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| -rw-r--r-- | nsprpub/pr/include/prenv.h | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/nsprpub/pr/include/prenv.h b/nsprpub/pr/include/prenv.h new file mode 100644 index 0000000000..550f05c936 --- /dev/null +++ b/nsprpub/pr/include/prenv.h @@ -0,0 +1,162 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#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) || ('\0' == *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_GetEnvSecure() -- get a security-sensitive environment variable +** +** Description: +** +** PR_GetEnvSecure() is similar to PR_GetEnv(), but it returns NULL if +** the program was run with elevated privilege (e.g., setuid or setgid +** on Unix). This can be used for cases like log file paths which +** could otherwise be used for privilege escalation. Note that some +** platforms may have platform-specific privilege elevation mechanisms +** not recognized by this function; see the implementation for details. +*/ +NSPR_API(char*) PR_GetEnvSecure(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); + +/* +** PR_DuplicateEnvironment() -- Obtain a copy of the environment. +** +** Description: +** PR_DuplicateEnvironment() copies the environment so that it can be +** modified without changing the current process's environment, and +** then passed to interfaces such as POSIX execve(). In particular, +** this avoids needing to allocate memory or take locks in the child +** after a fork(); neither of these is allowed by POSIX after a +** multithreaded process calls fork(), and PR_SetEnv does both. +** +** Inputs: +** none +** +** Returns: +** A pointer to a null-terminated array of null-terminated strings, +** like the traditional global variable "environ". The array and +** the strings are allocated with PR_Malloc(), and it is the +** caller's responsibility to free them. +** +** In case of memory allocation failure, or if the operating system +** doesn't support reading the entire environment through the global +** variable "environ" or similar, returns NULL instead. +** +** Restrictions: +** Similarly to PR_GetEnv(), this function may not interoperate as +** expected with the operating system's native environment accessors. +*/ +NSPR_API(char **) PR_DuplicateEnvironment(void); + +PR_END_EXTERN_C + +#endif /* prenv_h___ */ |