/* Return the initial module search path. */

#include "Python.h"
#include "internal/pystate.h"
#include "osdefs.h"

#include <sys/types.h>
#include <string.h>

#ifdef __APPLE__
# include <mach-o/dyld.h>
#endif

/* Search in some common locations for the associated Python libraries.
 *
 * Two directories must be found, the platform independent directory
 * (prefix), containing the common .py and .pyc files, and the platform
 * dependent directory (exec_prefix), containing the shared library
 * modules. Note that prefix and exec_prefix can be the same directory,
 * but for some installations, they are different.
 *
 * Py_GetPath() carries out separate searches for prefix and exec_prefix.
 * Each search tries a number of different locations until a ``landmark''
 * file or directory is found. If no prefix or exec_prefix is found, a
 * warning message is issued and the preprocessor defined PREFIX and
 * EXEC_PREFIX are used (even though they will not work); python carries on
 * as best as is possible, but most imports will fail.
 *
 * Before any searches are done, the location of the executable is
 * determined. If argv[0] has one or more slashes in it, it is used
 * unchanged. Otherwise, it must have been invoked from the shell's path,
 * so we search $PATH for the named executable and use that. If the
 * executable was not found on $PATH (or there was no $PATH environment
 * variable), the original argv[0] string is used.
 *
 * Next, the executable location is examined to see if it is a symbolic
 * link. If so, the link is chased (correctly interpreting a relative
 * pathname if one is found) and the directory of the link target is used.
 *
 * Finally, argv0_path is set to the directory containing the executable
 * (i.e. the last component is stripped).
 *
 * With argv0_path in hand, we perform a number of steps. The same steps
 * are performed for prefix and for exec_prefix, but with a different
 * landmark.
 *
 * Step 1. Are we running python out of the build directory? This is
 * checked by looking for a different kind of landmark relative to
 * argv0_path. For prefix, the landmark's path is derived from the VPATH
 * preprocessor variable (taking into account that its value is almost, but
 * not quite, what we need). For exec_prefix, the landmark is
 * pybuilddir.txt. If the landmark is found, we're done.
 *
 * For the remaining steps, the prefix landmark will always be
 * lib/python$VERSION/os.py and the exec_prefix will always be
 * lib/python$VERSION/lib-dynload, where $VERSION is Python's version
 * number as supplied by the Makefile. Note that this means that no more
 * build directory checking is performed; if the first step did not find
 * the landmarks, the assumption is that python is running from an
 * installed setup.
 *
 * Step 2. See if the $PYTHONHOME environment variable points to the
 * installed location of the Python libraries. If $PYTHONHOME is set, then
 * it points to prefix and exec_prefix. $PYTHONHOME can be a single
 * directory, which is used for both, or the prefix and exec_prefix
 * directories separated by a colon.
 *
 * Step 3. Try to find prefix and exec_prefix relative to argv0_path,
 * backtracking up the path until it is exhausted. This is the most common
 * step to succeed. Note that if prefix and exec_prefix are different,
 * exec_prefix is more likely to be found; however if exec_prefix is a
 * subdirectory of prefix, both will be found.
 *
 * Step 4. Search the directories pointed to by the preprocessor variables
 * PREFIX and EXEC_PREFIX. These are supplied by the Makefile but can be
 * passed in as options to the configure script.
 *
 * That's it!
 *
 * Well, almost. Once we have determined prefix and exec_prefix, the
 * preprocessor variable PYTHONPATH is used to construct a path. Each
 * relative path on PYTHONPATH is prefixed with prefix. Then the directory
 * containing the shared library modules is appended. The environment
 * variable $PYTHONPATH is inserted in front of it all. Finally, the
 * prefix and exec_prefix globals are tweaked so they reflect the values
 * expected by other code, by stripping the "lib/python$VERSION/..." stuff
 * off. If either points to the build directory, the globals are reset to
 * the corresponding preprocessor variables (so sys.prefix will reflect the
 * installation location, even though sys.path points into the build
 * directory). This seems to make more sense given that currently the only
 * known use of sys.prefix and sys.exec_prefix is for the ILU installation
 * process to find the installed Python tree.
 *
 * An embedding application can use Py_SetPath() to override all of
 * these authomatic path computations.
 *
 * NOTE: Windows MSVC builds use PC/getpathp.c instead!
 */

