Modules/mmapmodule.c

/*
 /  Author: Sam Rushing <rushing@nightmare.com>
 /  Hacked for Unix by A.M. Kuchling <amk1@bigfoot.com> 
 /  $Id$

 / mmapmodule.cpp -- map a view of a file into memory
 /
 / todo: need permission flags, perhaps a 'chsize' analog
 /   not all functions check range yet!!!
 /
 /
 / Note: This module currently only deals with 32-bit file
 /   sizes.
 /
 / The latest version of mmapfile is maintained by Sam at
 / ftp://squirl.nightmare.com/pub/python/python-ext.
*/

#include <Python.h>

#ifndef MS_WIN32
#define UNIX
#endif

#ifdef MS_WIN32
#include <windows.h>
#if _MSC_VER < 1200
#define INT_PTR unsigned long
#endif
#endif

#ifdef UNIX
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#endif

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

static PyObject *mmap_module_error;

typedef struct {
	PyObject_HEAD
	char *	data;
	size_t	size;
	size_t	pos;

#ifdef MS_WIN32
	HANDLE	map_handle;
	INT_PTR	file_handle;
	char *	tagname;
#endif

#ifdef UNIX
        int fd;
#endif
} mmap_object;

static void
mmap_object_dealloc(mmap_object *m_obj)
{
#ifdef MS_WIN32
	if (m_obj->data != NULL)
		UnmapViewOfFile (m_obj->data);
	if (m_obj->map_handle != INVALID_HANDLE_VALUE)
		CloseHandle (m_obj->map_handle);
	if ((HANDLE)m_obj->file_handle != INVALID_HANDLE_VALUE)
		CloseHandle ((HANDLE)m_obj->file_handle);
	if (m_obj->tagname)
		PyMem_Free(m_obj->tagname);
#endif /* MS_WIN32 */

#ifdef UNIX
	if (m_obj->data!=NULL) {
		msync(m_obj->data, m_obj->size, MS_SYNC);
		munmap(m_obj->data, m_obj->size);
	}
#endif /* UNIX */

	PyObject_Del(m_obj);
}

static PyObject *
mmap_close_method(mmap_object *self, PyObject *args)
{
        if (!PyArg_ParseTuple(args, ":close"))
		return NULL;
#ifdef MS_WIN32
	UnmapViewOfFile (self->data);
	CloseHandle (self->map_handle);
	CloseHandle ((HANDLE)self->file_handle);
	self->map_handle = (HANDLE) NULL;
#endif /* MS_WIN32 */

#ifdef UNIX
	munmap(self->data, self->size);
	self->data = NULL;
#endif

	Py_INCREF (Py_None);
	return (Py_None);
}

#ifdef MS_WIN32
#define CHECK_VALID(err)						\
do {									\
    if (!self->map_handle) {						\
	PyErr_SetString (PyExc_ValueError, "mmap closed or invalid");	\
	return err;							\
    }									\
} while (0)
#endif /* MS_WIN32 */

#ifdef UNIX
#define CHECK_VALID(err)						\
do {									\
    if (self->data == NULL) {						\
	PyErr_SetString (PyExc_ValueError, "mmap closed or invalid");	\
	return err;							\
	}								\
} while (0)
#endif /* UNIX */

static PyObject *
mmap_read_byte_method(mmap_object *self,
		      PyObject *args)
{
	char value;
	char *where;
	CHECK_VALID(NULL);
        if (!PyArg_ParseTuple(args, ":read_byte"))
		return NULL;
	if (self->pos < self->size) {
	        where = self->data + self->pos;
		value = (char) *(where);
		self->pos += 1;
		return Py_BuildValue("c", (char) *(where));
	} else {
		PyErr_SetString (PyExc_ValueError, "read byte out of range");
		return NULL;
	}
}

static PyObject *
mmap_read_line_method(mmap_object *self,
		     PyObject *args)
{
	char *start = self->data+self->pos;
	char *eof = self->data+self->size;
	char *eol;
	PyObject *result;

