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      1 /* -*- mode: C; c-file-style: "gnu" -*- */
      2 /* dbus-sysdeps.c Wrappers around system/libc features shared between UNIX and Windows (internal to D-Bus implementation)
      3  *
      4  * Copyright (C) 2002, 2003, 2006  Red Hat, Inc.
      5  * Copyright (C) 2003 CodeFactory AB
      6  *
      7  * Licensed under the Academic Free License version 2.1
      8  *
      9  * This program is free software; you can redistribute it and/or modify
     10  * it under the terms of the GNU General Public License as published by
     11  * the Free Software Foundation; either version 2 of the License, or
     12  * (at your option) any later version.
     13  *
     14  * This program is distributed in the hope that it will be useful,
     15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     17  * GNU General Public License for more details.
     18  *
     19  * You should have received a copy of the GNU General Public License
     20  * along with this program; if not, write to the Free Software
     21  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     22  *
     23  */
     24 
     25 #include "dbus-internals.h"
     26 #include "dbus-sysdeps.h"
     27 #include "dbus-threads.h"
     28 #include "dbus-protocol.h"
     29 #include "dbus-string.h"
     30 
     31 /* NOTE: If you include any unix/windows-specific headers here, you are probably doing something
     32  * wrong and should be putting some code in dbus-sysdeps-unix.c or dbus-sysdeps-win.c.
     33  *
     34  * These are the standard ANSI C headers...
     35  */
     36 #include <locale.h>
     37 #include <stdlib.h>
     38 #include <string.h>
     39 #include <stdio.h>
     40 
     41 /* This is UNIX-specific (on windows it's just in stdlib.h I believe)
     42  * but OK since the same stuff does exist on Windows in stdlib.h
     43  * and covered by a configure check.
     44  */
     45 #ifdef HAVE_ERRNO_H
     46 #include <errno.h>
     47 #endif
     48 
     49 _DBUS_DEFINE_GLOBAL_LOCK (win_fds);
     50 _DBUS_DEFINE_GLOBAL_LOCK (sid_atom_cache);
     51 
     52 /**
     53  * @defgroup DBusSysdeps Internal system-dependent API
     54  * @ingroup DBusInternals
     55  * @brief Internal system-dependent API available on UNIX and Windows
     56  *
     57  * The system-dependent API has a dual purpose. First, it encapsulates
     58  * all usage of operating system APIs for ease of auditing and to
     59  * avoid cluttering the rest of the code with bizarre OS quirks and
     60  * headers. Second, it abstracts different operating system APIs for
     61  * portability.
     62  *
     63  * @{
     64  */
     65 
     66 /**
     67  * Aborts the program with SIGABRT (dumping core).
     68  */
     69 void
     70 _dbus_abort (void)
     71 {
     72   const char *s;
     73 
     74   _dbus_print_backtrace ();
     75 
     76   s = _dbus_getenv ("DBUS_BLOCK_ON_ABORT");
     77   if (s && *s)
     78     {
     79       /* don't use _dbus_warn here since it can _dbus_abort() */
     80       fprintf (stderr, "  Process %lu sleeping for gdb attach\n", (unsigned long) _dbus_getpid());
     81       _dbus_sleep_milliseconds (1000 * 180);
     82     }
     83 
     84   abort ();
     85   _dbus_exit (1); /* in case someone manages to ignore SIGABRT ? */
     86 }
     87 
     88 /**
     89  * Wrapper for setenv(). If the value is #NULL, unsets
     90  * the environment variable.
     91  *
     92  * There is an unfixable memleak in that it is unsafe to
     93  * free memory malloced for use with setenv. This is because
     94  * we can not rely on internal implementation details of
     95  * the underlying libc library.
     96  *
     97  * @param varname name of environment variable
     98  * @param value value of environment variable
     99  * @returns #TRUE on success.