#ifdef __cplusplus
extern "C" {
#endif


#if !defined(PREFIX) || !defined(EXEC_PREFIX) || !defined(VERSION) || !defined(VPATH)
#error "PREFIX, EXEC_PREFIX, VERSION, and VPATH must be constant defined"
#endif

#ifndef LANDMARK
#define LANDMARK L"os.py"
#endif

#define DECODE_LOCALE_ERR(NAME, LEN) \
 ((LEN) == (size_t)-2) \
 ? _Py_INIT_USER_ERR("cannot decode " NAME) \
 : _Py_INIT_NO_MEMORY()

typedef struct {
 wchar_t *path_env; /* PATH environment variable */

 wchar_t *pythonpath; /* PYTHONPATH define */
 wchar_t *prefix; /* PREFIX define */
 wchar_t *exec_prefix; /* EXEC_PREFIX define */

 wchar_t *lib_python; /* "lib/pythonX.Y" */
 wchar_t argv0_path[MAXPATHLEN+1];
 wchar_t zip_path[MAXPATHLEN+1]; /* ".../lib/pythonXY.zip" */

 int prefix_found; /* found platform independent libraries? */
 int exec_prefix_found; /* found the platform dependent libraries? */
} PyCalculatePath;

static const wchar_t delimiter[2] = {DELIM, '0円'};
static const wchar_t separator[2] = {SEP, '0円'};


/* Get file status. Encode the path to the locale encoding. */
static int
_Py_wstat(const wchar_t* path, struct stat *buf)
{
 int err;
 char *fname;
 fname = _Py_EncodeLocaleRaw(path, NULL);
 if (fname == NULL) {
 errno = EINVAL;
 return -1;
 }
 err = stat(fname, buf);
 PyMem_RawFree(fname);
 return err;
}


static void
reduce(wchar_t *dir)
{
 size_t i = wcslen(dir);
 while (i > 0 && dir[i] != SEP)
 --i;
 dir[i] = '0円';
}


static int
isfile(wchar_t *filename) /* Is file, not directory */
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISREG(buf.st_mode)) {
 return 0;
 }
 return 1;
}


static int
ismodule(wchar_t *filename) /* Is module -- check for .pyc too */
{
 if (isfile(filename)) {
 return 1;
 }

 /* Check for the compiled version of prefix. */
 if (wcslen(filename) < MAXPATHLEN) {
 wcscat(filename, L"c");
 if (isfile(filename)) {
 return 1;
 }
 }
 return 0;
}


/* Is executable file */
static int
isxfile(wchar_t *filename)
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISREG(buf.st_mode)) {
 return 0;
 }
 if ((buf.st_mode & 0111) == 0) {
 return 0;
 }
 return 1;
}


/* Is directory */
static int
isdir(wchar_t *filename)
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISDIR(buf.st_mode)) {
 return 0;
 }
 return 1;
}


/* Add a path component, by appending stuff to buffer.
 buffer must have at least MAXPATHLEN + 1 bytes allocated, and contain a
 NUL-terminated string with no more than MAXPATHLEN characters (not counting
 the trailing NUL). It's a fatal error if it contains a string longer than
 that (callers must be careful!). If these requirements are met, it's
 guaranteed that buffer will still be a NUL-terminated string with no more
 than MAXPATHLEN characters at exit. If stuff is too long, only as much of
 stuff as fits will be appended.
*/
static void
joinpath(wchar_t *buffer, wchar_t *stuff)
{
 size_t n, k;
 if (stuff[0] == SEP) {
 n = 0;
 }
 else {
 n = wcslen(buffer);
 if (n > 0 && buffer[n-1] != SEP && n < MAXPATHLEN) {
 buffer[n++] = SEP;
 }
 }
 if (n > MAXPATHLEN) {
 Py_FatalError("buffer overflow in getpath.c's joinpath()");
 }
 k = wcslen(stuff);
 if (n + k > MAXPATHLEN) {
 k = MAXPATHLEN - n;
 }
 wcsncpy(buffer+n, stuff, k);
 buffer[n+k] = '0円';
}


