Python/import.c

/* Module definition and import implementation */

#include "Python.h"

#include "node.h"
#include "token.h"
#include "errcode.h"
#include "marshal.h"
#include "compile.h"
#include "eval.h"
#include "osdefs.h"
#include "importdl.h"
#ifdef macintosh
#include "macglue.h"
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

extern time_t PyOS_GetLastModificationTime(char *, FILE *);
						/* In getmtime.c */

/* Magic word to reject .pyc files generated by other Python versions */
/* Change for each incompatible change */
/* The value of CR and LF is incorporated so if you ever read or write
   a .pyc file in text mode the magic number will be wrong; also, the
   Apple MPW compiler swaps their values, botching string constants */
/* XXX Perhaps the magic number should be frozen and a version field
   added to the .pyc file header? */
/* New way to come up with the magic number: (YEAR-1995), MONTH, DAY */
#define MAGIC (60717 | ((long)'\r'<<16) | ((long)'\n'<<24))

/* Magic word as global; note that _PyImport_Init() can change the
   value of this global to accommodate for alterations of how the
   compiler works which are enabled by command line switches. */
static long pyc_magic = MAGIC;

/* See _PyImport_FixupExtension() below */
static PyObject *extensions = NULL;

/* This table is defined in config.c: */
extern struct _inittab _PyImport_Inittab[];

struct _inittab *PyImport_Inittab = _PyImport_Inittab;

/* these tables define the module suffixes that Python recognizes */
struct filedescr * _PyImport_Filetab = NULL;

#ifdef RISCOS
static const struct filedescr _PyImport_StandardFiletab[] = {
	{"/py", "r", PY_SOURCE},
	{"/pyc", "rb", PY_COMPILED},
	{0, 0}
};
#else
static const struct filedescr _PyImport_StandardFiletab[] = {
	{".py", "r", PY_SOURCE},
#ifdef MS_WIN32
	{".pyw", "r", PY_SOURCE},
#endif	
	{".pyc", "rb", PY_COMPILED},
	{0, 0}
};
#endif

/* Initialize things */

void
_PyImport_Init(void)
{
	const struct filedescr *scan;
	struct filedescr *filetab;
	int countD = 0;
	int countS = 0;

	/* prepare _PyImport_Filetab: copy entries from
	   _PyImport_DynLoadFiletab and _PyImport_StandardFiletab.
	 */
	for (scan = _PyImport_DynLoadFiletab; scan->suffix != NULL; ++scan)
		++countD;
	for (scan = _PyImport_StandardFiletab; scan->suffix != NULL; ++scan)
		++countS;
	filetab = PyMem_NEW(struct filedescr, countD + countS + 1);
	memcpy(filetab, _PyImport_DynLoadFiletab,
	       countD * sizeof(struct filedescr));
	memcpy(filetab + countD, _PyImport_StandardFiletab,
	       countS * sizeof(struct filedescr));
	filetab[countD + countS].suffix = NULL;

	_PyImport_Filetab = filetab;

	if (Py_OptimizeFlag) {
		/* Replace ".pyc" with ".pyo" in _PyImport_Filetab */
		for (; filetab->suffix != NULL; filetab++) {
#ifndef RISCOS
			if (strcmp(filetab->suffix, ".pyc") == 0)
				filetab->suffix = ".pyo";
#else
			if (strcmp(filetab->suffix, "/pyc") == 0)
				filetab->suffix = "/pyo";
#endif
		}
	}

	if (Py_UnicodeFlag) {
		/* Fix the pyc_magic so that byte compiled code created
		   using the all-Unicode method doesn't interfere with
		   code created in normal operation mode. */
		pyc_magic = MAGIC + 1;
	}
}

void
_PyImport_Fini(void)
{
	Py_XDECREF(extensions);
	extensions = NULL;
	PyMem_DEL(_PyImport_Filetab);
	_PyImport_Filetab = NULL;
}


/* Locking primitives to prevent parallel imports of the same module
   in different threads to return with a partially loaded module.
   These calls are serialized by the global interpreter lock. */

#ifdef WITH_THREAD

#include "pythread.h"

static PyThread_type_lock import_lock = 0;
static long import_lock_thread = -1;
static int import_lock_level = 0;

static void
lock_import(void)
{
	long me = PyThread_get_thread_ident();
	if (me == -1)
		return; /* Too bad */
	if (import_lock == NULL)
		import_lock = PyThread_allocate_lock();
	if (import_lock_thread == me) {
		import_lock_level++;
		return;
	}
	if (import_lock_thread != -1 || !PyThread_acquire_lock(import_lock, 0)) {
		PyThreadState *tstate = PyEval_SaveThread();
		PyThread_acquire_lock(import_lock, 1);
		PyEval_RestoreThread(tstate);
	}
	import_lock_thread = me;
	import_lock_level = 1;
}

static void
unlock_import(void)
{
	long me = PyThread_get_thread_ident();
	if (me == -1)
		return; /* Too bad */
	if (import_lock_thread != me)
		Py_FatalError("unlock_import: not holding the import lock");
	import_lock_level--;
	if (import_lock_level == 0) {
		import_lock_thread = -1;
		PyThread_release_lock(import_lock);
	}
}

#else

#define lock_import()
#define unlock_import()

#endif

static PyObject *
imp_lock_held(PyObject *self, PyObject *args)
{
	if (!PyArg_ParseTuple(args, ":lock_held"))
		return NULL;
#ifdef WITH_THREAD
	return PyInt_FromLong(import_lock_thread != -1);
#else
	return PyInt_FromLong(0);
#endif
}

/* Helper for sys */

PyObject *
PyImport_GetModuleDict(void)
{
	PyInterpreterState *interp = PyThreadState_Get()->interp;
	if (interp->modules == NULL)
		Py_FatalError("PyImport_GetModuleDict: no module dictionary!");
	return interp->modules;
}


/* List of names to clear in sys */
static char* sys_deletes[] = {
	"path", "argv", "ps1", "ps2", "exitfunc",
	"exc_type", "exc_value", "exc_traceback",
	"last_type", "last_value", "last_traceback",
	NULL
};

static char* sys_files[] = {
	"stdin", "__stdin__",
	"stdout", "__stdout__",
	"stderr", "__stderr__",
	NULL
};


/* Un-initialize things, as good as we can */

void
PyImport_Cleanup(void)
{
	int pos, ndone;
	char *name;
	PyObject *key, *value, *dict;
	PyInterpreterState *interp = PyThreadState_Get()->interp;
	PyObject *modules = interp->modules;

	if (modules == NULL)
		return; /* Already done */

	/* Delete some special variables first.  These are common
	   places where user values hide and people complain when their
	   destructors fail.  Since the modules containing them are
	   deleted *last* of all, they would come too late in the normal
	   destruction order.  Sigh. */

	value = PyDict_GetItemString(modules, "__builtin__");
	if (value != NULL && PyModule_Check(value)) {
		dict = PyModule_GetDict(value);
		if (Py_VerboseFlag)
			PySys_WriteStderr("# clear __builtin__._\n");
		PyDict_SetItemString(dict, "_", Py_None);
	}
	value = PyDict_GetItemString(modules, "sys");
	if (value != NULL && PyModule_Check(value)) {
		char **p;
		PyObject *v;
		dict = PyModule_GetDict(value);
		for (p = sys_deletes; *p != NULL; p++) {
			if (Py_VerboseFlag)
				PySys_WriteStderr("# clear sys.%s\n", *p);
			PyDict_SetItemString(dict, *p, Py_None);
		}
		for (p = sys_files; *p != NULL; p+=2) {
			if (Py_VerboseFlag)
				PySys_WriteStderr("# restore sys.%s\n", *p);
			v = PyDict_GetItemString(dict, *(p+1));
			if (v == NULL)
				v = Py_None;
			PyDict_SetItemString(dict, *p, v);
		}
	}

	/* First, delete __main__ */
	value = PyDict_GetItemString(modules, "__main__");
	if (value != NULL && PyModule_Check(value)) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# cleanup __main__\n");
		_PyModule_Clear(value);
		PyDict_SetItemString(modules, "__main__", Py_None);
	}

	/* The special treatment of __builtin__ here is because even
	   when it's not referenced as a module, its dictionary is
	   referenced by almost every module's __builtins__.  Since
	   deleting a module clears its dictionary (even if there are
	   references left to it), we need to delete the __builtin__
	   module last.  Likewise, we don't delete sys until the very
	   end because it is implicitly referenced (e.g. by print).