	CHECK_VALID(NULL);
        if (!PyArg_ParseTuple(args, ":readline"))
		return NULL;

	eol = memchr(start, '\n', self->size - self->pos);
	if (!eol)
		eol = eof;
	else
		++eol;		/* we're interested in the position after the
				   newline. */
	result = PyString_FromStringAndSize(start, (eol - start));
	self->pos += (eol - start);
	return (result);
}

static PyObject *
mmap_read_method(mmap_object *self,
		 PyObject *args)
{
	long num_bytes;
	PyObject *result;

	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple(args, "l:read", &num_bytes))
		return(NULL);

	/* silently 'adjust' out-of-range requests */
	if ((self->pos + num_bytes) > self->size) {
		num_bytes -= (self->pos+num_bytes) - self->size;
	}
	result = Py_BuildValue("s#", self->data+self->pos, num_bytes);
	self->pos += num_bytes;	 
	return (result);
}

static PyObject *
mmap_find_method(mmap_object *self,
		 PyObject *args)
{
	int start = self->pos;
	char *needle;
	int len;

	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "s#|i:find", &needle, &len, &start)) {
		return NULL;
	} else {
		char *p = self->data+self->pos;
		char *e = self->data+self->size;
		while (p < e) {
			char *s = p;
			char *n = needle;
			while ((s<e) && (*n) && !(*s-*n)) {
				s++, n++;
			}
			if (!*n) {
				return Py_BuildValue (
					"i",
					(int) (p - (self->data + start)));
			}
			p++;
		}
		return Py_BuildValue ("l", (long) -1);
	}
}

static PyObject *
mmap_write_method(mmap_object *self,
		  PyObject *args)
{
	long length;
	char *data;

	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "s#:write", &data, &length))
		return(NULL);

	if ((self->pos + length) > self->size) {
		PyErr_SetString (PyExc_ValueError, "data out of range");
		return NULL;
	}
	memcpy (self->data+self->pos, data, length);
	self->pos = self->pos+length;
	Py_INCREF (Py_None);
	return (Py_None);
}

static PyObject *
mmap_write_byte_method(mmap_object *self,
		       PyObject *args)
{
	char value;

	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "c:write_byte", &value))
		return(NULL);

	*(self->data+self->pos) = value;
	self->pos += 1;
	Py_INCREF (Py_None);
	return (Py_None);
}

static PyObject *
mmap_size_method(mmap_object *self,
		 PyObject *args)
{
	CHECK_VALID(NULL);
        if (!PyArg_ParseTuple(args, ":size"))
		return NULL;

#ifdef MS_WIN32
	if (self->file_handle != (INT_PTR) -1) {
		return (Py_BuildValue (
			"l", (long)
			GetFileSize ((HANDLE)self->file_handle, NULL)));
	} else {
		return (Py_BuildValue ("l", (long) self->size) );
	}
#endif /* MS_WIN32 */

#ifdef UNIX
	{
		struct stat buf;
		if (-1 == fstat(self->fd, &buf)) {
			PyErr_SetFromErrno(mmap_module_error);
			return NULL;
		}
		return (Py_BuildValue ("l", (long) buf.st_size) );
	}
#endif /* UNIX */
}

/* This assumes that you want the entire file mapped,
 / and when recreating the map will make the new file
 / have the new size
 /
 / Is this really necessary?  This could easily be done
 / from python by just closing and re-opening with the
 / new size?
 */

static PyObject *
mmap_resize_method(mmap_object *self,
		   PyObject *args)
{
	unsigned long new_size;
	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "l:resize", &new_size)) {
		return NULL;
#ifdef MS_WIN32
	} else { 
		DWORD dwErrCode = 0;
		/* First, unmap the file view */
		UnmapViewOfFile (self->data);
		/* Close the mapping object */
		CloseHandle ((HANDLE)self->map_handle);
		/* Move to the desired EOF position */
		SetFilePointer ((HANDLE)self->file_handle,
				new_size, NULL, FILE_BEGIN);
		/* Change the size of the file */
		SetEndOfFile ((HANDLE)self->file_handle);
		/* Create another mapping object and remap the file view */
		self->map_handle = CreateFileMapping (
			(HANDLE) self->file_handle,
			NULL,
			PAGE_READWRITE,
			0,
			new_size,
			self->tagname);
		if (self->map_handle != NULL) {
			self->data = (char *) MapViewOfFile (self->map_handle,
							     FILE_MAP_WRITE,
							     0,
							     0,
							     0);
			if (self->data != NULL) {
				self->size = new_size;
				Py_INCREF (Py_None);
				return Py_None;
			} else {
				dwErrCode = GetLastError();
			}
		} else {
			dwErrCode = GetLastError();
		}
		PyErr_SetFromWindowsErr(dwErrCode);
		return (NULL);
#endif /* MS_WIN32 */