/* copy_absolute requires that path be allocated at least
 MAXPATHLEN + 1 bytes and that p be no more than MAXPATHLEN bytes. */
static void
copy_absolute(wchar_t *path, wchar_t *p, size_t pathlen)
{
 if (p[0] == SEP) {
 wcscpy(path, p);
 }
 else {
 if (!_Py_wgetcwd(path, pathlen)) {
 /* unable to get the current directory */
 wcscpy(path, p);
 return;
 }
 if (p[0] == '.' && p[1] == SEP) {
 p += 2;
 }
 joinpath(path, p);
 }
}


/* absolutize() requires that path be allocated at least MAXPATHLEN+1 bytes. */
static void
absolutize(wchar_t *path)
{
 wchar_t buffer[MAXPATHLEN+1];

 if (path[0] == SEP) {
 return;
 }
 copy_absolute(buffer, path, MAXPATHLEN+1);
 wcscpy(path, buffer);
}


#if defined(__CYGWIN__) || defined(__MINGW32__)
/* add_exe_suffix requires that progpath be allocated at least
 MAXPATHLEN + 1 bytes.
*/

#ifndef EXE_SUFFIX
#define EXE_SUFFIX L".exe"
#endif

static void
add_exe_suffix(wchar_t *progpath)
{
 /* Check for already have an executable suffix */
 size_t n = wcslen(progpath);
 size_t s = wcslen(EXE_SUFFIX);
 if (wcsncasecmp(EXE_SUFFIX, progpath+n-s, s) != 0) {
 if (n + s > MAXPATHLEN) {
 Py_FatalError("progpath overflow in getpath.c's add_exe_suffix()");
 }
 /* Save original path for revert */
 wchar_t orig[MAXPATHLEN+1];
 wcsncpy(orig, progpath, MAXPATHLEN);

 wcsncpy(progpath+n, EXE_SUFFIX, s);
 progpath[n+s] = '0円';

 if (!isxfile(progpath)) {
 /* Path that added suffix is invalid */
 wcsncpy(progpath, orig, MAXPATHLEN);
 }
 }
}
#endif


/* search_for_prefix requires that argv0_path be no more than MAXPATHLEN
 bytes long.
*/
static int
search_for_prefix(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, wchar_t *prefix)
{
 size_t n;
 wchar_t *vpath;

 /* If PYTHONHOME is set, we believe it unconditionally */
 if (core_config->home) {
 wcsncpy(prefix, core_config->home, MAXPATHLEN);
 prefix[MAXPATHLEN] = L'0円';
 wchar_t *delim = wcschr(prefix, DELIM);
 if (delim) {
 *delim = L'0円';
 }
 joinpath(prefix, calculate->lib_python);
 joinpath(prefix, LANDMARK);
 return 1;
 }

 /* Check to see if argv[0] is in the build directory */
 wcsncpy(prefix, calculate->argv0_path, MAXPATHLEN);
 prefix[MAXPATHLEN] = L'0円';
 joinpath(prefix, L"Modules/Setup");
 if (isfile(prefix)) {
 /* Check VPATH to see if argv0_path is in the build directory. */
 vpath = Py_DecodeLocale(VPATH, NULL);
 if (vpath != NULL) {
 wcsncpy(prefix, calculate->argv0_path, MAXPATHLEN);
 prefix[MAXPATHLEN] = L'0円';
 joinpath(prefix, vpath);
 PyMem_RawFree(vpath);
 joinpath(prefix, L"Lib");
 joinpath(prefix, LANDMARK);
 if (ismodule(prefix)) {
 return -1;
 }
 }
 }

 /* Search from argv0_path, until root is found */
 copy_absolute(prefix, calculate->argv0_path, MAXPATHLEN+1);
 do {
 n = wcslen(prefix);
 joinpath(prefix, calculate->lib_python);
 joinpath(prefix, LANDMARK);
 if (ismodule(prefix)) {
 return 1;
 }
 prefix[n] = L'0円';
 reduce(prefix);
 } while (prefix[0]);

