include/SDL_test_crc32.h
author David Ludwig <dludwig@pobox.com>
Sat, 29 Nov 2014 10:09:30 -0500
changeset 9247 eddb899239fe
parent 9233 b8eaf9623c0b
child 9619 b94b6d0bff0f
permissions -rw-r--r--
WinRT: bug and data-integrity fixes for SDL_GetPrefPath()

This change does a few things, all with regards to the WinRT implementation of
SDL_GetPrefPath():

1. it fixes a bug whereby SDL_GetPrefPath() did not create the directory it
returned. On other SDL platforms, SDL_GetPrefPath() will create separate
directories for its 'org' and 'app' folders. Without this, attempts to create
files in the pref-path would fail, unless those directories were first created
by the app, or by some other library the app used. This change makes sure
that these directories get created, before SDL_GetPrefPath() returns to its
caller(s).


2. it defaults to having SDL_GetPrefPath() return a WinRT 'Local' folder
on all platforms. Previously, for Windows Store apps, it would have used a
different, 'Roaming' folder. Files in Roaming folders can be automatically,
and synchronized across multiple devices by Windows. This synchronization can
happen while the app runs, with new files being copied into a running app's
pref-path. Unless an app is specifically designed to handle this scenario,
there is a chance that save-data could be overwritten in unwanted or
unexpected ways.

The default is now to use a Local folder, which does not get synchronized, and
which is arguably a bit safer to use. Apps that wish to use Roaming folders
can do so by setting SDL_HINT_WINRT_PREF_PATH_ROOT to "roaming", however it
is recommended that one first read Microsoft's documentation for Roaming
files, a link to which is provided in README-winrt.md.

To preserve older pref-path selection behavior (found in SDL 2.0.3, as well as
many pre-2.0.4 versions of SDL from hg.libsdl.org), which uses a Roaming path
in Windows Store apps, and a Local path in Windows Phone, set
SDL_HINT_WINRT_PREF_PATH_ROOT to "old".

Please note that Roaming paths are not supported on Windows Phone 8.0, due to
limitations in the OS itself. Attempts to use this will fail.
(Windows Phone 8.1 does not have this limitation, however.)


3. It makes SDL_GetPrefPath(), when on Windows Phone 8.0, and when
SDL_HINT_WINRT_PREF_PATH_ROOT is set to "roaming", return NULL, rather than
silently defaulting to a Local path (then switching to a Roaming path if and
when the user upgraded to Windows Phone 8.1).
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 
    22 /**
    23  *  \file SDL_test_crc32.h
    24  *
    25  *  Include file for SDL test framework.
    26  *
    27  *  This code is a part of the SDL2_test library, not the main SDL library.
    28  */
    29 
    30 /*
    31 
    32  Implements CRC32 calculations (default output is Perl String::CRC32 compatible).
    33 
    34 */
    35 
    36 #ifndef _SDL_test_crc32_h
    37 #define _SDL_test_crc32_h
    38 
    39 #include "begin_code.h"
    40 /* Set up for C function definitions, even when using C++ */
    41 #ifdef __cplusplus
    42 extern "C" {
    43 #endif
    44 
    45 
    46 /* ------------ Definitions --------- */
    47 
    48 /* Definition shared by all CRC routines */
    49 
    50 #ifndef CrcUint32
    51  #define CrcUint32  unsigned int
    52 #endif
    53 #ifndef CrcUint8
    54  #define CrcUint8   unsigned char
    55 #endif
    56 
    57 #ifdef ORIGINAL_METHOD
    58  #define CRC32_POLY 0x04c11db7   /* AUTODIN II, Ethernet, & FDDI */
    59 #else
    60  #define CRC32_POLY 0xEDB88320   /* Perl String::CRC32 compatible */
    61 #endif
    62 
    63 /**
    64  * Data structure for CRC32 (checksum) computation
    65  */
    66   typedef struct {
    67     CrcUint32    crc32_table[256]; /* CRC table */
    68   } SDLTest_Crc32Context;
    69 
    70 /* ---------- Function Prototypes ------------- */
    71 
    72 /**
    73  * \brief Initialize the CRC context
    74  *
    75  * Note: The function initializes the crc table required for all crc calculations.
    76  *
    77  * \param crcContext        pointer to context variable
    78  *
    79  * \returns 0 for OK, -1 on error
    80  *
    81  */
    82  int SDLTest_Crc32Init(SDLTest_Crc32Context * crcContext);
    83 
    84 
    85 /**
    86  * \brief calculate a crc32 from a data block
    87  *
    88  * \param crcContext         pointer to context variable
    89  * \param inBuf              input buffer to checksum
    90  * \param inLen              length of input buffer
    91  * \param crc32              pointer to Uint32 to store the final CRC into
    92  *
    93  * \returns 0 for OK, -1 on error
    94  *
    95  */
    96 int SDLTest_crc32Calc(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32);
    97 
    98 /* Same routine broken down into three steps */
    99 int SDLTest_Crc32CalcStart(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32);
   100 int SDLTest_Crc32CalcEnd(SDLTest_Crc32Context * crcContext, CrcUint32 *crc32);
   101 int SDLTest_Crc32CalcBuffer(SDLTest_Crc32Context * crcContext, CrcUint8 *inBuf, CrcUint32 inLen, CrcUint32 *crc32);
   102 
   103 
   104 /**
   105  * \brief clean up CRC context
   106  *
   107  * \param crcContext        pointer to context variable
   108  *
   109  * \returns 0 for OK, -1 on error
   110  *
   111 */
   112 
   113 int SDLTest_Crc32Done(SDLTest_Crc32Context * crcContext);
   114 
   115 
   116 /* Ends C function definitions when using C++ */
   117 #ifdef __cplusplus
   118 }
   119 #endif
   120 #include "close_code.h"
   121 
   122 #endif /* _SDL_test_crc32_h */
   123 
   124 /* vi: set ts=4 sw=4 expandtab: */