path: root/Modules/zipimport.c

#include "Python.h"
#include "internal/import.h"
#include "internal/pystate.h"
#include "structmember.h"
#include "osdefs.h"
#include "marshal.h"
#include <time.h>


#define IS_SOURCE   0x0
#define IS_BYTECODE 0x1
#define IS_PACKAGE  0x2

struct st_zip_searchorder {
    char suffix[14];
    int type;
};

#ifdef ALTSEP
_Py_IDENTIFIER(replace);
#endif

/* zip_searchorder defines how we search for a module in the Zip
   archive: we first search for a package __init__, then for
   non-package .pyc, and .py entries. The .pyc entries
   are swapped by initzipimport() if we run in optimized mode. Also,
   '/' is replaced by SEP there. */
static struct st_zip_searchorder zip_searchorder[] = {
    {"/__init__.pyc", IS_PACKAGE | IS_BYTECODE},
    {"/__init__.py", IS_PACKAGE | IS_SOURCE},
    {".pyc", IS_BYTECODE},
    {".py", IS_SOURCE},
    {"", 0}
};

/* zipimporter object definition and support */

typedef struct _zipimporter ZipImporter;

struct _zipimporter {
    PyObject_HEAD
    PyObject *archive;  /* pathname of the Zip archive,
                           decoded from the filesystem encoding */
    PyObject *prefix;   /* file prefix: "a/sub/directory/",
                           encoded to the filesystem encoding */
    PyObject *files;    /* dict with file info {path: toc_entry} */
};

static PyObject *ZipImportError;
/* read_directory() cache */
static PyObject *zip_directory_cache = NULL;

/* forward decls */
static PyObject *read_directory(PyObject *archive);
static PyObject *get_data(PyObject *archive, PyObject *toc_entry);
static PyObject *get_module_code(ZipImporter *self, PyObject *fullname,
                                 int *p_ispackage, PyObject **p_modpath);

static PyTypeObject ZipImporter_Type;

#define ZipImporter_Check(op) PyObject_TypeCheck(op, &ZipImporter_Type)

/*[clinic input]
module zipimport
class zipimport.zipimporter "ZipImporter *" "&ZipImporter_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=9db8b61557d911e7]*/
#include "clinic/zipimport.c.h"


/* zipimporter.__init__
   Split the "subdirectory" from the Zip archive path, lookup a matching
   entry in sys.path_importer_cache, fetch the file directory from there
   if found, or else read it from the archive. */

/*[clinic input]
zipimport.zipimporter.__init__

    archivepath as path: object(converter="PyUnicode_FSDecoder")
        A path-like object to a zipfile, or to a specific path inside
        a zipfile.
    /

Create a new zipimporter instance.

'archivepath' must be a path-like object to a zipfile, or to a specific path
inside a zipfile. For example, it can be '/tmp/myimport.zip', or
'/tmp/myimport.zip/mydirectory', if mydirectory is a valid directory inside
the archive.

'ZipImportError' is raised if 'archivepath' doesn't point to a valid Zip
archive.

The 'archive' attribute of the zipimporter object contains the name of the
zipfile targeted.

[clinic start generated code]*/

static int
zipimport_zipimporter___init___impl(ZipImporter *self, PyObject *path)
/*[clinic end generated code: output=141558fefdb46dc8 input=92b9ebeed1f6a704]*/
{
    PyObject *files, *tmp;
    PyObject *filename = NULL;
    Py_ssize_t len, flen;

    if (PyUnicode_READY(path) == -1)
        return -1;

    len = PyUnicode_GET_LENGTH(path);
    if (len == 0) {
        PyErr_SetString(ZipImportError, "archive path is empty");
        goto error;
    }

#ifdef ALTSEP
    tmp = _PyObject_CallMethodId(path, &PyId_replace, "CC", ALTSEP, SEP);
    if (!tmp)
        goto error;
    Py_DECREF(path);
    path = tmp;
#endif

    filename = path;
    Py_INCREF(filename);
    flen = len;
    for (;;) {
        struct stat statbuf;
        int rv;

        rv = _Py_stat(filename, &statbuf);
        if (rv == -2)
            goto error;
        if (rv == 0) {
            /* it exists */
            if (!S_ISREG(statbuf.st_mode))
                /* it's a not file */
                Py_CLEAR(filename);
            break;
        }
        Py_CLEAR(filename);
        /* back up one path element */
        flen = PyUnicode_FindChar(path, SEP, 0, flen, -1);
        if (flen == -1)
            break;
        filename = PyUnicode_Substring(path, 0, flen);
        if (filename == NULL)
            goto error;
    }
    if (filename == NULL) {
        PyErr_SetString(ZipImportError, "not a Zip file");
        goto error;
    }

    if (PyUnicode_READY(filename) < 0)
        goto error;

    files = PyDict_GetItem(zip_directory_cache, filename);
    if (files == NULL) {
        files = read_directory(filename);
        if (files == NULL)
            goto error;
        if (PyDict_SetItem(zip_directory_cache, filename, files) != 0)
            goto error;
    }
    else
        Py_INCREF(files);
    Py_XSETREF(self->files, files);

    /* Transfer reference */
    Py_XSETREF(self->archive, filename);
    filename = NULL;