#ifdef UNIX
#ifndef HAVE_MREMAP 
} else {
	PyErr_SetString(PyExc_SystemError,
			"mmap: resizing not available--no mremap()");
	return NULL;
#else
} else {
	void *newmap;

#ifdef MREMAP_MAYMOVE
	newmap = mremap(self->data, self->size, new_size, MREMAP_MAYMOVE);
#else
	newmap = mremap(self->data, self->size, new_size, 0);
#endif
	if (newmap == (void *)-1) 
	{
		PyErr_SetFromErrno(mmap_module_error);
		return NULL;
	}
	self->data = newmap;
	self->size = new_size;
	Py_INCREF(Py_None);
	return Py_None;
#endif /* HAVE_MREMAP */
#endif /* UNIX */
}
}

static PyObject *
mmap_tell_method(mmap_object *self, PyObject *args)
{
	CHECK_VALID(NULL);
        if (!PyArg_ParseTuple(args, ":tell"))
		return NULL;
	return (Py_BuildValue ("l", (long) self->pos) );
}

static PyObject *
mmap_flush_method(mmap_object *self, PyObject *args)
{
	size_t offset	= 0;
	size_t size = self->size;
	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "|ll:flush", &offset, &size)) {
		return NULL;
	} else if ((offset + size) > self->size) {
		PyErr_SetString (PyExc_ValueError,
				 "flush values out of range");
		return NULL;
	} else {
#ifdef MS_WIN32
		return (Py_BuildValue("l", (long)
                                      FlushViewOfFile(self->data+offset, size)));
#endif /* MS_WIN32 */
#ifdef UNIX
		/* XXX semantics of return value? */
		/* XXX flags for msync? */
		if (-1 == msync(self->data + offset, size,
				MS_SYNC))
		{
			PyErr_SetFromErrno(mmap_module_error);
			return NULL;
		}
		return Py_BuildValue ("l", (long) 0);	
#endif /* UNIX */   
	}
}

static PyObject *
mmap_seek_method(mmap_object *self, PyObject *args)
{
	int dist;
	int how=0;
	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "i|i:seek", &dist, &how)) {
		return(NULL);
	} else {
		size_t where;
		switch (how) {
		case 0: /* relative to start */
			if (dist < 0)
				goto onoutofrange;
			where = dist;
			break;
		case 1: /* relative to current position */
			if ((int)self->pos + dist < 0)
				goto onoutofrange;
			where = self->pos + dist;
			break;
		case 2: /* relative to end */
			if ((int)self->size + dist < 0)
				goto onoutofrange;
			where = self->size + dist;
			break;
		default:
			PyErr_SetString (PyExc_ValueError,
					 "unknown seek type");
			return NULL;
		}
		if (where > self->size)
			goto onoutofrange;
		self->pos = where;
		Py_INCREF (Py_None);
		return (Py_None);
	}

onoutofrange:
	PyErr_SetString (PyExc_ValueError, "seek out of range");
	return NULL;
}

static PyObject *
mmap_move_method(mmap_object *self, PyObject *args)
{
	unsigned long dest, src, count;
	CHECK_VALID(NULL);
	if (!PyArg_ParseTuple (args, "iii:move", &dest, &src, &count)) {
		return NULL;
	} else {
		/* bounds check the values */
		if (/* end of source after end of data?? */
			((src+count) > self->size)
			/* dest will fit? */
			|| (dest+count > self->size)) {
			PyErr_SetString (PyExc_ValueError,
					 "source or destination out of range");
			return NULL;
		} else {
			memmove (self->data+dest, self->data+src, count);
			Py_INCREF (Py_None);
			return Py_None;
		}
	}
}