 /* Look at configure's PREFIX */
 wcsncpy(prefix, calculate->prefix, MAXPATHLEN);
 prefix[MAXPATHLEN] = L'0円';
 joinpath(prefix, calculate->lib_python);
 joinpath(prefix, LANDMARK);
 if (ismodule(prefix)) {
 return 1;
 }

 /* Fail */
 return 0;
}


static void
calculate_prefix(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, wchar_t *prefix)
{
 calculate->prefix_found = search_for_prefix(core_config, calculate, prefix);
 if (!calculate->prefix_found) {
 if (!Py_FrozenFlag) {
 fprintf(stderr,
 "Could not find platform independent libraries <prefix>\n");
 }
 wcsncpy(prefix, calculate->prefix, MAXPATHLEN);
 joinpath(prefix, calculate->lib_python);
 }
 else {
 reduce(prefix);
 }
}


static void
calculate_reduce_prefix(PyCalculatePath *calculate, wchar_t *prefix)
{
 /* Reduce prefix and exec_prefix to their essence,
 * e.g. /usr/local/lib/python1.5 is reduced to /usr/local.
 * If we're loading relative to the build directory,
 * return the compiled-in defaults instead.
 */
 if (calculate->prefix_found > 0) {
 reduce(prefix);
 reduce(prefix);
 /* The prefix is the root directory, but reduce() chopped
 * off the "/". */
 if (!prefix[0]) {
 wcscpy(prefix, separator);
 }
 }
 else {
 wcsncpy(prefix, calculate->prefix, MAXPATHLEN);
 }
}


/* search_for_exec_prefix requires that argv0_path be no more than
 MAXPATHLEN bytes long.
*/
static int
search_for_exec_prefix(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, wchar_t *exec_prefix)
{
 size_t n;

 /* If PYTHONHOME is set, we believe it unconditionally */
 if (core_config->home) {
 wchar_t *delim = wcschr(core_config->home, DELIM);
 if (delim) {
 wcsncpy(exec_prefix, delim+1, MAXPATHLEN);
 }
 else {
 wcsncpy(exec_prefix, core_config->home, MAXPATHLEN);
 }
 exec_prefix[MAXPATHLEN] = L'0円';
 joinpath(exec_prefix, calculate->lib_python);
 joinpath(exec_prefix, L"lib-dynload");
 return 1;
 }

 /* Check to see if argv[0] is in the build directory. "pybuilddir.txt"
 is written by setup.py and contains the relative path to the location
 of shared library modules. */
 wcsncpy(exec_prefix, calculate->argv0_path, MAXPATHLEN);
 exec_prefix[MAXPATHLEN] = L'0円';
 joinpath(exec_prefix, L"pybuilddir.txt");
 if (isfile(exec_prefix)) {
 FILE *f = _Py_wfopen(exec_prefix, L"rb");
 if (f == NULL) {
 errno = 0;
 }
 else {
 char buf[MAXPATHLEN+1];
 wchar_t *rel_builddir_path;
 n = fread(buf, 1, MAXPATHLEN, f);
 buf[n] = '0円';
 fclose(f);
 rel_builddir_path = _Py_DecodeUTF8_surrogateescape(buf, n);
 if (rel_builddir_path) {
 wcsncpy(exec_prefix, calculate->argv0_path, MAXPATHLEN);
 exec_prefix[MAXPATHLEN] = L'0円';
 joinpath(exec_prefix, rel_builddir_path);
 PyMem_RawFree(rel_builddir_path );
 return -1;
 }
 }
 }

 /* Search from argv0_path, until root is found */
 copy_absolute(exec_prefix, calculate->argv0_path, MAXPATHLEN+1);
 do {
 n = wcslen(exec_prefix);
 joinpath(exec_prefix, calculate->lib_python);
 joinpath(exec_prefix, L"lib-dynload");
 if (isdir(exec_prefix)) {
 return 1;
 }
 exec_prefix[n] = L'0円';
 reduce(exec_prefix);
 } while (exec_prefix[0]);