	   Also note that we 'delete' modules by replacing their entry
	   in the modules dict with None, rather than really deleting
	   them; this avoids a rehash of the modules dictionary and
	   also marks them as "non existent" so they won't be
	   re-imported. */

	/* Next, repeatedly delete modules with a reference count of
	   one (skipping __builtin__ and sys) and delete them */
	do {
		ndone = 0;
		pos = 0;
		while (PyDict_Next(modules, &pos, &key, &value)) {
			if (value->ob_refcnt != 1)
				continue;
			if (PyString_Check(key) && PyModule_Check(value)) {
				name = PyString_AS_STRING(key);
				if (strcmp(name, "__builtin__") == 0)
					continue;
				if (strcmp(name, "sys") == 0)
					continue;
				if (Py_VerboseFlag)
					PySys_WriteStderr(
						"# cleanup[1] %s\n", name);
				_PyModule_Clear(value);
				PyDict_SetItem(modules, key, Py_None);
				ndone++;
			}
		}
	} while (ndone > 0);

	/* Next, delete all modules (still skipping __builtin__ and sys) */
	pos = 0;
	while (PyDict_Next(modules, &pos, &key, &value)) {
		if (PyString_Check(key) && PyModule_Check(value)) {
			name = PyString_AS_STRING(key);
			if (strcmp(name, "__builtin__") == 0)
				continue;
			if (strcmp(name, "sys") == 0)
				continue;
			if (Py_VerboseFlag)
				PySys_WriteStderr("# cleanup[2] %s\n", name);
			_PyModule_Clear(value);
			PyDict_SetItem(modules, key, Py_None);
		}
	}

	/* Next, delete sys and __builtin__ (in that order) */
	value = PyDict_GetItemString(modules, "sys");
	if (value != NULL && PyModule_Check(value)) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# cleanup sys\n");
		_PyModule_Clear(value);
		PyDict_SetItemString(modules, "sys", Py_None);
	}
	value = PyDict_GetItemString(modules, "__builtin__");
	if (value != NULL && PyModule_Check(value)) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# cleanup __builtin__\n");
		_PyModule_Clear(value);
		PyDict_SetItemString(modules, "__builtin__", Py_None);
	}

	/* Finally, clear and delete the modules directory */
	PyDict_Clear(modules);
	interp->modules = NULL;
	Py_DECREF(modules);
}


/* Helper for pythonrun.c -- return magic number */

long
PyImport_GetMagicNumber(void)
{
	return pyc_magic;
}


/* Magic for extension modules (built-in as well as dynamically
   loaded).  To prevent initializing an extension module more than
   once, we keep a static dictionary 'extensions' keyed by module name
   (for built-in modules) or by filename (for dynamically loaded
   modules), containing these modules.  A copy of the module's
   dictionary is stored by calling _PyImport_FixupExtension()
   immediately after the module initialization function succeeds.  A
   copy can be retrieved from there by calling
   _PyImport_FindExtension(). */

PyObject *
_PyImport_FixupExtension(char *name, char *filename)
{
	PyObject *modules, *mod, *dict, *copy;
	if (extensions == NULL) {
		extensions = PyDict_New();
		if (extensions == NULL)
			return NULL;
	}
	modules = PyImport_GetModuleDict();
	mod = PyDict_GetItemString(modules, name);
	if (mod == NULL || !PyModule_Check(mod)) {
		PyErr_Format(PyExc_SystemError,
		  "_PyImport_FixupExtension: module %.200s not loaded", name);
		return NULL;
	}
	dict = PyModule_GetDict(mod);
	if (dict == NULL)
		return NULL;
	copy = PyDict_Copy(dict);
	if (copy == NULL)
		return NULL;
	PyDict_SetItemString(extensions, filename, copy);
	Py_DECREF(copy);
	return copy;
}

PyObject *
_PyImport_FindExtension(char *name, char *filename)
{
	PyObject *dict, *mod, *mdict;
	if (extensions == NULL)
		return NULL;
	dict = PyDict_GetItemString(extensions, filename);
	if (dict == NULL)
		return NULL;
	mod = PyImport_AddModule(name);
	if (mod == NULL)
		return NULL;
	mdict = PyModule_GetDict(mod);
	if (mdict == NULL)
		return NULL;
	if (PyDict_Update(mdict, dict))
		return NULL;
	if (Py_VerboseFlag)
		PySys_WriteStderr("import %s # previously loaded (%s)\n",
			name, filename);
	return mod;
}


/* Get the module object corresponding to a module name.
   First check the modules dictionary if there's one there,
   if not, create a new one and insert in in the modules dictionary.
   Because the former action is most common, THIS DOES NOT RETURN A
   'NEW' REFERENCE! */

PyObject *
PyImport_AddModule(char *name)
{
	PyObject *modules = PyImport_GetModuleDict();
	PyObject *m;

	if ((m = PyDict_GetItemString(modules, name)) != NULL &&
	    PyModule_Check(m))
		return m;
	m = PyModule_New(name);
	if (m == NULL)
		return NULL;
	if (PyDict_SetItemString(modules, name, m) != 0) {
		Py_DECREF(m);
		return NULL;
	}
	Py_DECREF(m); /* Yes, it still exists, in modules! */

	return m;
}


/* Execute a code object in a module and return the module object
   WITH INCREMENTED REFERENCE COUNT */

PyObject *
PyImport_ExecCodeModule(char *name, PyObject *co)
{
	return PyImport_ExecCodeModuleEx(name, co, (char *)NULL);
}

PyObject *
PyImport_ExecCodeModuleEx(char *name, PyObject *co, char *pathname)
{
	PyObject *modules = PyImport_GetModuleDict();
	PyObject *m, *d, *v;

	m = PyImport_AddModule(name);
	if (m == NULL)
		return NULL;
	d = PyModule_GetDict(m);
	if (PyDict_GetItemString(d, "__builtins__") == NULL) {
		if (PyDict_SetItemString(d, "__builtins__",
					 PyEval_GetBuiltins()) != 0)
			return NULL;
	}
	/* Remember the filename as the __file__ attribute */
	v = NULL;
	if (pathname != NULL) {
		v = PyString_FromString(pathname);
		if (v == NULL)
			PyErr_Clear();
	}
	if (v == NULL) {
		v = ((PyCodeObject *)co)->co_filename;
		Py_INCREF(v);
	}
	if (PyDict_SetItemString(d, "__file__", v) != 0)
		PyErr_Clear(); /* Not important enough to report */
	Py_DECREF(v);

	v = PyEval_EvalCode((PyCodeObject *)co, d, d);
	if (v == NULL)
		return NULL;
	Py_DECREF(v);

	if ((m = PyDict_GetItemString(modules, name)) == NULL) {
		PyErr_Format(PyExc_ImportError,
			     "Loaded module %.200s not found in sys.modules",
			     name);
		return NULL;
	}

	Py_INCREF(m);

	return m;
}


/* Given a pathname for a Python source file, fill a buffer with the
   pathname for the corresponding compiled file.  Return the pathname
   for the compiled file, or NULL if there's no space in the buffer.
   Doesn't set an exception. */

static char *
make_compiled_pathname(char *pathname, char *buf, size_t buflen)
{
	size_t len = strlen(pathname);
	if (len+2 > buflen)
		return NULL;

#ifdef MS_WIN32
	/* Treat .pyw as if it were .py.  The case of ".pyw" must match
	   that used in _PyImport_StandardFiletab. */
	if (len >= 4 && strcmp(&pathname[len-4], ".pyw") == 0)
		--len;	/* pretend 'w' isn't there */
#endif
	memcpy(buf, pathname, len);
	buf[len] = Py_OptimizeFlag ? 'o' : 'c';
	buf[len+1] = '\0';

	return buf;
}


/* Given a pathname for a Python source file, its time of last
   modification, and a pathname for a compiled file, check whether the
   compiled file represents the same version of the source.  If so,
   return a FILE pointer for the compiled file, positioned just after
   the header; if not, return NULL.
   Doesn't set an exception. */

static FILE *
check_compiled_module(char *pathname, long mtime, char *cpathname)
{
	FILE *fp;
	long magic;
	long pyc_mtime;

	fp = fopen(cpathname, "rb");
	if (fp == NULL)
		return NULL;
	magic = PyMarshal_ReadLongFromFile(fp);
	if (magic != pyc_magic) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# %s has bad magic\n", cpathname);
		fclose(fp);
		return NULL;
	}
	pyc_mtime = PyMarshal_ReadLongFromFile(fp);
	if (pyc_mtime != mtime) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# %s has bad mtime\n", cpathname);
		fclose(fp);
		return NULL;
	}
	if (Py_VerboseFlag)
		PySys_WriteStderr("# %s matches %s\n", cpathname, pathname);
	return fp;
}


/* Read a code object from a file and check it for validity */

static PyCodeObject *
read_compiled_module(char *cpathname, FILE *fp)
{
	PyObject *co;

	co = PyMarshal_ReadLastObjectFromFile(fp);
	/* Ugly: rd_object() may return NULL with or without error */
	if (co == NULL || !PyCode_Check(co)) {
		if (!PyErr_Occurred())
			PyErr_Format(PyExc_ImportError,
			    "Non-code object in %.200s", cpathname);
		Py_XDECREF(co);
		return NULL;
	}
	return (PyCodeObject *)co;
}


