/* GLIB - Library of useful routines for C programming

 * Copyright (C) 1995-1998  Peter Mattis, Spencer Kimball and Josh MacDonald

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 */

/*

 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS

 * file for a list of people on the GLib Team.  See the ChangeLog

 * files for a list of changes.  These files are distributed with

 * GLib at ftp://ftp.gtk.org/pub/gtk/. 

 */

/* 

 * MT safe for the unix part, FIXME: make the win32 part MT safe as well.

 */

#include "config.h"

#include "gutils.h"

#include "gutilsprivate.h"

#include <stdarg.h>

#include <stdlib.h>

#include <stdio.h>

#include <locale.h>

#include <string.h>

#include <ctype.h>    /* For tolower() */

#include <errno.h>

#include <sys/types.h>

#include <sys/stat.h>

#ifdef G_OS_UNIX

#include <pwd.h>

#include <sys/utsname.h>

#include <unistd.h>

#endif

#include <sys/types.h>

#ifdef HAVE_SYS_PARAM_H

#include <sys/param.h>

#endif

#ifdef HAVE_CRT_EXTERNS_H 

#include <crt_externs.h> /* for _NSGetEnviron */

#endif

#ifdef HAVE_SYS_AUXV_H

#include <sys/auxv.h>

#endif

#include "glib-init.h"

#include "glib-private.h"

#include "genviron.h"

#include "gfileutils.h"

#include "ggettext.h"

#include "ghash.h"

#include "gthread.h"

#include "gtestutils.h"

#include "gunicode.h"

#include "gstrfuncs.h"

#include "garray.h"

#include "glibintl.h"

#include "gstdio.h"

#ifdef G_PLATFORM_WIN32

#include "gconvert.h"

#include "gwin32.h"

#endif

/**

 * SECTION:misc_utils

 * @title: Miscellaneous Utility Functions

 * @short_description: a selection of portable utility functions

 *

 * These are portable utility functions.

 */

#ifdef G_PLATFORM_WIN32

#  include <windows.h>

#  ifndef GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS

#    define GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT 2

#    define GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS 4

#  endif

#  include <lmcons.h>   /* For UNLEN */

#endif /* G_PLATFORM_WIN32 */

#ifdef G_OS_WIN32

#  include <direct.h>

#  include <shlobj.h>

#  include <process.h>

#endif

#ifdef HAVE_CODESET

#include <langinfo.h>

#endif

#ifdef G_PLATFORM_WIN32

gchar *

_glib_get_dll_directory (void)

{

  gchar *retval;

  gchar *p;

  wchar_t wc_fn[MAX_PATH];

#ifdef DLL_EXPORT

  if (glib_dll == NULL)

    return NULL;

#endif

  /* This code is different from that in

   * g_win32_get_package_installation_directory_of_module() in that

   * here we return the actual folder where the GLib DLL is. We don't

   * do the check for it being in a "bin" or "lib" subfolder and then

   * returning the parent of that.

   *

   * In a statically built GLib, glib_dll will be NULL and we will

   * thus look up the application's .exe file's location.

   */

  if (!GetModuleFileNameW (glib_dll, wc_fn, MAX_PATH))

    return NULL;

  retval = g_utf16_to_utf8 (wc_fn, -1, NULL, NULL, NULL);

  p = strrchr (retval, G_DIR_SEPARATOR);

  if (p == NULL)

    {

      /* Wtf? */

      return NULL;

    }

  *p = '\0';

  return retval;

}

#endif

/**

 * g_memmove: 

 * @dest: the destination address to copy the bytes to.

 * @src: the source address to copy the bytes from.

 * @len: the number of bytes to copy.

 *

 * Copies a block of memory @len bytes long, from @src to @dest.

 * The source and destination areas may overlap.

 *

 * Deprecated:2.40: Just use memmove().

 */

#ifdef G_OS_WIN32

#undef g_atexit

#endif

/**

 * g_atexit:

 * @func: (scope async): the function to call on normal program termination.

 * 

 * Specifies a function to be called at normal program termination.

 *

 * Since GLib 2.8.2, on Windows g_atexit() actually is a preprocessor

 * macro that maps to a call to the atexit() function in the C

 * library. This means that in case the code that calls g_atexit(),

 * i.e. atexit(), is in a DLL, the function will be called when the

 * DLL is detached from the program. This typically makes more sense

 * than that the function is called when the GLib DLL is detached,

 * which happened earlier when g_atexit() was a function in the GLib

 * DLL.