    100  */
    101 dbus_bool_t
    102 _dbus_setenv (const char *varname,
    103               const char *value)
    104 {
    105   _dbus_assert (varname != NULL);
    106 
    107   if (value == NULL)
    108     {
    109 #ifdef HAVE_UNSETENV
    110       unsetenv (varname);
    111       return TRUE;
    112 #else
    113       char *putenv_value;
    114       size_t len;
    115 
    116       len = strlen (varname);
    117 
    118       /* Use system malloc to avoid memleaks that dbus_malloc
    119        * will get upset about.
    120        */
    121 
    122       putenv_value = malloc (len + 1);
    123       if (putenv_value == NULL)
    124         return FALSE;
    125 
    126       strcpy (putenv_value, varname);
    127 
    128       return (putenv (putenv_value) == 0);
    129 #endif
    130     }
    131   else
    132     {
    133 #ifdef HAVE_SETENV
    134       return (setenv (varname, value, TRUE) == 0);
    135 #else
    136       char *putenv_value;
    137       size_t len;
    138       size_t varname_len;
    139       size_t value_len;
    140 
    141       varname_len = strlen (varname);
    142       value_len = strlen (value);
    143 
    144       len = varname_len + value_len + 1 /* '=' */ ;
    145 
    146       /* Use system malloc to avoid memleaks that dbus_malloc
    147        * will get upset about.
    148        */
    149 
    150       putenv_value = malloc (len + 1);
    151       if (putenv_value == NULL)
    152         return FALSE;
    153 
    154       strcpy (putenv_value, varname);
    155       strcpy (putenv_value + varname_len, "=");
    156       strcpy (putenv_value + varname_len + 1, value);
    157 
    158       return (putenv (putenv_value) == 0);
    159 #endif
    160     }
    161 }
    162 
    163 /**
    164  * Wrapper for getenv().
    165  *
    166  * @param varname name of environment variable
    167  * @returns value of environment variable or #NULL if unset
    168  */
    169 const char*
    170 _dbus_getenv (const char *varname)
    171 {
    172   return getenv (varname);
    173 }
    174 
    175 /** @} */
    176 
    177 /**
    178  * @addtogroup DBusString
    179  *
    180  * @{
    181  */
    182 /**
    183  * Appends an integer to a DBusString.
    184  *
    185  * @param str the string
    186  * @param value the integer value
    187  * @returns #FALSE if not enough memory or other failure.
    188  */
    189 dbus_bool_t
    190 _dbus_string_append_int (DBusString *str,
    191                          long        value)
    192 {
    193   /* this calculation is from comp.lang.c faq */
    194 #define MAX_LONG_LEN ((sizeof (long) * 8 + 2) / 3 + 1)  /* +1 for '-' */
    195   int orig_len;
    196   int i;
    197   char *buf;
    198 
    199   orig_len = _dbus_string_get_length (str);
    200 
    201   if (!_dbus_string_lengthen (str, MAX_LONG_LEN))
    202     return FALSE;
    203 
    204   buf = _dbus_string_get_data_len (str, orig_len, MAX_LONG_LEN);
    205 
    206   snprintf (buf, MAX_LONG_LEN, "%ld", value);
    207 
    208   i = 0;
    209   while (*buf)
    210     {
    211       ++buf;
    212       ++i;
    213     }
    214 
    215   _dbus_string_shorten (str, MAX_LONG_LEN - i);
    216 
    217   return TRUE;
    218 }
    219 
    220 /**
    221  * Appends an unsigned integer to a DBusString.
    222  *
    223  * @param str the string
    224  * @param value the integer value
    225  * @returns #FALSE if not enough memory or other failure.
