2

    80 // for alignment. So the following RVCT generated code ensures

    81 // wchar_t strings are 2 byte aligned:-

    82 //

    83 // "AREA ||.constwstring||, DATA, READONLY, MERGE=2, STRINGS, ALIGN=1"

    84 #define _ROMLIT16(name,s) \

    85 	const static TRomLitC16 name={((EPtrC<<KShiftDesType16) | (sizeof(L##s)/2-1)), L##s}

    86 

    87 struct TRomLitC16

    88 	{

    89 	operator const TDesC16 *() const

    90 		{ return reinterpret_cast<const TDesC16*>(this); }

    91 	operator const TDesC16 &() const

    92 		{ return *(TDesC16 *)this; }

    93 	const TDesC16& operator()() const

    94 		{ return *(TDesC16 *)this; }

    95 	operator const __TRefDesC16() const

    96 		{ return *(TDesC16 *)this; }

    97 	TUint iTypeLength;

    98 	const __TText *iPtr;

    99 	};

   100 

   101 #endif