 *

 * The behaviour of atexit() in the context of dynamically loaded

 * modules is not formally specified and varies wildly.

 *

 * On POSIX systems, calling g_atexit() (or atexit()) in a dynamically

 * loaded module which is unloaded before the program terminates might

 * well cause a crash at program exit.

 *

 * Some POSIX systems implement atexit() like Windows, and have each

 * dynamically loaded module maintain an own atexit chain that is

 * called when the module is unloaded.

 *

 * On other POSIX systems, before a dynamically loaded module is

 * unloaded, the registered atexit functions (if any) residing in that

 * module are called, regardless where the code that registered them

 * resided. This is presumably the most robust approach.

 *

 * As can be seen from the above, for portability it's best to avoid

 * calling g_atexit() (or atexit()) except in the main executable of a

 * program.

 *

 * Deprecated:2.32: It is best to avoid g_atexit().

 */

G_GNUC_BEGIN_IGNORE_DEPRECATIONS

void

g_atexit (GVoidFunc func)

{

  gint result;

  int errsv;

  result = atexit ((void (*)(void)) func);

  errsv = errno;

  if (result)

    {

      g_error ("Could not register atexit() function: %s",

               g_strerror (errsv));

    }

}

G_GNUC_END_IGNORE_DEPRECATIONS

/* Based on execvp() from GNU Libc.

 * Some of this code is cut-and-pasted into gspawn.c

 */

static gchar*

my_strchrnul (const gchar *str, 

        gchar        c)

{

  gchar *p = (gchar*)str;

  while (*p && (*p != c))

    ++p;

  return p;

}

#ifdef G_OS_WIN32

static gchar *inner_find_program_in_path (const gchar *program);

gchar*

g_find_program_in_path (const gchar *program)

{

  const gchar *last_dot = strrchr (program, '.');

  if (last_dot == NULL ||

      strchr (last_dot, '\\') != NULL ||

      strchr (last_dot, '/') != NULL)

    {

      const gint program_length = strlen (program);

      gchar *pathext = g_build_path (";",

             ".exe;.cmd;.bat;.com",

             g_getenv ("PATHEXT"),

             NULL);

      gchar *p;

      gchar *decorated_program;

      gchar *retval;

      p = pathext;

      do

  {

    gchar *q = my_strchrnul (p, ';');

    decorated_program = g_malloc (program_length + (q-p) + 1);

    memcpy (decorated_program, program, program_length);

    memcpy (decorated_program+program_length, p, q-p);

    decorated_program [program_length + (q-p)] = '\0';

    retval = inner_find_program_in_path (decorated_program);

    g_free (decorated_program);

    if (retval != NULL)

      {

        g_free (pathext);

        return retval;

      }

    p = q;

  } while (*p++ != '\0');

      g_free (pathext);

      return NULL;

    }

  else

    return inner_find_program_in_path (program);

}

#endif

/**

 * g_find_program_in_path:

 * @program: (type filename): a program name in the GLib file name encoding

 * 

 * Locates the first executable named @program in the user's path, in the

 * same way that execvp() would locate it. Returns an allocated string

 * with the absolute path name, or %NULL if the program is not found in

 * the path. If @program is already an absolute path, returns a copy of

 * @program if @program exists and is executable, and %NULL otherwise.

 *  

 * On Windows, if @program does not have a file type suffix, tries

 * with the suffixes .exe, .cmd, .bat and .com, and the suffixes in

 * the `PATHEXT` environment variable. 

 * 

 * On Windows, it looks for the file in the same way as CreateProcess() 

 * would. This means first in the directory where the executing

 * program was loaded from, then in the current directory, then in the

 * Windows 32-bit system directory, then in the Windows directory, and

 * finally in the directories in the `PATH` environment variable. If

 * the program is found, the return value contains the full name

 * including the type suffix.