static struct PyMethodDef mmap_object_methods[] = {
	{"close",	(PyCFunction) mmap_close_method,	1},
	{"find",	(PyCFunction) mmap_find_method,		1},
	{"flush",	(PyCFunction) mmap_flush_method,	1},
	{"move",	(PyCFunction) mmap_move_method,		1},
	{"read",	(PyCFunction) mmap_read_method,		1},
	{"read_byte",	(PyCFunction) mmap_read_byte_method,  	1},
	{"readline",	(PyCFunction) mmap_read_line_method,	1},
	{"resize",	(PyCFunction) mmap_resize_method,	1},
	{"seek",	(PyCFunction) mmap_seek_method,		1},
	{"size",	(PyCFunction) mmap_size_method,		1},
	{"tell",	(PyCFunction) mmap_tell_method,		1},
	{"write",	(PyCFunction) mmap_write_method,	1},
	{"write_byte",	(PyCFunction) mmap_write_byte_method,	1},
	{NULL,	   NULL}       /* sentinel */
};

/* Functions for treating an mmap'ed file as a buffer */

static int
mmap_buffer_getreadbuf(mmap_object *self, int index, const void **ptr)
{
	CHECK_VALID(-1);
	if ( index != 0 ) {
		PyErr_SetString(PyExc_SystemError,
				"Accessing non-existent mmap segment");
		return -1;
	}
	*ptr = self->data;
	return self->size;
}

static int
mmap_buffer_getwritebuf(mmap_object *self, int index, const void **ptr)
{  
	CHECK_VALID(-1);
	if ( index != 0 ) {
		PyErr_SetString(PyExc_SystemError,
				"Accessing non-existent mmap segment");
		return -1;
	}
	*ptr = self->data;
	return self->size;
}

static int
mmap_buffer_getsegcount(mmap_object *self, int *lenp)
{
	CHECK_VALID(-1);
	if (lenp) 
		*lenp = self->size;
	return 1;
}

static int
mmap_buffer_getcharbuffer(mmap_object *self, int index, const void **ptr)
{
	if ( index != 0 ) {
		PyErr_SetString(PyExc_SystemError,
				"accessing non-existent buffer segment");
		return -1;
	}
	*ptr = (const char *)self->data;
	return self->size;
}

static PyObject *
mmap_object_getattr(mmap_object *self, char *name)
{
	return Py_FindMethod (mmap_object_methods, (PyObject *)self, name);
}

static int
mmap_length(mmap_object *self)
{
	CHECK_VALID(-1);
	return self->size;
}

static PyObject *
mmap_item(mmap_object *self, int i)
{
	CHECK_VALID(NULL);
	if (i < 0 || (size_t)i >= self->size) {
		PyErr_SetString(PyExc_IndexError, "mmap index out of range");
		return NULL;
	}
	return PyString_FromStringAndSize(self->data + i, 1);
}

static PyObject *
mmap_slice(mmap_object *self, int ilow, int ihigh)
{
	CHECK_VALID(NULL);
	if (ilow < 0)
		ilow = 0;
	else if ((size_t)ilow > self->size)
		ilow = self->size;
	if (ihigh < 0)
		ihigh = 0;
	if (ihigh < ilow)
		ihigh = ilow;
	else if ((size_t)ihigh > self->size)
		ihigh = self->size;
    
	return PyString_FromStringAndSize(self->data + ilow, ihigh-ilow);
}

static PyObject *
mmap_concat(mmap_object *self, PyObject *bb)
{
	CHECK_VALID(NULL);
	PyErr_SetString(PyExc_SystemError,
			"mmaps don't support concatenation");
	return NULL;
}

static PyObject *
mmap_repeat(mmap_object *self, int n)
{
	CHECK_VALID(NULL);
	PyErr_SetString(PyExc_SystemError,
			"mmaps don't support repeat operation");
	return NULL;
}

static int
mmap_ass_slice(mmap_object *self, int ilow, int ihigh, PyObject *v)
{
	const char *buf;