 /* Look at configure's EXEC_PREFIX */
 wcsncpy(exec_prefix, calculate->exec_prefix, MAXPATHLEN);
 exec_prefix[MAXPATHLEN] = L'0円';
 joinpath(exec_prefix, calculate->lib_python);
 joinpath(exec_prefix, L"lib-dynload");
 if (isdir(exec_prefix)) {
 return 1;
 }

 /* Fail */
 return 0;
}


static void
calculate_exec_prefix(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, wchar_t *exec_prefix)
{
 calculate->exec_prefix_found = search_for_exec_prefix(core_config,
 calculate,
 exec_prefix);
 if (!calculate->exec_prefix_found) {
 if (!Py_FrozenFlag) {
 fprintf(stderr,
 "Could not find platform dependent libraries <exec_prefix>\n");
 }
 wcsncpy(exec_prefix, calculate->exec_prefix, MAXPATHLEN);
 joinpath(exec_prefix, L"lib/lib-dynload");
 }
 /* If we found EXEC_PREFIX do *not* reduce it! (Yet.) */
}


static void
calculate_reduce_exec_prefix(PyCalculatePath *calculate, wchar_t *exec_prefix)
{
 if (calculate->exec_prefix_found > 0) {
 reduce(exec_prefix);
 reduce(exec_prefix);
 reduce(exec_prefix);
 if (!exec_prefix[0]) {
 wcscpy(exec_prefix, separator);
 }
 }
 else {
 wcsncpy(exec_prefix, calculate->exec_prefix, MAXPATHLEN);
 }
}


static _PyInitError
calculate_program_full_path(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, _PyPathConfig *config)
{
 wchar_t program_full_path[MAXPATHLEN+1];
 memset(program_full_path, 0, sizeof(program_full_path));

#ifdef __APPLE__
#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_4
 uint32_t nsexeclength = MAXPATHLEN;
#else
 unsigned long nsexeclength = MAXPATHLEN;
#endif
 char execpath[MAXPATHLEN+1];
#endif

 /* If there is no slash in the argv0 path, then we have to
 * assume python is on the user's $PATH, since there's no
 * other way to find a directory to start the search from. If
 * $PATH isn't exported, you lose.
 */
 if (wcschr(core_config->program_name, SEP)) {
 wcsncpy(program_full_path, core_config->program_name, MAXPATHLEN);
 }
#ifdef __APPLE__
 /* On Mac OS X, if a script uses an interpreter of the form
 * "#!/opt/python2.3/bin/python", the kernel only passes "python"
 * as argv[0], which falls through to the $PATH search below.
 * If /opt/python2.3/bin isn't in your path, or is near the end,
 * this algorithm may incorrectly find /usr/bin/python. To work
 * around this, we can use _NSGetExecutablePath to get a better
 * hint of what the intended interpreter was, although this
 * will fail if a relative path was used. but in that case,
 * absolutize() should help us out below
 */
 else if(0 == _NSGetExecutablePath(execpath, &nsexeclength) &&
 execpath[0] == SEP)
 {
 size_t len;
 wchar_t *path = Py_DecodeLocale(execpath, &len);
 if (path == NULL) {
 return DECODE_LOCALE_ERR("executable path", len);
 }
 wcsncpy(program_full_path, path, MAXPATHLEN);
 PyMem_RawFree(path);
 }
#endif /* __APPLE__ */
 else if (calculate->path_env) {
 wchar_t *path = calculate->path_env;
 while (1) {
 wchar_t *delim = wcschr(path, DELIM);

 if (delim) {
 size_t len = delim - path;
 if (len > MAXPATHLEN) {
 len = MAXPATHLEN;
 }
 wcsncpy(program_full_path, path, len);
 program_full_path[len] = '0円';
 }
 else {
 wcsncpy(program_full_path, path, MAXPATHLEN);
 }

 joinpath(program_full_path, core_config->program_name);
 if (isxfile(program_full_path)) {
 break;
 }