 *

 * Returns: (type filename) (transfer full) (nullable): a newly-allocated

 *   string with the absolute path, or %NULL

 **/

#ifdef G_OS_WIN32

static gchar *

inner_find_program_in_path (const gchar *program)

#else

gchar*

g_find_program_in_path (const gchar *program)

#endif

{

  const gchar *path, *p;

  gchar *name, *freeme;

#ifdef G_OS_WIN32

  const gchar *path_copy;

  gchar *filename = NULL, *appdir = NULL;

  gchar *sysdir = NULL, *windir = NULL;

  int n;

  wchar_t wfilename[MAXPATHLEN], wsysdir[MAXPATHLEN],

    wwindir[MAXPATHLEN];

#endif

  gsize len;

  gsize pathlen;

  g_return_val_if_fail (program != NULL, NULL);

  /* If it is an absolute path, or a relative path including subdirectories,

   * don't look in PATH.

   */

  if (g_path_is_absolute (program)

      || strchr (program, G_DIR_SEPARATOR) != NULL

#ifdef G_OS_WIN32

      || strchr (program, '/') != NULL

#endif

      )

    {

      if (g_file_test (program, G_FILE_TEST_IS_EXECUTABLE) &&

    !g_file_test (program, G_FILE_TEST_IS_DIR))

        return g_strdup (program);

      else

        return NULL;

    }

  path = g_getenv ("PATH");

#if defined(G_OS_UNIX)

  if (path == NULL)

    {

      /* There is no 'PATH' in the environment.  The default

       * search path in GNU libc is the current directory followed by

       * the path 'confstr' returns for '_CS_PATH'.

       */

      /* In GLib we put . last, for security, and don't use the

       * unportable confstr(); UNIX98 does not actually specify

       * what to search if PATH is unset. POSIX may, dunno.

       */

      path = "/bin:/usr/bin:.";

    }

#else

  n = GetModuleFileNameW (NULL, wfilename, MAXPATHLEN);

  if (n > 0 && n < MAXPATHLEN)

    filename = g_utf16_to_utf8 (wfilename, -1, NULL, NULL, NULL);

  n = GetSystemDirectoryW (wsysdir, MAXPATHLEN);

  if (n > 0 && n < MAXPATHLEN)

    sysdir = g_utf16_to_utf8 (wsysdir, -1, NULL, NULL, NULL);

  n = GetWindowsDirectoryW (wwindir, MAXPATHLEN);

  if (n > 0 && n < MAXPATHLEN)

    windir = g_utf16_to_utf8 (wwindir, -1, NULL, NULL, NULL);

  if (filename)

    {

      appdir = g_path_get_dirname (filename);

      g_free (filename);

    }

  path = g_strdup (path);

  if (windir)

    {

      const gchar *tem = path;

      path = g_strconcat (windir, ";", path, NULL);

      g_free ((gchar *) tem);

      g_free (windir);

    }

  if (sysdir)

    {

      const gchar *tem = path;

      path = g_strconcat (sysdir, ";", path, NULL);

      g_free ((gchar *) tem);

      g_free (sysdir);

    }

  {

    const gchar *tem = path;

    path = g_strconcat (".;", path, NULL);

    g_free ((gchar *) tem);

  }

  if (appdir)

    {

      const gchar *tem = path;

      path = g_strconcat (appdir, ";", path, NULL);

      g_free ((gchar *) tem);

      g_free (appdir);

    }

  path_copy = path;

#endif

  len = strlen (program) + 1;

  pathlen = strlen (path);

  freeme = name = g_malloc (pathlen + len + 1);

  /* Copy the file name at the top, including '\0'  */

  memcpy (name + pathlen + 1, program, len);

  name = name + pathlen;

  /* And add the slash before the filename  */

  *name = G_DIR_SEPARATOR;

  p = path;

  do

    {

      char *startp;

      path = p;

      p = my_strchrnul (path, G_SEARCHPATH_SEPARATOR);

      if (p == path)

        /* Two adjacent colons, or a colon at the beginning or the end

         * of 'PATH' means to search the current directory.

         */

        startp = name + 1;

      else

        startp = memcpy (name - (p - path), path, p - path);

      if (g_file_test (startp, G_FILE_TEST_IS_EXECUTABLE) &&

    !g_file_test (startp, G_FILE_TEST_IS_DIR))

        {

          gchar *ret;

          ret = g_strdup (startp);

          g_free (freeme);

#ifdef G_OS_WIN32

    g_free ((gchar *) path_copy);

#endif

          return ret;

        }

    }

  while (*p++ != '\0');

  g_free (freeme);

#ifdef G_OS_WIN32

  g_free ((gchar *) path_copy);

#endif

  return NULL;

}

/* The functions below are defined this way for compatibility reasons.

