reactos/sdk/lib/ucrt/env/setenv.cpp

373 lines
14 KiB
C++

//
// setenv.cpp
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// Internal functions for setting or removing variables from an environment. The
// logic for manipulating the environment data structures is split across this
// file and environment_initialization.cpp.
//
#include <corecrt_internal.h>
#include <corecrt_internal_traits.h>
#include <limits.h>
#include <stdlib.h>
static char**& __cdecl get_environment(char) throw() { return _environ_table.value(); }
static wchar_t**& __cdecl get_environment(wchar_t) throw() { return _wenviron_table.value(); }
static wchar_t**& __cdecl get_other_environment(char) throw() { return _wenviron_table.value(); }
static char**& __cdecl get_other_environment(wchar_t) throw() { return _environ_table.value(); }
static char**& __cdecl get_initial_environment(char) throw() { return __dcrt_initial_narrow_environment; }
static wchar_t**& __cdecl get_initial_environment(wchar_t) throw() { return __dcrt_initial_wide_environment; }
// Makes a copy of the provided environment and returns the copy. The caller is
// responsible for freeing the returned array (using the CRT free). Returns
// nullptr on failure; terminates the process on allocation failure.
template <typename Character>
static Character** __cdecl copy_environment(Character** const old_environment) throw()
{
typedef __crt_char_traits<Character> traits;
if (!old_environment)
{
return nullptr;
}
// Count the number of environment variables:
size_t entry_count = 0;
for (Character** it = old_environment; *it; ++it)
{
++entry_count;
}
// We need one pointer for each string, plus one null pointer at the end:
__crt_unique_heap_ptr<Character*> new_environment(_calloc_crt_t(Character*, entry_count + 1));
if (!new_environment)
{
abort();
}
Character** old_it = old_environment;
Character** new_it = new_environment.get();
for (; *old_it; ++old_it, ++new_it)
{
size_t const required_count = traits::tcslen(*old_it) + 1;
*new_it = _calloc_crt_t(Character, required_count).detach();
if (!*new_it)
{
abort();
}
_ERRCHECK(traits::tcscpy_s(*new_it, required_count, *old_it));
}
return new_environment.detach();
}
// If the current environment is the initial environment, this function clones
// the current environment so that it is not the initial environment. This
// should be called any time that we are about to modify the current environment
// but we do not know whether the current environment is the initial environment.
template <typename Character>
static void __cdecl ensure_current_environment_is_not_initial_environment_nolock() throw()
{
if (get_environment(Character()) == get_initial_environment(Character()))
{
get_environment(Character()) = copy_environment(get_environment(Character()));
}
}
// Finds an environment variable in the specified environment. If a variable
// with the given name is found, its index in the environment is returned. If
// no such environment is found, the total number of environment variables is
// returned, multiplied by -1. Note that a return value of 0 may indicate
// either that the variable was found at index 0 or there are zero variables
// in the environment. Be sure to check for this case.
template <typename Character>
static ptrdiff_t __cdecl find_in_environment_nolock(
Character const* const name,
size_t const length
) throw()
{
typedef __crt_char_traits<Character> traits;
Character** const environment = get_environment(Character());
Character** it = nullptr;
for (it = environment; *it; ++it)
{
// See if the first 'length' characters match:
if (traits::tcsnicoll(name, *it, length) != 0)
{
continue;
}
// Ensure that the next character of the environment is an '=' or '\0':
if ((*it)[length] != '=' && (*it)[length] != '\0')
{
continue;
}
// Otherwise, this entry matched; return its index in the environment:
return static_cast<ptrdiff_t>(it - environment);
}
// No entry matched; return the total number of strings, multiplied by -1:
return -static_cast<ptrdiff_t>(it - environment);
}
/***
*int __dcrt_set_variable_in_narrow_environment(option) - add/replace/remove variable in environment
*
*Purpose:
* option should be of the form "option=value". If a string with the
* given option part already exists, it is replaced with the given
* string; otherwise the given string is added to the environment.
* If the string is of the form "option=", then the string is
* removed from the environment, if it exists. If the string has
* no equals sign, error is returned.
*
*Entry:
* TCHAR **poption - pointer to option string to set in the environment list.
* should be of the form "option=value".
* This function takes ownership of this pointer in the success case.
* int primary - Only the primary call to _crt[w]setenv needs to
* create new copies or set the OS environment.
* 1 indicates that this is the primary call.
*
*Exit:
* returns 0 if OK, -1 if fails.
* If *poption is non-null on exit, we did not free it, and the caller should
* If *poption is null on exit, we did free it, and the caller should not.
*
*Exceptions:
*
*Warnings:
* This code will not work if variables are removed from the environment
* by deleting them from environ[]. Use _putenv("option=") to remove a
* variable.
*
* The option argument will be taken ownership of by this code and may be freed!
*
*******************************************************************************/
template <typename Character>
static int __cdecl common_set_variable_in_environment_nolock(
Character* const option,
int const is_top_level_call
) throw()
{
typedef __crt_char_traits<Character> traits;
// Check that the option string is valid first. Find the '=' and verify
// that '=' is not the first character in the string:
_VALIDATE_RETURN_NOEXC(option != nullptr, EINVAL, -1);
__crt_unique_heap_ptr<Character> owned_option(option);
Character* const equal_sign = traits::tcschr(option, '=');
_VALIDATE_RETURN_NOEXC(equal_sign != nullptr && equal_sign != option, EINVAL, -1);
// Internal consistency check: The environment string should never use
// buffers larger than _MAX_ENV. See also the SetEnvironmentVariable SDK
// function.
