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
27 * allow others to use your version of this file under the MPL,
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 <security_asn1/prtypes.h>
39
40/*******************************************************************************/
41/*******************************************************************************/
42/****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
43/*******************************************************************************/
44/*******************************************************************************/
45
46PR_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*/
120NSPR_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*/
143NSPR_API(PRStatus) PR_SetEnv(const char *string);
144
145/*
146** DEPRECATED.  Use PR_SetEnv() instead.
147*/
148#ifdef XP_MAC
149NSPR_API(PRIntn) PR_PutEnv(const char *string);
150#endif
151
152PR_END_EXTERN_C
153
154#endif /* prenv_h___ */
155