 * See the note in gutils.h.

 */

/**

 * g_bit_nth_lsf:

 * @mask: a #gulong containing flags

 * @nth_bit: the index of the bit to start the search from

 *

 * Find the position of the first bit set in @mask, searching

 * from (but not including) @nth_bit upwards. Bits are numbered

 * from 0 (least significant) to sizeof(#gulong) * 8 - 1 (31 or 63,

 * usually). To start searching from the 0th bit, set @nth_bit to -1.

 *

 * Returns: the index of the first bit set which is higher than @nth_bit, or -1

 *    if no higher bits are set

 */

gint

(g_bit_nth_lsf) (gulong mask,

                 gint   nth_bit)

{

  return g_bit_nth_lsf_impl (mask, nth_bit);

}

/**

 * g_bit_nth_msf:

 * @mask: a #gulong containing flags

 * @nth_bit: the index of the bit to start the search from

 *

 * Find the position of the first bit set in @mask, searching

 * from (but not including) @nth_bit downwards. Bits are numbered

 * from 0 (least significant) to sizeof(#gulong) * 8 - 1 (31 or 63,

 * usually). To start searching from the last bit, set @nth_bit to

 * -1 or GLIB_SIZEOF_LONG * 8.

 *

 * Returns: the index of the first bit set which is lower than @nth_bit, or -1

 *    if no lower bits are set

 */

gint

(g_bit_nth_msf) (gulong mask,

                 gint   nth_bit)

{

  return g_bit_nth_msf_impl (mask, nth_bit);

}

/**

 * g_bit_storage:

 * @number: a #guint

 *

 * Gets the number of bits used to hold @number,

 * e.g. if @number is 4, 3 bits are needed.

 *

 * Returns: the number of bits used to hold @number

 */

guint

(g_bit_storage) (gulong number)

{

  return g_bit_storage_impl (number);

}

G_LOCK_DEFINE_STATIC (g_utils_global);

typedef struct

{

  gchar *user_name;

  gchar *real_name;

  gchar *home_dir;

} UserDatabaseEntry;

/* These must all be read/written with @g_utils_global held. */

static  gchar   *g_user_data_dir = NULL;

static  gchar  **g_system_data_dirs = NULL;

static  gchar   *g_user_cache_dir = NULL;

static  gchar   *g_user_config_dir = NULL;

static  gchar   *g_user_runtime_dir = NULL;

static  gchar  **g_system_config_dirs = NULL;

static  gchar  **g_user_special_dirs = NULL;

/* fifteen minutes of fame for everybody */

#define G_USER_DIRS_EXPIRE      15 * 60

#ifdef G_OS_WIN32

static gchar *

get_special_folder (int csidl)

{

  wchar_t path[MAX_PATH+1];

  HRESULT hr;

  LPITEMIDLIST pidl = NULL;

  BOOL b;

  gchar *retval = NULL;

  hr = SHGetSpecialFolderLocation (NULL, csidl, &pidl);

  if (hr == S_OK)

    {

      b = SHGetPathFromIDListW (pidl, path);

      if (b)

  retval = g_utf16_to_utf8 (path, -1, NULL, NULL, NULL);

      CoTaskMemFree (pidl);

    }

  return retval;

}

static char *

get_windows_directory_root (void)

{

  wchar_t wwindowsdir[MAX_PATH];

  if (GetWindowsDirectoryW (wwindowsdir, G_N_ELEMENTS (wwindowsdir)))

    {

      /* Usually X:\Windows, but in terminal server environments

       * might be an UNC path, AFAIK.

       */

      char *windowsdir = g_utf16_to_utf8 (wwindowsdir, -1, NULL, NULL, NULL);

      char *p;

      if (windowsdir == NULL)

  return g_strdup ("C:\\");

      p = (char *) g_path_skip_root (windowsdir);

      if (G_IS_DIR_SEPARATOR (p[-1]) && p[-2] != ':')

  p--;

      *p = '\0';

      return windowsdir;

    }

  else

    return g_strdup ("C:\\");

}

#endif

/* HOLDS: g_utils_global_lock */

static UserDatabaseEntry *

g_get_user_database_entry (void)

{

  static UserDatabaseEntry *entry;

  if (g_once_init_enter (&entry))

    {

      static UserDatabaseEntry e;

#ifdef G_OS_UNIX

      {

        struct passwd *pw = NULL;

        gpointer buffer = NULL;

        gint error;

        gchar *logname;