    /* Check if there is a prefix directory following the filename. */
    if (flen != len) {
        tmp = PyUnicode_Substring(path, flen+1,
                                  PyUnicode_GET_LENGTH(path));
        if (tmp == NULL)
            goto error;
        Py_XSETREF(self->prefix, tmp);
        if (PyUnicode_READ_CHAR(path, len-1) != SEP) {
            /* add trailing SEP */
            tmp = PyUnicode_FromFormat("%U%c", self->prefix, SEP);
            if (tmp == NULL)
                goto error;
            Py_SETREF(self->prefix, tmp);
        }
    }
    else {
        Py_XSETREF(self->prefix, PyUnicode_New(0, 0));
    }
    Py_DECREF(path);
    return 0;

error:
    Py_DECREF(path);
    Py_XDECREF(filename);
    return -1;
}

/* GC support. */
static int
zipimporter_traverse(PyObject *obj, visitproc visit, void *arg)
{
    ZipImporter *self = (ZipImporter *)obj;
    Py_VISIT(self->files);
    return 0;
}

static void
zipimporter_dealloc(ZipImporter *self)
{
    PyObject_GC_UnTrack(self);
    Py_XDECREF(self->archive);
    Py_XDECREF(self->prefix);
    Py_XDECREF(self->files);
    Py_TYPE(self)->tp_free((PyObject *)self);
}

static PyObject *
zipimporter_repr(ZipImporter *self)
{
    if (self->archive == NULL)
        return PyUnicode_FromString("<zipimporter object \"???\">");
    else if (self->prefix != NULL && PyUnicode_GET_LENGTH(self->prefix) != 0)
        return PyUnicode_FromFormat("<zipimporter object \"%U%c%U\">",
                                    self->archive, SEP, self->prefix);
    else
        return PyUnicode_FromFormat("<zipimporter object \"%U\">",
                                    self->archive);
}

/* return fullname.split(".")[-1] */
static PyObject *
get_subname(PyObject *fullname)
{
    Py_ssize_t len, dot;
    if (PyUnicode_READY(fullname) < 0)
        return NULL;
    len = PyUnicode_GET_LENGTH(fullname);
    dot = PyUnicode_FindChar(fullname, '.', 0, len, -1);
    if (dot == -1) {
        Py_INCREF(fullname);
        return fullname;
    } else
        return PyUnicode_Substring(fullname, dot+1, len);
}

/* Given a (sub)modulename, write the potential file path in the
   archive (without extension) to the path buffer. Return the
   length of the resulting string.

   return self.prefix + name.replace('.', os.sep) */
static PyObject*
make_filename(PyObject *prefix, PyObject *name)
{
    PyObject *pathobj;
    Py_UCS4 *p, *buf;
    Py_ssize_t len;

    len = PyUnicode_GET_LENGTH(prefix) + PyUnicode_GET_LENGTH(name) + 1;
    p = buf = PyMem_New(Py_UCS4, len);
    if (buf == NULL) {
        PyErr_NoMemory();
        return NULL;
    }

    if (!PyUnicode_AsUCS4(prefix, p, len, 0)) {
        PyMem_Free(buf);
        return NULL;
    }
    p += PyUnicode_GET_LENGTH(prefix);
    len -= PyUnicode_GET_LENGTH(prefix);
    if (!PyUnicode_AsUCS4(name, p, len, 1)) {
        PyMem_Free(buf);
        return NULL;
    }
    for (; *p; p++) {
        if (*p == '.')
            *p = SEP;
    }
    pathobj = PyUnicode_FromKindAndData(PyUnicode_4BYTE_KIND,
                                        buf, p-buf);
    PyMem_Free(buf);
    return pathobj;
}

enum zi_module_info {
    MI_ERROR,
    MI_NOT_FOUND,
    MI_MODULE,
    MI_PACKAGE
};

/* Does this path represent a directory?
   on error, return < 0
   if not a dir, return 0
   if a dir, return 1
*/
static int
check_is_directory(ZipImporter *self, PyObject* prefix, PyObject *path)
{
    PyObject *dirpath;
    int res;

    /* See if this is a "directory". If so, it's eligible to be part
       of a namespace package. We test by seeing if the name, with an
       appended path separator, exists. */
    dirpath = PyUnicode_FromFormat("%U%U%c", prefix, path, SEP);
    if (dirpath == NULL)
        return -1;
    /* If dirpath is present in self->files, we have a directory. */
    res = PyDict_Contains(self->files, dirpath);
    Py_DECREF(dirpath);
    return res;
}

/* Return some information about a module. */
static enum zi_module_info
get_module_info(ZipImporter *self, PyObject *fullname)
{
    PyObject *subname;
    PyObject *path, *fullpath, *item;
    struct st_zip_searchorder *zso;

    if (self->prefix == NULL) {
        PyErr_SetString(PyExc_ValueError,
                        "zipimporter.__init__() wasn't called");
        return MI_ERROR;
    }

    subname = get_subname(fullname);
    if (subname == NULL)
        return MI_ERROR;

    path = make_filename(self->prefix, subname);
    Py_DECREF(subname);
    if (path == NULL)
        return MI_ERROR;

    for (zso = zip_searchorder; *zso->suffix; zso++) {
        fullpath = PyUnicode_FromFormat("%U%s", path, zso->suffix);
        if (fullpath == NULL) {
            Py_DECREF(path);
            return MI_ERROR;
        }
        item = PyDict_GetItem(self->files, fullpath);
        Py_DECREF(fullpath);
        if (item != NULL) {
            Py_DECREF(path);
            if (zso->type & IS_PACKAGE)
                return MI_PACKAGE;
            else
                return MI_MODULE;
        }
    }
    Py_DECREF(path);
    return MI_NOT_FOUND;
}

typedef enum {
    FL_ERROR = -1,       /* error */
    FL_NOT_FOUND,        /* no loader or namespace portions found */
    FL_MODULE_FOUND,     /* module/package found */
    FL_NS_FOUND          /* namespace portion found: */
                         /* *namespace_portion will point to the name */
} find_loader_result;

/* The guts of "find_loader" and "find_module".
*/
static find_loader_result
find_loader(ZipImporter *self, PyObject *fullname, PyObject **namespace_portion)
{
    enum zi_module_info mi;

    *namespace_portion = NULL;

    mi = get_module_info(self, fullname);
    if (mi == MI_ERROR)
        return FL_ERROR;
    if (mi == MI_NOT_FOUND) {
        /* Not a module or regular package. See if this is a directory, and
           therefore possibly a portion of a namespace package. */
        find_loader_result result = FL_NOT_FOUND;
        PyObject *subname;
        int is_dir;

        /* We're only interested in the last path component of fullname;
           earlier components are recorded in self->prefix. */
        subname = get_subname(fullname);
        if (subname == NULL) {
            return FL_ERROR;
        }

        is_dir = check_is_directory(self, self->prefix, subname);
        if (is_dir < 0)
            result = FL_ERROR;
        else if (is_dir) {
            /* This is possibly a portion of a namespace
               package. Return the string representing its path,
               without a trailing separator. */
            *namespace_portion = PyUnicode_FromFormat("%U%c%U%U",
                                                      self->archive, SEP,
                                                      self->prefix, subname);
            if (*namespace_portion == NULL)
                result = FL_ERROR;
            else
                result = FL_NS_FOUND;
        }
        Py_DECREF(subname);
        return result;
    }
    /* This is a module or package. */
    return FL_MODULE_FOUND;
}

/*[clinic input]
zipimport.zipimporter.find_module

    fullname: unicode
    path: object = None
    /

Search for a module specified by 'fullname'.

