/* Return the initial module search path. */

#include "Python.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

 * Modules/Setup.  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.

 */

#ifdef __cplusplus

 extern "C" {

#endif

#ifndef VERSION

#define VERSION "2.1"

#endif

#ifndef VPATH

#define VPATH "."

#endif

#ifndef PREFIX

#  ifdef __VMS

#    define PREFIX ""

#  else

#    define PREFIX "/usr/local"

#  endif

#endif

#ifndef EXEC_PREFIX

#define EXEC_PREFIX PREFIX

#endif

#ifndef PYTHONPATH

#define PYTHONPATH PREFIX "/lib/python" VERSION ":" \

              EXEC_PREFIX "/lib/python" VERSION "/lib-dynload"

#endif

#ifndef LANDMARK

#define LANDMARK "os.py"

#endif

static char prefix[MAXPATHLEN+1];

static char exec_prefix[MAXPATHLEN+1];

static char progpath[MAXPATHLEN+1];

static char *module_search_path = NULL;

static char lib_python[] = "lib/python" VERSION;

static void

reduce(char *dir)

{

    size_t i = strlen(dir);

    while (i > 0 && dir[i] != SEP)

        --i;

    dir[i] = '\0';

}

static int

isfile(char *filename)          /* Is file, not directory */

{

    struct stat buf;

    if (stat(filename, &buf) != 0)

        return 0;

    if (!S_ISREG(buf.st_mode))

        return 0;

    return 1;

}

static int

ismodule(char *filename)        /* Is module -- check for .pyc/.pyo too */

{

    if (isfile(filename))

        return 1;

    /* Check for the compiled version of prefix. */

    if (strlen(filename) < MAXPATHLEN) {

        strcat(filename, Py_OptimizeFlag ? "o" : "c");

        if (isfile(filename))

            return 1;

    }

    return 0;

}

static int

isxfile(char *filename)         /* Is executable file */

{

    struct stat buf;

    if (stat(filename, &buf) != 0)

        return 0;

    if (!S_ISREG(buf.st_mode))

        return 0;

    if ((buf.st_mode & 0111) == 0)

        return 0;

    return 1;

}

static int

isdir(char *filename)                   /* Is directory */

{

    struct stat buf;

    if (stat(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(char *buffer, char *stuff)

{

    size_t n, k;

    if (stuff[0] == SEP)

        n = 0;

    else {

        n = strlen(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 = strlen(stuff);

    if (n + k > MAXPATHLEN)

        k = MAXPATHLEN - n;

    strncpy(buffer+n, stuff, k);

    buffer[n+k] = '\0';

}

/* 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(char *path, char *p)

{

    if (p[0] == SEP)

        strcpy(path, p);

    else {

        getcwd(path, MAXPATHLEN);

        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(char *path)

{

    char buffer[MAXPATHLEN + 1];

    if (path[0] == SEP)

        return;

    copy_absolute(buffer, path);

    strcpy(path, buffer);

}

/* search_for_prefix requires that argv0_path be no more than MAXPATHLEN

   bytes long.

*/

static int

search_for_prefix(char *argv0_path, char *home)

{

    size_t n;

    char *vpath;

    /* If PYTHONHOME is set, we believe it unconditionally */

    if (home) {

        char *delim;

        strncpy(prefix, home, MAXPATHLEN);

        delim = strchr(prefix, DELIM);

        if (delim)

            *delim = '\0';

        joinpath(prefix, lib_python);

        joinpath(prefix, LANDMARK);

        return 1;

    }

    /* Check to see if argv[0] is in the build directory */

    strcpy(prefix, argv0_path);

    joinpath(prefix, "Modules/Setup");

    if (isfile(prefix)) {

        /* Check VPATH to see if argv0_path is in the build directory. */

        vpath = VPATH;

        strcpy(prefix, argv0_path);

        joinpath(prefix, vpath);

        joinpath(prefix, "Lib");

        joinpath(prefix, LANDMARK);

        if (ismodule(prefix))

            return -1;

    }

    /* Search from argv0_path, until root is found */

    copy_absolute(prefix, argv0_path);

    do {

        n = strlen(prefix);

        joinpath(prefix, lib_python);

        joinpath(prefix, LANDMARK);

        if (ismodule(prefix))

            return 1;

        prefix[n] = '\0';

        reduce(prefix);

    } while (prefix[0]);

    /* Look at configure's PREFIX */

    strncpy(prefix, PREFIX, MAXPATHLEN);

    joinpath(prefix, lib_python);

    joinpath(prefix, LANDMARK);

    if (ismodule(prefix))

        return 1;

    /* Fail */

    return 0;

}

/* search_for_exec_prefix requires that argv0_path be no more than

   MAXPATHLEN bytes long.