/* Load a module from a compiled file, execute it, and return its
   module object WITH INCREMENTED REFERENCE COUNT */

static PyObject *
load_compiled_module(char *name, char *cpathname, FILE *fp)
{
	long magic;
	PyCodeObject *co;
	PyObject *m;

	magic = PyMarshal_ReadLongFromFile(fp);
	if (magic != pyc_magic) {
		PyErr_Format(PyExc_ImportError,
			     "Bad magic number in %.200s", cpathname);
		return NULL;
	}
	(void) PyMarshal_ReadLongFromFile(fp);
	co = read_compiled_module(cpathname, fp);
	if (co == NULL)
		return NULL;
	if (Py_VerboseFlag)
		PySys_WriteStderr("import %s # precompiled from %s\n",
			name, cpathname);
	m = PyImport_ExecCodeModuleEx(name, (PyObject *)co, cpathname);
	Py_DECREF(co);

	return m;
}

/* Parse a source file and return the corresponding code object */

static PyCodeObject *
parse_source_module(char *pathname, FILE *fp)
{
	PyCodeObject *co;
	node *n;

	n = PyParser_SimpleParseFile(fp, pathname, Py_file_input);
	if (n == NULL)
		return NULL;
	co = PyNode_Compile(n, pathname);
	PyNode_Free(n);

	return co;
}


/* Helper to open a bytecode file for writing in exclusive mode */

static FILE *
open_exclusive(char *filename)
{
#if defined(O_EXCL)&&defined(O_CREAT)&&defined(O_WRONLY)&&defined(O_TRUNC)
	/* Use O_EXCL to avoid a race condition when another process tries to
	   write the same file.  When that happens, our open() call fails,
	   which is just fine (since it's only a cache).
	   XXX If the file exists and is writable but the directory is not
	   writable, the file will never be written.  Oh well.
	*/
	int fd;
	(void) unlink(filename);
	fd = open(filename, O_EXCL|O_CREAT|O_WRONLY|O_TRUNC
#ifdef O_BINARY
				|O_BINARY   /* necessary for Windows */
#endif

			, 0666);
	if (fd < 0)
		return NULL;
	return fdopen(fd, "wb");
#else
	/* Best we can do -- on Windows this can't happen anyway */
	return fopen(filename, "wb");
#endif
}


/* Write a compiled module to a file, placing the time of last
   modification of its source into the header.
   Errors are ignored, if a write error occurs an attempt is made to
   remove the file. */

static void
write_compiled_module(PyCodeObject *co, char *cpathname, long mtime)
{
	FILE *fp;

	fp = open_exclusive(cpathname);
	if (fp == NULL) {
		if (Py_VerboseFlag)
			PySys_WriteStderr(
				"# can't create %s\n", cpathname);
		return;
	}
	PyMarshal_WriteLongToFile(pyc_magic, fp);
	/* First write a 0 for mtime */
	PyMarshal_WriteLongToFile(0L, fp);
	PyMarshal_WriteObjectToFile((PyObject *)co, fp);
	if (ferror(fp)) {
		if (Py_VerboseFlag)
			PySys_WriteStderr("# can't write %s\n", cpathname);
		/* Don't keep partial file */
		fclose(fp);
		(void) unlink(cpathname);
		return;
	}
	/* Now write the true mtime */
	fseek(fp, 4L, 0);
	PyMarshal_WriteLongToFile(mtime, fp);
	fflush(fp);
	fclose(fp);
	if (Py_VerboseFlag)
		PySys_WriteStderr("# wrote %s\n", cpathname);
#ifdef macintosh
	PyMac_setfiletype(cpathname, 'Pyth', 'PYC ');
#endif
}


/* Load a source module from a given file and return its module
   object WITH INCREMENTED REFERENCE COUNT.  If there's a matching
   byte-compiled file, use that instead. */

static PyObject *
load_source_module(char *name, char *pathname, FILE *fp)
{
	time_t mtime;
	FILE *fpc;
	char buf[MAXPATHLEN+1];
	char *cpathname;
	PyCodeObject *co;
	PyObject *m;

	mtime = PyOS_GetLastModificationTime(pathname, fp);
	if (mtime == (time_t)(-1))
		return NULL;
#if SIZEOF_TIME_T > 4
	/* Python's .pyc timestamp handling presumes that the timestamp fits
	   in 4 bytes. This will be fine until sometime in the year 2038,
	   when a 4-byte signed time_t will overflow.
	 */
	if (mtime >> 32) {
		PyErr_SetString(PyExc_OverflowError,
			"modification time overflows a 4 byte field");
		return NULL;
	}
#endif
	cpathname = make_compiled_pathname(pathname, buf, 
					   (size_t)MAXPATHLEN + 1);
	if (cpathname != NULL &&
	    (fpc = check_compiled_module(pathname, mtime, cpathname))) {
		co = read_compiled_module(cpathname, fpc);
		fclose(fpc);
		if (co == NULL)
			return NULL;
		if (Py_VerboseFlag)
			PySys_WriteStderr("import %s # precompiled from %s\n",
				name, cpathname);
		pathname = cpathname;
	}
	else {
		co = parse_source_module(pathname, fp);
		if (co == NULL)
			return NULL;
		if (Py_VerboseFlag)
			PySys_WriteStderr("import %s # from %s\n",
				name, pathname);
		write_compiled_module(co, cpathname, mtime);
	}
	m = PyImport_ExecCodeModuleEx(name, (PyObject *)co, pathname);
	Py_DECREF(co);

	return m;
}


/* Forward */
static PyObject *load_module(char *, FILE *, char *, int);
static struct filedescr *find_module(char *, PyObject *,
				     char *, size_t, FILE **);
static struct _frozen *find_frozen(char *name);

/* Load a package and return its module object WITH INCREMENTED
   REFERENCE COUNT */

static PyObject *
load_package(char *name, char *pathname)
{
	PyObject *m, *d, *file, *path;
	int err;
	char buf[MAXPATHLEN+1];
	FILE *fp = NULL;
	struct filedescr *fdp;

	m = PyImport_AddModule(name);
	if (m == NULL)
		return NULL;
	if (Py_VerboseFlag)
		PySys_WriteStderr("import %s # directory %s\n",
			name, pathname);
	d = PyModule_GetDict(m);
	file = PyString_FromString(pathname);
	if (file == NULL)
		return NULL;
	path = Py_BuildValue("[O]", file);
	if (path == NULL) {
		Py_DECREF(file);
		return NULL;
	}
	err = PyDict_SetItemString(d, "__file__", file);
	if (err == 0)
		err = PyDict_SetItemString(d, "__path__", path);
	if (err != 0) {
		m = NULL;
		goto cleanup;
	}
	buf[0] = '\0';
	fdp = find_module("__init__", path, buf, sizeof(buf), &fp);
	if (fdp == NULL) {
		if (PyErr_ExceptionMatches(PyExc_ImportError)) {
			PyErr_Clear();
		}
		else
			m = NULL;
		goto cleanup;
	}
	m = load_module(name, fp, buf, fdp->type);
	if (fp != NULL)
		fclose(fp);
  cleanup:
	Py_XDECREF(path);
	Py_XDECREF(file);
	return m;
}


/* Helper to test for built-in module */

static int
is_builtin(char *name)
{
	int i;
	for (i = 0; PyImport_Inittab[i].name != NULL; i++) {
		if (strcmp(name, PyImport_Inittab[i].name) == 0) {
			if (PyImport_Inittab[i].initfunc == NULL)
				return -1;
			else
				return 1;
		}
	}
	return 0;
}


/* Search the path (default sys.path) for a module.  Return the
   corresponding filedescr struct, and (via return arguments) the
   pathname and an open file.  Return NULL if the module is not found. */

#ifdef MS_COREDLL
extern FILE *PyWin_FindRegisteredModule(const char *, struct filedescr **,
					char *, int);
#endif

static int case_ok(char *, int, int, char *);
static int find_init_module(char *); /* Forward */

static struct filedescr *
find_module(char *realname, PyObject *path, char *buf, size_t buflen,
	    FILE **p_fp)
{
	int i, npath;
	size_t len, namelen;
	struct filedescr *fdp = NULL;
	FILE *fp = NULL;
#ifndef RISCOS
	struct stat statbuf;
#endif
	static struct filedescr fd_frozen = {"", "", PY_FROZEN};
	static struct filedescr fd_builtin = {"", "", C_BUILTIN};
	static struct filedescr fd_package = {"", "", PKG_DIRECTORY};
	char name[MAXPATHLEN+1];

	if (strlen(realname) > MAXPATHLEN) {
		PyErr_SetString(PyExc_OverflowError,
				"module name is too long");
		return NULL;
	}
	strcpy(name, realname);

	if (path != NULL && PyString_Check(path)) {
		/* The only type of submodule allowed inside a "frozen"
		   package are other frozen modules or packages. */
		if (PyString_Size(path) + 1 + strlen(name) >= (size_t)buflen) {
			PyErr_SetString(PyExc_ImportError,
					"full frozen module name too long");
			return NULL;
		}
		strcpy(buf, PyString_AsString(path));
		strcat(buf, ".");
		strcat(buf, name);
		strcpy(name, buf);
		if (find_frozen(name) != NULL) {
			strcpy(buf, name);
			return &fd_frozen;
		}
		PyErr_Format(PyExc_ImportError,
			     "No frozen submodule named %.200s", name);
		return NULL;
	}
	if (path == NULL) {
		if (is_builtin(name)) {
			strcpy(buf, name);
			return &fd_builtin;
		}
		if ((find_frozen(name)) != NULL) {
			strcpy(buf, name);
			return &fd_frozen;
		}

