1 files changed, 117 insertions, 0 deletions
diff --git a/python/werkzeug/posixemulation.py b/python/werkzeug/posixemulation.py
new file mode 100644
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+++ b/python/werkzeug/posixemulation.py
@@ -0,0 +1,117 @@
+# -*- coding: utf-8 -*-
+r"""
+    werkzeug.posixemulation
+    ~~~~~~~~~~~~~~~~~~~~~~~
+
+    Provides a POSIX emulation for some features that are relevant to
+    web applications.  The main purpose is to simplify support for
+    systems such as Windows NT that are not 100% POSIX compatible.
+
+    Currently this only implements a :func:`rename` function that
+    follows POSIX semantics.  Eg: if the target file already exists it
+    will be replaced without asking.
+
+    This module was introduced in 0.6.1 and is not a public interface.
+    It might become one in later versions of Werkzeug.
+
+    :copyright: 2007 Pallets
+    :license: BSD-3-Clause
+"""
+import errno
+import os
+import random
+import sys
+import time
+
+from ._compat import to_unicode
+from .filesystem import get_filesystem_encoding
+
+can_rename_open_file = False
+
+if os.name == "nt":
+    try:
+        import ctypes
+
+        _MOVEFILE_REPLACE_EXISTING = 0x1
+        _MOVEFILE_WRITE_THROUGH = 0x8
+        _MoveFileEx = ctypes.windll.kernel32.MoveFileExW
+
+        def _rename(src, dst):
+            src = to_unicode(src, get_filesystem_encoding())
+            dst = to_unicode(dst, get_filesystem_encoding())
+            if _rename_atomic(src, dst):
+                return True
+            retry = 0
+            rv = False
+            while not rv and retry < 100:
+                rv = _MoveFileEx(
+                    src, dst, _MOVEFILE_REPLACE_EXISTING | _MOVEFILE_WRITE_THROUGH
+                )
+                if not rv:
+                    time.sleep(0.001)
+                    retry += 1
+            return rv
+
+        # new in Vista and Windows Server 2008
+        _CreateTransaction = ctypes.windll.ktmw32.CreateTransaction
+        _CommitTransaction = ctypes.windll.ktmw32.CommitTransaction
+        _MoveFileTransacted = ctypes.windll.kernel32.MoveFileTransactedW
+        _CloseHandle = ctypes.windll.kernel32.CloseHandle
+        can_rename_open_file = True
+
+        def _rename_atomic(src, dst):
+            ta = _CreateTransaction(None, 0, 0, 0, 0, 1000, "Werkzeug rename")
+            if ta == -1:
+                return False
+            try:
+                retry = 0
+                rv = False
+                while not rv and retry < 100:
+                    rv = _MoveFileTransacted(
+                        src,
+                        dst,
+                        None,
+                        None,
+                        _MOVEFILE_REPLACE_EXISTING | _MOVEFILE_WRITE_THROUGH,
+                        ta,
+                    )
+                    if rv:
+                        rv = _CommitTransaction(ta)
+                        break
+                    else:
+                        time.sleep(0.001)
+                        retry += 1
+                return rv
+            finally:
+                _CloseHandle(ta)
+
+    except Exception:
+
+        def _rename(src, dst):
+            return False
+
+        def _rename_atomic(src, dst):
+            return False
+
+    def rename(src, dst):
+        # Try atomic or pseudo-atomic rename
+        if _rename(src, dst):
+            return
+        # Fall back to "move away and replace"
+        try:
+            os.rename(src, dst)
+        except OSError as e:
+            if e.errno != errno.EEXIST:
+                raise
+            old = "%s-%08x" % (dst, random.randint(0, sys.maxsize))
+            os.rename(dst, old)
+            os.rename(src, dst)
+            try:
+                os.unlink(old)
+            except Exception:
+                pass
+
+
+else:
+    rename = os.rename
+    can_rename_open_file = True