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sortix--sortix/libc/stdlib/unsetenv.cpp

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/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2014.
This file is part of the Sortix C Library.
The Sortix C Library is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
The Sortix C Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
stdlib/unsetenv.cpp
Unset an environment variable.
*******************************************************************************/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static inline
bool matches_environment_variable(const char* what,
const char* name, size_t name_length)
{
return !strncmp(what, name, name_length) && what[name_length] == '=';
}
extern "C" int unsetenv(const char* name)
{
if ( !name )
return errno = EINVAL, -1;
// Verify the name doesn't contain a '=' character.
size_t name_length = 0;
while ( name[name_length] )
if ( name[name_length++] == '=' )
return errno = EINVAL, -1;
if ( !environ )
return 0;
// Delete all variables from the environment with the given name.
for ( size_t i = 0; environ[i]; i++ )
{
if ( matches_environment_variable(environ[i], name, name_length) )
{
// Free the string and move the array around in constant time if
// the setenv implementation is in control of the array.
if ( environ == __environ_malloced )
{
free(environ[i]);
environ[i] = environ[__environ_used-1];
environ[--__environ_used] = NULL;
}
// Otherwise, we'll simply clear that entry in environ, but we can't
// do it in constant time as we don't know how large the array is.
else
{
for ( size_t n = i; environ[n]; n++ )
environ[n] = environ[n+1];
}
// This entry was deleted so we'll need to process it again.
i--;
}
}
return 0;
}