#ifdef MS_COREDLL
		fp = PyWin_FindRegisteredModule(name, &fdp, buf, buflen);
		if (fp != NULL) {
			*p_fp = fp;
			return fdp;
		}
#endif
		path = PySys_GetObject("path");
	}
	if (path == NULL || !PyList_Check(path)) {
		PyErr_SetString(PyExc_ImportError,
				"sys.path must be a list of directory names");
		return NULL;
	}
	npath = PyList_Size(path);
	namelen = strlen(name);
	for (i = 0; i < npath; i++) {
		PyObject *v = PyList_GetItem(path, i);
		if (!PyString_Check(v))
			continue;
		len = PyString_Size(v);
		if (len + 2 + namelen + MAXSUFFIXSIZE >= buflen)
			continue; /* Too long */
		strcpy(buf, PyString_AsString(v));
		if (strlen(buf) != len)
			continue; /* v contains '\0' */
#ifdef macintosh
#ifdef INTERN_STRINGS
		/*
		** Speedup: each sys.path item is interned, and
		** FindResourceModule remembers which items refer to
		** folders (so we don't have to bother trying to look
		** into them for resources).
		*/
		PyString_InternInPlace(&PyList_GET_ITEM(path, i));
		v = PyList_GET_ITEM(path, i);
#endif
		if (PyMac_FindResourceModule((PyStringObject *)v, name, buf)) {
			static struct filedescr resfiledescr =
				{"", "", PY_RESOURCE};

			return &resfiledescr;
		}
		if (PyMac_FindCodeResourceModule((PyStringObject *)v, name, buf)) {
			static struct filedescr resfiledescr =
				{"", "", PY_CODERESOURCE};

			return &resfiledescr;
		}
#endif
		if (len > 0 && buf[len-1] != SEP
#ifdef ALTSEP
		    && buf[len-1] != ALTSEP
#endif
		    )
			buf[len++] = SEP;
		strcpy(buf+len, name);
		len += namelen;

		/* Check for package import (buf holds a directory name,
		   and there's an __init__ module in that directory */
#ifdef HAVE_STAT
		if (stat(buf, &statbuf) == 0 &&       /* it exists */
		    S_ISDIR(statbuf.st_mode) &&       /* it's a directory */
		    find_init_module(buf) &&          /* it has __init__.py */
		    case_ok(buf, len, namelen, name)) /* and case matches */
			return &fd_package;
#else
		/* XXX How are you going to test for directories? */
#ifdef RISCOS
		if (isdir(buf) &&
		    find_init_module(buf) &&
		    case_ok(buf, len, namelen, name))
			return &fd_package;
#endif
#endif
#ifdef macintosh
		fdp = PyMac_FindModuleExtension(buf, &len, name);
		if (fdp) {
#else
		for (fdp = _PyImport_Filetab; fdp->suffix != NULL; fdp++) {
			strcpy(buf+len, fdp->suffix);
			if (Py_VerboseFlag > 1)
				PySys_WriteStderr("# trying %s\n", buf);
#endif /* !macintosh */
			fp = fopen(buf, fdp->mode);
			if (fp != NULL) {
				if (case_ok(buf, len, namelen, name))
					break;
				else {	 /* continue search */
					fclose(fp);
					fp = NULL;
				}
			}
		}
		if (fp != NULL)
			break;
	}
	if (fp == NULL) {
		PyErr_Format(PyExc_ImportError,
			     "No module named %.200s", name);
		return NULL;
	}
	*p_fp = fp;
	return fdp;
}

/* case_ok(char* buf, int len, int namelen, char* name)
 * The arguments here are tricky, best shown by example:
 *    /a/b/c/d/e/f/g/h/i/j/k/some_long_module_name.py\0
 *    ^                      ^                   ^    ^
 *    |--------------------- buf ---------------------|
 *    |------------------- len ------------------|
 *                           |------ name -------|
 *                           |----- namelen -----|
 * buf is the full path, but len only counts up to (& exclusive of) the
 * extension.  name is the module name, also exclusive of extension.
 *
 * We've already done a successful stat() or fopen() on buf, so know that
 * there's some match, possibly case-insensitive.
 *
 * case_ok() is to return 1 if there's a case-sensitive match for
 * name, else 0.  case_ok() is also to return 1 if envar PYTHONCASEOK
 * exists.
 *
 * case_ok() is used to implement case-sensitive import semantics even
 * on platforms with case-insensitive filesystems.  It's trivial to implement
 * for case-sensitive filesystems.  It's pretty much a cross-platform
 * nightmare for systems with case-insensitive filesystems.
 */

/* First we may need a pile of platform-specific header files; the sequence
 * of #if's here should match the sequence in the body of case_ok().
 */
#if defined(MS_WIN32) || defined(__CYGWIN__)
#include <windows.h>
#ifdef __CYGWIN__
#include <sys/cygwin.h>
#endif

#elif defined(DJGPP)
#include <dir.h>

#elif defined(macintosh)
#include <TextUtils.h>
#ifdef USE_GUSI1
#include "TFileSpec.h"		/* for Path2FSSpec() */
#endif

#elif defined(__MACH__) && defined(__APPLE__) && defined(HAVE_DIRENT_H)
#include <sys/types.h>
#include <dirent.h>

#elif defined(RISCOS)
#include "oslib/osfscontrol.h"
#endif

static int
case_ok(char *buf, int len, int namelen, char *name)
{
/* Pick a platform-specific implementation; the sequence of #if's here should
 * match the sequence just above.
 */

/* MS_WIN32 || __CYGWIN__ */
#if defined(MS_WIN32) || defined(__CYGWIN__)
	WIN32_FIND_DATA data;
	HANDLE h;
#ifdef __CYGWIN__
	char tempbuf[MAX_PATH];
#endif

	if (Py_GETENV("PYTHONCASEOK") != NULL)
		return 1;

#ifdef __CYGWIN__
	cygwin32_conv_to_win32_path(buf, tempbuf);
	h = FindFirstFile(tempbuf, &data);
#else
	h = FindFirstFile(buf, &data);
#endif
	if (h == INVALID_HANDLE_VALUE) {
		PyErr_Format(PyExc_NameError,
		  "Can't find file for module %.100s\n(filename %.300s)",
		  name, buf);
		return 0;
	}
	FindClose(h);
	return strncmp(data.cFileName, name, namelen) == 0;

/* DJGPP */
#elif defined(DJGPP)
	struct ffblk ffblk;
	int done;

	if (Py_GETENV("PYTHONCASEOK") != NULL)
		return 1;

	done = findfirst(buf, &ffblk, FA_ARCH|FA_RDONLY|FA_HIDDEN|FA_DIREC);
	if (done) {
		PyErr_Format(PyExc_NameError,
		  "Can't find file for module %.100s\n(filename %.300s)",
		  name, buf);
		return 0;
	}
	return strncmp(ffblk.ff_name, name, namelen) == 0;

/* macintosh */
#elif defined(macintosh)
	FSSpec fss;
	OSErr err;

	if (Py_GETENV("PYTHONCASEOK") != NULL)
		return 1;

#ifndef USE_GUSI1
	err = FSMakeFSSpec(0, 0, Pstring(buf), &fss);
#else
	/* GUSI's Path2FSSpec() resolves all possible aliases nicely on
	   the way, which is fine for all directories, but here we need
	   the original name of the alias file (say, Dlg.ppc.slb, not
	   toolboxmodules.ppc.slb). */
	char *colon;
	err = Path2FSSpec(buf, &fss);
	if (err == noErr) {
		colon = strrchr(buf, ':'); /* find filename */
		if (colon != NULL)
			err = FSMakeFSSpec(fss.vRefNum, fss.parID,
					   Pstring(colon+1), &fss);
		else
			err = FSMakeFSSpec(fss.vRefNum, fss.parID,
					   fss.name, &fss);
	}
#endif
	if (err) {
		PyErr_Format(PyExc_NameError,
		     "Can't find file for module %.100s\n(filename %.300s)",
		     name, buf);
		return 0;
	}
	return fss.name[0] >= namelen &&
	       strncmp(name, (char *)fss.name+1, namelen) == 0;

/* new-fangled macintosh (macosx) */
#elif defined(__MACH__) && defined(__APPLE__) && defined(HAVE_DIRENT_H)
	DIR *dirp;
	struct dirent *dp;
	char dirname[MAXPATHLEN + 1];
	const int dirlen = len - namelen - 1; /* don't want trailing SEP */

	if (Py_GETENV("PYTHONCASEOK") != NULL)
		return 1;

	/* Copy the dir component into dirname; substitute "." if empty */
	if (dirlen <= 0) {
		dirname[0] = '.';
		dirname[1] = '\0';
	}
	else {
		assert(dirlen <= MAXPATHLEN);
		memcpy(dirname, buf, dirlen);
		dirname[dirlen] = '\0';
	}
	/* Open the directory and search the entries for an exact match. */
	dirp = opendir(dirname);
	if (dirp) {
		char *nameWithExt = buf + len - namelen;
		while ((dp = readdir(dirp)) != NULL) {
			const int thislen =
#ifdef _DIRENT_HAVE_D_NAMELEN
						dp->d_namlen;
#else
						strlen(dp->d_name);
#endif
			if (thislen >= namelen &&
			    strcmp(dp->d_name, nameWithExt) == 0) {
				(void)closedir(dirp);
				return 1; /* Found */
			}
		}
		(void)closedir(dirp);
	}
	return 0 ; /* Not found */

