From db5fe667311745a2bc86355620354449721545f3 Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Sat, 27 Dec 2008 15:50:40 +0000
Subject: [PATCH] Merged revisions 67946 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/trunk
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........
  r67946 | antoine.pitrou | 2008-12-27 16:43:12 +0100 (sam., 27 déc. 2008) | 4 lines

  Issue #4756: zipfile.is_zipfile() now supports file-like objects.
  Patch by Gabriel Genellina.
........
---
 Doc/library/zipfile.rst  |  6 ++++--
 Lib/test/test_zipfile.py | 39 ++++++++++++++++++++++++++++++++++-----
 Lib/zipfile.py           | 26 +++++++++++++++++++-------
 Misc/NEWS                |  3 +++
 4 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/Doc/library/zipfile.rst b/Doc/library/zipfile.rst
index 49267c070d5785..75860cc928a146 100644
--- a/Doc/library/zipfile.rst
+++ b/Doc/library/zipfile.rst
@@ -64,9 +64,11 @@ The module defines the following items:
 .. function:: is_zipfile(filename)
 
    Returns ``True`` if *filename* is a valid ZIP file based on its magic number,
-   otherwise returns ``False``.  This module does not currently handle ZIP files
-   which have appended comments.
+   otherwise returns ``False``.  *filename* may be a file or file-like object too.
+   This module does not currently handle ZIP files which have appended comments.
 
+   .. versionchanged:: 2.7
+   Support for file and file-like objects.
 
 .. data:: ZIP_STORED
 
diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index 9e565fb153f899..678ac9fc00f54f 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -621,20 +621,49 @@ def testCloseErroneousFile(self):
     def testIsZipErroneousFile(self):
         # This test checks that the is_zipfile function correctly identifies
         # a file that is not a zip file
-        fp = open(TESTFN, "w")
-        fp.write("this is not a legal zip file\n")
-        fp.close()
+
+        # - passing a filename
+        with open(TESTFN, "w") as fp:
+            fp.write("this is not a legal zip file\n")
         chk = zipfile.is_zipfile(TESTFN)
-        self.assert_(chk is False)
+        self.assert_(not chk)
+        # - passing a file object
+        with open(TESTFN, "rb") as fp:
+            chk = zipfile.is_zipfile(fp)
+            self.assert_(not chk)
+        # - passing a file-like object
+        fp = io.BytesIO()
+        fp.write(b"this is not a legal zip file\n")
+        chk = zipfile.is_zipfile(fp)
+        self.assert_(not chk)
+        fp.seek(0,0)
+        chk = zipfile.is_zipfile(fp)
+        self.assert_(not chk)
 
     def testIsZipValidFile(self):
         # This test checks that the is_zipfile function correctly identifies
         # a file that is a zip file
+
+        # - passing a filename
         zipf = zipfile.ZipFile(TESTFN, mode="w")
         zipf.writestr("foo.txt", b"O, for a Muse of Fire!")
         zipf.close()
         chk = zipfile.is_zipfile(TESTFN)
-        self.assert_(chk is True)
+        self.assert_(chk)
+        # - passing a file object
+        with open(TESTFN, "rb") as fp:
+            chk = zipfile.is_zipfile(fp)
+            self.assert_(chk)
+            fp.seek(0,0)
+            zip_contents = fp.read()
+        # - passing a file-like object
+        fp = io.BytesIO()
+        fp.write(zip_contents)
+        chk = zipfile.is_zipfile(fp)
+        self.assert_(chk)
+        fp.seek(0,0)
+        chk = zipfile.is_zipfile(fp)
+        self.assert_(chk)
 
     def testNonExistentFileRaisesIOError(self):
         # make sure we don't raise an AttributeError when a partially-constructed
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 46ec6ef065e566..5054097528876c 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -130,18 +130,30 @@ class LargeZipFile(Exception):
 _CD64_DIRECTORY_SIZE = 8
 _CD64_OFFSET_START_CENTDIR = 9
 
-def is_zipfile(filename):
-    """Quickly see if file is a ZIP file by checking the magic number."""
+def _check_zipfile(fp):
     try:
-        fpin = io.open(filename, "rb")
-        endrec = _EndRecData(fpin)
-        fpin.close()
-        if endrec:
-            return True                 # file has correct magic number
+        if _EndRecData(fp):
+            return True         # file has correct magic number
     except IOError:
         pass
     return False
 
+def is_zipfile(filename):
+    """Quickly see if a file is a ZIP file by checking the magic number.
+
+    The filename argument may be a file or file-like object too.
+    """
+    result = False
+    try:
+        if hasattr(filename, "read"):
+            result = _check_zipfile(fp=filename)
+        else:
+            with open(filename, "rb") as fp:
+                result = _check_zipfile(fp)
+    except IOError:
+        pass
+    return result
+
 def _EndRecData64(fpin, offset, endrec):
     """
     Read the ZIP64 end-of-archive records and use that to update endrec
diff --git a/Misc/NEWS b/Misc/NEWS
index e247506af5728e..ed62a01c655201 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -59,6 +59,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #4756: zipfile.is_zipfile() now supports file-like objects. Patch by
+  Gabriel Genellina.
+
 - Issue #4574: reading an UTF16-encoded text file crashes if \r on 64-char
   boundary.