/* Return the initial module search path. */

/* This version used by OS/2+EMX */

/* ----------------------------------------------------------------

   PATH RULES FOR OS/2+EMX:

   This describes how sys.path is formed on OS/2+EMX.  It describes the 

   functionality, not the implementation (ie, the order in which these 

   are actually fetched is different)

   * Python always adds an empty entry at the start, which corresponds

     to the current directory.

   * If the PYTHONPATH env. var. exists, its entries are added next.

   * We attempt to locate the "Python Home" - if the PYTHONHOME env var

     is set, we believe it.  Otherwise, we use the path of our host .EXE's

     to try and locate our "landmark" (lib\\os.py) and deduce our home.

     - If we DO have a Python Home: The relevant sub-directories (Lib, 

       plat-win, lib-tk, etc) are based on the Python Home

     - If we DO NOT have a Python Home, the core Python Path is

       loaded from the registry.  This is the main PythonPath key, 

       and both HKLM and HKCU are combined to form the path)

   * Iff - we can not locate the Python Home, and have not had a PYTHONPATH

     specified (ie, we have _nothing_ we can assume is a good path), a

     default path with relative entries is used (eg. .\Lib;.\plat-win, etc)

  The end result of all this is:

  * When running python.exe, or any other .exe in the main Python directory

    (either an installed version, or directly from the PCbuild directory),

    the core path is deduced.

  * When Python is hosted in another exe (different directory, embedded via 

    COM, etc), the Python Home will not be deduced, so the core path from

    the registry is used.  Other "application paths "in the registry are 

    always read.

  * If Python can't find its home and there is no registry (eg, frozen

    exe, some very strange installation setup) you get a path with

    some default, but relative, paths.

   ---------------------------------------------------------------- */

#include "Python.h"

#include "osdefs.h"

#ifndef PYOS_OS2

#error This file only compilable on OS/2

#endif

#define INCL_DOS

#include <os2.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <string.h>

#if HAVE_UNISTD_H

#include <unistd.h>

#endif /* HAVE_UNISTD_H */

/* Search in some common locations for the associated Python libraries.

 *

 * Py_GetPath() tries to return a sensible Python module search path.

 *

 * The approach is an adaptation for Windows of the strategy used in

 * ../Modules/getpath.c; it uses the Windows Registry as one of its

 * information sources.

 */

#ifndef LANDMARK

#if defined(PYCC_GCC)

#define LANDMARK "lib/os.py"

#else

#define LANDMARK "lib\\os.py"

#endif

#endif

static char prefix[MAXPATHLEN+1];

static char progpath[MAXPATHLEN+1];

static char *module_search_path = NULL;

static int

is_sep(char ch)	/* determine if "ch" is a separator character */

{

#ifdef ALTSEP

	return ch == SEP || ch == ALTSEP;

#else

	return ch == SEP;

#endif

}

/* assumes 'dir' null terminated in bounds.

 * Never writes beyond existing terminator.

 */

static void

reduce(char *dir)

{

	size_t i = strlen(dir);

	while (i > 0 && !is_sep(dir[i]))

		--i;

	dir[i] = '\0';

}

static int

exists(char *filename)

{

	struct stat buf;

	return stat(filename, &buf) == 0;

}

/* Is module  (check for .pyc/.pyo too)

 * Assumes 'filename' MAXPATHLEN+1 bytes long - 

 * may extend 'filename' by one character.

 */

static int

ismodule(char *filename)

{

	if (exists(filename))

		return 1;

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

	if (strlen(filename) < MAXPATHLEN) {

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

		if (exists(filename))

			return 1;

	}

	return 0;

}

/* 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

join(char *buffer, char *stuff)

{

	size_t n, k;

	if (is_sep(stuff[0]))

		n = 0;

	else {

		n = strlen(buffer);

		if (n > 0 && !is_sep(buffer[n-1]) && n < MAXPATHLEN)

			buffer[n++] = SEP;

	}

	if (n > MAXPATHLEN)

		Py_FatalError("buffer overflow in getpathp.c's joinpath()");

	k = strlen(stuff);

	if (n + k > MAXPATHLEN)

		k = MAXPATHLEN - n;

	strncpy(buffer+n, stuff, k);

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

}

/* gotlandmark only called by search_for_prefix, which ensures

 * 'prefix' is null terminated in bounds.  join() ensures

 * 'landmark' can not overflow prefix if too long.

 */

static int

gotlandmark(char *landmark)

{

	int n, ok;

	n = strlen(prefix);

	join(prefix, landmark);

	ok = ismodule(prefix);

	prefix[n] = '\0';

	return ok;

}

/* assumes argv0_path is MAXPATHLEN+1 bytes long, already \0 term'd. 

 * assumption provided by only caller, calculate_path()

 */

static int

search_for_prefix(char *argv0_path, char *landmark)

{

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

	strcpy(prefix, argv0_path);

	do {

		if (gotlandmark(landmark))

			return 1;

		reduce(prefix);

	} while (prefix[0]);

	return 0;

}

static void

get_progpath(void)

{

	extern char *Py_GetProgramName(void);

	char *path = getenv("PATH");

	char *prog = Py_GetProgramName();

	PPIB pib;

	if ((DosGetInfoBlocks(NULL, &pib) == 0) &&

	    (DosQueryModuleName(pib->pib_hmte, sizeof(progpath), progpath) == 0))

		return;

	if (prog == NULL || *prog == '\0')

		prog = "python";

	/* 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.