/* RISC OS */
#elif defined(RISCOS)
	char canon[MAXPATHLEN+1]; /* buffer for the canonical form of the path */
	char buf2[MAXPATHLEN+2];
	char *nameWithExt = buf+len-namelen;
	int canonlen;
	os_error *e;

	if (Py_GETENV("PYTHONCASEOK") != NULL)
		return 1;

	/* workaround:
	   append wildcard, otherwise case of filename wouldn't be touched */
	strcpy(buf2, buf);
	strcat(buf2, "*");

	e = xosfscontrol_canonicalise_path(buf2,canon,0,0,MAXPATHLEN+1,&canonlen);
	canonlen = MAXPATHLEN+1-canonlen;
	if (e || canonlen<=0 || canonlen>(MAXPATHLEN+1) )
		return 0;
	if (strcmp(nameWithExt, canon+canonlen-strlen(nameWithExt))==0)
		return 1; /* match */

	return 0;

/* assuming it's a case-sensitive filesystem, so there's nothing to do! */
#else
	return 1;

#endif
}


#ifdef HAVE_STAT
/* Helper to look for __init__.py or __init__.py[co] in potential package */
static int
find_init_module(char *buf)
{
	const size_t save_len = strlen(buf);
	size_t i = save_len;
	char *pname;  /* pointer to start of __init__ */
	struct stat statbuf;

/*	For calling case_ok(buf, len, namelen, name):
 *	/a/b/c/d/e/f/g/h/i/j/k/some_long_module_name.py\0
 *	^                      ^                   ^    ^
 *	|--------------------- buf ---------------------|
 *	|------------------- len ------------------|
 *	                       |------ name -------|
 *	                       |----- namelen -----|
 */
	if (save_len + 13 >= MAXPATHLEN)
		return 0;
	buf[i++] = SEP;
	pname = buf + i;
	strcpy(pname, "__init__.py");
	if (stat(buf, &statbuf) == 0) {
		if (case_ok(buf,
			    save_len + 9,	/* len("/__init__") */
		            8,   		/* len("__init__") */
		            pname)) {
			buf[save_len] = '\0';
			return 1;
		}
	}
	i += strlen(pname);
	strcpy(buf+i, Py_OptimizeFlag ? "o" : "c");
	if (stat(buf, &statbuf) == 0) {
		if (case_ok(buf,
			    save_len + 9,	/* len("/__init__") */
		            8,   		/* len("__init__") */
		            pname)) {
			buf[save_len] = '\0';
			return 1;
		}
	}
	buf[save_len] = '\0';
	return 0;
}

#else

#ifdef RISCOS
static int
find_init_module(buf)
	char *buf;
{
	int save_len = strlen(buf);
	int i = save_len;

	if (save_len + 13 >= MAXPATHLEN)
		return 0;
	buf[i++] = SEP;
	strcpy(buf+i, "__init__/py");
	if (isfile(buf)) {
		buf[save_len] = '\0';
		return 1;
	}

	if (Py_OptimizeFlag)
		strcpy(buf+i, "o");
	else
		strcpy(buf+i, "c");
	if (isfile(buf)) {
		buf[save_len] = '\0';
		return 1;
	}
	buf[save_len] = '\0';
	return 0;
}
#endif /*RISCOS*/

#endif /* HAVE_STAT */


static int init_builtin(char *); /* Forward */

/* Load an external module using the default search path and return
   its module object WITH INCREMENTED REFERENCE COUNT */

static PyObject *
load_module(char *name, FILE *fp, char *buf, int type)
{
	PyObject *modules;
	PyObject *m;
	int err;

	/* First check that there's an open file (if we need one)  */
	switch (type) {
	case PY_SOURCE:
	case PY_COMPILED:
		if (fp == NULL) {
			PyErr_Format(PyExc_ValueError,
			   "file object required for import (type code %d)",
				     type);
			return NULL;
		}
	}

	switch (type) {

	case PY_SOURCE:
		m = load_source_module(name, buf, fp);
		break;

	case PY_COMPILED:
		m = load_compiled_module(name, buf, fp);
		break;

#ifdef HAVE_DYNAMIC_LOADING
	case C_EXTENSION:
		m = _PyImport_LoadDynamicModule(name, buf, fp);
		break;
#endif

#ifdef macintosh
	case PY_RESOURCE:
		m = PyMac_LoadResourceModule(name, buf);
		break;
	case PY_CODERESOURCE:
		m = PyMac_LoadCodeResourceModule(name, buf);
		break;
#endif

	case PKG_DIRECTORY:
		m = load_package(name, buf);
		break;

	case C_BUILTIN:
	case PY_FROZEN:
		if (buf != NULL && buf[0] != '\0')
			name = buf;
		if (type == C_BUILTIN)
			err = init_builtin(name);
		else
			err = PyImport_ImportFrozenModule(name);
		if (err < 0)
			return NULL;
		if (err == 0) {
			PyErr_Format(PyExc_ImportError,
				     "Purported %s module %.200s not found",
				     type == C_BUILTIN ?
						"builtin" : "frozen",
				     name);
			return NULL;
		}
		modules = PyImport_GetModuleDict();
		m = PyDict_GetItemString(modules, name);
		if (m == NULL) {
			PyErr_Format(
				PyExc_ImportError,
				"%s module %.200s not properly initialized",
				type == C_BUILTIN ?
					"builtin" : "frozen",
				name);
			return NULL;
		}
		Py_INCREF(m);
		break;

	default:
		PyErr_Format(PyExc_ImportError,
			     "Don't know how to import %.200s (type code %d)",
			      name, type);
		m = NULL;

	}

	return m;
}


/* Initialize a built-in module.
   Return 1 for succes, 0 if the module is not found, and -1 with
   an exception set if the initialization failed. */

static int
init_builtin(char *name)
{
	struct _inittab *p;

	if (_PyImport_FindExtension(name, name) != NULL)
		return 1;

	for (p = PyImport_Inittab; p->name != NULL; p++) {
		if (strcmp(name, p->name) == 0) {
			if (p->initfunc == NULL) {
				PyErr_Format(PyExc_ImportError,
				    "Cannot re-init internal module %.200s",
				    name);
				return -1;
			}
			if (Py_VerboseFlag)
				PySys_WriteStderr("import %s # builtin\n", name);
			(*p->initfunc)();
			if (PyErr_Occurred())
				return -1;
			if (_PyImport_FixupExtension(name, name) == NULL)
				return -1;
			return 1;
		}
	}
	return 0;
}


/* Frozen modules */

static struct _frozen *
find_frozen(char *name)
{
	struct _frozen *p;

	for (p = PyImport_FrozenModules; ; p++) {
		if (p->name == NULL)
			return NULL;
		if (strcmp(p->name, name) == 0)
			break;
	}
	return p;
}

static PyObject *
get_frozen_object(char *name)
{
	struct _frozen *p = find_frozen(name);
	int size;

	if (p == NULL) {
		PyErr_Format(PyExc_ImportError,
			     "No such frozen object named %.200s",
			     name);
		return NULL;
	}
	if (p->code == NULL) {
		PyErr_Format(PyExc_ImportError,
			     "Excluded frozen object named %.200s",
			     name);
		return NULL;
	}
	size = p->size;
	if (size < 0)
		size = -size;
	return PyMarshal_ReadObjectFromString((char *)p->code, size);
}

/* Initialize a frozen module.
   Return 1 for succes, 0 if the module is not found, and -1 with
   an exception set if the initialization failed.
   This function is also used from frozenmain.c */

int
PyImport_ImportFrozenModule(char *name)
{
	struct _frozen *p = find_frozen(name);
	PyObject *co;
	PyObject *m;
	int ispackage;
	int size;

	if (p == NULL)
		return 0;
	if (p->code == NULL) {
		PyErr_Format(PyExc_ImportError,
			     "Excluded frozen object named %.200s",
			     name);
		return -1;
	}
	size = p->size;
	ispackage = (size < 0);
	if (ispackage)
		size = -size;
	if (Py_VerboseFlag)
		PySys_WriteStderr("import %s # frozen%s\n",
			name, ispackage ? " package" : "");
	co = PyMarshal_ReadObjectFromString((char *)p->code, size);
	if (co == NULL)
		return -1;
	if (!PyCode_Check(co)) {
		Py_DECREF(co);
		PyErr_Format(PyExc_TypeError,
			     "frozen object %.200s is not a code object",
			     name);
		return -1;
	}
	if (ispackage) {
		/* Set __path__ to the package name */
		PyObject *d, *s;
		int err;
		m = PyImport_AddModule(name);
		if (m == NULL)
			return -1;
		d = PyModule_GetDict(m);
		s = PyString_InternFromString(name);
		if (s == NULL)
			return -1;
		err = PyDict_SetItemString(d, "__path__", s);
		Py_DECREF(s);
		if (err != 0)
			return err;
	}
	m = PyImport_ExecCodeModuleEx(name, co, "<frozen>");
	Py_DECREF(co);
	if (m == NULL)
		return -1;
	Py_DECREF(m);
	return 1;
}


/* Import a module, either built-in, frozen, or external, and return
   its module object WITH INCREMENTED REFERENCE COUNT */