 if (!delim) {
 program_full_path[0] = L'0円';
 break;
 }
 path = delim + 1;
 }
 }
 else {
 program_full_path[0] = '0円';
 }
 if (program_full_path[0] != SEP && program_full_path[0] != '0円') {
 absolutize(program_full_path);
 }
#if defined(__CYGWIN__) || defined(__MINGW32__)
 /* For these platforms it is necessary to ensure that the .exe suffix
 * is appended to the filename, otherwise there is potential for
 * sys.executable to return the name of a directory under the same
 * path (bpo-28441).
 */
 if (program_full_path[0] != '0円') {
 add_exe_suffix(program_full_path);
 }
#endif

 config->program_full_path = _PyMem_RawWcsdup(program_full_path);
 if (config->program_full_path == NULL) {
 return _Py_INIT_NO_MEMORY();
 }
 return _Py_INIT_OK();
}


static _PyInitError
calculate_argv0_path(PyCalculatePath *calculate, const wchar_t *program_full_path)
{
 wcsncpy(calculate->argv0_path, program_full_path, MAXPATHLEN);
 calculate->argv0_path[MAXPATHLEN] = '0円';

#ifdef WITH_NEXT_FRAMEWORK
 NSModule pythonModule;

 /* On Mac OS X we have a special case if we're running from a framework.
 ** This is because the python home should be set relative to the library,
 ** which is in the framework, not relative to the executable, which may
 ** be outside of the framework. Except when we're in the build directory...
 */
 pythonModule = NSModuleForSymbol(NSLookupAndBindSymbol("_Py_Initialize"));
 /* Use dylib functions to find out where the framework was loaded from */
 const char* modPath = NSLibraryNameForModule(pythonModule);
 if (modPath != NULL) {
 /* We're in a framework. */
 /* See if we might be in the build directory. The framework in the
 ** build directory is incomplete, it only has the .dylib and a few
 ** needed symlinks, it doesn't have the Lib directories and such.
 ** If we're running with the framework from the build directory we must
 ** be running the interpreter in the build directory, so we use the
 ** build-directory-specific logic to find Lib and such.
 */
 size_t len;
 wchar_t* wbuf = Py_DecodeLocale(modPath, &len);
 if (wbuf == NULL) {
 return DECODE_LOCALE_ERR("framework location", len);
 }

 wcsncpy(calculate->argv0_path, wbuf, MAXPATHLEN);
 reduce(calculate->argv0_path);
 joinpath(calculate->argv0_path, calculate->lib_python);
 joinpath(calculate->argv0_path, LANDMARK);
 if (!ismodule(calculate->argv0_path)) {
 /* We are in the build directory so use the name of the
 executable - we know that the absolute path is passed */
 wcsncpy(calculate->argv0_path, program_full_path, MAXPATHLEN);
 }
 else {
 /* Use the location of the library as the program_full_path */
 wcsncpy(calculate->argv0_path, wbuf, MAXPATHLEN);
 }
 PyMem_RawFree(wbuf);
 }
#endif

#if HAVE_READLINK
 wchar_t tmpbuffer[MAXPATHLEN+1];
 int linklen = _Py_wreadlink(program_full_path, tmpbuffer, MAXPATHLEN);
 while (linklen != -1) {
 if (tmpbuffer[0] == SEP) {
 /* tmpbuffer should never be longer than MAXPATHLEN,
 but extra check does not hurt */
 wcsncpy(calculate->argv0_path, tmpbuffer, MAXPATHLEN);
 }
 else {
 /* Interpret relative to program_full_path */
 reduce(calculate->argv0_path);
 joinpath(calculate->argv0_path, tmpbuffer);
 }
 linklen = _Py_wreadlink(calculate->argv0_path, tmpbuffer, MAXPATHLEN);
 }
#endif /* HAVE_READLINK */

 reduce(calculate->argv0_path);
 /* At this point, argv0_path is guaranteed to be less than
 MAXPATHLEN bytes long. */
 return _Py_INIT_OK();
}