_ASSERTE(equal_sign - option < _MAX_ENV);
_ASSERTE(traits::tcsnlen(equal_sign + 1, _MAX_ENV) < _MAX_ENV);
// If the character following '=' is the terminator, we are removing the
// environment variable. Otherwise, we are adding or updating the variable:
bool const is_removal = *(equal_sign + 1) == '\0';
// At program startup, the initial environment (__dcrt_initial_narrow_environment), which is passed
// to main(), is backed by the same environment arrays as the global
// environment used by getenv, setenv, et al. We cannot modify thie initial
// environment, so we make a copy of it the first time we need to make any
// modifications to the global environment:
ensure_current_environment_is_not_initial_environment_nolock<Character>();
// If the required environment does not exist, see if the other environment
// exists; if it does, convert it to create the required environment. These
// functions will reenter this function once for each environment variable;
// we use the top-level call flag to stop recursion.
if (!get_environment(Character()))
{
if (is_top_level_call && get_other_environment(Character()))
{
_VALIDATE_RETURN_NOEXC(traits::get_or_create_environment_nolock() != nullptr, EINVAL, -1);
// The call to get_or_create_environment() may have initialized the
// current environment to the same environment that is the initial
// environment. Re-check and make a new copy of the environment to
// modify if necessary.
ensure_current_environment_is_not_initial_environment_nolock<Character>();
}
else
{
// If the environment doesn't exist and the requested operation is a
// removal, there is nothing to do (there is nothing to remove):
if (is_removal)
{
return 0;
}
// Create a new environment for each environment that does not exist.
// Just start each off as an empty environment:
if (!_environ_table.value())
{
_environ_table.value() = _calloc_crt_t(char*, 1).detach();
}
if (!_environ_table.value())
{
return -1;
}
if (!_wenviron_table.value())
{
_wenviron_table.value() = _calloc_crt_t(wchar_t*, 1).detach();
}
if (!_wenviron_table.value())
{
return -1;
}
}
}
// At this point, either [1] only one environment exists, or [2] both of the
// environments exist and are in-sync. The only way they can get out of sync
// is if there are conversion problems. For example, if the user sets two
// Unicode environment variables, FOO1 and FOO2, and the conversion of these
// to multibyte yields FOO? and FOO?, then these environment blocks will
// differ.
Character** const environment = get_environment(Character());
if (!environment)
{
_ASSERTE(("CRT logic error in setenv", 0));
return -1;
}
// Try to find the option in the environment...
ptrdiff_t const option_index = find_in_environment_nolock(option, equal_sign - option);
// ... if the string is already in the environment, we free up the original
// string, then install the new string or shrink the environment:
if (option_index >= 0 && environment[0])
{
_free_crt(environment[option_index]);
// If this is a removal, shrink the environment:
if (is_removal)
{
// Shift all of the entries down by one element:
size_t i = static_cast<size_t>(option_index);
for (; environment[i]; ++i)
{
environment[i] = environment[i + 1];
}
// Shrink the environment memory block. At this point, i is the
// number of elements remaining in the environment. This realloc
// should never fail, since we are shrinking the block, but it is
// best to be careful. If it does fail, it doesn't matter.
Character** new_environment = _recalloc_crt_t(Character*, environment, i).detach();
if (new_environment)
{
get_environment(Character()) = new_environment;
}
}
// If this is a replacement, replace the variable:
else
{
environment[option_index] = owned_option.detach();
}
}
// Otherwise, the string is not in the environment:
else
{
// If this is a removal, it is a no-op: the variable does not exist.
if (is_removal)
{
return 0;
}
// Otherwise, we need to append the string to the environment table, and
// we must grow the table to do this:
else
{
size_t const environment_count = static_cast<size_t>(-option_index);
if (environment_count + 2 < environment_count)
{
return -1;
}
if (environment_count + 2 >= SIZE_MAX / sizeof(Character*))
{
return -1;
}
Character** const new_environment = _recalloc_crt_t(Character*, environment, environment_count + 2).detach();
if (!new_environment)
{
return -1;
}
new_environment[environment_count] = owned_option.detach();
new_environment[environment_count + 1] = nullptr;
get_environment(Character()) = new_environment;
}
}
// Update the operating system environment. Do not give an error if this
// fails since the failure will not affect the user code unless it is making
// direct calls to the operating system. We only need to do this for one of
// the environments; the operating system synchronizes with the other
// environment automatically.
if (is_top_level_call)
{
size_t const count = traits::tcslen(option) + 2;
__crt_unique_heap_ptr<Character> const buffer(_calloc_crt_t(Character, count));
if (!buffer)
{
return 0;
}
Character* const name = buffer.get();
_ERRCHECK(traits::tcscpy_s(name, count, option));
Character* const value = name + (equal_sign - option) + 1;
*(value - 1) = '\0'; // Overwrite the '=' with a null terminator
if (traits::set_environment_variable(name, is_removal ? nullptr : value) == 0)
{
errno = EILSEQ;
return -1;
}
}
return 0;
}
extern "C" int __cdecl __dcrt_set_variable_in_narrow_environment_nolock(
char* const option,
int const is_top_level_call
)
{
return common_set_variable_in_environment_nolock(option, is_top_level_call);
}
extern "C" int __cdecl __dcrt_set_variable_in_wide_environment_nolock(
wchar_t* const option,
int const is_top_level_call
)
{
return common_set_variable_in_environment_nolock(option, is_top_level_call);
}