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