'fullname' must be the fully qualified (dotted) module name. It returns the
zipimporter instance itself if the module was found, or None if it wasn't.
The optional 'path' argument is ignored -- it's there for compatibility
with the importer protocol.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_find_module_impl(ZipImporter *self, PyObject *fullname,
                                       PyObject *path)
/*[clinic end generated code: output=506087f609466dc7 input=e3528520e075063f]*/
{
    PyObject *namespace_portion = NULL;
    PyObject *result = NULL;

    switch (find_loader(self, fullname, &namespace_portion)) {
    case FL_ERROR:
        return NULL;
    case FL_NS_FOUND:
        /* A namespace portion is not allowed via find_module, so return None. */
        Py_DECREF(namespace_portion);
        /* FALL THROUGH */
    case FL_NOT_FOUND:
        result = Py_None;
        break;
    case FL_MODULE_FOUND:
        result = (PyObject *)self;
        break;
    default:
        PyErr_BadInternalCall();
        return NULL;
    }
    Py_INCREF(result);
    return result;
}


/*[clinic input]
zipimport.zipimporter.find_loader

    fullname: unicode
    path: object = None
    /

Search for a module specified by 'fullname'.

'fullname' must be the fully qualified (dotted) module name. It returns the
zipimporter instance itself if the module was found, a string containing the
full path name if it's possibly a portion of a namespace package,
or None otherwise. The optional 'path' argument is ignored -- it's
there for compatibility with the importer protocol.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_find_loader_impl(ZipImporter *self, PyObject *fullname,
                                       PyObject *path)
/*[clinic end generated code: output=601599a43bc0f49a input=dc73f275b0d5be23]*/
{
    PyObject *result = NULL;
    PyObject *namespace_portion = NULL;

    switch (find_loader(self, fullname, &namespace_portion)) {
    case FL_ERROR:
        return NULL;
    case FL_NOT_FOUND:        /* Not found, return (None, []) */
        result = Py_BuildValue("O[]", Py_None);
        break;
    case FL_MODULE_FOUND:     /* Return (self, []) */
        result = Py_BuildValue("O[]", self);
        break;
    case FL_NS_FOUND:         /* Return (None, [namespace_portion]) */
        result = Py_BuildValue("O[O]", Py_None, namespace_portion);
        Py_DECREF(namespace_portion);
        return result;
    default:
        PyErr_BadInternalCall();
        return NULL;
    }
    return result;
}

/*[clinic input]
zipimport.zipimporter.load_module

    fullname: unicode
    /

Load the module specified by 'fullname'.

'fullname' must be the fully qualified (dotted) module name. It returns the
imported module, or raises ZipImportError if it wasn't found.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_load_module_impl(ZipImporter *self, PyObject *fullname)
/*[clinic end generated code: output=7303cebf88d47953 input=c236e2e8621f04ef]*/
{
    PyObject *code = NULL, *mod, *dict;
    PyObject *modpath = NULL;
    int ispackage;

    if (PyUnicode_READY(fullname) == -1)
        return NULL;

    code = get_module_code(self, fullname, &ispackage, &modpath);
    if (code == NULL)
        goto error;

    mod = PyImport_AddModuleObject(fullname);
    if (mod == NULL)
        goto error;
    dict = PyModule_GetDict(mod);

    /* mod.__loader__ = self */
    if (PyDict_SetItemString(dict, "__loader__", (PyObject *)self) != 0)
        goto error;

    if (ispackage) {
        /* add __path__ to the module *before* the code gets
           executed */
        PyObject *pkgpath, *fullpath, *subname;
        int err;

        subname = get_subname(fullname);
        if (subname == NULL)
            goto error;

        fullpath = PyUnicode_FromFormat("%U%c%U%U",
                                self->archive, SEP,
                                self->prefix, subname);
        Py_DECREF(subname);
        if (fullpath == NULL)
            goto error;

        pkgpath = Py_BuildValue("[N]", fullpath);
        if (pkgpath == NULL)
            goto error;
        err = PyDict_SetItemString(dict, "__path__", pkgpath);
        Py_DECREF(pkgpath);
        if (err != 0)
            goto error;
    }
    mod = PyImport_ExecCodeModuleObject(fullname, code, modpath, NULL);
    Py_CLEAR(code);
    if (mod == NULL)
        goto error;

    if (Py_VerboseFlag)
        PySys_FormatStderr("import %U # loaded from Zip %U\n",
                           fullname, modpath);
    Py_DECREF(modpath);
    return mod;
error:
    Py_XDECREF(code);
    Py_XDECREF(modpath);
    return NULL;
}

/*[clinic input]
zipimport.zipimporter.get_filename

    fullname: unicode
    /

Return the filename for the specified module.
[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_get_filename_impl(ZipImporter *self,
                                        PyObject *fullname)
/*[clinic end generated code: output=c5b92b58bea86506 input=28d2eb57e4f25c8a]*/
{
    PyObject *code, *modpath;
    int ispackage;

    /* Deciding the filename requires working out where the code
       would come from if the module was actually loaded */
    code = get_module_code(self, fullname, &ispackage, &modpath);
    if (code == NULL)
        return NULL;
    Py_DECREF(code); /* Only need the path info */

    return modpath;
}

/*[clinic input]
zipimport.zipimporter.is_package

    fullname: unicode
    /

Return True if the module specified by fullname is a package.