/* Search for an "pyvenv.cfg" environment configuration file, first in the
 executable's directory and then in the parent directory.
 If found, open it for use when searching for prefixes.
*/
static void
calculate_read_pyenv(PyCalculatePath *calculate)
{
 wchar_t tmpbuffer[MAXPATHLEN+1];
 wchar_t *env_cfg = L"pyvenv.cfg";
 FILE *env_file;

 wcscpy(tmpbuffer, calculate->argv0_path);

 joinpath(tmpbuffer, env_cfg);
 env_file = _Py_wfopen(tmpbuffer, L"r");
 if (env_file == NULL) {
 errno = 0;

 reduce(tmpbuffer);
 reduce(tmpbuffer);
 joinpath(tmpbuffer, env_cfg);

 env_file = _Py_wfopen(tmpbuffer, L"r");
 if (env_file == NULL) {
 errno = 0;
 }
 }

 if (env_file == NULL) {
 return;
 }

 /* Look for a 'home' variable and set argv0_path to it, if found */
 if (_Py_FindEnvConfigValue(env_file, L"home", tmpbuffer, MAXPATHLEN)) {
 wcscpy(calculate->argv0_path, tmpbuffer);
 }
 fclose(env_file);
}


static void
calculate_zip_path(PyCalculatePath *calculate, const wchar_t *prefix)
{
 wcsncpy(calculate->zip_path, prefix, MAXPATHLEN);
 calculate->zip_path[MAXPATHLEN] = L'0円';

 if (calculate->prefix_found > 0) {
 /* Use the reduced prefix returned by Py_GetPrefix() */
 reduce(calculate->zip_path);
 reduce(calculate->zip_path);
 }
 else {
 wcsncpy(calculate->zip_path, calculate->prefix, MAXPATHLEN);
 }
 joinpath(calculate->zip_path, L"lib/python00.zip");

 /* Replace "00" with version */
 size_t bufsz = wcslen(calculate->zip_path);
 calculate->zip_path[bufsz - 6] = VERSION[0];
 calculate->zip_path[bufsz - 5] = VERSION[2];
}


static _PyInitError
calculate_module_search_path(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate,
 const wchar_t *prefix, const wchar_t *exec_prefix,
 _PyPathConfig *config)
{
 /* Calculate size of return buffer */
 size_t bufsz = 0;
 if (core_config->module_search_path_env != NULL) {
 bufsz += wcslen(core_config->module_search_path_env) + 1;
 }

 wchar_t *defpath = calculate->pythonpath;
 size_t prefixsz = wcslen(prefix) + 1;
 while (1) {
 wchar_t *delim = wcschr(defpath, DELIM);

 if (defpath[0] != SEP) {
 /* Paths are relative to prefix */
 bufsz += prefixsz;
 }

 if (delim) {
 bufsz += delim - defpath + 1;
 }
 else {
 bufsz += wcslen(defpath) + 1;
 break;
 }
 defpath = delim + 1;
 }

 bufsz += wcslen(calculate->zip_path) + 1;
 bufsz += wcslen(exec_prefix) + 1;

 /* Allocate the buffer */
 wchar_t *buf = PyMem_RawMalloc(bufsz * sizeof(wchar_t));
 if (buf == NULL) {
 return _Py_INIT_NO_MEMORY();
 }
 buf[0] = '0円';

 /* Run-time value of $PYTHONPATH goes first */
 if (core_config->module_search_path_env) {
 wcscpy(buf, core_config->module_search_path_env);
 wcscat(buf, delimiter);
 }

 /* Next is the default zip path */
 wcscat(buf, calculate->zip_path);
 wcscat(buf, delimiter);

 /* Next goes merge of compile-time $PYTHONPATH with
 * dynamically located prefix.
 */
 defpath = calculate->pythonpath;
 while (1) {
 wchar_t *delim = wcschr(defpath, DELIM);

 if (defpath[0] != SEP) {
 wcscat(buf, prefix);
 if (prefixsz >= 2 && prefix[prefixsz - 2] != SEP &&
 defpath[0] != (delim ? DELIM : L'0円'))
 {
 /* not empty */
 wcscat(buf, separator);
 }
 }

 if (delim) {
 size_t len = delim - defpath + 1;
 size_t end = wcslen(buf) + len;
 wcsncat(buf, defpath, len);
 buf[end] = '0円';
 }
 else {
 wcscat(buf, defpath);
 break;
 }
 defpath = delim + 1;
 }
 wcscat(buf, delimiter);