#  if defined (HAVE_GETPWUID_R)

        struct passwd pwd;

#    ifdef _SC_GETPW_R_SIZE_MAX

        /* This reurns the maximum length */

        glong bufsize = sysconf (_SC_GETPW_R_SIZE_MAX);

        if (bufsize < 0)

          bufsize = 64;

#    else /* _SC_GETPW_R_SIZE_MAX */

        glong bufsize = 64;

#    endif /* _SC_GETPW_R_SIZE_MAX */

        logname = (gchar *) g_getenv ("LOGNAME");

        do

          {

            g_free (buffer);

            /* we allocate 6 extra bytes to work around a bug in

             * Mac OS < 10.3. See #156446

             */

            buffer = g_malloc (bufsize + 6);

            errno = 0;

            if (logname) {

              error = getpwnam_r (logname, &pwd, buffer, bufsize, &pw);

              if (!pw || (pw->pw_uid != getuid ())) {

                /* LOGNAME is lying, fall back to looking up the uid */

                error = getpwuid_r (getuid (), &pwd, buffer, bufsize, &pw);

              }

            } else {

              error = getpwuid_r (getuid (), &pwd, buffer, bufsize, &pw);

            }

            error = error < 0 ? errno : error;

            if (!pw)

              {

                /* we bail out prematurely if the user id can't be found

                 * (should be pretty rare case actually), or if the buffer

                 * should be sufficiently big and lookups are still not

                 * successful.

                 */

                if (error == 0 || error == ENOENT)

                  {

                    g_warning ("getpwuid_r(): failed due to unknown user id (%lu)",

                               (gulong) getuid ());

                    break;

                  }

                if (bufsize > 32 * 1024)

                  {

                    g_warning ("getpwuid_r(): failed due to: %s.",

                               g_strerror (error));

                    break;

                  }

                bufsize *= 2;

              }

          }

        while (!pw);

#  endif /* HAVE_GETPWUID_R */

        if (!pw)

          {

            pw = getpwuid (getuid ());

          }

        if (pw)

          {

            e.user_name = g_strdup (pw->pw_name);

#ifndef __BIONIC__

            if (pw->pw_gecos && *pw->pw_gecos != '\0' && pw->pw_name)

              {

                gchar **gecos_fields;

                gchar **name_parts;

                /* split the gecos field and substitute '&' */

                gecos_fields = g_strsplit (pw->pw_gecos, ",", 0);

                name_parts = g_strsplit (gecos_fields[0], "&", 0);

                pw->pw_name[0] = g_ascii_toupper (pw->pw_name[0]);

                e.real_name = g_strjoinv (pw->pw_name, name_parts);

                g_strfreev (gecos_fields);

                g_strfreev (name_parts);

              }

#endif

            if (!e.home_dir)

              e.home_dir = g_strdup (pw->pw_dir);

          }

        g_free (buffer);

      }

#endif /* G_OS_UNIX */

#ifdef G_OS_WIN32

      {

        guint len = UNLEN+1;

        wchar_t buffer[UNLEN+1];

        if (GetUserNameW (buffer, (LPDWORD) &len))

          {

            e.user_name = g_utf16_to_utf8 (buffer, -1, NULL, NULL, NULL);

            e.real_name = g_strdup (e.user_name);

          }

      }

#endif /* G_OS_WIN32 */

      if (!e.user_name)

        e.user_name = g_strdup ("somebody");

      if (!e.real_name)

        e.real_name = g_strdup ("Unknown");

      g_once_init_leave (&entry, &e);

    }

  return entry;

}

/**

 * g_get_user_name:

 *

 * Gets the user name of the current user. The encoding of the returned

 * string is system-defined. On UNIX, it might be the preferred file name

 * encoding, or something else, and there is no guarantee that it is even

 * consistent on a machine. On Windows, it is always UTF-8.

 *

 * Returns: (type filename) (transfer none): the user name of the current user.

 */

const gchar *

g_get_user_name (void)

{

  UserDatabaseEntry *entry;

  entry = g_get_user_database_entry ();

  return entry->user_name;

}

/**

 * g_get_real_name:

 *

 * Gets the real name of the user. This usually comes from the user's

 * entry in the `passwd` file. The encoding of the returned string is

 * system-defined. (On Windows, it is, however, always UTF-8.) If the

 * real user name cannot be determined, the string "Unknown" is 

 * returned.