Raise ZipImportError if the module couldn't be found.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_is_package_impl(ZipImporter *self, PyObject *fullname)
/*[clinic end generated code: output=c32958c2a5216ae6 input=a7ba752f64345062]*/
{
    enum zi_module_info mi;

    mi = get_module_info(self, fullname);
    if (mi == MI_ERROR)
        return NULL;
    if (mi == MI_NOT_FOUND) {
        PyErr_Format(ZipImportError, "can't find module %R", fullname);
        return NULL;
    }
    return PyBool_FromLong(mi == MI_PACKAGE);
}


/*[clinic input]
zipimport.zipimporter.get_data

    pathname as path: unicode
    /

Return the data associated with 'pathname'.

Raise OSError if the file was not found.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_get_data_impl(ZipImporter *self, PyObject *path)
/*[clinic end generated code: output=65dc506aaa268436 input=fa6428b74843c4ae]*/
{
    PyObject *key;
    PyObject *toc_entry;
    Py_ssize_t path_start, path_len, len;

    if (self->archive == NULL) {
        PyErr_SetString(PyExc_ValueError,
                        "zipimporter.__init__() wasn't called");
        return NULL;
    }

#ifdef ALTSEP
    path = _PyObject_CallMethodId((PyObject *)&PyUnicode_Type, &PyId_replace,
                                  "OCC", path, ALTSEP, SEP);
    if (!path)
        return NULL;
#else
    Py_INCREF(path);
#endif
    if (PyUnicode_READY(path) == -1)
        goto error;

    path_len = PyUnicode_GET_LENGTH(path);

    len = PyUnicode_GET_LENGTH(self->archive);
    path_start = 0;
    if (PyUnicode_Tailmatch(path, self->archive, 0, len, -1)
        && PyUnicode_READ_CHAR(path, len) == SEP) {
        path_start = len + 1;
    }

    key = PyUnicode_Substring(path, path_start, path_len);
    if (key == NULL)
        goto error;
    toc_entry = PyDict_GetItem(self->files, key);
    if (toc_entry == NULL) {
        PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, key);
        Py_DECREF(key);
        goto error;
    }
    Py_DECREF(key);
    Py_DECREF(path);
    return get_data(self->archive, toc_entry);
  error:
    Py_DECREF(path);
    return NULL;
}

/*[clinic input]
zipimport.zipimporter.get_code

    fullname: unicode
    /

Return the code object for the specified module.

Raise ZipImportError if the module couldn't be found.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_get_code_impl(ZipImporter *self, PyObject *fullname)
/*[clinic end generated code: output=b923c37fa99cbac4 input=2761412bc37f3549]*/
{
    return get_module_code(self, fullname, NULL, NULL);
}

/*[clinic input]
zipimport.zipimporter.get_source

    fullname: unicode
    /

Return the source code for the specified module.

Raise ZipImportError if the module couldn't be found, return None if the
archive does contain the module, but has no source for it.

[clinic start generated code]*/

static PyObject *
zipimport_zipimporter_get_source_impl(ZipImporter *self, PyObject *fullname)
/*[clinic end generated code: output=bc059301b0c33729 input=4e4b186f2e690716]*/
{
    PyObject *toc_entry;
    PyObject *subname, *path, *fullpath;
    enum zi_module_info mi;

    mi = get_module_info(self, fullname);
    if (mi == MI_ERROR)
        return NULL;
    if (mi == MI_NOT_FOUND) {
        PyErr_Format(ZipImportError, "can't find module %R", fullname);
        return NULL;
    }

    subname = get_subname(fullname);
    if (subname == NULL)
        return NULL;

    path = make_filename(self->prefix, subname);
    Py_DECREF(subname);
    if (path == NULL)
        return NULL;

    if (mi == MI_PACKAGE)
        fullpath = PyUnicode_FromFormat("%U%c__init__.py", path, SEP);
    else
        fullpath = PyUnicode_FromFormat("%U.py", path);
    Py_DECREF(path);
    if (fullpath == NULL)
        return NULL;

    toc_entry = PyDict_GetItem(self->files, fullpath);
    Py_DECREF(fullpath);
    if (toc_entry != NULL) {
        PyObject *res, *bytes;
        bytes = get_data(self->archive, toc_entry);
        if (bytes == NULL)
            return NULL;
        res = PyUnicode_FromStringAndSize(PyBytes_AS_STRING(bytes),
                                          PyBytes_GET_SIZE(bytes));
        Py_DECREF(bytes);
        return res;
    }

    /* we have the module, but no source */
    Py_RETURN_NONE;
}


static PyMethodDef zipimporter_methods[] = {
    ZIPIMPORT_ZIPIMPORTER_FIND_MODULE_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_FIND_LOADER_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_LOAD_MODULE_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_GET_FILENAME_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_IS_PACKAGE_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_GET_DATA_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_GET_CODE_METHODDEF
    ZIPIMPORT_ZIPIMPORTER_GET_SOURCE_METHODDEF
    {NULL,              NULL}   /* sentinel */
};

static PyMemberDef zipimporter_members[] = {
    {"archive",  T_OBJECT, offsetof(ZipImporter, archive),  READONLY},
    {"prefix",   T_OBJECT, offsetof(ZipImporter, prefix),   READONLY},
    {"_files",   T_OBJECT, offsetof(ZipImporter, files),    READONLY},
    {NULL}
};

#define DEFERRED_ADDRESS(ADDR) 0

static PyTypeObject ZipImporter_Type = {
    PyVarObject_HEAD_INIT(DEFERRED_ADDRESS(&PyType_Type), 0)
    "zipimport.zipimporter",
    sizeof(ZipImporter),
    0,                                          /* tp_itemsize */
    (destructor)zipimporter_dealloc,            /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_reserved */
    (reprfunc)zipimporter_repr,                 /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
        Py_TPFLAGS_HAVE_GC,                     /* tp_flags */
    zipimport_zipimporter___init____doc__,      /* tp_doc */
    zipimporter_traverse,                       /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    zipimporter_methods,                        /* tp_methods */
    zipimporter_members,                        /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    0,                                          /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    (initproc)zipimport_zipimporter___init__,   /* tp_init */
    PyType_GenericAlloc,                        /* tp_alloc */
    PyType_GenericNew,                          /* tp_new */
    PyObject_GC_Del,                            /* tp_free */
};


