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119 lines
4.4 KiB
C
119 lines
4.4 KiB
C
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef prenv_h___
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#define prenv_h___
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#include "prtypes.h"
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/*******************************************************************************/
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/*******************************************************************************/
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/****************** THESE FUNCTIONS MAY NOT BE THREAD SAFE *********************/
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/*******************************************************************************/
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/*******************************************************************************/
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PR_BEGIN_EXTERN_C
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/*
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** PR_GetEnv() -- Retrieve value of environment variable
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**
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** Description:
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** PR_GetEnv() is modeled on Unix getenv().
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**
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**
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** Inputs:
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** var -- The name of the environment variable
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**
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** Returns:
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** The value of the environment variable 'var' or NULL if
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** the variable is undefined.
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**
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** Restrictions:
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** You'd think that a POSIX getenv(), putenv() would be
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** consistently implemented everywhere. Surprise! It is not. On
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** some platforms, a putenv() where the argument is of
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** the form "name" causes the named environment variable to
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** be un-set; that is: a subsequent getenv() returns NULL. On
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** other platforms, the putenv() fails, on others, it is a
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** no-op. Similarly, a putenv() where the argument is of the
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** form "name=" causes the named environment variable to be
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** un-set; a subsequent call to getenv() returns NULL. On
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** other platforms, a subsequent call to getenv() returns a
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** pointer to a null-string (a byte of zero).
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**
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** PR_GetEnv(), PR_SetEnv() provide a consistent behavior
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** across all supported platforms. There are, however, some
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** restrictions and some practices you must use to achieve
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** consistent results everywhere.
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**
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** When manipulating the environment there is no way to un-set
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** an environment variable across all platforms. We suggest
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** you interpret the return of a pointer to null-string to
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** mean the same as a return of NULL from PR_GetEnv().
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**
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** A call to PR_SetEnv() where the parameter is of the form
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** "name" will return PR_FAILURE; the environment remains
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** unchanged. A call to PR_SetEnv() where the parameter is
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** of the form "name=" may un-set the envrionment variable on
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** some platforms; on others it may set the value of the
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** environment variable to the null-string.
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**
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** For example, to test for NULL return or return of the
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** null-string from PR_GetEnv(), use the following code
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** fragment:
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**
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** char *val = PR_GetEnv("foo");
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** if ((NULL == val) || ('\0' == *val)) {
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** ... interpret this as un-set ...
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** }
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**
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** The caller must ensure that the string passed
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** to PR_SetEnv() is persistent. That is: The string should
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** not be on the stack, where it can be overwritten
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** on return from the function calling PR_SetEnv().
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** Similarly, the string passed to PR_SetEnv() must not be
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** overwritten by other actions of the process. ... Some
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** platforms use the string by reference rather than copying
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** it into the environment space. ... You have been warned!
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**
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** Use of platform-native functions that manipulate the
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** environment (getenv(), putenv(),
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** SetEnvironmentVariable(), etc.) must not be used with
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** NSPR's similar functions. The platform-native functions
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** may not be thread safe and/or may operate on different
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** conceptual environment space than that operated upon by
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** NSPR's functions or other environment manipulating
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** functions on the same platform. (!)
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**
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*/
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NSPR_API(char*) PR_GetEnv(const char *var);
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/*
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** PR_SetEnv() -- set, unset or change an environment variable
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**
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** Description:
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** PR_SetEnv() is modeled on the Unix putenv() function.
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**
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** Inputs:
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** string -- pointer to a caller supplied
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** constant, persistent string of the form name=value. Where
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** name is the name of the environment variable to be set or
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** changed; value is the value assigned to the variable.
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**
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** Returns:
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** PRStatus.
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**
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** Restrictions:
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** See the Restrictions documented in the description of
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** PR_GetEnv() in this header file.
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**
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**
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*/
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NSPR_API(PRStatus) PR_SetEnv(const char *string);
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PR_END_EXTERN_C
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#endif /* prenv_h___ */
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