windows-server-2003/base/crts/crtw32/misc/getenv.c

/***
*getenv.c - get the value of an environment variable
*
*       Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       defines getenv() - searches the environment for a string variable
*       and returns the value of it.
*
*Revision History:
*       11-22-83  RN    initial version
*       04-13-87  JCR   added const to declaration
*       11-09-87  SKS   avoid indexing past end of strings (add strlen check)
*       12-11-87  JCR   Added "_LOAD_DS" to declaration
*       06-01-88  PHG   Merged normal/DLL versions
*       03-14-90  GJF   Replaced _LOAD_DS with _CALLTYPE1, added #include
*                       <cruntime.h>, removed #include <register.h> and fixed
*                       the copyright. Also, cleaned up the formatting a bit.
*       04-05-90  GJF   Added #include <string.h>.
*       07-25-90  SBM   Removed redundant include (stdio.h)
*       08-13-90  SBM   Compiles cleanly with -W3 (made length unsigned int)
*       10-04-90  GJF   New-style function declarator.
*       01-18-91  GJF   ANSI naming.
*       02-06-91  SRW   Added _WIN32_ conditional for GetEnvironmentVariable
*       02-18-91  SRW   Removed _WIN32_ conditional for GetEnvironmentVariable
*       01-10-92  GJF   Final unlock and return statements shouldn't be in
*                       if-block.
*       03-11-92  GJF   Use case-insensitive comparison for Win32.
*       04-27-92  GJF   Repackaged MTHREAD support for Win32 to create a
*                       _getenv_lk.
*       06-05-92  PLM   Added _MAC_ 
*       06-10-92  PLM   Added _envinit for _MAC_ 
*       04-06-93  SKS   Replace _CRTAPI* with __cdecl
*                       Remove OS/2, POSIX support
*       04-08-93  SKS   Replace strnicmp() with ANSI-conforming _strnicmp()
*       09-14-93  GJF   Small change for Posix compatibility.
*       11-29-93  CFW   Wide char enable.
*       12-07-93  CFW   Change _TCHAR to _TSCHAR.
*       01-15-94  CFW   Use _tcsnicoll for global match.
*       02-04-94  CFW   POSIXify.
*       03-31-94  CFW   Should be ifndef POSIX.
*       02-14-95  CFW   Debug CRT allocs.
*       02-16-95  JWM   Spliced _WIN32 & Mac versions.
*       08-01-96  RDK   For Pmac, change data type of initialization pointer.
*       07-09-97  GJF   Added a check that the environment initialization has
*                       been executed. Also, detab-ed and got rid of obsolete
*                       _CALLTYPE1 macros.
*       03-05-98  GJF   Exception-safe locking.
*       12-18-98  GJF   Changes for 64-bit size_t.
*       04-28-99  PML   Wrap __declspec(allocate()) in _CRTALLOC macro.
*       05-17-99  PML   Remove all Macintosh support.
*
*******************************************************************************/

#include <sect_attribs.h>
#include <cruntime.h>
#include <internal.h>
#include <mtdll.h>
#include <stdlib.h>
#include <string.h>
#include <tchar.h>

#ifndef CRTDLL

/*
 * Flag checked by getenv() and _putenv() to determine if the environment has
 * been initialized.
 */
extern int __env_initialized;

#endif

/***
*char *getenv(option) - search environment for a string
*
*Purpose:
*       searches the environment for a string of the form "option=value",
*       if found, return value, otherwise NULL.
*
*Entry:
*       const char *option - variable to search for in environment
*
*Exit:
*       returns the value part of the environment string if found,
*       otherwise NULL
*
*Exceptions:
*
*******************************************************************************/

#ifdef  _MT


#ifdef  WPRFLAG
wchar_t * __cdecl _wgetenv (
#else
char * __cdecl getenv (
#endif
        const _TSCHAR *option
        )
{
        _TSCHAR *retval;

        _mlock( _ENV_LOCK );

        __try {
#ifdef  WPRFLAG
            retval = _wgetenv_lk(option);
#else
            retval = _getenv_lk(option);
#endif
        }
        __finally {
            _munlock( _ENV_LOCK );
        }

        return(retval);

}


#ifdef  WPRFLAG
wchar_t * __cdecl _wgetenv_lk (
#else
char * __cdecl _getenv_lk (
#endif
        const _TSCHAR *option
        )

#else   /* ndef _MT */

#ifdef  WPRFLAG
wchar_t * __cdecl _wgetenv (
#else
char * __cdecl getenv (
#endif
        const _TSCHAR *option
        )

#endif  /* _MT */

{
#ifdef  _POSIX_
        char **search = environ;
#else
        _TSCHAR **search = _tenviron;
#endif
        size_t length;

#ifndef CRTDLL
        /*
         * Make sure the environment is initialized.
         */
        if ( !__env_initialized ) 
            return NULL;
#endif  /* CRTDLL */

        /*
         * At startup, we obtain the 'native' flavor of environment strings
         * from the OS. So a "main" program has _environ and a "wmain" has
         * _wenviron loaded at startup. Only when the user gets or puts the
         * 'other' flavor do we convert it.
         */

#ifndef _POSIX_

#ifdef  WPRFLAG
        if (!search && _environ)
        {
            /* don't have requested type, but other exists, so convert it */
            if (__mbtow_environ() != 0)
                return NULL;

            /* now requested type exists */
            search = _wenviron;
        }
#else
        if (!search && _wenviron)
        {
            /* don't have requested type, but other exists, so convert it */
            if (__wtomb_environ() != 0)
                return NULL;

            /* now requested type exists */
            search = _environ;
        }
#endif

#endif  /* _POSIX_ */

        if (search && option)
        {
                length = _tcslen(option);

                /*
                ** Make sure `*search' is long enough to be a candidate
                ** (We must NOT index past the '\0' at the end of `*search'!)
                ** and that it has an equal sign (`=') in the correct spot.
                ** If both of these requirements are met, compare the strings.
                */
                while (*search)
                {
                        if (_tcslen(*search) > length && (*(*search + length)
                        == _T('=')) && (_tcsnicoll(*search, option, length) == 0)) {
                                return(*search + length + 1);
                        }

                        search++;
                }
        }

        return(NULL);
}