prenv.h
上传用户:goldcmy89
上传日期:2017-12-03
资源大小:2246k
文件大小:6k
- /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
- /* ***** BEGIN LICENSE BLOCK *****
- * Version: MPL 1.1/GPL 2.0/LGPL 2.1
- *
- * The contents of this file are subject to the Mozilla Public License Version
- * 1.1 (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- * http://www.mozilla.org/MPL/
- *
- * Software distributed under the License is distributed on an "AS IS" basis,
- * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
- * for the specific language governing rights and limitations under the
- * License.
- *
- * The Original Code is the Netscape Portable Runtime (NSPR).
- *
- * The Initial Developer of the Original Code is
- * Netscape Communications Corporation.
- * Portions created by the Initial Developer are Copyright (C) 1998-2000
- * the Initial Developer. All Rights Reserved.
- *
- * Contributor(s):
- *
- * Alternatively, the contents of this file may be used under the terms of
- * either the GNU General Public License Version 2 or later (the "GPL"), or
- * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
- * in which case the provisions of the GPL or the LGPL are applicable instead
- * of those above. If you wish to allow use of your version of this file only
- * under the terms of either the GPL or the LGPL, and not to allow others to
- * use your version of this file under the terms of the MPL, indicate your
- * decision by deleting the provisions above and replace them with the notice
- * and other provisions required by the GPL or the LGPL. If you do not delete
- * the provisions above, a recipient may use your version of this file under
- * the terms of any one of the MPL, the GPL or the LGPL.
- *
- * ***** END LICENSE BLOCK ***** */
- #ifndef prenv_h___
- #define prenv_h___
- #include "prtypes.h"
- /*******************************************************************************/
- /*******************************************************************************/
- /****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
- /*******************************************************************************/
- /*******************************************************************************/
- PR_BEGIN_EXTERN_C
- /*
- ** PR_GetEnv() -- Retrieve value of environment variable
- **
- ** Description:
- ** PR_GetEnv() is modeled on Unix getenv().
- **
- **
- ** Inputs:
- ** var -- The name of the environment variable
- **
- ** Returns:
- ** The value of the environment variable 'var' or NULL if
- ** the variable is undefined.
- **
- ** Restrictions:
- ** You'd think that a POSIX getenv(), putenv() would be
- ** consistently implemented everywhere. Surprise! It is not. On
- ** some platforms, a putenv() where the argument is of
- ** the form "name" causes the named environment variable to
- ** be un-set; that is: a subsequent getenv() returns NULL. On
- ** other platforms, the putenv() fails, on others, it is a
- ** no-op. Similarly, a putenv() where the argument is of the
- ** form "name=" causes the named environment variable to be
- ** un-set; a subsequent call to getenv() returns NULL. On
- ** other platforms, a subsequent call to getenv() returns a
- ** pointer to a null-string (a byte of zero).
- **
- ** PR_GetEnv(), PR_SetEnv() provide a consistent behavior
- ** across all supported platforms. There are, however, some
- ** restrictions and some practices you must use to achieve
- ** consistent results everywhere.
- **
- ** When manipulating the environment there is no way to un-set
- ** an environment variable across all platforms. We suggest
- ** you interpret the return of a pointer to null-string to
- ** mean the same as a return of NULL from PR_GetEnv().
- **
- ** A call to PR_SetEnv() where the parameter is of the form
- ** "name" will return PR_FAILURE; the environment remains
- ** unchanged. A call to PR_SetEnv() where the parameter is
- ** of the form "name=" may un-set the envrionment variable on
- ** some platforms; on others it may set the value of the
- ** environment variable to the null-string.
- **
- ** For example, to test for NULL return or return of the
- ** null-string from PR_GetEnv(), use the following code
- ** fragment:
- **
- ** char *val = PR_GetEnv("foo");
- ** if ((NULL == val) || (' ' == *val)) {
- ** ... interpret this as un-set ...
- ** }
- **
- ** The caller must ensure that the string passed
- ** to PR_SetEnv() is persistent. That is: The string should
- ** not be on the stack, where it can be overwritten
- ** on return from the function calling PR_SetEnv().
- ** Similarly, the string passed to PR_SetEnv() must not be
- ** overwritten by other actions of the process. ... Some
- ** platforms use the string by reference rather than copying
- ** it into the environment space. ... You have been warned!
- **
- ** Use of platform-native functions that manipulate the
- ** environment (getenv(), putenv(),
- ** SetEnvironmentVariable(), etc.) must not be used with
- ** NSPR's similar functions. The platform-native functions
- ** may not be thread safe and/or may operate on different
- ** conceptual environment space than that operated upon by
- ** NSPR's functions or other environment manipulating
- ** functions on the same platform. (!)
- **
- */
- NSPR_API(char*) PR_GetEnv(const char *var);
- /*
- ** PR_SetEnv() -- set, unset or change an environment variable
- **
- ** Description:
- ** PR_SetEnv() is modeled on the Unix putenv() function.
- **
- ** Inputs:
- ** string -- pointer to a caller supplied
- ** constant, persistent string of the form name=value. Where
- ** name is the name of the environment variable to be set or
- ** changed; value is the value assigned to the variable.
- **
- ** Returns:
- ** PRStatus.
- **
- ** Restrictions:
- ** See the Restrictions documented in the description of
- ** PR_GetEnv() in this header file.
- **
- **
- */
- NSPR_API(PRStatus) PR_SetEnv(const char *string);
- /*
- ** DEPRECATED. Use PR_SetEnv() instead.
- */
- #ifdef XP_MAC
- NSPR_API(PRIntn) PR_PutEnv(const char *string);
- #endif
- PR_END_EXTERN_C
- #endif /* prenv_h___ */