    226  */
    227 dbus_bool_t
    228 _dbus_string_append_uint (DBusString    *str,
    229                           unsigned long  value)
    230 {
    231   /* this is wrong, but definitely on the high side. */
    232 #define MAX_ULONG_LEN (MAX_LONG_LEN * 2)
    233   int orig_len;
    234   int i;
    235   char *buf;
    236 
    237   orig_len = _dbus_string_get_length (str);
    238 
    239   if (!_dbus_string_lengthen (str, MAX_ULONG_LEN))
    240     return FALSE;
    241 
    242   buf = _dbus_string_get_data_len (str, orig_len, MAX_ULONG_LEN);
    243 
    244   snprintf (buf, MAX_ULONG_LEN, "%lu", value);
    245 
    246   i = 0;
    247   while (*buf)
    248     {
    249       ++buf;
    250       ++i;
    251     }
    252 
    253   _dbus_string_shorten (str, MAX_ULONG_LEN - i);
    254 
    255   return TRUE;
    256 }
    257 
    258 #ifdef DBUS_BUILD_TESTS
    259 /**
    260  * Appends a double to a DBusString.
    261  *
    262  * @param str the string
    263  * @param value the floating point value
    264  * @returns #FALSE if not enough memory or other failure.
    265  */
    266 dbus_bool_t
    267 _dbus_string_append_double (DBusString *str,
    268                             double      value)
    269 {
    270 #define MAX_DOUBLE_LEN 64 /* this is completely made up :-/ */
    271   int orig_len;
    272   char *buf;
    273   int i;
    274 
    275   orig_len = _dbus_string_get_length (str);
    276 
    277   if (!_dbus_string_lengthen (str, MAX_DOUBLE_LEN))
    278     return FALSE;
    279 
    280   buf = _dbus_string_get_data_len (str, orig_len, MAX_DOUBLE_LEN);
    281 
    282   snprintf (buf, MAX_LONG_LEN, "%g", value);
    283 
    284   i = 0;
    285   while (*buf)
    286     {
    287       ++buf;
    288       ++i;
    289     }
    290 
    291   _dbus_string_shorten (str, MAX_DOUBLE_LEN - i);
    292 
    293   return TRUE;
    294 }
    295 #endif /* DBUS_BUILD_TESTS */
    296 
    297 /**
    298  * Parses an integer contained in a DBusString. Either return parameter
    299  * may be #NULL if you aren't interested in it. The integer is parsed
    300  * and stored in value_return. Return parameters are not initialized
    301  * if the function returns #FALSE.
    302  *
    303  * @param str the string
    304  * @param start the byte index of the start of the integer
    305  * @param value_return return location of the integer value or #NULL
    306  * @param end_return return location of the end of the integer, or #NULL
    307  * @returns #TRUE on success
    308  */
    309 dbus_bool_t
    310 _dbus_string_parse_int (const DBusString *str,
    311                         int               start,
    312                         long             *value_return,
    313                         int              *end_return)
    314 {
    315   long v;
    316   const char *p;
    317   char *end;
    318 
    319   p = _dbus_string_get_const_data_len (str, start,
    320                                        _dbus_string_get_length (str) - start);
    321 
    322   end = NULL;
    323   errno = 0;
    324   v = strtol (p, &end, 0);
    325   if (end == NULL || end == p || errno != 0)
    326     return FALSE;
    327 
    328   if (value_return)
    329     *value_return = v;
    330   if (end_return)
    331     *end_return = start + (end - p);
    332 
    333   return TRUE;
    334 }
    335 
    336 /**
    337  * Parses an unsigned integer contained in a DBusString. Either return
    338  * parameter may be #NULL if you aren't interested in it. The integer
    339  * is parsed and stored in value_return. Return parameters are not
    340  * initialized if the function returns #FALSE.