 *

 * Returns: (type filename) (transfer none): the user's real name.

 */

const gchar *

g_get_real_name (void)

{

  UserDatabaseEntry *entry;

  entry = g_get_user_database_entry ();

  return entry->real_name;

}

/* Protected by @g_utils_global_lock. */

static gchar *g_home_dir = NULL;  /* (owned) (nullable before initialised) */

static gchar *

g_build_home_dir (void)

{

  gchar *home_dir;

  /* We first check HOME and use it if it is set */

  home_dir = g_strdup (g_getenv ("HOME"));

#ifdef G_OS_WIN32

  /* Only believe HOME if it is an absolute path and exists.

   *

   * We only do this check on Windows for a couple of reasons.

   * Historically, we only did it there because we used to ignore $HOME

   * on UNIX.  There are concerns about enabling it now on UNIX because

   * of things like autofs.  In short, if the user has a bogus value in

   * $HOME then they get what they pay for...

   */

  if (home_dir != NULL)

    {

      if (!(g_path_is_absolute (home_dir) &&

            g_file_test (home_dir, G_FILE_TEST_IS_DIR)))

        g_clear_pointer (&home_dir, g_free);

    }

  /* In case HOME is Unix-style (it happens), convert it to

   * Windows style.

   */

  if (home_dir != NULL)

    {

      gchar *p;

      while ((p = strchr (home_dir, '/')) != NULL)

        *p = '\\';

    }

  if (home_dir == NULL)

    {

      /* USERPROFILE is probably the closest equivalent to $HOME? */

      if (g_getenv ("USERPROFILE") != NULL)

        home_dir = g_strdup (g_getenv ("USERPROFILE"));

    }

  if (home_dir == NULL)

    home_dir = get_special_folder (CSIDL_PROFILE);

  if (home_dir == NULL)

    home_dir = get_windows_directory_root ();

#endif /* G_OS_WIN32 */

  if (home_dir == NULL)

    {

      /* If we didn't get it from any of those methods, we will have

       * to read the user database entry.

       */

      UserDatabaseEntry *entry = g_get_user_database_entry ();

      home_dir = g_strdup (entry->home_dir);

    }

  /* If we have been denied access to /etc/passwd (for example, by an

   * overly-zealous LSM), make up a junk value. The return value at this

   * point is explicitly documented as ‘undefined’. */

  if (home_dir == NULL)

    {

      g_warning ("Could not find home directory: $HOME is not set, and "

                 "user database could not be read.");

      home_dir = g_strdup ("/");

    }

  return g_steal_pointer (&home_dir);

}

/**

 * g_get_home_dir:

 *

 * Gets the current user's home directory.

 *

 * As with most UNIX tools, this function will return the value of the

 * `HOME` environment variable if it is set to an existing absolute path

 * name, falling back to the `passwd` file in the case that it is unset.

 *

 * If the path given in `HOME` is non-absolute, does not exist, or is

 * not a directory, the result is undefined.

 *

 * Before version 2.36 this function would ignore the `HOME` environment

 * variable, taking the value from the `passwd` database instead. This was

 * changed to increase the compatibility of GLib with other programs (and

 * the XDG basedir specification) and to increase testability of programs

 * based on GLib (by making it easier to run them from test frameworks).

 *

 * If your program has a strong requirement for either the new or the

 * old behaviour (and if you don't wish to increase your GLib

 * dependency to ensure that the new behaviour is in effect) then you

 * should either directly check the `HOME` environment variable yourself

 * or unset it before calling any functions in GLib.

 *

 * Returns: (type filename) (transfer none): the current user's home directory

 */

const gchar *

g_get_home_dir (void)

{

  const gchar *home_dir;

  G_LOCK (g_utils_global);

  if (g_home_dir == NULL)

    g_home_dir = g_build_home_dir ();

  home_dir = g_home_dir;

  G_UNLOCK (g_utils_global);

  return home_dir;

}

/**

 * g_get_tmp_dir:

 *

 * Gets the directory to use for temporary files.

 *

 * On UNIX, this is taken from the `TMPDIR` environment variable.

 * If the variable is not set, `P_tmpdir` is

 * used, as defined by the system C library. Failing that, a

 * hard-coded default of "/tmp" is returned.