/* implementation */

/* Given a buffer, return the unsigned int that is represented by the first
   4 bytes, encoded as little endian. This partially reimplements
   marshal.c:r_long() */
static unsigned int
get_uint32(const unsigned char *buf)
{
    unsigned int x;
    x =  buf[0];
    x |= (unsigned int)buf[1] <<  8;
    x |= (unsigned int)buf[2] << 16;
    x |= (unsigned int)buf[3] << 24;
    return x;
}

/* Given a buffer, return the unsigned int that is represented by the first
   2 bytes, encoded as little endian. This partially reimplements
   marshal.c:r_short() */
static unsigned short
get_uint16(const unsigned char *buf)
{
    unsigned short x;
    x =  buf[0];
    x |= (unsigned short)buf[1] <<  8;
    return x;
}

static void
set_file_error(PyObject *archive, int eof)
{
    if (eof) {
        PyErr_SetString(PyExc_EOFError, "EOF read where not expected");
    }
    else {
        PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, archive);
    }
}

/*
   read_directory(archive) -> files dict (new reference)

   Given a path to a Zip archive, build a dict, mapping file names
   (local to the archive, using SEP as a separator) to toc entries.

   A toc_entry is a tuple:

   (__file__,      # value to use for __file__, available for all files,
                   # encoded to the filesystem encoding
    compress,      # compression kind; 0 for uncompressed
    data_size,     # size of compressed data on disk
    file_size,     # size of decompressed data
    file_offset,   # offset of file header from start of archive
    time,          # mod time of file (in dos format)
    date,          # mod data of file (in dos format)
    crc,           # crc checksum of the data
   )

   Directories can be recognized by the trailing SEP in the name,
   data_size and file_offset are 0.
*/
static PyObject *
read_directory(PyObject *archive)
{
    PyObject *files = NULL;
    FILE *fp;
    unsigned short flags, compress, time, date, name_size;
    unsigned int crc, data_size, file_size, header_size, header_offset;
    unsigned long file_offset, header_position;
    unsigned long arc_offset;  /* Absolute offset to start of the zip-archive. */
    unsigned int count, i;
    unsigned char buffer[46];
    char name[MAXPATHLEN + 5];
    PyObject *nameobj = NULL;
    PyObject *path;
    const char *charset;
    int bootstrap;
    const char *errmsg = NULL;

    fp = _Py_fopen_obj(archive, "rb");
    if (fp == NULL) {
        if (PyErr_ExceptionMatches(PyExc_OSError)) {
            _PyErr_FormatFromCause(ZipImportError,
                                   "can't open Zip file: %R", archive);
        }
        return NULL;
    }

    if (fseek(fp, -22, SEEK_END) == -1) {
        goto file_error;
    }
    header_position = (unsigned long)ftell(fp);
    if (header_position == (unsigned long)-1) {
        goto file_error;
    }
    assert(header_position <= (unsigned long)LONG_MAX);
    if (fread(buffer, 1, 22, fp) != 22) {
        goto file_error;
    }
    if (get_uint32(buffer) != 0x06054B50u) {
        /* Bad: End of Central Dir signature */
        errmsg = "not a Zip file";
        goto invalid_header;
    }

    header_size = get_uint32(buffer + 12);
    header_offset = get_uint32(buffer + 16);
    if (header_position < header_size) {
        errmsg = "bad central directory size";
        goto invalid_header;
    }
    if (header_position < header_offset) {
        errmsg = "bad central directory offset";
        goto invalid_header;
    }
    if (header_position - header_size < header_offset) {
        errmsg = "bad central directory size or offset";
        goto invalid_header;
    }
    header_position -= header_size;
    arc_offset = header_position - header_offset;

    files = PyDict_New();
    if (files == NULL) {
        goto error;
    }
    /* Start of Central Directory */
    count = 0;
    if (fseek(fp, (long)header_position, 0) == -1) {
        goto file_error;
    }
    for (;;) {
        PyObject *t;
        size_t n;
        int err;

        n = fread(buffer, 1, 46, fp);
        if (n < 4) {
            goto eof_error;
        }
        /* Start of file header */
        if (get_uint32(buffer) != 0x02014B50u) {
            break;              /* Bad: Central Dir File Header */
        }
        if (n != 46) {
            goto eof_error;
        }
        flags = get_uint16(buffer + 8);
        compress = get_uint16(buffer + 10);
        time = get_uint16(buffer + 12);
        date = get_uint16(buffer + 14);
        crc = get_uint32(buffer + 16);
        data_size = get_uint32(buffer + 20);
        file_size = get_uint32(buffer + 24);
        name_size = get_uint16(buffer + 28);
        header_size = (unsigned int)name_size +
           get_uint16(buffer + 30) /* extra field */ +
           get_uint16(buffer + 32) /* comment */;

        file_offset = get_uint32(buffer + 42);
        if (file_offset > header_offset) {
            errmsg = "bad local header offset";
            goto invalid_header;
        }
        file_offset += arc_offset;

        if (name_size > MAXPATHLEN) {
            name_size = MAXPATHLEN;
        }
        if (fread(name, 1, name_size, fp) != name_size) {
            goto file_error;
        }
        name[name_size] = '\0';  /* Add terminating null byte */
#if SEP != '/'
        for (i = 0; i < name_size; i++) {
            if (name[i] == '/') {
                name[i] = SEP;
            }
        }
#endif
        /* Skip the rest of the header.
         * On Windows, calling fseek to skip over the fields we don't use is
         * slower than reading the data because fseek flushes stdio's
         * internal buffers.  See issue #8745. */
        assert(header_size <= 3*0xFFFFu);
        for (i = name_size; i < header_size; i++) {
            if (getc(fp) == EOF) {
                goto file_error;
            }
        }

        bootstrap = 0;
        if (flags & 0x0800) {
            charset = "utf-8";
        }
        else if (!PyThreadState_GET()->interp->codecs_initialized) {
            /* During bootstrap, we may need to load the encodings
               package from a ZIP file. But the cp437 encoding is implemented
               in Python in the encodings package.