    341  *
    342  * @param str the string
    343  * @param start the byte index of the start of the integer
    344  * @param value_return return location of the integer value or #NULL
    345  * @param end_return return location of the end of the integer, or #NULL
    346  * @returns #TRUE on success
    347  */
    348 dbus_bool_t
    349 _dbus_string_parse_uint (const DBusString *str,
    350                          int               start,
    351                          unsigned long    *value_return,
    352                          int              *end_return)
    353 {
    354   unsigned long v;
    355   const char *p;
    356   char *end;
    357 
    358   p = _dbus_string_get_const_data_len (str, start,
    359                                        _dbus_string_get_length (str) - start);
    360 
    361   end = NULL;
    362   errno = 0;
    363   v = strtoul (p, &end, 0);
    364   if (end == NULL || end == p || errno != 0)
    365     return FALSE;
    366 
    367   if (value_return)
    368     *value_return = v;
    369   if (end_return)
    370     *end_return = start + (end - p);
    371 
    372   return TRUE;
    373 }
    374 
    375 #ifdef DBUS_BUILD_TESTS
    376 static dbus_bool_t
    377 ascii_isspace (char c)
    378 {
    379   return (c == ' ' ||
    380 	  c == '\f' ||
    381 	  c == '\n' ||
    382 	  c == '\r' ||
    383 	  c == '\t' ||
    384 	  c == '\v');
    385 }
    386 #endif /* DBUS_BUILD_TESTS */
    387 
    388 #ifdef DBUS_BUILD_TESTS
    389 static dbus_bool_t
    390 ascii_isdigit (char c)
    391 {
    392   return c >= '0' && c <= '9';
    393 }
    394 #endif /* DBUS_BUILD_TESTS */
    395 
    396 #ifdef DBUS_BUILD_TESTS
    397 static dbus_bool_t
    398 ascii_isxdigit (char c)
    399 {
    400   return (ascii_isdigit (c) ||
    401 	  (c >= 'a' && c <= 'f') ||
    402 	  (c >= 'A' && c <= 'F'));
    403 }
    404 #endif /* DBUS_BUILD_TESTS */
    405 
    406 #ifdef DBUS_BUILD_TESTS
    407 /* Calls strtod in a locale-independent fashion, by looking at
    408  * the locale data and patching the decimal comma to a point.
    409  *
    410  * Relicensed from glib.
    411  */
    412 static double
    413 ascii_strtod (const char *nptr,
    414 	      char      **endptr)
    415 {
    416   char *fail_pos;
    417   double val;
    418   struct lconv *locale_data;
    419   const char *decimal_point;
    420   int decimal_point_len;
    421   const char *p, *decimal_point_pos;
    422   const char *end = NULL; /* Silence gcc */
    423 
    424   fail_pos = NULL;
    425 
    426   locale_data = localeconv ();
    427   decimal_point = locale_data->decimal_point;
    428   decimal_point_len = strlen (decimal_point);
    429 
    430   _dbus_assert (decimal_point_len != 0);
    431 
    432   decimal_point_pos = NULL;
    433   if (decimal_point[0] != '.' ||
    434       decimal_point[1] != 0)
    435     {
    436       p = nptr;
    437       /* Skip leading space */
    438       while (ascii_isspace (*p))
    439 	p++;
    440 
    441       /* Skip leading optional sign */
    442       if (*p == '+' || *p == '-')
    443 	p++;
    444 
    445       if (p[0] == '0' &&
    446 	  (p[1] == 'x' || p[1] == 'X'))
    447 	{
    448 	  p += 2;
    449 	  /* HEX - find the (optional) decimal point */
    450 
    451 	  while (ascii_isxdigit (*p))
    452 	    p++;
    453 
    454 	  if (*p == '.')
    455 	    {
    456 	      decimal_point_pos = p++;
    457 
    458 	      while (ascii_isxdigit (*p))
    459 		p++;
    460 
    461 	      if (*p == 'p' || *p == 'P')
    462 		p++;
    463 	      if (*p == '+' || *p == '-')
    464 		p++;
    465 	      while (ascii_isdigit (*p))
    466 		p++;
    467 	      end = p;
    468 	    }
    469 	}
    470       else
    471 	{
    472 	  while (ascii_isdigit (*p))
    473 	    p++;
    474 
    475 	  if (*p == '.')
