Windows Compatibility Functions

## Windows Compatibility Functions Windows Compatibility Functions — UNIX emulation on Windows |

## Synopsis

    #include <glib.h>

    #define             MAXPATHLEN
    gchar*              g_win32_error_message               (gint error);
    gchar*              g_win32_getlocale                   (void);
    gchar*              g_win32_get_package_installation_directory
                                                            (const gchar *package,
                                                             const gchar *dll_name);
    gchar*              g_win32_get_package_installation_directory_of_module
                                                            (gpointer hmodule);
    gchar*              g_win32_get_package_installation_subdirectory
                                                            (const gchar *package,
                                                             const gchar *dll_name,
                                                             const gchar *subdir);
    guint               g_win32_get_windows_version         (void);
    gchar*              g_win32_locale_filename_from_utf8   (const gchar *utf8filename);
    #define             G_WIN32_DLLMAIN_FOR_DLL_NAME        (static, dll_name)
    #define             G_WIN32_HAVE_WIDECHAR_API           ()
    #define             G_WIN32_IS_NT_BASED                 ()

## Description

These functions provide some level of UNIX emulation on the Windows platform. If your application really needs the POSIX APIs, we suggest you try the Cygwin project.

## Details

### MAXPATHLEN

    #define MAXPATHLEN 1024

Provided for UNIX emulation on Windows; equivalent to UNIX macro `MAXPATHLEN`, which is the maximum length of a filename (including full path).

### g_win32_error_message ()

    gchar*              g_win32_error_message               (gint error);

Translate a Win32 error code (as returned by `GetLastError()`) into the corresponding message. The message is either language neutral, or in the thread's language, or the user's language, the system's language, or US English (see docs for `FormatMessage()`). The returned string is in UTF-8. It should be deallocated with `g_free()`.

`error` : | error code.
Returns : | newly-allocated error message

### g_win32_getlocale ()

    gchar*              g_win32_getlocale                   (void);

The `setlocale()` function in the Microsoft C library uses locale names of the form "English_United States.1252" etc. We want the UNIXish standard form "en_US", "zh_TW" etc. This function gets the current thread locale from Windows - without any encoding info - and returns it as a string of the above form for use in forming file names etc. The returned string should be deallocated with `g_free()`.

Returns : | newly-allocated locale name.

### g_win32_get_package_installation_directory ()

    gchar*              g_win32_get_package_installation_directory
                                                            (const gchar *package,
                                                             const gchar *dll_name);

Try to determine the installation directory for a software package.

This function will be deprecated in the future. Use `g_win32_get_package_installation_directory_of_module()` instead.

The use of `package` is deprecated. You should always pass `NULL`.

The original intended use of `package` was for a short identifier of the package, typically the same identifier as used for `GETTEXT_PACKAGE` in software configured using GNU autotools. The function first looks in the Windows Registry for the value `#InstallationDirectory` in the key `#HKLM\Software\`package``, and if that value exists and is a string, returns that.

It is strongly recommended that packagers of GLib-using libraries for Windows do not store installation paths in the Registry to be used by this function as that interfers with having several parallel installations of the library. Enabling multiple installations of different versions of some GLib-using library, or GLib itself, is desirable for various reasons.

For this reason it is recommeded to always pass `NULL` as `package` to this function, to avoid the temptation to use the Registry. In version 2.18 of GLib the `package` parameter will be ignored and this function won't look in the Registry at all.

If `package` is `NULL`, or the above value isn't found in the Registry, but `dll_name` is non-`NULL`, it should name a DLL loaded into the current process. Typically that would be the name of the DLL calling this function, looking for its installation directory. The function then asks Windows what directory that DLL was loaded from. If that directory's last component is "bin" or "lib", the parent directory is returned, otherwise the directory itself. If that DLL isn't loaded, the function proceeds as if `dll_name` was `NULL`.

If both `package` and `dll_name` are `NULL`, the directory from where the main executable of the process was loaded is used instead in the same way as above.

`package` : | You should pass `NULL` for this.
`dll_name` : | The name of a DLL that a package provides in UTF-8, or `NULL`.
Returns : | a string containing the installation directory for `package`. The string is in the GLib file name encoding, i.e. UTF-8. The return value should be freed with `g_free()` when not needed any longer. If the function fails `NULL` is returned.

### g_win32_get_package_installation_directory_of_module ()

    gchar*              g_win32_get_package_installation_directory_of_module
                                                            (gpointer hmodule);

This function tries to determine the installation directory of a software package based on the location of a DLL of the software package.

`hmodule` should be the handle of a loaded DLL or `NULL`. The function looks up the directory that DLL was loaded from. If `hmodule` is NULL, the directory the main executable of the current process is looked up. If that directory's last component is "bin" or "lib", its parent directory is returned, otherwise the directory itself.