PyObject *
PyImport_ImportModule(char *name)
{
	PyObject *pname;
	PyObject *result;

	pname = PyString_FromString(name);
	result = PyImport_Import(pname);
	Py_DECREF(pname);
	return result;
}

/* Forward declarations for helper routines */
static PyObject *get_parent(PyObject *globals, char *buf, int *p_buflen);
static PyObject *load_next(PyObject *mod, PyObject *altmod,
			   char **p_name, char *buf, int *p_buflen);
static int mark_miss(char *name);
static int ensure_fromlist(PyObject *mod, PyObject *fromlist,
			   char *buf, int buflen, int recursive);
static PyObject * import_submodule(PyObject *mod, char *name, char *fullname);

/* The Magnum Opus of dotted-name import :-) */

static PyObject *
import_module_ex(char *name, PyObject *globals, PyObject *locals,
		 PyObject *fromlist)
{
	char buf[MAXPATHLEN+1];
	int buflen = 0;
	PyObject *parent, *head, *next, *tail;

	parent = get_parent(globals, buf, &buflen);
	if (parent == NULL)
		return NULL;

	head = load_next(parent, Py_None, &name, buf, &buflen);
	if (head == NULL)
		return NULL;

	tail = head;
	Py_INCREF(tail);
	while (name) {
		next = load_next(tail, tail, &name, buf, &buflen);
		Py_DECREF(tail);
		if (next == NULL) {
			Py_DECREF(head);
			return NULL;
		}
		tail = next;
	}

	if (fromlist != NULL) {
		if (fromlist == Py_None || !PyObject_IsTrue(fromlist))
			fromlist = NULL;
	}

	if (fromlist == NULL) {
		Py_DECREF(tail);
		return head;
	}

	Py_DECREF(head);
	if (!ensure_fromlist(tail, fromlist, buf, buflen, 0)) {
		Py_DECREF(tail);
		return NULL;
	}

	return tail;
}

PyObject *
PyImport_ImportModuleEx(char *name, PyObject *globals, PyObject *locals,
			PyObject *fromlist)
{
	PyObject *result;
	lock_import();
	result = import_module_ex(name, globals, locals, fromlist);
	unlock_import();
	return result;
}

static PyObject *
get_parent(PyObject *globals, char *buf, int *p_buflen)
{
	static PyObject *namestr = NULL;
	static PyObject *pathstr = NULL;
	PyObject *modname, *modpath, *modules, *parent;

	if (globals == NULL || !PyDict_Check(globals))
		return Py_None;

	if (namestr == NULL) {
		namestr = PyString_InternFromString("__name__");
		if (namestr == NULL)
			return NULL;
	}
	if (pathstr == NULL) {
		pathstr = PyString_InternFromString("__path__");
		if (pathstr == NULL)
			return NULL;
	}

	*buf = '\0';
	*p_buflen = 0;
	modname = PyDict_GetItem(globals, namestr);
	if (modname == NULL || !PyString_Check(modname))
		return Py_None;

	modpath = PyDict_GetItem(globals, pathstr);
	if (modpath != NULL) {
		int len = PyString_GET_SIZE(modname);
		if (len > MAXPATHLEN) {
			PyErr_SetString(PyExc_ValueError,
					"Module name too long");
			return NULL;
		}
		strcpy(buf, PyString_AS_STRING(modname));
		*p_buflen = len;
	}
	else {
		char *start = PyString_AS_STRING(modname);
		char *lastdot = strrchr(start, '.');
		size_t len;
		if (lastdot == NULL)
			return Py_None;
		len = lastdot - start;
		if (len >= MAXPATHLEN) {
			PyErr_SetString(PyExc_ValueError,
					"Module name too long");
			return NULL;
		}
		strncpy(buf, start, len);
		buf[len] = '\0';
		*p_buflen = len;
	}

	modules = PyImport_GetModuleDict();
	parent = PyDict_GetItemString(modules, buf);
	if (parent == NULL)
		parent = Py_None;
	return parent;
	/* We expect, but can't guarantee, if parent != None, that:
	   - parent.__name__ == buf
	   - parent.__dict__ is globals
	   If this is violated...  Who cares? */
}

/* altmod is either None or same as mod */
static PyObject *
load_next(PyObject *mod, PyObject *altmod, char **p_name, char *buf,
	  int *p_buflen)
{
	char *name = *p_name;
	char *dot = strchr(name, '.');
	size_t len;
	char *p;
	PyObject *result;

	if (dot == NULL) {
		*p_name = NULL;
		len = strlen(name);
	}
	else {
		*p_name = dot+1;
		len = dot-name;
	}
	if (len == 0) {
		PyErr_SetString(PyExc_ValueError,
				"Empty module name");
		return NULL;
	}

	p = buf + *p_buflen;
	if (p != buf)
		*p++ = '.';
	if (p+len-buf >= MAXPATHLEN) {
		PyErr_SetString(PyExc_ValueError,
				"Module name too long");
		return NULL;
	}
	strncpy(p, name, len);
	p[len] = '\0';
	*p_buflen = p+len-buf;

	result = import_submodule(mod, p, buf);
	if (result == Py_None && altmod != mod) {
		Py_DECREF(result);
		/* Here, altmod must be None and mod must not be None */
		result = import_submodule(altmod, p, p);
		if (result != NULL && result != Py_None) {
			if (mark_miss(buf) != 0) {
				Py_DECREF(result);
				return NULL;
			}
			strncpy(buf, name, len);
			buf[len] = '\0';
			*p_buflen = len;
		}
	}
	if (result == NULL)
		return NULL;

	if (result == Py_None) {
		Py_DECREF(result);
		PyErr_Format(PyExc_ImportError,
			     "No module named %.200s", name);
		return NULL;
	}

	return result;
}

static int
mark_miss(char *name)
{
	PyObject *modules = PyImport_GetModuleDict();
	return PyDict_SetItemString(modules, name, Py_None);
}

static int
ensure_fromlist(PyObject *mod, PyObject *fromlist, char *buf, int buflen,
		int recursive)
{
	int i;

	if (!PyObject_HasAttrString(mod, "__path__"))
		return 1;

	for (i = 0; ; i++) {
		PyObject *item = PySequence_GetItem(fromlist, i);
		int hasit;
		if (item == NULL) {
			if (PyErr_ExceptionMatches(PyExc_IndexError)) {
				PyErr_Clear();
				return 1;
			}
			return 0;
		}
		if (!PyString_Check(item)) {
			PyErr_SetString(PyExc_TypeError,
					"Item in ``from list'' not a string");
			Py_DECREF(item);
			return 0;
		}
		if (PyString_AS_STRING(item)[0] == '*') {
			PyObject *all;
			Py_DECREF(item);
			/* See if the package defines __all__ */
			if (recursive)
				continue; /* Avoid endless recursion */
			all = PyObject_GetAttrString(mod, "__all__");
			if (all == NULL)
				PyErr_Clear();
			else {
				if (!ensure_fromlist(mod, all, buf, buflen, 1))
					return 0;
				Py_DECREF(all);
			}
			continue;
		}
		hasit = PyObject_HasAttr(mod, item);
		if (!hasit) {
			char *subname = PyString_AS_STRING(item);
			PyObject *submod;
			char *p;
			if (buflen + strlen(subname) >= MAXPATHLEN) {
				PyErr_SetString(PyExc_ValueError,
						"Module name too long");
				Py_DECREF(item);
				return 0;
			}
			p = buf + buflen;
			*p++ = '.';
			strcpy(p, subname);
			submod = import_submodule(mod, subname, buf);
			Py_XDECREF(submod);
			if (submod == NULL) {
				Py_DECREF(item);
				return 0;
			}
		}
		Py_DECREF(item);
	}

	/* NOTREACHED */
}

static PyObject *
import_submodule(PyObject *mod, char *subname, char *fullname)
{
	PyObject *modules = PyImport_GetModuleDict();
	PyObject *m, *res = NULL;

	/* Require:
	   if mod == None: subname == fullname
	   else: mod.__name__ + "." + subname == fullname
	*/

	if ((m = PyDict_GetItemString(modules, fullname)) != NULL) {
		Py_INCREF(m);
	}
	else {
		PyObject *path;
		char buf[MAXPATHLEN+1];
		struct filedescr *fdp;
		FILE *fp = NULL;

		if (mod == Py_None)
			path = NULL;
		else {
			path = PyObject_GetAttrString(mod, "__path__");
			if (path == NULL) {
				PyErr_Clear();
				Py_INCREF(Py_None);
				return Py_None;
			}
		}

		buf[0] = '\0';
		fdp = find_module(subname, path, buf, MAXPATHLEN+1, &fp);
		Py_XDECREF(path);
		if (fdp == NULL) {
			if (!PyErr_ExceptionMatches(PyExc_ImportError))
				return NULL;
			PyErr_Clear();
			Py_INCREF(Py_None);
			return Py_None;
		}
		m = load_module(fullname, fp, buf, fdp->type);
		if (fp)
			fclose(fp);
		if (mod != Py_None) {
			/* Irrespective of the success of this load, make a
			   reference to it in the parent package module.
			   A copy gets saved in the modules dictionary
			   under the full name, so get a reference from
			   there, if need be.  (The exception is when
			   the load failed with a SyntaxError -- then
			   there's no trace in sys.modules.  In that case,
			   of course, do nothing extra.) */
			res = m;
			if (res == NULL)
				res = PyDict_GetItemString(modules, fullname);
			if (res != NULL &&
			    PyObject_SetAttrString(mod, subname, res) < 0) {
				Py_XDECREF(m);
				m = NULL;
			}
		}
	}

	return m;
}


/* Re-import a module of any kind and return its module object, WITH
   INCREMENTED REFERENCE COUNT */