    476 	    {
    477 	      decimal_point_pos = p++;
    478 
    479 	      while (ascii_isdigit (*p))
    480 		p++;
    481 
    482 	      if (*p == 'e' || *p == 'E')
    483 		p++;
    484 	      if (*p == '+' || *p == '-')
    485 		p++;
    486 	      while (ascii_isdigit (*p))
    487 		p++;
    488 	      end = p;
    489 	    }
    490 	}
    491       /* For the other cases, we need not convert the decimal point */
    492     }
    493 
    494   /* Set errno to zero, so that we can distinguish zero results
    495      and underflows */
    496   errno = 0;
    497 
    498   if (decimal_point_pos)
    499     {
    500       char *copy, *c;
    501 
    502       /* We need to convert the '.' to the locale specific decimal point */
    503       copy = dbus_malloc (end - nptr + 1 + decimal_point_len);
    504 
    505       c = copy;
    506       memcpy (c, nptr, decimal_point_pos - nptr);
    507       c += decimal_point_pos - nptr;
    508       memcpy (c, decimal_point, decimal_point_len);
    509       c += decimal_point_len;
    510       memcpy (c, decimal_point_pos + 1, end - (decimal_point_pos + 1));
    511       c += end - (decimal_point_pos + 1);
    512       *c = 0;
    513 
    514       val = strtod (copy, &fail_pos);
    515 
    516       if (fail_pos)
    517 	{
    518 	  if (fail_pos > decimal_point_pos)
    519 	    fail_pos = (char *)nptr + (fail_pos - copy) - (decimal_point_len - 1);
    520 	  else
    521 	    fail_pos = (char *)nptr + (fail_pos - copy);
    522 	}
    523 
    524       dbus_free (copy);
    525 
    526     }
    527   else
    528     val = strtod (nptr, &fail_pos);
    529 
    530   if (endptr)
    531     *endptr = fail_pos;
    532 
    533   return val;
    534 }
    535 #endif /* DBUS_BUILD_TESTS */
    536 
    537 #ifdef DBUS_BUILD_TESTS
    538 /**
    539  * Parses a floating point number contained in a DBusString. Either
    540  * return parameter may be #NULL if you aren't interested in it. The
    541  * integer is parsed and stored in value_return. Return parameters are
    542  * not initialized if the function returns #FALSE.
    543  *
    544  * @param str the string
    545  * @param start the byte index of the start of the float
    546  * @param value_return return location of the float value or #NULL
    547  * @param end_return return location of the end of the float, or #NULL
    548  * @returns #TRUE on success
    549  */
    550 dbus_bool_t
    551 _dbus_string_parse_double (const DBusString *str,
    552                            int               start,
    553                            double           *value_return,
    554                            int              *end_return)
    555 {
    556   double v;
    557   const char *p;
    558   char *end;
    559 
    560   p = _dbus_string_get_const_data_len (str, start,
    561                                        _dbus_string_get_length (str) - start);
    562 
    563   end = NULL;
    564   errno = 0;
    565   v = ascii_strtod (p, &end);
    566   if (end == NULL || end == p || errno != 0)
    567     return FALSE;
    568 
    569   if (value_return)
    570     *value_return = v;
    571   if (end_return)
    572     *end_return = start + (end - p);
    573 
    574   return TRUE;
    575 }
    576 #endif /* DBUS_BUILD_TESTS */
    577 
    578 /** @} */ /* DBusString group */
    579 
    580 /**
    581  * @addtogroup DBusInternalsUtils
    582  * @{
    583  */
    584 
    585 /**
    586  * Frees the members of info
    587  * (but not info itself)
    588  * @param info the user info struct
    589  */
    590 void
    591 _dbus_user_info_free (DBusUserInfo *info)
    592 {
    593   dbus_free (info->group_ids);
    594   dbus_free (info->username);
    595   dbus_free (info->homedir);
    596 }
    597 
    598 /**
    599  * Frees the members of info (but not info itself).