	CHECK_VALID(-1);
	if (ilow < 0)
		ilow = 0;
	else if ((size_t)ilow > self->size)
		ilow = self->size;
	if (ihigh < 0)
		ihigh = 0;
	if (ihigh < ilow)
		ihigh = ilow;
	else if ((size_t)ihigh > self->size)
		ihigh = self->size;
    
	if (! (PyString_Check(v)) ) {
		PyErr_SetString(PyExc_IndexError, 
				"mmap slice assignment must be a string");
		return -1;
	}
	if ( PyString_Size(v) != (ihigh - ilow) ) {
		PyErr_SetString(PyExc_IndexError, 
				"mmap slice assignment is wrong size");
		return -1;
	}
	buf = PyString_AsString(v);
	memcpy(self->data + ilow, buf, ihigh-ilow);
	return 0;
}

static int
mmap_ass_item(mmap_object *self, int i, PyObject *v)
{
	const char *buf;
 
	CHECK_VALID(-1);
	if (i < 0 || (size_t)i >= self->size) {
		PyErr_SetString(PyExc_IndexError, "mmap index out of range");
		return -1;
	}
	if (! (PyString_Check(v) && PyString_Size(v)==1) ) {
		PyErr_SetString(PyExc_IndexError, 
			"mmap assignment must be single-character string");
		return -1;
	}
	buf = PyString_AsString(v);
	self->data[i] = buf[0];
	return 0;
}

static PySequenceMethods mmap_as_sequence = {
	(inquiry)mmap_length,		       /*sq_length*/
	(binaryfunc)mmap_concat,	       /*sq_concat*/
	(intargfunc)mmap_repeat,	       /*sq_repeat*/
	(intargfunc)mmap_item,		       /*sq_item*/
	(intintargfunc)mmap_slice,	       /*sq_slice*/
	(intobjargproc)mmap_ass_item,	       /*sq_ass_item*/
	(intintobjargproc)mmap_ass_slice,      /*sq_ass_slice*/
};

static PyBufferProcs mmap_as_buffer = {
	(getreadbufferproc)mmap_buffer_getreadbuf,
	(getwritebufferproc)mmap_buffer_getwritebuf,
	(getsegcountproc)mmap_buffer_getsegcount,
	(getcharbufferproc)mmap_buffer_getcharbuffer,
};

static PyTypeObject mmap_object_type = {
	PyObject_HEAD_INIT(0) /* patched in module init */
	0,					/* ob_size */
	"mmap",					/* tp_name */
	sizeof(mmap_object),			/* tp_size */
	0,					/* tp_itemsize */
	/* methods */
	(destructor) mmap_object_dealloc,	/* tp_dealloc */
	0,					/* tp_print */
	(getattrfunc) mmap_object_getattr,	/* tp_getattr */
	0,					/* tp_setattr */
	0,					/* tp_compare */
	0,					/* tp_repr */
	0,					/* tp_as_number */
	&mmap_as_sequence,			/*tp_as_sequence*/
	0,					/*tp_as_mapping*/
	0,					/*tp_hash*/
	0,					/*tp_call*/
	0,					/*tp_str*/
	0,					/*tp_getattro*/
	0,					/*tp_setattro*/
	&mmap_as_buffer,			/*tp_as_buffer*/
	Py_TPFLAGS_HAVE_GETCHARBUFFER,		/*tp_flags*/
	0,					/*tp_doc*/
};


/* extract the map size from the given PyObject

   The map size is restricted to [0, INT_MAX] because this is the current
   Python limitation on object sizes. Although the mmap object *could* handle
   a larger map size, there is no point because all the useful operations
   (len(), slicing(), sequence indexing) are limited by a C int.