 /* Finally, on goes the directory for dynamic-load modules */
 wcscat(buf, exec_prefix);

 config->module_search_path = buf;
 return _Py_INIT_OK();
}


static _PyInitError
calculate_init(PyCalculatePath *calculate,
 const _PyCoreConfig *core_config)
{
 size_t len;
 const char *path = getenv("PATH");
 if (path) {
 calculate->path_env = Py_DecodeLocale(path, &len);
 if (!calculate->path_env) {
 return DECODE_LOCALE_ERR("PATH environment variable", len);
 }
 }

 calculate->pythonpath = Py_DecodeLocale(PYTHONPATH, &len);
 if (!calculate->pythonpath) {
 return DECODE_LOCALE_ERR("PYTHONPATH define", len);
 }
 calculate->prefix = Py_DecodeLocale(PREFIX, &len);
 if (!calculate->prefix) {
 return DECODE_LOCALE_ERR("PREFIX define", len);
 }
 calculate->exec_prefix = Py_DecodeLocale(EXEC_PREFIX, &len);
 if (!calculate->prefix) {
 return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
 }
 calculate->lib_python = Py_DecodeLocale("lib/python" VERSION, &len);
 if (!calculate->lib_python) {
 return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
 }
 return _Py_INIT_OK();
}


static void
calculate_free(PyCalculatePath *calculate)
{
 PyMem_RawFree(calculate->pythonpath);
 PyMem_RawFree(calculate->prefix);
 PyMem_RawFree(calculate->exec_prefix);
 PyMem_RawFree(calculate->lib_python);
 PyMem_RawFree(calculate->path_env);
}


static _PyInitError
calculate_path_impl(const _PyCoreConfig *core_config,
 PyCalculatePath *calculate, _PyPathConfig *config)
{
 _PyInitError err;

 err = calculate_program_full_path(core_config, calculate, config);
 if (_Py_INIT_FAILED(err)) {
 return err;
 }

 err = calculate_argv0_path(calculate, config->program_full_path);
 if (_Py_INIT_FAILED(err)) {
 return err;
 }

 calculate_read_pyenv(calculate);

 wchar_t prefix[MAXPATHLEN+1];
 memset(prefix, 0, sizeof(prefix));
 calculate_prefix(core_config, calculate, prefix);

 calculate_zip_path(calculate, prefix);

 wchar_t exec_prefix[MAXPATHLEN+1];
 memset(exec_prefix, 0, sizeof(exec_prefix));
 calculate_exec_prefix(core_config, calculate, exec_prefix);

 if ((!calculate->prefix_found || !calculate->exec_prefix_found) &&
 !Py_FrozenFlag)
 {
 fprintf(stderr,
 "Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]\n");
 }

 err = calculate_module_search_path(core_config, calculate,
 prefix, exec_prefix, config);
 if (_Py_INIT_FAILED(err)) {
 return err;
 }

 calculate_reduce_prefix(calculate, prefix);

 config->prefix = _PyMem_RawWcsdup(prefix);
 if (config->prefix == NULL) {
 return _Py_INIT_NO_MEMORY();
 }

 calculate_reduce_exec_prefix(calculate, exec_prefix);

 config->exec_prefix = _PyMem_RawWcsdup(exec_prefix);
 if (config->exec_prefix == NULL) {
 return _Py_INIT_NO_MEMORY();
 }

 return _Py_INIT_OK();
}


_PyInitError
_PyPathConfig_Calculate(_PyPathConfig *config, const _PyCoreConfig *core_config)
{
 PyCalculatePath calculate;
 memset(&calculate, 0, sizeof(calculate));

 _PyInitError err = calculate_init(&calculate, core_config);
 if (_Py_INIT_FAILED(err)) {
 goto done;
 }

 err = calculate_path_impl(core_config, &calculate, config);
 if (_Py_INIT_FAILED(err)) {
 goto done;
 }

 err = _Py_INIT_OK();

done:
 calculate_free(&calculate);
 return err;
}

#ifdef __cplusplus
}
#endif