    600  *
    601  * @param info the group info
    602  */
    603 void
    604 _dbus_group_info_free (DBusGroupInfo    *info)
    605 {
    606   dbus_free (info->groupname);
    607 }
    608 
    609 /**
    610  * Sets fields in DBusCredentials to DBUS_PID_UNSET,
    611  * DBUS_UID_UNSET, DBUS_GID_UNSET.
    612  *
    613  * @param credentials the credentials object to fill in
    614  */
    615 void
    616 _dbus_credentials_clear (DBusCredentials *credentials)
    617 {
    618   credentials->pid = DBUS_PID_UNSET;
    619   credentials->uid = DBUS_UID_UNSET;
    620   credentials->gid = DBUS_GID_UNSET;
    621 }
    622 
    623 /**
    624  * Checks whether the provided_credentials are allowed to log in
    625  * as the expected_credentials.
    626  *
    627  * @param expected_credentials credentials we're trying to log in as
    628  * @param provided_credentials credentials we have
    629  * @returns #TRUE if we can log in
    630  */
    631 dbus_bool_t
    632 _dbus_credentials_match (const DBusCredentials *expected_credentials,
    633                          const DBusCredentials *provided_credentials)
    634 {
    635   if (provided_credentials->uid == DBUS_UID_UNSET)
    636     return FALSE;
    637   else if (expected_credentials->uid == DBUS_UID_UNSET)
    638     return FALSE;
    639   else if (provided_credentials->uid == 0)
    640     return TRUE;
    641   else if (provided_credentials->uid == expected_credentials->uid)
    642     return TRUE;
    643   else
    644     return FALSE;
    645 }
    646 
    647 _DBUS_DEFINE_GLOBAL_LOCK (atomic);
    648 
    649 #ifdef DBUS_USE_ATOMIC_INT_486
    650 /* Taken from CVS version 1.7 of glibc's sysdeps/i386/i486/atomicity.h */
    651 /* Since the asm stuff here is gcc-specific we go ahead and use "inline" also */
    652 static inline dbus_int32_t
    653 atomic_exchange_and_add (DBusAtomic            *atomic,
    654                          volatile dbus_int32_t  val)
    655 {
    656   register dbus_int32_t result;
    657 
    658   __asm__ __volatile__ ("lock; xaddl %0,%1"
    659                         : "=r" (result), "=m" (atomic->value)
    660 			: "0" (val), "m" (atomic->value));
    661   return result;
    662 }
    663 #endif
    664 
    665 /**
    666  * Atomically increments an integer
    667  *
    668  * @param atomic pointer to the integer to increment
    669  * @returns the value before incrementing
    670  *
    671  * @todo implement arch-specific faster atomic ops
    672  */
    673 dbus_int32_t
    674 _dbus_atomic_inc (DBusAtomic *atomic)
    675 {
    676 #ifdef DBUS_USE_ATOMIC_INT_486
    677   return atomic_exchange_and_add (atomic, 1);
    678 #else
    679   dbus_int32_t res;
    680   _DBUS_LOCK (atomic);
    681   res = atomic->value;
    682   atomic->value += 1;
    683   _DBUS_UNLOCK (atomic);
    684   return res;
    685 #endif
    686 }
    687 
    688 /**
    689  * Atomically decrement an integer
    690  *
    691  * @param atomic pointer to the integer to decrement
    692  * @returns the value before decrementing
    693  *
    694  * @todo implement arch-specific faster atomic ops
    695  */
    696 dbus_int32_t
    697 _dbus_atomic_dec (DBusAtomic *atomic)
    698 {
    699 #ifdef DBUS_USE_ATOMIC_INT_486
    700   return atomic_exchange_and_add (atomic, -1);
    701 #else
    702   dbus_int32_t res;
    703 
    704   _DBUS_LOCK (atomic);
    705   res = atomic->value;
    706   atomic->value -= 1;
    707   _DBUS_UNLOCK (atomic);
    708   return res;
    709 #endif
    710 }
    711 
    712 void
    713 _dbus_generate_pseudorandom_bytes_buffer (char *buffer,
    714                                           int   n_bytes)
    715 {
    716   long tv_usec;
    717   int i;
    718 
    719   /* fall back to pseudorandom */
    720   _dbus_verbose ("Falling back to pseudorandom for %d bytes\n",
    721                  n_bytes);
    722 
    723   _dbus_get_current_time (NULL, &tv_usec);
    724   srand (tv_usec);
    725 
    726   i = 0;
    727   while (i < n_bytes)
    728     {
    729       double r;
    730       unsigned int b;
    731 
    732       r = rand ();
    733       b = (r / (double) RAND_MAX) * 255.0;
    734 
    735       buffer[i] = b;
    736 
    737       ++i;
    738     }
    739 }
    740 
    741 /**
    742  * Fills n_bytes of the given buffer with random bytes.