   Returns -1 on error, with an appropriate Python exception raised. On
   success, the map size is returned. */
static int
_GetMapSize(PyObject *o)
{
	if (PyInt_Check(o)) {
		long i = PyInt_AsLong(o);
		if (PyErr_Occurred())
			return -1;
		if (i < 0)
			goto onnegoverflow;
		if (i > INT_MAX)
			goto onposoverflow;
		return (int)i;
	}
	else if (PyLong_Check(o)) {
		long i = PyLong_AsLong(o);
		if (PyErr_Occurred()) {
			/* yes negative overflow is mistaken for positive overflow
			   but not worth the trouble to check sign of 'i' */
			if (PyErr_ExceptionMatches(PyExc_OverflowError))
				goto onposoverflow;
			else
				return -1;
		}
		if (i < 0)
			goto onnegoverflow;
		if (i > INT_MAX)
			goto onposoverflow;
		return (int)i;
	}
	else {
		PyErr_SetString(PyExc_TypeError,
			"map size must be an integral value");
		return -1;
	}

onnegoverflow:
	PyErr_SetString(PyExc_OverflowError,
		"memory mapped size must be positive");
	return -1;

onposoverflow:
	PyErr_SetString(PyExc_OverflowError,
		"memory mapped size is too large (limited by C int)");
	return -1;
}

#ifdef UNIX 
static PyObject *
new_mmap_object(PyObject *self, PyObject *args, PyObject *kwdict)
{
	mmap_object *m_obj;
	PyObject *map_size_obj = NULL;
	int map_size;
	int fd, flags = MAP_SHARED, prot = PROT_WRITE | PROT_READ;
	char *keywords[] = {"file", "size", "flags", "prot", NULL};

	if (!PyArg_ParseTupleAndKeywords(args, kwdict, 
					 "iO|ii", keywords, 
					 &fd, &map_size_obj, &flags, &prot)
		)
		return NULL;
	map_size = _GetMapSize(map_size_obj);
	if (map_size < 0)
		return NULL;
	
	m_obj = PyObject_New (mmap_object, &mmap_object_type);
	if (m_obj == NULL) {return NULL;}
	m_obj->size = (size_t) map_size;
	m_obj->pos = (size_t) 0;
	m_obj->fd = fd;
	m_obj->data = mmap(NULL, map_size, 
			   prot, flags,
			   fd, 0);
	if (m_obj->data == (void *)-1)
	{
		Py_DECREF(m_obj);
		PyErr_SetFromErrno(mmap_module_error);
		return NULL;
	}
	return (PyObject *)m_obj;
}
#endif /* UNIX */

#ifdef MS_WIN32
static PyObject *
new_mmap_object(PyObject *self, PyObject *args)
{
	mmap_object *m_obj;
	PyObject *map_size_obj = NULL;
	int map_size;
	char *tagname = "";

	DWORD dwErr = 0;
	int fileno;
	INT_PTR fh = 0;

	/* Patch the object type */
	mmap_object_type.ob_type = &PyType_Type;

	if (!PyArg_ParseTuple(args,
			  "iO|z",
			  &fileno,
			  &map_size_obj,
			  &tagname)
		)
		return NULL;
  
	map_size = _GetMapSize(map_size_obj);
	if (map_size < 0)
		return NULL;
	
	/* if an actual filename has been specified */
	if (fileno != 0) {
		fh = _get_osfhandle(fileno);
		if (fh==-1) {
		    PyErr_SetFromErrno(mmap_module_error);
		    return NULL;
		}
		/* Win9x appears to need us seeked to zero */
		fseek(&_iob[fileno], 0, SEEK_SET);
	}

	m_obj = PyObject_New (mmap_object, &mmap_object_type);
	if (m_obj==NULL)
		return NULL;
	/* Set every field to an invalid marker, so we can safely
	   destruct the object in the face of failure */
	m_obj->data = NULL;
	m_obj->file_handle = (INT_PTR)INVALID_HANDLE_VALUE;
	m_obj->map_handle = INVALID_HANDLE_VALUE;
	m_obj->tagname = NULL;

	if (fh) {
		/* It is necessary to duplicate the handle, so the
		   Python code can close it on us */
		if (!DuplicateHandle(
			    GetCurrentProcess(), /* source process handle */
			    (HANDLE)fh, /* handle to be duplicated */
			    GetCurrentProcess(), /* target proc handle */
			    (LPHANDLE)&m_obj->file_handle, /* result */
			    0, /* access - ignored due to options value */
			    FALSE, /* inherited by child processes? */
			    DUPLICATE_SAME_ACCESS)) { /* options */
			dwErr = GetLastError();
			Py_DECREF(m_obj);
			PyErr_SetFromWindowsErr(dwErr);
			return NULL;
		}
		if (!map_size) {
			m_obj->size = GetFileSize ((HANDLE)fh, NULL);
		} else {
			m_obj->size = map_size;
		}
	}
	else {
		m_obj->size = map_size;
	}