PyObject *
PyImport_ReloadModule(PyObject *m)
{
	PyObject *modules = PyImport_GetModuleDict();
	PyObject *path = NULL;
	char *name, *subname;
	char buf[MAXPATHLEN+1];
	struct filedescr *fdp;
	FILE *fp = NULL;

	if (m == NULL || !PyModule_Check(m)) {
		PyErr_SetString(PyExc_TypeError,
				"reload() argument must be module");
		return NULL;
	}
	name = PyModule_GetName(m);
	if (name == NULL)
		return NULL;
	if (m != PyDict_GetItemString(modules, name)) {
		PyErr_Format(PyExc_ImportError,
			     "reload(): module %.200s not in sys.modules",
			     name);
		return NULL;
	}
	subname = strrchr(name, '.');
	if (subname == NULL)
		subname = name;
	else {
		PyObject *parentname, *parent;
		parentname = PyString_FromStringAndSize(name, (subname-name));
		if (parentname == NULL)
			return NULL;
		parent = PyDict_GetItem(modules, parentname);
		Py_DECREF(parentname);
		if (parent == NULL) {
			PyErr_Format(PyExc_ImportError,
			    "reload(): parent %.200s not in sys.modules",
			    name);
			return NULL;
		}
		subname++;
		path = PyObject_GetAttrString(parent, "__path__");
		if (path == NULL)
			PyErr_Clear();
	}
	buf[0] = '\0';
	fdp = find_module(subname, path, buf, MAXPATHLEN+1, &fp);
	Py_XDECREF(path);
	if (fdp == NULL)
		return NULL;
	m = load_module(name, fp, buf, fdp->type);
	if (fp)
		fclose(fp);
	return m;
}


/* Higher-level import emulator which emulates the "import" statement
   more accurately -- it invokes the __import__() function from the
   builtins of the current globals.  This means that the import is
   done using whatever import hooks are installed in the current
   environment, e.g. by "rexec".
   A dummy list ["__doc__"] is passed as the 4th argument so that
   e.g. PyImport_Import(PyString_FromString("win32com.client.gencache"))
   will return <module "gencache"> instead of <module "win32com">. */

PyObject *
PyImport_Import(PyObject *module_name)
{
	static PyObject *silly_list = NULL;
	static PyObject *builtins_str = NULL;
	static PyObject *import_str = NULL;
	PyObject *globals = NULL;
	PyObject *import = NULL;
	PyObject *builtins = NULL;
	PyObject *r = NULL;

	/* Initialize constant string objects */
	if (silly_list == NULL) {
		import_str = PyString_InternFromString("__import__");
		if (import_str == NULL)
			return NULL;
		builtins_str = PyString_InternFromString("__builtins__");
		if (builtins_str == NULL)
			return NULL;
		silly_list = Py_BuildValue("[s]", "__doc__");
		if (silly_list == NULL)
			return NULL;
	}

	/* Get the builtins from current globals */
	globals = PyEval_GetGlobals();
	if (globals != NULL) {
	        Py_INCREF(globals);
		builtins = PyObject_GetItem(globals, builtins_str);
		if (builtins == NULL)
			goto err;
	}
	else {
		/* No globals -- use standard builtins, and fake globals */
		PyErr_Clear();

		builtins = PyImport_ImportModuleEx("__builtin__",
						   NULL, NULL, NULL);
		if (builtins == NULL)
			return NULL;
		globals = Py_BuildValue("{OO}", builtins_str, builtins);
		if (globals == NULL)
			goto err;
	}

	/* Get the __import__ function from the builtins */
	if (PyDict_Check(builtins)) {
		import = PyObject_GetItem(builtins, import_str);
		if (import == NULL)
			PyErr_SetObject(PyExc_KeyError, import_str);
	}
	else
		import = PyObject_GetAttr(builtins, import_str);
	if (import == NULL)
		goto err;

	/* Call the _import__ function with the proper argument list */
	r = PyObject_CallFunction(import, "OOOO",
				  module_name, globals, globals, silly_list);

  err:
	Py_XDECREF(globals);
	Py_XDECREF(builtins);
	Py_XDECREF(import);

	return r;
}


/* Module 'imp' provides Python access to the primitives used for
   importing modules.
*/

static PyObject *
imp_get_magic(PyObject *self, PyObject *args)
{
	char buf[4];

	if (!PyArg_ParseTuple(args, ":get_magic"))
		return NULL;
	buf[0] = (char) ((pyc_magic >>  0) & 0xff);
	buf[1] = (char) ((pyc_magic >>  8) & 0xff);
	buf[2] = (char) ((pyc_magic >> 16) & 0xff);
	buf[3] = (char) ((pyc_magic >> 24) & 0xff);

	return PyString_FromStringAndSize(buf, 4);
}

static PyObject *
imp_get_suffixes(PyObject *self, PyObject *args)
{
	PyObject *list;
	struct filedescr *fdp;

	if (!PyArg_ParseTuple(args, ":get_suffixes"))
		return NULL;
	list = PyList_New(0);
	if (list == NULL)
		return NULL;
	for (fdp = _PyImport_Filetab; fdp->suffix != NULL; fdp++) {
		PyObject *item = Py_BuildValue("ssi",
				       fdp->suffix, fdp->mode, fdp->type);
		if (item == NULL) {
			Py_DECREF(list);
			return NULL;
		}
		if (PyList_Append(list, item) < 0) {
			Py_DECREF(list);
			Py_DECREF(item);
			return NULL;
		}
		Py_DECREF(item);
	}
	return list;
}

static PyObject *
call_find_module(char *name, PyObject *path)
{
	extern int fclose(FILE *);
	PyObject *fob, *ret;
	struct filedescr *fdp;
	char pathname[MAXPATHLEN+1];
	FILE *fp = NULL;

	pathname[0] = '\0';
	if (path == Py_None)
		path = NULL;
	fdp = find_module(name, path, pathname, MAXPATHLEN+1, &fp);
	if (fdp == NULL)
		return NULL;
	if (fp != NULL) {
		fob = PyFile_FromFile(fp, pathname, fdp->mode, fclose);
		if (fob == NULL) {
			fclose(fp);
			return NULL;
		}
	}
	else {
		fob = Py_None;
		Py_INCREF(fob);
	}
	ret = Py_BuildValue("Os(ssi)",
		      fob, pathname, fdp->suffix, fdp->mode, fdp->type);
	Py_DECREF(fob);
	return ret;
}

static PyObject *
imp_find_module(PyObject *self, PyObject *args)
{
	char *name;
	PyObject *path = NULL;
	if (!PyArg_ParseTuple(args, "s|O:find_module", &name, &path))
		return NULL;
	return call_find_module(name, path);
}

static PyObject *
imp_init_builtin(PyObject *self, PyObject *args)
{
	char *name;
	int ret;
	PyObject *m;
	if (!PyArg_ParseTuple(args, "s:init_builtin", &name))
		return NULL;
	ret = init_builtin(name);
	if (ret < 0)
		return NULL;
	if (ret == 0) {
		Py_INCREF(Py_None);
		return Py_None;
	}
	m = PyImport_AddModule(name);
	Py_XINCREF(m);
	return m;
}

static PyObject *
imp_init_frozen(PyObject *self, PyObject *args)
{
	char *name;
	int ret;
	PyObject *m;
	if (!PyArg_ParseTuple(args, "s:init_frozen", &name))
		return NULL;
	ret = PyImport_ImportFrozenModule(name);
	if (ret < 0)
		return NULL;
	if (ret == 0) {
		Py_INCREF(Py_None);
		return Py_None;
	}
	m = PyImport_AddModule(name);
	Py_XINCREF(m);
	return m;
}

static PyObject *
imp_get_frozen_object(PyObject *self, PyObject *args)
{
	char *name;

	if (!PyArg_ParseTuple(args, "s:get_frozen_object", &name))
		return NULL;
	return get_frozen_object(name);
}

static PyObject *
imp_is_builtin(PyObject *self, PyObject *args)
{
	char *name;
	if (!PyArg_ParseTuple(args, "s:is_builtin", &name))
		return NULL;
	return PyInt_FromLong(is_builtin(name));
}

static PyObject *
imp_is_frozen(PyObject *self, PyObject *args)
{
	char *name;
	struct _frozen *p;
	if (!PyArg_ParseTuple(args, "s:is_frozen", &name))
		return NULL;
	p = find_frozen(name);
	return PyInt_FromLong((long) (p == NULL ? 0 : p->size));
}

static FILE *
get_file(char *pathname, PyObject *fob, char *mode)
{
	FILE *fp;
	if (fob == NULL) {
		fp = fopen(pathname, mode);
		if (fp == NULL)
			PyErr_SetFromErrno(PyExc_IOError);
	}
	else {
		fp = PyFile_AsFile(fob);
		if (fp == NULL)
			PyErr_SetString(PyExc_ValueError,
					"bad/closed file object");
	}
	return fp;
}

static PyObject *
imp_load_compiled(PyObject *self, PyObject *args)
{
	char *name;
	char *pathname;
	PyObject *fob = NULL;
	PyObject *m;
	FILE *fp;
	if (!PyArg_ParseTuple(args, "ss|O!:load_compiled", &name, &pathname,
			      &PyFile_Type, &fob))
		return NULL;
	fp = get_file(pathname, fob, "rb");
	if (fp == NULL)
		return NULL;
	m = load_compiled_module(name, pathname, fp);
	if (fob == NULL)
		fclose(fp);
	return m;
}