    743  *
    744  * @param buffer an allocated buffer
    745  * @param n_bytes the number of bytes in buffer to write to
    746  */
    747 void
    748 _dbus_generate_random_bytes_buffer (char *buffer,
    749                                     int   n_bytes)
    750 {
    751   DBusString str;
    752 
    753   if (!_dbus_string_init (&str))
    754     {
    755       _dbus_generate_pseudorandom_bytes_buffer (buffer, n_bytes);
    756       return;
    757     }
    758 
    759   if (!_dbus_generate_random_bytes (&str, n_bytes))
    760     {
    761       _dbus_string_free (&str);
    762       _dbus_generate_pseudorandom_bytes_buffer (buffer, n_bytes);
    763       return;
    764     }
    765 
    766   _dbus_string_copy_to_buffer (&str, buffer, n_bytes);
    767 
    768   _dbus_string_free (&str);
    769 }
    770 
    771 /**
    772  * Generates the given number of random bytes, where the bytes are
    773  * chosen from the alphanumeric ASCII subset.
    774  *
    775  * @param str the string
    776  * @param n_bytes the number of random ASCII bytes to append to string
    777  * @returns #TRUE on success, #FALSE if no memory or other failure
    778  */
    779 dbus_bool_t
    780 _dbus_generate_random_ascii (DBusString *str,
    781                              int         n_bytes)
    782 {
    783   static const char letters[] =
    784     "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
    785   int i;
    786   int len;
    787 
    788   if (!_dbus_generate_random_bytes (str, n_bytes))
    789     return FALSE;
    790 
    791   len = _dbus_string_get_length (str);
    792   i = len - n_bytes;
    793   while (i < len)
    794     {
    795       _dbus_string_set_byte (str, i,
    796                              letters[_dbus_string_get_byte (str, i) %
    797                                      (sizeof (letters) - 1)]);
    798 
    799       ++i;
    800     }
    801 
    802   _dbus_assert (_dbus_string_validate_ascii (str, len - n_bytes,
    803                                              n_bytes));
    804 
    805   return TRUE;
    806 }
    807 
    808 /**
    809  * Gets a UID from a UID string.
    810  *
    811  * @param uid_str the UID in string form
    812  * @param uid UID to fill in
    813  * @returns #TRUE if successfully filled in UID
    814  */
    815 dbus_bool_t
    816 _dbus_parse_uid (const DBusString      *uid_str,
    817                  dbus_uid_t            *uid)
    818 {
    819   int end;
    820   long val;
    821 
    822   if (_dbus_string_get_length (uid_str) == 0)
    823     {
    824       _dbus_verbose ("UID string was zero length\n");
    825       return FALSE;
    826     }
    827 
    828   val = -1;
    829   end = 0;
    830   if (!_dbus_string_parse_int (uid_str, 0, &val,
    831                                &end))
    832     {
    833       _dbus_verbose ("could not parse string as a UID\n");
    834       return FALSE;
    835     }
    836 
    837   if (end != _dbus_string_get_length (uid_str))
    838     {
    839       _dbus_verbose ("string contained trailing stuff after UID\n");
    840       return FALSE;
    841     }
    842 
    843   *uid = val;
    844 
    845   return TRUE;
    846 }
    847 
    848 /**
    849  * Converts a UNIX or Windows errno
    850  * into a #DBusError name.