	 */

#ifdef ALTSEP

	if (strchr(prog, SEP) || strchr(prog, ALTSEP))

#else

	if (strchr(prog, SEP))

#endif

		strncpy(progpath, prog, MAXPATHLEN);

	else if (path) {

		while (1) {

			char *delim = strchr(path, DELIM);

			if (delim) {

				size_t len = delim - path;

				/* ensure we can't overwrite buffer */

#if !defined(PYCC_GCC)

				len = min(MAXPATHLEN,len);

#else

				len = MAXPATHLEN < len ? MAXPATHLEN : len;

#endif

				strncpy(progpath, path, len);

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

			}

			else

				strncpy(progpath, path, MAXPATHLEN);

			/* join() is safe for MAXPATHLEN+1 size buffer */

			join(progpath, prog);

			if (exists(progpath))

				break;

			if (!delim) {

				progpath[0] = '\0';

				break;

			}

			path = delim + 1;

		}

	}

	else

		progpath[0] = '\0';

}

static void

calculate_path(void)

{

	char argv0_path[MAXPATHLEN+1];

	char *buf;

	size_t bufsz;

	char *pythonhome = Py_GetPythonHome();

	char *envpath = getenv("PYTHONPATH");

	char zip_path[MAXPATHLEN+1];

	size_t len;

	get_progpath();

	/* progpath guaranteed \0 terminated in MAXPATH+1 bytes. */

	strcpy(argv0_path, progpath);

	reduce(argv0_path);

	if (pythonhome == NULL || *pythonhome == '\0') {

		if (search_for_prefix(argv0_path, LANDMARK))

			pythonhome = prefix;

		else

			pythonhome = NULL;

	}

	else

		strncpy(prefix, pythonhome, MAXPATHLEN);

	if (envpath && *envpath == '\0')

		envpath = NULL;

	/* Calculate zip archive path */

	strncpy(zip_path, progpath, MAXPATHLEN);

	zip_path[MAXPATHLEN] = '\0';

	len = strlen(zip_path);

	if (len > 4) {

		zip_path[len-3] = 'z';  /* change ending to "zip" */

		zip_path[len-2] = 'i';

		zip_path[len-1] = 'p';

	}

	else {

		zip_path[0] = 0;

	}

	/* We need to construct a path from the following parts.

	 * (1) the PYTHONPATH environment variable, if set;

	 * (2) the zip archive file path;

	 * (3) the PYTHONPATH config macro, with the leading "."

	 *     of each component replaced with pythonhome, if set;

	 * (4) the directory containing the executable (argv0_path).

	 * The length calculation calculates #3 first.

	 */

	/* Calculate size of return buffer */

	if (pythonhome != NULL) {

		char *p;

		bufsz = 1;	

		for (p = PYTHONPATH; *p; p++) {

			if (*p == DELIM)

				bufsz++; /* number of DELIM plus one */

		}

		bufsz *= strlen(pythonhome);

	}

	else

		bufsz = 0;

	bufsz += strlen(PYTHONPATH) + 1;

	bufsz += strlen(argv0_path) + 1;

	bufsz += strlen(zip_path) + 1;

	if (envpath != NULL)

		bufsz += strlen(envpath) + 1;

	module_search_path = buf = malloc(bufsz);

	if (buf == NULL) {

		/* We can't exit, so print a warning and limp along */

		fprintf(stderr, "Can't malloc dynamic PYTHONPATH.\n");

		if (envpath) {

			fprintf(stderr, "Using environment $PYTHONPATH.\n");

			module_search_path = envpath;

		}

		else {

			fprintf(stderr, "Using default static path.\n");

			module_search_path = PYTHONPATH;

		}

		return;

	}

	if (envpath) {

		strcpy(buf, envpath);

		buf = strchr(buf, '\0');

		*buf++ = DELIM;

	}

	if (zip_path[0]) {

		strcpy(buf, zip_path);

		buf = strchr(buf, '\0');

		*buf++ = DELIM;

	}

	if (pythonhome == NULL) {

		strcpy(buf, PYTHONPATH);

		buf = strchr(buf, '\0');

	}

	else {

		char *p = PYTHONPATH;

		char *q;

		size_t n;

		for (;;) {

			q = strchr(p, DELIM);

			if (q == NULL)

				n = strlen(p);

			else

				n = q-p;

			if (p[0] == '.' && is_sep(p[1])) {

				strcpy(buf, pythonhome);

				buf = strchr(buf, '\0');

				p++;

				n--;

			}

			strncpy(buf, p, n);

			buf += n;

			if (q == NULL)

				break;

			*buf++ = DELIM;

			p = q+1;

		}

	}

	if (argv0_path) {

		*buf++ = DELIM;

		strcpy(buf, argv0_path);

		buf = strchr(buf, '\0');

	}

	*buf = '\0';

}

/* External interface */

char *

Py_GetPath(void)

{

	if (!module_search_path)

		calculate_path();

	return module_search_path;

}

char *

Py_GetPrefix(void)

{

	if (!module_search_path)

		calculate_path();

	return prefix;

}

char *

Py_GetExecPrefix(void)

{

	return Py_GetPrefix();

}

char *

Py_GetProgramFullPath(void)

{

	if (!module_search_path)

		calculate_path();

	return progpath;

}