third_party/npapi/npspy/extern/nspr/prenv.h

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /*
   3  * The contents of this file are subject to the Mozilla Public
   4  * License Version 1.1 (the "License"); you may not use this file
   5  * except in compliance with the License. You may obtain a copy of
   6  * the License at http://www.mozilla.org/MPL/
   7  *
   8  * Software distributed under the License is distributed on an "AS
   9  * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
  10  * implied. See the License for the specific language governing
  11  * rights and limitations under the License.
  12  *
  13  * The Original Code is the Netscape Portable Runtime (NSPR).
  14  *
  15  * The Initial Developer of the Original Code is Netscape
  16  * Communications Corporation.  Portions created by Netscape are
  17  * Copyright (C) 1998-2000 Netscape Communications Corporation.  All
  18  * Rights Reserved.
  19  *
  20  * Contributor(s):
  21  *
  22  * Alternatively, the contents of this file may be used under the
  23  * terms of the GNU General Public License Version 2 or later (the
  24  * "GPL"), in which case the provisions of the GPL are applicable
  25  * instead of those above.  If you wish to allow use of your
  26  * version of this file only under the terms of the GPL and not to
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  28  * indicate your decision by deleting the provisions above and
  29  * replace them with the notice and other provisions requiored by
  30  * the GPL.  If you do not delete the provisions above, a recipient
  31  * may use your version of this file under either the MPL or the
  32  * GPL.
  33  */
  34
  35 #ifndef prenv_h___
  36 #define prenv_h___
  37
  38 #include "prtypes.h"
  39
  40 /*******************************************************************************/
  41 /*******************************************************************************/
  42 /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
  43 /*******************************************************************************/
  44 /*******************************************************************************/
  45
  46 PR_BEGIN_EXTERN_C
  47
  48 /*
  49 ** PR_GetEnv() -- Retrieve value of environment variable
  50 **
  51 ** Description:
  52 ** PR_GetEnv() is modeled on Unix getenv().
  53 **
  54 **
  55 ** Inputs:
  56 **   var -- The name of the environment variable
  57 **
  58 ** Returns:
  59 **   The value of the environment variable 'var' or NULL if
  60 ** the variable is undefined.
  61 **
  62 ** Restrictions:
  63 **   You'd think that a POSIX getenv(), putenv() would be
  64 **   consistently implemented everywhere. Surprise! It is not. On
  65 **   some platforms, a putenv() where the argument is of
  66 **   the form "name"  causes the named environment variable to
  67 **   be un-set; that is: a subsequent getenv() returns NULL. On
  68 **   other platforms, the putenv() fails, on others, it is a
  69 **   no-op. Similarly, a putenv() where the argument is of the
  70 **   form "name=" causes the named environment variable to be
  71 **   un-set; a subsequent call to getenv() returns NULL. On
  72 **   other platforms, a subsequent call to getenv() returns a
  73 **   pointer to a null-string (a byte of zero).
  74 **
  75 **   PR_GetEnv(), PR_SetEnv() provide a consistent behavior
  76 **   across all supported platforms. There are, however, some
  77 **   restrictions and some practices you must use to achieve
  78 **   consistent results everywhere.
  79 **
  80 **   When manipulating the environment there is no way to un-set
  81 **   an environment variable across all platforms. We suggest
  82 **   you interpret the return of a pointer to null-string to
  83 **   mean the same as a return of NULL from PR_GetEnv().
  84 **
  85 **   A call to PR_SetEnv() where the parameter is of the form
  86 **   "name" will return PR_FAILURE; the environment remains
  87 **   unchanged. A call to PR_SetEnv() where the parameter is
  88 **   of the form "name=" may un-set the envrionment variable on
  89 **   some platforms; on others it may set the value of the
  90 **   environment variable to the null-string.
  91 **
  92 **   For example, to test for NULL return or return of the
  93 **   null-string from PR_GetEnv(), use the following code
  94 **   fragment:
  95 **
  96 **      char *val = PR_GetEnv("foo");
  97 **      if ((NULL == val) || ('\0' == *val)) {
  98 **          ... interpret this as un-set ...
  99 **      }
 100 **
 101 **   The caller must ensure that the string passed
 102 **   to PR_SetEnv() is persistent. That is: The string should
 103 **   not be on the stack, where it can be overwritten
 104 **   on return from the function calling PR_SetEnv().
 105 **   Similarly, the string passed to PR_SetEnv() must not be
 106 **   overwritten by other actions of the process. ... Some
 107 **   platforms use the string by reference rather than copying
 108 **   it into the environment space. ... You have been warned!
 109 **
 110 **   Use of platform-native functions that manipulate the
 111 **   environment (getenv(), putenv(),
 112 **   SetEnvironmentVariable(), etc.) must not be used with
 113 **   NSPR's similar functions. The platform-native functions
 114 **   may not be thread safe and/or may operate on different
 115 **   conceptual environment space than that operated upon by
 116 **   NSPR's functions or other environment manipulating
 117 **   functions on the same platform. (!)
 118 **
 119 */
 120 NSPR_API(char*) PR_GetEnv(const char *var);
 121
 122 /*
 123 ** PR_SetEnv() -- set, unset or change an environment variable
 124 **
 125 ** Description:
 126 ** PR_SetEnv() is modeled on the Unix putenv() function.
 127 **
 128 ** Inputs:
 129 **   string -- pointer to a caller supplied
 130 **   constant, persistent string of the form name=value. Where
 131 **   name is the name of the environment variable to be set or
 132 **   changed; value is the value assigned to the variable.
 133 **
 134 ** Returns:
 135 **   PRStatus.
 136 **
 137 ** Restrictions:
 138 **   See the Restrictions documented in the description of
 139 **   PR_GetEnv() in this header file.
 140 **
 141 **
 142 */
 143 NSPR_API(PRStatus) PR_SetEnv(const char *string);
 144
 145 /*
 146 ** DEPRECATED.  Use PR_SetEnv() instead.
 147 */
 148 #ifdef XP_MAC
 149 NSPR_API(PRIntn) PR_PutEnv(const char *string);
 150 #endif
 151
 152 PR_END_EXTERN_C
 153
 154 #endif /* prenv_h___ */