 *

 * On Windows, the `TEMP` environment variable is used, with the

 * root directory of the Windows installation (eg: "C:\") used

 * as a default.

 *

 * The encoding of the returned string is system-defined. On Windows,

 * it is always UTF-8. The return value is never %NULL or the empty

 * string.

 *

 * Returns: (type filename) (transfer none): the directory to use for temporary files.

 */

const gchar *

g_get_tmp_dir (void)

{

  static gchar *tmp_dir;

  if (g_once_init_enter (&tmp_dir))

    {

      gchar *tmp;

#ifdef G_OS_WIN32

      tmp = g_strdup (g_getenv ("TEMP"));

      if (tmp == NULL || *tmp == '\0')

        {

          g_free (tmp);

          tmp = get_windows_directory_root ();

        }

#else /* G_OS_WIN32 */

      tmp = g_strdup (g_getenv ("TMPDIR"));

#ifdef P_tmpdir

      if (tmp == NULL || *tmp == '\0')

        {

          gsize k;

          g_free (tmp);

          tmp = g_strdup (P_tmpdir);

          k = strlen (tmp);

          if (k > 1 && G_IS_DIR_SEPARATOR (tmp[k - 1]))

            tmp[k - 1] = '\0';

        }

#endif /* P_tmpdir */

      if (tmp == NULL || *tmp == '\0')

        {

          g_free (tmp);

          tmp = g_strdup ("/tmp");

        }

#endif /* !G_OS_WIN32 */

      g_once_init_leave (&tmp_dir, tmp);

    }

  return tmp_dir;

}

/**

 * g_get_host_name:

 *

 * Return a name for the machine. 

 *

 * The returned name is not necessarily a fully-qualified domain name,

 * or even present in DNS or some other name service at all. It need

 * not even be unique on your local network or site, but usually it

 * is. Callers should not rely on the return value having any specific

 * properties like uniqueness for security purposes. Even if the name

 * of the machine is changed while an application is running, the

 * return value from this function does not change. The returned

 * string is owned by GLib and should not be modified or freed. If no

 * name can be determined, a default fixed string "localhost" is

 * returned.

 *

 * The encoding of the returned string is UTF-8.

 *

 * Returns: (transfer none): the host name of the machine.

 *

 * Since: 2.8

 */

const gchar *

g_get_host_name (void)

{

  static gchar *hostname;

  if (g_once_init_enter (&hostname))

    {

      gboolean failed;

      gchar *utmp;

#ifndef G_OS_WIN32

      gsize size;

      /* The number 256 * 256 is taken from the value of _POSIX_HOST_NAME_MAX,

       * which is 255. Since we use _POSIX_HOST_NAME_MAX + 1 (= 256) in the

       * fallback case, we pick 256 * 256 as the size of the larger buffer here.

       * It should be large enough. It doesn't looks reasonable to name a host

       * with a string that is longer than 64 KiB.

       */

      const gsize size_large = (gsize) 256 * 256;

      gchar *tmp;

#ifdef _SC_HOST_NAME_MAX

      {

        glong max;

        max = sysconf (_SC_HOST_NAME_MAX);

        if (max > 0 && (gsize) max <= G_MAXSIZE - 1)

          size = (gsize) max + 1;

        else

#ifdef HOST_NAME_MAX

          size = HOST_NAME_MAX + 1;

#else

          size = _POSIX_HOST_NAME_MAX + 1;

#endif /* HOST_NAME_MAX */

      }

#else

      /* Fallback to some reasonable value */

      size = 256;

#endif /* _SC_HOST_NAME_MAX */

      tmp = g_malloc (size);

      failed = (gethostname (tmp, size) == -1);

      if (failed && size < size_large)

        {

          /* Try again with a larger buffer if 'size' may be too small. */

          g_free (tmp);

          tmp = g_malloc (size_large);

          failed = (gethostname (tmp, size_large) == -1);

        }

      if (failed)

        g_clear_pointer (&tmp, g_free);

      utmp = tmp;

#else

      wchar_t tmp[MAX_COMPUTERNAME_LENGTH + 1];

      DWORD size = sizeof (tmp) / sizeof (tmp[0]);

      failed = (!GetComputerNameW (tmp, &size));

      if (!failed)

        utmp = g_utf16_to_utf8 (tmp, size, NULL, NULL, NULL);

      if (utmp == NULL)

        failed = TRUE;

#endif