*/

static int

search_for_exec_prefix(char *argv0_path, char *home)

{

    size_t n;

    /* If PYTHONHOME is set, we believe it unconditionally */

    if (home) {

        char *delim;

        delim = strchr(home, DELIM);

        if (delim)

            strncpy(exec_prefix, delim+1, MAXPATHLEN);

        else

            strncpy(exec_prefix, home, MAXPATHLEN);

        joinpath(exec_prefix, lib_python);

        joinpath(exec_prefix, "lib-dynload");

        return 1;

    }

    /* Check to see if argv[0] is in the build directory */

    strcpy(exec_prefix, argv0_path);

    joinpath(exec_prefix, "Modules/Setup");

    if (isfile(exec_prefix)) {

        reduce(exec_prefix);

        return -1;

    }

    /* Search from argv0_path, until root is found */

    copy_absolute(exec_prefix, argv0_path);

    do {

        n = strlen(exec_prefix);

        joinpath(exec_prefix, lib_python);

        joinpath(exec_prefix, "lib-dynload");

        if (isdir(exec_prefix))

            return 1;

        exec_prefix[n] = '\0';

        reduce(exec_prefix);

    } while (exec_prefix[0]);

    /* Look at configure's EXEC_PREFIX */

    strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);

    joinpath(exec_prefix, lib_python);

    joinpath(exec_prefix, "lib-dynload");

    if (isdir(exec_prefix))

        return 1;

    /* Fail */

    return 0;

}

static void

calculate_path(void)

{

    extern char *Py_GetProgramName(void);

    static char delimiter[2] = {DELIM, '\0'};

    static char separator[2] = {SEP, '\0'};

    char *pythonpath = PYTHONPATH;

    char *rtpypath = Py_GETENV("PYTHONPATH");

    char *home = Py_GetPythonHome();

    char *path = getenv("PATH");

    char *prog = Py_GetProgramName();

    char argv0_path[MAXPATHLEN+1];

    char zip_path[MAXPATHLEN+1];

    int pfound, efound; /* 1 if found; -1 if found build directory */

    char *buf;

    size_t bufsz;

    size_t prefixsz;

    char *defpath = pythonpath;

#ifdef WITH_NEXT_FRAMEWORK

    NSModule pythonModule;

#endif

#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

#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 (strchr(prog, SEP))

		strncpy(progpath, prog, 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(progpath, &nsexeclength) && progpath[0] == SEP)

       ;

#endif /* __APPLE__ */

	else if (path) {

		while (1) {

			char *delim = strchr(path, DELIM);

			if (delim) {

				size_t len = delim - path;

				if (len > MAXPATHLEN)

					len = MAXPATHLEN;

				strncpy(progpath, path, len);

				*(progpath + len) = '\0';

			}

			else

				strncpy(progpath, path, MAXPATHLEN);

			joinpath(progpath, prog);

			if (isxfile(progpath))

				break;

			if (!delim) {

				progpath[0] = '\0';

				break;

			}

			path = delim + 1;

		}

	}

	else

		progpath[0] = '\0';

	if (progpath[0] != SEP)

		absolutize(progpath);

	strncpy(argv0_path, progpath, MAXPATHLEN);

	argv0_path[MAXPATHLEN] = '\0';

#ifdef WITH_NEXT_FRAMEWORK

	/* 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 */

    buf = (char *)NSLibraryNameForModule(pythonModule);

    if (buf != 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.

        */

        strncpy(argv0_path, buf, MAXPATHLEN);

        reduce(argv0_path);

        joinpath(argv0_path, lib_python);

        joinpath(argv0_path, LANDMARK);

        if (!ismodule(argv0_path)) {

                /* We are in the build directory so use the name of the

                   executable - we know that the absolute path is passed */

                strncpy(argv0_path, prog, MAXPATHLEN);

        }

        else {

                /* Use the location of the library as the progpath */

                strncpy(argv0_path, buf, MAXPATHLEN);

        }

    }

#endif

#if HAVE_READLINK

    {

        char tmpbuffer[MAXPATHLEN+1];

        int linklen = readlink(progpath, tmpbuffer, MAXPATHLEN);

        while (linklen != -1) {

            /* It's not null terminated! */

            tmpbuffer[linklen] = '\0';

            if (tmpbuffer[0] == SEP)

                /* tmpbuffer should never be longer than MAXPATHLEN,

                   but extra check does not hurt */

                strncpy(argv0_path, tmpbuffer, MAXPATHLEN);

            else {

                /* Interpret relative to progpath */

                reduce(argv0_path);

                joinpath(argv0_path, tmpbuffer);

            }

            linklen = readlink(argv0_path, tmpbuffer, MAXPATHLEN);

        }

    }

#endif /* HAVE_READLINK */

    reduce(argv0_path);

    /* At this point, argv0_path is guaranteed to be less than

       MAXPATHLEN bytes long.

    */

    if (!(pfound = search_for_prefix(argv0_path, home))) {

        if (!Py_FrozenFlag)

            fprintf(stderr,

                "Could not find platform independent libraries <prefix>\n");

        strncpy(prefix, PREFIX, MAXPATHLEN);

        joinpath(prefix, lib_python);

    }

    else

        reduce(prefix);

    strncpy(zip_path, prefix, MAXPATHLEN);

    zip_path[MAXPATHLEN] = '\0';

    if (pfound > 0) { /* Use the reduced prefix returned by Py_GetPrefix() */

        reduce(zip_path);

        reduce(zip_path);

    }

    else

        strncpy(zip_path, PREFIX, MAXPATHLEN);

    joinpath(zip_path, "lib/python00.zip");

    bufsz = strlen(zip_path);	/* Replace "00" with version */

    zip_path[bufsz - 6] = VERSION[0];