	/* set the initial position */
	m_obj->pos = (size_t) 0;

	/* set the tag name */
	if (tagname != NULL) {
		m_obj->tagname = PyMem_Malloc(strlen(tagname)+1);
		if (m_obj->tagname == NULL) {
			PyErr_NoMemory();
			Py_DECREF(m_obj);
			return NULL;
		}
		strcpy(m_obj->tagname, tagname);
	}
	else
		m_obj->tagname = NULL;

	m_obj->map_handle = CreateFileMapping ((HANDLE) m_obj->file_handle,
					       NULL,
					       PAGE_READWRITE,
					       0,
					       m_obj->size,
					       tagname);
	if (m_obj->map_handle != NULL) {
		m_obj->data = (char *) MapViewOfFile (m_obj->map_handle,
						      FILE_MAP_WRITE,
						      0,
						      0,
						      0);
		if (m_obj->data != NULL) {
			return ((PyObject *) m_obj);
		} else {
		    dwErr = GetLastError();
		}
	} else {
		dwErr = GetLastError();
	}
	Py_DECREF(m_obj);
	PyErr_SetFromWindowsErr(dwErr);
	return (NULL);
}
#endif /* MS_WIN32 */

/* List of functions exported by this module */
static struct PyMethodDef mmap_functions[] = {
	{"mmap",	(PyCFunction) new_mmap_object, 
	 METH_VARARGS|METH_KEYWORDS},
	{NULL,		NULL}	     /* Sentinel */
};

#ifdef MS_WIN32
__declspec(dllexport) void
#endif /* MS_WIN32 */
#ifdef UNIX
extern void
#endif

initmmap(void)
{
	PyObject *dict, *module;
	module = Py_InitModule ("mmap", mmap_functions);
	dict = PyModule_GetDict (module);
	mmap_module_error = PyExc_EnvironmentError;
	Py_INCREF(mmap_module_error);
	PyDict_SetItemString (dict, "error", mmap_module_error);
#ifdef PROT_EXEC
	PyDict_SetItemString (dict, "PROT_EXEC", PyInt_FromLong(PROT_EXEC) );
#endif
#ifdef PROT_READ
	PyDict_SetItemString (dict, "PROT_READ", PyInt_FromLong(PROT_READ) );
#endif
#ifdef PROT_WRITE
	PyDict_SetItemString (dict, "PROT_WRITE", PyInt_FromLong(PROT_WRITE) );
#endif

#ifdef MAP_SHARED
	PyDict_SetItemString (dict, "MAP_SHARED", PyInt_FromLong(MAP_SHARED) );
#endif
#ifdef MAP_PRIVATE
	PyDict_SetItemString (dict, "MAP_PRIVATE",
			      PyInt_FromLong(MAP_PRIVATE) );
#endif
#ifdef MAP_DENYWRITE
	PyDict_SetItemString (dict, "MAP_DENYWRITE",
			      PyInt_FromLong(MAP_DENYWRITE) );
#endif
#ifdef MAP_EXECUTABLE
	PyDict_SetItemString (dict, "MAP_EXECUTABLE",
			      PyInt_FromLong(MAP_EXECUTABLE) );
#endif
#ifdef MAP_ANON
	PyDict_SetItemString (dict, "MAP_ANON", PyInt_FromLong(MAP_ANON) );
	PyDict_SetItemString (dict, "MAP_ANONYMOUS",
			      PyInt_FromLong(MAP_ANON) );
#endif

#ifdef UNIX
	PyDict_SetItemString (dict, "PAGESIZE",
			      PyInt_FromLong( (long)getpagesize() ) );
#endif
#ifdef MS_WIN32
	{
	    SYSTEM_INFO si;
	    GetSystemInfo(&si);
	    PyDict_SetItemString (dict, "PAGESIZE",
				  PyInt_FromLong( si.dwPageSize ) );
	}
#endif /* MS_WIN32 */

}