Backporting from Zope3/ZODB4: exposed the Win32 UnlockFile function,

which is used by Barry's new LockFile class.  The effect of leaving
regions of a file locked when closing the file, or when exiting the
process, is undefined on Windows, and the new scheme restricts itself
to operations with defined semantics.

src/ZODB/winlock.c

@@ -2,19 +2,19 @@
 
   Copyright (c) 2001, 2002 Zope Corporation and Contributors.
   All Rights Reserved.
-  
+
   This software is subject to the provisions of the Zope Public License,
   Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
   THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
   WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
   FOR A PARTICULAR PURPOSE
-  
+
  ****************************************************************************/
-static char winlock_doc_string[] = 
+static char winlock_doc_string[] =
 "Lock files on Windows."
 "\n"
-"$Id: winlock.c,v 1.8 2002/02/11 23:40:42 gvanrossum Exp $\n";
+"$Id: winlock.c,v 1.9 2003/02/28 20:37:59 tim_one Exp $\n";
 
 #include "Python.h"
 
@@ -25,32 +25,55 @@ static PyObject *Error;
 #include <windows.h>
 #include <io.h>
 
-static PyObject *	
+/* LOCK_FUNC is the shared type of Win32 LockFile and UnlockFile. */
+typedef WINBASEAPI BOOL WINAPI LOCK_FUNC(HANDLE, DWORD, DWORD, DWORD, DWORD);
+
+static PyObject *
+common(LOCK_FUNC func, PyObject *args)
+{
+	int fileno;
+	long h, ofslo, ofshi, lenlo, lenhi;
+
+	if (! PyArg_ParseTuple(args, "illll", &fileno,
+			       &ofslo, &ofshi,
+			       &lenlo, &lenhi))
+		return NULL;
+
+	h = _get_osfhandle(fileno);
+	if (h == -1) {
+		PyErr_SetString(Error, "_get_osfhandle failed");
+		return NULL;
+	}
+	if (func((HANDLE)h, ofslo, ofshi, lenlo, lenhi)) {
+		Py_INCREF(Py_None);
+		return Py_None;
+	}
+	PyErr_SetObject(Error, PyInt_FromLong(GetLastError()));
+	return NULL;
+}
+
+static PyObject *
 winlock(PyObject *ignored, PyObject *args)
 {
-  int fileno;
-  long h, ol, oh, ll, lh;
-  
-  if (! PyArg_ParseTuple(args, "illll", &fileno, &ol, &oh, &ll, &lh))
-    return NULL;
-
-  if ((h=_get_osfhandle(fileno))==-1) {
-    PyErr_SetString(Error, "_get_osfhandle failed");
-    return NULL;
-  }
-  if (LockFile((HANDLE)h, ol, oh, ll, lh)) {
-    Py_INCREF(Py_None);
-    return Py_None;
-  }
-  PyErr_SetObject(Error, PyInt_FromLong(GetLastError()));
-  return NULL;
+	return common(LockFile, args);
+}
+
+static PyObject *
+winunlock(PyObject *ignored, PyObject *args)
+{
+	return common(UnlockFile, args);
 }
 
 static struct PyMethodDef methods[] = {
-  {"LockFile",	(PyCFunction)winlock,	1,
-   "LockFile(fileno, offsetLow, offsetHigh, lengthLow, lengthHigh ) -- "
-   "Lock the file associated with fileno"},
-  {NULL,		NULL}		/* sentinel */
+    {"LockFile",	(PyCFunction)winlock,	METH_VARARGS,
+     "LockFile(fileno, offsetLow, offsetHigh, lengthLow, lengthHigh) -- "
+     "Lock the file associated with fileno"},
+
+    {"UnlockFile",	(PyCFunction)winunlock,	METH_VARARGS,
+     "UnlockFile(fileno, offsetLow, offsetHigh, lengthLow, lengthHigh) -- "
+     "Unlock the file associated with fileno"},
+
+    {NULL,		NULL}		/* sentinel */
 };
 #else
 
@@ -66,16 +89,17 @@ static struct PyMethodDef methods[] = {
 #define DL_EXPORT(RTYPE) RTYPE
 #endif
 DL_EXPORT(void)
-initwinlock(void) {
-  PyObject *m, *d;
+initwinlock(void)
+{
+	PyObject *m, *d;
 
-  if (!(Error=PyString_FromString("winlock.error"))) 
-      return;
+	if (!(Error=PyString_FromString("winlock.error")))
+		return;
 
-  /* Create the module and add the functions */
-  m = Py_InitModule4("winlock", methods, winlock_doc_string, (PyObject*)NULL,
-		     PYTHON_API_VERSION);
+	/* Create the module and add the functions */
+	m = Py_InitModule4("winlock", methods, winlock_doc_string,
+			   (PyObject*)NULL, PYTHON_API_VERSION);
 
-  d = PyModule_GetDict(m);
-  PyDict_SetItemString(d, "error", Error);
+	d = PyModule_GetDict(m);
+	PyDict_SetItemString(d, "error", Error);
 }