#ifdef HAVE_DYNAMIC_LOADING

static PyObject *
imp_load_dynamic(PyObject *self, PyObject *args)
{
	char *name;
	char *pathname;
	PyObject *fob = NULL;
	PyObject *m;
	FILE *fp = NULL;
	if (!PyArg_ParseTuple(args, "ss|O!:load_dynamic", &name, &pathname,
			      &PyFile_Type, &fob))
		return NULL;
	if (fob) {
		fp = get_file(pathname, fob, "r");
		if (fp == NULL)
			return NULL;
	}
	m = _PyImport_LoadDynamicModule(name, pathname, fp);
	return m;
}

#endif /* HAVE_DYNAMIC_LOADING */

static PyObject *
imp_load_source(PyObject *self, PyObject *args)
{
	char *name;
	char *pathname;
	PyObject *fob = NULL;
	PyObject *m;
	FILE *fp;
	if (!PyArg_ParseTuple(args, "ss|O!:load_source", &name, &pathname,
			      &PyFile_Type, &fob))
		return NULL;
	fp = get_file(pathname, fob, "r");
	if (fp == NULL)
		return NULL;
	m = load_source_module(name, pathname, fp);
	if (fob == NULL)
		fclose(fp);
	return m;
}

#ifdef macintosh
static PyObject *
imp_load_resource(PyObject *self, PyObject *args)
{
	char *name;
	char *pathname;
	PyObject *m;

	if (!PyArg_ParseTuple(args, "ss:load_resource", &name, &pathname))
		return NULL;
	m = PyMac_LoadResourceModule(name, pathname);
	return m;
}
#endif /* macintosh */

static PyObject *
imp_load_module(PyObject *self, PyObject *args)
{
	char *name;
	PyObject *fob;
	char *pathname;
	char *suffix; /* Unused */
	char *mode;
	int type;
	FILE *fp;

	if (!PyArg_ParseTuple(args, "sOs(ssi):load_module",
			      &name, &fob, &pathname,
			      &suffix, &mode, &type))
		return NULL;
	if (*mode && (*mode != 'r' || strchr(mode, '+') != NULL)) {
		PyErr_Format(PyExc_ValueError,
			     "invalid file open mode %.200s", mode);
		return NULL;
	}
	if (fob == Py_None)
		fp = NULL;
	else {
		if (!PyFile_Check(fob)) {
			PyErr_SetString(PyExc_ValueError,
				"load_module arg#2 should be a file or None");
			return NULL;
		}
		fp = get_file(pathname, fob, mode);
		if (fp == NULL)
			return NULL;
	}
	return load_module(name, fp, pathname, type);
}

static PyObject *
imp_load_package(PyObject *self, PyObject *args)
{
	char *name;
	char *pathname;
	if (!PyArg_ParseTuple(args, "ss:load_package", &name, &pathname))
		return NULL;
	return load_package(name, pathname);
}

static PyObject *
imp_new_module(PyObject *self, PyObject *args)
{
	char *name;
	if (!PyArg_ParseTuple(args, "s:new_module", &name))
		return NULL;
	return PyModule_New(name);
}

/* Doc strings */

static char doc_imp[] = "\
This module provides the components needed to build your own\n\
__import__ function.  Undocumented functions are obsolete.\n\
";

static char doc_find_module[] = "\
find_module(name, [path]) -> (file, filename, (suffix, mode, type))\n\
Search for a module.  If path is omitted or None, search for a\n\
built-in, frozen or special module and continue search in sys.path.\n\
The module name cannot contain '.'; to search for a submodule of a\n\
package, pass the submodule name and the package's __path__.\
";

static char doc_load_module[] = "\
load_module(name, file, filename, (suffix, mode, type)) -> module\n\
Load a module, given information returned by find_module().\n\
The module name must include the full package name, if any.\
";

static char doc_get_magic[] = "\
get_magic() -> string\n\
Return the magic number for .pyc or .pyo files.\
";

static char doc_get_suffixes[] = "\
get_suffixes() -> [(suffix, mode, type), ...]\n\
Return a list of (suffix, mode, type) tuples describing the files\n\
that find_module() looks for.\
";

static char doc_new_module[] = "\
new_module(name) -> module\n\
Create a new module.  Do not enter it in sys.modules.\n\
The module name must include the full package name, if any.\
";

static char doc_lock_held[] = "\
lock_held() -> 0 or 1\n\
Return 1 if the import lock is currently held.\n\
On platforms without threads, return 0.\
";

static PyMethodDef imp_methods[] = {
	{"find_module",		imp_find_module,	1, doc_find_module},
	{"get_magic",		imp_get_magic,		1, doc_get_magic},
	{"get_suffixes",	imp_get_suffixes,	1, doc_get_suffixes},
	{"load_module",		imp_load_module,	1, doc_load_module},
	{"new_module",		imp_new_module,		1, doc_new_module},
	{"lock_held",		imp_lock_held,		1, doc_lock_held},
	/* The rest are obsolete */
	{"get_frozen_object",	imp_get_frozen_object,	1},
	{"init_builtin",	imp_init_builtin,	1},
	{"init_frozen",		imp_init_frozen,	1},
	{"is_builtin",		imp_is_builtin,		1},
	{"is_frozen",		imp_is_frozen,		1},
	{"load_compiled",	imp_load_compiled,	1},
#ifdef HAVE_DYNAMIC_LOADING
	{"load_dynamic",	imp_load_dynamic,	1},
#endif
	{"load_package",	imp_load_package,	1},
#ifdef macintosh
	{"load_resource",	imp_load_resource,	1},
#endif
	{"load_source",		imp_load_source,	1},
	{NULL,			NULL}		/* sentinel */
};

static int
setint(PyObject *d, char *name, int value)
{
	PyObject *v;
	int err;

	v = PyInt_FromLong((long)value);
	err = PyDict_SetItemString(d, name, v);
	Py_XDECREF(v);
	return err;
}

void
initimp(void)
{
	PyObject *m, *d;

	m = Py_InitModule4("imp", imp_methods, doc_imp,
			   NULL, PYTHON_API_VERSION);
	d = PyModule_GetDict(m);

	if (setint(d, "SEARCH_ERROR", SEARCH_ERROR) < 0) goto failure;
	if (setint(d, "PY_SOURCE", PY_SOURCE) < 0) goto failure;
	if (setint(d, "PY_COMPILED", PY_COMPILED) < 0) goto failure;
	if (setint(d, "C_EXTENSION", C_EXTENSION) < 0) goto failure;
	if (setint(d, "PY_RESOURCE", PY_RESOURCE) < 0) goto failure;
	if (setint(d, "PKG_DIRECTORY", PKG_DIRECTORY) < 0) goto failure;
	if (setint(d, "C_BUILTIN", C_BUILTIN) < 0) goto failure;
	if (setint(d, "PY_FROZEN", PY_FROZEN) < 0) goto failure;
	if (setint(d, "PY_CODERESOURCE", PY_CODERESOURCE) < 0) goto failure;

  failure:
	;
}


/* API for embedding applications that want to add their own entries
   to the table of built-in modules.  This should normally be called
   *before* Py_Initialize().  When the table resize fails, -1 is
   returned and the existing table is unchanged.

   After a similar function by Just van Rossum. */

int
PyImport_ExtendInittab(struct _inittab *newtab)
{
	static struct _inittab *our_copy = NULL;
	struct _inittab *p;
	int i, n;

	/* Count the number of entries in both tables */
	for (n = 0; newtab[n].name != NULL; n++)
		;
	if (n == 0)
		return 0; /* Nothing to do */
	for (i = 0; PyImport_Inittab[i].name != NULL; i++)
		;

	/* Allocate new memory for the combined table */
	p = our_copy;
	PyMem_RESIZE(p, struct _inittab, i+n+1);
	if (p == NULL)
		return -1;

	/* Copy the tables into the new memory */
	if (our_copy != PyImport_Inittab)
		memcpy(p, PyImport_Inittab, (i+1) * sizeof(struct _inittab));
	PyImport_Inittab = our_copy = p;
	memcpy(p+i, newtab, (n+1) * sizeof(struct _inittab));

	return 0;
}

/* Shorthand to add a single entry given a name and a function */

int
PyImport_AppendInittab(char *name, void (*initfunc)(void))
{
	struct _inittab newtab[2];

	memset(newtab, '\0', sizeof newtab);

	newtab[0].name = name;
	newtab[0].initfunc = initfunc;

	return PyImport_ExtendInittab(newtab);
}