It thus makes sense to pass only the handle to a "public" DLL of a software package to this function, as such DLLs typically are known to be installed in a "bin" or occasionally "lib" subfolder of the installation folder. DLLs that are of the dynamically loaded module or plugin variety are often located in more private locations deeper down in the tree, from which it is impossible for GLib to deduce the root of the package installation.

The typical use case for this function is to have a `DllMain()` that saves the handle for the DLL. Then when code in the DLL needs to construct names of files in the installation tree it calls this function passing the DLL handle.

`hmodule` : | The Win32 handle for a DLL loaded into the current process, or `NULL`
Returns : | a string containing the guessed installation directory for the software package `hmodule` is from. The string is in the GLib file name encoding, i.e. UTF-8. The return value should be freed with `g_free()` when not needed any longer. If the function fails `NULL` is returned.

Since 2.16

### g_win32_get_package_installation_subdirectory ()

    gchar*              g_win32_get_package_installation_subdirectory
                                                            (const gchar *package,
                                                             const gchar *dll_name,
                                                             const gchar *subdir);

This function will be deprecated in the future. Use `g_win32_get_package_installation_directory_of_module()` instead.

Returns a newly-allocated string containing the path of the subdirectory `subdir` in the return value from calling `g_win32_get_package_installation_directory()` with the `package` and `dll_name` parameters. See the documentation for `g_win32_get_package_installation_directory()` for more details. In particular, note that it is deprecated to pass anything except NULL as `package`.

`package` : | You should pass `NULL` for this.
`dll_name` : | The name of a DLL that a package provides, in UTF-8, or `NULL`.
`subdir` : | A subdirectory of the package installation directory, also in UTF-8
Returns : | a string containing the complete path to `subdir` inside the installation directory of `package`. The returned string is in the GLib file name encoding, i.e. UTF-8. The return value should be freed with `g_free()` when no longer needed. If something goes wrong, `NULL` is returned.

### g_win32_get_windows_version ()

    guint               g_win32_get_windows_version         (void);

Returns version information for the Windows operating system the code is running on. See MSDN documentation for the `GetVersion()` function. To summarize, the most significant bit is one on Win9x, and zero on NT-based systems. Since version 2.14, GLib works only on NT-based systems, so checking whether your are running on Win9x in your own software is moot. The least significant byte is 4 on Windows NT 4, and 5 on Windows XP. Software that needs really detailled version and feature information should use Win32 API like `GetVersionEx()` and `VerifyVersionInfo()`.

Returns : | The version information.

Since 2.6

### g_win32_locale_filename_from_utf8 ()

    gchar*              g_win32_locale_filename_from_utf8   (const gchar *utf8filename);

Converts a filename from UTF-8 to the system codepage.

On NT-based Windows, on NTFS file systems, file names are in Unicode. It is quite possible that Unicode file names contain characters not representable in the system codepage. (For instance, Greek or Cyrillic characters on Western European or US Windows installations, or various less common CJK characters on CJK Windows installations.)

In such a case, and if the filename refers to an existing file, and the file system stores alternate short (8.3) names for directory entries, the short form of the filename is returned. Note that the "short" name might in fact be longer than the Unicode name if the Unicode name has very short pathname components containing non-ASCII characters. If no system codepage name for the file is possible, `NULL` is returned.

The return value is dynamically allocated and should be freed with `g_free()` when no longer needed.

`utf8filename` : | a UTF-8 encoded filename.
Returns : | The converted filename, or `NULL` on conversion failure and lack of short names.

Since 2.8

### G_WIN32_DLLMAIN_FOR_DLL_NAME()

    #define             G_WIN32_DLLMAIN_FOR_DLL_NAME(static, dll_name)

On Windows, this macro defines a `DllMain()` function that stores the actual DLL name that the code being compiled will be included in.

On non-Windows platforms, expands to nothing.

`static` : | empty or "static".
`dll_name` : | the name of the (pointer to the) char array where the DLL name will be stored. If this is used, you must also include `windows.h`. If you need a more complex DLL entry point function, you cannot use this.

### G_WIN32_HAVE_WIDECHAR_API()

    #define G_WIN32_HAVE_WIDECHAR_API() TRUE

On Windows, this macro defines an expression which evaluates to `TRUE` if the code is running on a version of Windows where the wide character versions of the Win32 API functions, and the wide chaacter versions of the C library functions work. (They are always present in the DLLs, but don't work on Windows 9x and Me.)

On non-Windows platforms, it is not defined.

Since 2.6

### G_WIN32_IS_NT_BASED()

    #define G_WIN32_IS_NT_BASED() TRUE

On Windows, this macro defines an expression which evaluates to `TRUE` if the code is running on an NT-based Windows operating system.

On non-Windows platforms, it is not defined.

Since 2.6