    851  *
    852  * @todo should cover more errnos, specifically those
    853  * from open().
    854  *
    855  * @param error_number the errno.
    856  * @returns an error name
    857  */
    858 const char*
    859 _dbus_error_from_errno (int error_number)
    860 {
    861   switch (error_number)
    862     {
    863     case 0:
    864       return DBUS_ERROR_FAILED;
    865 
    866 #ifdef EPROTONOSUPPORT
    867     case EPROTONOSUPPORT:
    868       return DBUS_ERROR_NOT_SUPPORTED;
    869 #endif
    870 #ifdef EAFNOSUPPORT
    871     case EAFNOSUPPORT:
    872       return DBUS_ERROR_NOT_SUPPORTED;
    873 #endif
    874 #ifdef ENFILE
    875     case ENFILE:
    876       return DBUS_ERROR_LIMITS_EXCEEDED; /* kernel out of memory */
    877 #endif
    878 #ifdef EMFILE
    879     case EMFILE:
    880       return DBUS_ERROR_LIMITS_EXCEEDED;
    881 #endif
    882 #ifdef EACCES
    883     case EACCES:
    884       return DBUS_ERROR_ACCESS_DENIED;
    885 #endif
    886 #ifdef EPERM
    887     case EPERM:
    888       return DBUS_ERROR_ACCESS_DENIED;
    889 #endif
    890 #ifdef ENOBUFS
    891     case ENOBUFS:
    892       return DBUS_ERROR_NO_MEMORY;
    893 #endif
    894 #ifdef ENOMEM
    895     case ENOMEM:
    896       return DBUS_ERROR_NO_MEMORY;
    897 #endif
    898 #ifdef EINVAL
    899     case EINVAL:
    900       return DBUS_ERROR_FAILED;
    901 #endif
    902 #ifdef EBADF
    903     case EBADF:
    904       return DBUS_ERROR_FAILED;
    905 #endif
    906 #ifdef EFAULT
    907     case EFAULT:
    908       return DBUS_ERROR_FAILED;
    909 #endif
    910 #ifdef ENOTSOCK
    911     case ENOTSOCK:
    912       return DBUS_ERROR_FAILED;
    913 #endif
    914 #ifdef EISCONN
    915     case EISCONN:
    916       return DBUS_ERROR_FAILED;
    917 #endif
    918 #ifdef ECONNREFUSED
    919     case ECONNREFUSED:
    920       return DBUS_ERROR_NO_SERVER;
    921 #endif
    922 #ifdef ETIMEDOUT
    923     case ETIMEDOUT:
    924       return DBUS_ERROR_TIMEOUT;
    925 #endif
    926 #ifdef ENETUNREACH
    927     case ENETUNREACH:
    928       return DBUS_ERROR_NO_NETWORK;
    929 #endif
    930 #ifdef EADDRINUSE
    931     case EADDRINUSE:
    932       return DBUS_ERROR_ADDRESS_IN_USE;
    933 #endif
    934 #ifdef EEXIST
    935     case EEXIST:
    936       return DBUS_ERROR_FILE_EXISTS;
    937 #endif
    938 #ifdef ENOENT
    939     case ENOENT:
    940       return DBUS_ERROR_FILE_NOT_FOUND;
    941 #endif
    942     }
    943 
    944   return DBUS_ERROR_FAILED;
    945 }
    946 
    947 /** @} end of sysdeps */
    948 
    949 /* tests in dbus-sysdeps-util.c */
    950