               Break out of this dependency by assuming that the path to
               the encodings module is ASCII-only. */
            charset = "ascii";
            bootstrap = 1;
        }
        else {
            charset = "cp437";
        }
        nameobj = PyUnicode_Decode(name, name_size, charset, NULL);
        if (nameobj == NULL) {
            if (bootstrap) {
                PyErr_Format(PyExc_NotImplementedError,
                    "bootstrap issue: python%i%i.zip contains non-ASCII "
                    "filenames without the unicode flag",
                    PY_MAJOR_VERSION, PY_MINOR_VERSION);
            }
            goto error;
        }
        if (PyUnicode_READY(nameobj) == -1) {
            goto error;
        }
        path = PyUnicode_FromFormat("%U%c%U", archive, SEP, nameobj);
        if (path == NULL) {
            goto error;
        }
        t = Py_BuildValue("NHIIkHHI", path, compress, data_size,
                          file_size, file_offset, time, date, crc);
        if (t == NULL) {
            goto error;
        }
        err = PyDict_SetItem(files, nameobj, t);
        Py_CLEAR(nameobj);
        Py_DECREF(t);
        if (err != 0) {
            goto error;
        }
        count++;
    }
    fclose(fp);
    if (Py_VerboseFlag) {
        PySys_FormatStderr("# zipimport: found %u names in %R\n",
                           count, archive);
    }
    return files;

eof_error:
    set_file_error(archive, !ferror(fp));
    goto error;

file_error:
    PyErr_Format(ZipImportError, "can't read Zip file: %R", archive);
    goto error;

invalid_header:
    assert(errmsg != NULL);
    PyErr_Format(ZipImportError, "%s: %R", errmsg, archive);
    goto error;

error:
    fclose(fp);
    Py_XDECREF(files);
    Py_XDECREF(nameobj);
    return NULL;
}

/* Return the zlib.decompress function object, or NULL if zlib couldn't
   be imported. The function is cached when found, so subsequent calls
   don't import zlib again. */
static PyObject *
get_decompress_func(void)
{
    static int importing_zlib = 0;
    PyObject *zlib;
    PyObject *decompress;
    _Py_IDENTIFIER(decompress);

    if (importing_zlib != 0)
        /* Someone has a zlib.pyc in their Zip file;
           let's avoid a stack overflow. */
        return NULL;
    importing_zlib = 1;
    zlib = PyImport_ImportModuleNoBlock("zlib");
    importing_zlib = 0;
    if (zlib != NULL) {
        decompress = _PyObject_GetAttrId(zlib,
                                         &PyId_decompress);
        Py_DECREF(zlib);
    }
    else {
        PyErr_Clear();
        decompress = NULL;
    }
    if (Py_VerboseFlag)
        PySys_WriteStderr("# zipimport: zlib %s\n",
            zlib != NULL ? "available": "UNAVAILABLE");
    return decompress;
}

/* Given a path to a Zip file and a toc_entry, return the (uncompressed)
   data as a new reference. */
static PyObject *
get_data(PyObject *archive, PyObject *toc_entry)
{
    PyObject *raw_data = NULL, *data, *decompress;
    char *buf;
    FILE *fp;
    PyObject *datapath;
    unsigned short compress, time, date;
    unsigned int crc;
    Py_ssize_t data_size, file_size, bytes_size;
    long file_offset, header_size;
    unsigned char buffer[30];
    const char *errmsg = NULL;

    if (!PyArg_ParseTuple(toc_entry, "OHnnlHHI", &datapath, &compress,
                          &data_size, &file_size, &file_offset, &time,
                          &date, &crc)) {
        return NULL;
    }
    if (data_size < 0) {
        PyErr_Format(ZipImportError, "negative data size");
        return NULL;
    }

    fp = _Py_fopen_obj(archive, "rb");
    if (!fp) {
        return NULL;
    }
    /* Check to make sure the local file header is correct */
    if (fseek(fp, file_offset, 0) == -1) {
        goto file_error;
    }
    if (fread(buffer, 1, 30, fp) != 30) {
        goto eof_error;
    }
    if (get_uint32(buffer) != 0x04034B50u) {
        /* Bad: Local File Header */
        errmsg = "bad local file header";
        goto invalid_header;
    }

    header_size = (unsigned int)30 +
        get_uint16(buffer + 26) /* file name */ +
        get_uint16(buffer + 28) /* extra field */;
    if (file_offset > LONG_MAX - header_size) {
        errmsg = "bad local file header size";
        goto invalid_header;
    }
    file_offset += header_size;  /* Start of file data */

    if (data_size > LONG_MAX - 1) {
        fclose(fp);
        PyErr_NoMemory();
        return NULL;
    }
    bytes_size = compress == 0 ? data_size : data_size + 1;
    if (bytes_size == 0) {
        bytes_size++;
    }
    raw_data = PyBytes_FromStringAndSize((char *)NULL, bytes_size);
    if (raw_data == NULL) {
        goto error;
    }
    buf = PyBytes_AsString(raw_data);

    if (fseek(fp, file_offset, 0) == -1) {
        goto file_error;
    }
    if (fread(buf, 1, data_size, fp) != (size_t)data_size) {
        PyErr_SetString(PyExc_OSError,
                        "zipimport: can't read data");
        goto error;
    }

    fclose(fp);
    fp = NULL;

    if (compress != 0) {
        buf[data_size] = 'Z';  /* saw this in zipfile.py */
        data_size++;
    }
    buf[data_size] = '\0';

    if (compress == 0) {  /* data is not compressed */
        data = PyBytes_FromStringAndSize(buf, data_size);
        Py_DECREF(raw_data);
        return data;
    }

