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

@@ -14,7 +14,7 @@
 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"
 
@@ -25,20 +25,26 @@ static PyObject *Error;
 #include <windows.h>
 #include <io.h>
 
+/* LOCK_FUNC is the shared type of Win32 LockFile and UnlockFile. */
+typedef WINBASEAPI BOOL WINAPI LOCK_FUNC(HANDLE, DWORD, DWORD, DWORD, DWORD);
+
 static PyObject *
-winlock(PyObject *ignored, PyObject *args)
+common(LOCK_FUNC func, PyObject *args)
 {
 	int fileno;
-  long h, ol, oh, ll, lh;
+	long h, ofslo, ofshi, lenlo, lenhi;
 
-  if (! PyArg_ParseTuple(args, "illll", &fileno, &ol, &oh, &ll, &lh))
+	if (! PyArg_ParseTuple(args, "illll", &fileno,
+			       &ofslo, &ofshi,
+			       &lenlo, &lenhi))
 		return NULL;
 
-  if ((h=_get_osfhandle(fileno))==-1) {
+	h = _get_osfhandle(fileno);
+	if (h == -1) {
 		PyErr_SetString(Error, "_get_osfhandle failed");
 		return NULL;
 	}
-  if (LockFile((HANDLE)h, ol, oh, ll, lh)) {
+	if (func((HANDLE)h, ofslo, ofshi, lenlo, lenhi)) {
 		Py_INCREF(Py_None);
 		return Py_None;
 	}
@@ -46,10 +52,27 @@ winlock(PyObject *ignored, PyObject *args)
 	return NULL;
 }
 
+static PyObject *
+winlock(PyObject *ignored, PyObject *args)
+{
+	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 ) -- "
+    {"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
@@ -66,15 +89,16 @@ static struct PyMethodDef methods[] = {
 #define DL_EXPORT(RTYPE) RTYPE
 #endif
 DL_EXPORT(void)
-initwinlock(void) {
+initwinlock(void)
+{
 	PyObject *m, *d;
 
 	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);
+	m = Py_InitModule4("winlock", methods, winlock_doc_string,
+			   (PyObject*)NULL, PYTHON_API_VERSION);
 
 	d = PyModule_GetDict(m);
 	PyDict_SetItemString(d, "error", Error);