    /* Decompress with zlib */
    decompress = get_decompress_func();
    if (decompress == NULL) {
        PyErr_SetString(ZipImportError,
                        "can't decompress data; "
                        "zlib not available");
        goto error;
    }
    data = PyObject_CallFunction(decompress, "Oi", raw_data, -15);
    Py_DECREF(decompress);
    Py_DECREF(raw_data);
    if (data != NULL && !PyBytes_Check(data)) {
        PyErr_Format(PyExc_TypeError,
                     "zlib.decompress() must return a bytes object, not "
                     "%.200s",
                     Py_TYPE(data)->tp_name);
        Py_DECREF(data);
        return NULL;
    }
    return data;

eof_error:
    set_file_error(archive, !ferror(fp));
    goto error;

file_error:
    PyErr_Format(ZipImportError, "can't read Zip file: %R", archive);
    goto error;

invalid_header:
    assert(errmsg != NULL);
    PyErr_Format(ZipImportError, "%s: %R", errmsg, archive);
    goto error;

error:
    if (fp != NULL) {
        fclose(fp);
    }
    Py_XDECREF(raw_data);
    return NULL;
}

/* Lenient date/time comparison function. The precision of the mtime
   in the archive is lower than the mtime stored in a .pyc: we
   must allow a difference of at most one second. */
static int
eq_mtime(time_t t1, time_t t2)
{
    time_t d = t1 - t2;
    if (d < 0)
        d = -d;
    /* dostime only stores even seconds, so be lenient */
    return d <= 1;
}

/* Given the contents of a .pyc file in a buffer, unmarshal the data
   and return the code object. Return None if it the magic word doesn't
   match (we do this instead of raising an exception as we fall back
   to .py if available and we don't want to mask other errors).
   Returns a new reference. */
static PyObject *
unmarshal_code(PyObject *pathname, PyObject *data, time_t mtime)
{
    PyObject *code;
    unsigned char *buf = (unsigned char *)PyBytes_AsString(data);
    Py_ssize_t size = PyBytes_Size(data);

    if (size < 16) {
        PyErr_SetString(ZipImportError,
                        "bad pyc data");
        return NULL;
    }

    if (get_uint32(buf) != (unsigned int)PyImport_GetMagicNumber()) {
        if (Py_VerboseFlag) {
            PySys_FormatStderr("# %R has bad magic\n",
                               pathname);
        }
        Py_RETURN_NONE;  /* signal caller to try alternative */
    }

    uint32_t flags = get_uint32(buf + 4);
    if (flags != 0) {
        // Hash-based pyc. We currently refuse to handle checked hash-based
        // pycs. We could validate hash-based pycs against the source, but it
        // seems likely that most people putting hash-based pycs in a zipfile
        // will use unchecked ones.
        if (strcmp(_Py_CheckHashBasedPycsMode, "never") &&
            (flags != 0x1 || !strcmp(_Py_CheckHashBasedPycsMode, "always")))
            Py_RETURN_NONE;
    } else if ((mtime != 0 && !eq_mtime(get_uint32(buf + 8), mtime))) {
        if (Py_VerboseFlag) {
            PySys_FormatStderr("# %R has bad mtime\n",
                               pathname);
        }
        Py_RETURN_NONE;  /* signal caller to try alternative */
    }

    /* XXX the pyc's size field is ignored; timestamp collisions are probably
       unimportant with zip files. */
    code = PyMarshal_ReadObjectFromString((char *)buf + 16, size - 16);
    if (code == NULL) {
        return NULL;
    }
    if (!PyCode_Check(code)) {
        Py_DECREF(code);
        PyErr_Format(PyExc_TypeError,
             "compiled module %R is not a code object",
             pathname);
        return NULL;
    }
    return code;
}

/* Replace any occurrences of "\r\n?" in the input string with "\n".
   This converts DOS and Mac line endings to Unix line endings.
   Also append a trailing "\n" to be compatible with
   PyParser_SimpleParseFile(). Returns a new reference. */
static PyObject *
normalize_line_endings(PyObject *source)
{
    char *buf, *q, *p;
    PyObject *fixed_source;
    int len = 0;

    p = PyBytes_AsString(source);
    if (p == NULL) {
        return PyBytes_FromStringAndSize("\n\0", 2);
    }

    /* one char extra for trailing \n and one for terminating \0 */
    buf = (char *)PyMem_Malloc(PyBytes_Size(source) + 2);
    if (buf == NULL) {
        PyErr_SetString(PyExc_MemoryError,
                        "zipimport: no memory to allocate "
                        "source buffer");
        return NULL;
    }
    /* replace "\r\n?" by "\n" */
    for (q = buf; *p != '\0'; p++) {
        if (*p == '\r') {
            *q++ = '\n';
            if (*(p + 1) == '\n')
                p++;
        }
        else
            *q++ = *p;
        len++;
    }
    *q++ = '\n';  /* add trailing \n */
    *q = '\0';
    fixed_source = PyBytes_FromStringAndSize(buf, len + 2);
    PyMem_Free(buf);
    return fixed_source;
}

/* Given a string buffer containing Python source code, compile it
   and return a code object as a new reference. */
static PyObject *
compile_source(PyObject *pathname, PyObject *source)
{
    PyObject *code, *fixed_source;

    fixed_source = normalize_line_endings(source);
    if (fixed_source == NULL) {
        return NULL;
    }

    code = Py_CompileStringObject(PyBytes_AsString(fixed_source),
                                  pathname, Py_file_input, NULL, -1);

    Py_DECREF(fixed_source);
    return code;
}

/* Convert the date/time values found in the Zip archive to a value
   that's compatible with the time stamp stored in .pyc files. */
static time_t
parse_dostime(int dostime, int dosdate)
{
    struct tm stm;

    memset((void *) &stm, '\0', sizeof(stm));

    stm.tm_sec   =  (dostime        & 0x1f) * 2;
    stm.tm_min   =  (dostime >> 5)  & 0x3f;
    stm.tm_hour  =  (dostime >> 11) & 0x1f;
    stm.tm_mday  =   dosdate        & 0x1f;
    stm.tm_mon   = ((dosdate >> 5)  & 0x0f) - 1;
    stm.tm_year  = ((dosdate >> 9)  & 0x7f) + 80;
    stm.tm_isdst =   -1; /* wday/yday is ignored */

    return mktime(&stm);
}

/* Given a path to a .pyc file in the archive, return the
   modification time of the matching .py file, or 0 if no source
   is available. */
static time_t
get_mtime_of_source(ZipImporter *self, PyObject *path)
{
    PyObject *toc_entry, *stripped;
    time_t mtime;

    /* strip 'c' from *.pyc */
    if (PyUnicode_READY(path) == -1)
        return (time_t)-1;
    stripped = PyUnicode_FromKindAndData(PyUnicode_KIND(path),
                                         PyUnicode_DATA(path),
                                         PyUnicode_GET_LENGTH(path) - 1);
    if (stripped == NULL)
        return (time_t)-1;

    toc_entry = PyDict_GetItem(self->files, stripped);
    Py_DECREF(stripped);
    if (toc_entry != NULL && PyTuple_Check(toc_entry) &&
        PyTuple_Size(toc_entry) == 8) {
        /* fetch the time stamp of the .py file for comparison
           with an embedded pyc time stamp */
        int time, date;
        time = PyLong_AsLong(PyTuple_GetItem(toc_entry, 5));
        date = PyLong_AsLong(PyTuple_GetItem(toc_entry, 6));
        mtime = parse_dostime(time, date);
    } else
        mtime = 0;
    return mtime;
}

/* Return the code object for the module named by 'fullname' from the
   Zip archive as a new reference. */
static PyObject *
get_code_from_data(ZipImporter *self, int ispackage, int isbytecode,
                   time_t mtime, PyObject *toc_entry)
{
    PyObject *data, *modpath, *code;

    data = get_data(self->archive, toc_entry);
    if (data == NULL)
        return NULL;

    modpath = PyTuple_GetItem(toc_entry, 0);
    if (isbytecode)
        code = unmarshal_code(modpath, data, mtime);
    else
        code = compile_source(modpath, data);
    Py_DECREF(data);
    return code;
}

/* Get the code object associated with the module specified by
   'fullname'. */
static PyObject *
get_module_code(ZipImporter *self, PyObject *fullname,
                int *p_ispackage, PyObject **p_modpath)
{
    PyObject *code = NULL, *toc_entry, *subname;
    PyObject *path, *fullpath = NULL;
    struct st_zip_searchorder *zso;

    if (self->prefix == NULL) {
        PyErr_SetString(PyExc_ValueError,
                        "zipimporter.__init__() wasn't called");
        return NULL;
    }

    subname = get_subname(fullname);
    if (subname == NULL)
        return NULL;

    path = make_filename(self->prefix, subname);
    Py_DECREF(subname);
    if (path == NULL)
        return NULL;

    for (zso = zip_searchorder; *zso->suffix; zso++) {
        code = NULL;

        fullpath = PyUnicode_FromFormat("%U%s", path, zso->suffix);
        if (fullpath == NULL)
            goto exit;

        if (Py_VerboseFlag > 1)
            PySys_FormatStderr("# trying %U%c%U\n",
                               self->archive, (int)SEP, fullpath);
        toc_entry = PyDict_GetItem(self->files, fullpath);
        if (toc_entry != NULL) {
            time_t mtime = 0;
            int ispackage = zso->type & IS_PACKAGE;
            int isbytecode = zso->type & IS_BYTECODE;

            if (isbytecode) {
                mtime = get_mtime_of_source(self, fullpath);
                if (mtime == (time_t)-1 && PyErr_Occurred()) {
                    goto exit;
                }
            }
            Py_CLEAR(fullpath);
            if (p_ispackage != NULL)
                *p_ispackage = ispackage;
            code = get_code_from_data(self, ispackage,
                                      isbytecode, mtime,
                                      toc_entry);
            if (code == Py_None) {
                /* bad magic number or non-matching mtime
                   in byte code, try next */
                Py_DECREF(code);
                continue;
            }
            if (code != NULL && p_modpath != NULL) {
                *p_modpath = PyTuple_GetItem(toc_entry, 0);
                Py_INCREF(*p_modpath);
            }
            goto exit;
        }
        else
            Py_CLEAR(fullpath);
    }
    PyErr_Format(ZipImportError, "can't find module %R", fullname);
exit:
    Py_DECREF(path);
    Py_XDECREF(fullpath);
    return code;
}


/* Module init */

PyDoc_STRVAR(zipimport_doc,
"zipimport provides support for importing Python modules from Zip archives.\n\
\n\
This module exports three objects:\n\
- zipimporter: a class; its constructor takes a path to a Zip archive.\n\
- ZipImportError: exception raised by zipimporter objects. It's a\n\
  subclass of ImportError, so it can be caught as ImportError, too.\n\
- _zip_directory_cache: a dict, mapping archive paths to zip directory\n\
  info dicts, as used in zipimporter._files.\n\
\n\
It is usually not needed to use the zipimport module explicitly; it is\n\
used by the builtin import mechanism for sys.path items that are paths\n\
to Zip archives.");

static struct PyModuleDef zipimportmodule = {
    PyModuleDef_HEAD_INIT,
    "zipimport",
    zipimport_doc,
    -1,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL
};

PyMODINIT_FUNC
PyInit_zipimport(void)
{
    PyObject *mod;

    if (PyType_Ready(&ZipImporter_Type) < 0)
        return NULL;

    /* Correct directory separator */
    zip_searchorder[0].suffix[0] = SEP;
    zip_searchorder[1].suffix[0] = SEP;

    mod = PyModule_Create(&zipimportmodule);
    if (mod == NULL)
        return NULL;

    ZipImportError = PyErr_NewException("zipimport.ZipImportError",
                                        PyExc_ImportError, NULL);
    if (ZipImportError == NULL)
        return NULL;

    Py_INCREF(ZipImportError);
    if (PyModule_AddObject(mod, "ZipImportError",
                           ZipImportError) < 0)
        return NULL;

    Py_INCREF(&ZipImporter_Type);
    if (PyModule_AddObject(mod, "zipimporter",
                           (PyObject *)&ZipImporter_Type) < 0)
        return NULL;

    zip_directory_cache = PyDict_New();
    if (zip_directory_cache == NULL)
        return NULL;
    Py_INCREF(zip_directory_cache);
    if (PyModule_AddObject(mod, "_zip_directory_cache",
                           zip_directory_cache) < 0)
        return NULL;
    return mod;
}