From e6267adc965927e45a96bfc375c517af42c76147 Mon Sep 17 00:00:00 2001
From: Danny Lin <danny0838@gmail.com>
Date: Wed, 24 Jun 2026 22:58:07 +0800
Subject: [PATCH 1/4] gh-152140: Replace `_Extra` class with
 `ZipFile._strip_extra_fields()`

The `_Extra` class was over-engineered. Its only active usage was its
`strip()` method, called by `ZipFile._write_end_record()` to provide
the stripping logic for ZIP64 fields.  The context-dependent nature of
extra fields also made it difficult to be reused by `_decodeExtra()`
or other methods efficiently.  Additionally, its `split()` method
called `_Extra` directly rather than utilizing `cls`, which was a
suboptimal pattern that hindered extensibility.

Remove the `_Extra` class entirely and reimplement it as a private
static method `_strip_extra_fields()` that processes a bytearray
inside `ZipFile`, positioned directly beneath its caller.  This
eliminates dead and suboptimal code, achieves clean encapsulation
and code locality, and improves performance by avoiding temporary
class allocations.
---
 Lib/test/test_zipfile/test_core.py | 56 +++++++++++------------
 Lib/zipfile/__init__.py            | 73 ++++++++++++++----------------
 2 files changed, 60 insertions(+), 69 deletions(-)

diff --git a/Lib/test/test_zipfile/test_core.py b/Lib/test/test_zipfile/test_core.py
index 4f20209927e7b3..43a2fddfd4e173 100644
--- a/Lib/test/test_zipfile/test_core.py
+++ b/Lib/test/test_zipfile/test_core.py
@@ -5840,20 +5840,23 @@ class StripExtraTests(unittest.TestCase):
 
     ZIP64_EXTRA = 1
 
+    @classmethod
+    def setUpClass(cls):
+        cls.strip_extra = staticmethod(zipfile.ZipFile._strip_extra_fields)
+
     def test_no_data(self):
         s = struct.Struct("<HH")
         a = s.pack(self.ZIP64_EXTRA, 0)
         b = s.pack(2, 0)
         c = s.pack(3, 0)
 
-        self.assertEqual(b'', zipfile._Extra.strip(a, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b, zipfile._Extra.strip(b, (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b+b"z", zipfile._Extra.strip(b+b"z", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b'', self.strip_extra(a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b, self.strip_extra(b, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+b"z", self.strip_extra(b+b"z", (self.ZIP64_EXTRA,)))
 
-        self.assertEqual(b+c, zipfile._Extra.strip(a+b+c, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b+c, zipfile._Extra.strip(b+a+c, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b+c, zipfile._Extra.strip(b+c+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(a+b+c, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(b+a+c, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(b+c+a, (self.ZIP64_EXTRA,)))
 
     def test_with_data(self):
         s = struct.Struct("<HH")
@@ -5861,38 +5864,33 @@ def test_with_data(self):
         b = s.pack(2, 2) + b"bb"
         c = s.pack(3, 3) + b"ccc"
 
-        self.assertEqual(b"", zipfile._Extra.strip(a, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b, zipfile._Extra.strip(b, (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b+b"z", zipfile._Extra.strip(b+b"z", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"", self.strip_extra(a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b, self.strip_extra(b, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+b"z", self.strip_extra(b+b"z", (self.ZIP64_EXTRA,)))
 
-        self.assertEqual(b+c, zipfile._Extra.strip(a+b+c, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b+c, zipfile._Extra.strip(b+a+c, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b+c, zipfile._Extra.strip(b+c+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(a+b+c, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(b+a+c, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+c, self.strip_extra(b+c+a, (self.ZIP64_EXTRA,)))
 
     def test_multiples(self):
         s = struct.Struct("<HH")
         a = s.pack(self.ZIP64_EXTRA, 1) + b"a"
         b = s.pack(2, 2) + b"bb"
 
-        self.assertEqual(b"", zipfile._Extra.strip(a+a, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b"", zipfile._Extra.strip(a+a+a, (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b"z", zipfile._Extra.strip(a+a+b"z", (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b+b"z", zipfile._Extra.strip(a+a+b+b"z", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"", self.strip_extra(a+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"", self.strip_extra(a+a+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"z", self.strip_extra(a+a+b"z", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b+b"z", self.strip_extra(a+a+b+b"z", (self.ZIP64_EXTRA,)))
 
-        self.assertEqual(b, zipfile._Extra.strip(a+a+b, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b, zipfile._Extra.strip(a+b+a, (self.ZIP64_EXTRA,)))
-        self.assertEqual(b, zipfile._Extra.strip(b+a+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b, self.strip_extra(a+a+b, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b, self.strip_extra(a+b+a, (self.ZIP64_EXTRA,)))
+        self.assertEqual(b, self.strip_extra(b+a+a, (self.ZIP64_EXTRA,)))
 
     def test_too_short(self):
-        self.assertEqual(b"", zipfile._Extra.strip(b"", (self.ZIP64_EXTRA,)))
-        self.assertEqual(b"z", zipfile._Extra.strip(b"z", (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b"zz", zipfile._Extra.strip(b"zz", (self.ZIP64_EXTRA,)))
-        self.assertEqual(
-            b"zzz", zipfile._Extra.strip(b"zzz", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"", self.strip_extra(b"", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"z", self.strip_extra(b"z", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"zz", self.strip_extra(b"zz", (self.ZIP64_EXTRA,)))
+        self.assertEqual(b"zzz", self.strip_extra(b"zzz", (self.ZIP64_EXTRA,)))
 
 
 class StatIO(_pyio.BytesIO):
diff --git a/Lib/zipfile/__init__.py b/Lib/zipfile/__init__.py
index 084a47518a935c..de57ff9c40ede9 100644
--- a/Lib/zipfile/__init__.py
+++ b/Lib/zipfile/__init__.py
@@ -194,43 +194,6 @@ class LargeZipFile(Exception):
 
 _DD_SIGNATURE = 0x08074b50
 
-
-class _Extra(bytes):
-    FIELD_STRUCT = struct.Struct('<HH')
-
-    def __new__(cls, val, id=None):
-        return super().__new__(cls, val)
-
-    def __init__(self, val, id=None):
-        self.id = id
-
-    @classmethod
-    def read_one(cls, raw):
-        try:
-            xid, xlen = cls.FIELD_STRUCT.unpack(raw[:4])
-        except struct.error:
-            xid = None
-            xlen = 0
-        return cls(raw[:4+xlen], xid), raw[4+xlen:]
-
-    @classmethod
-    def split(cls, data):
-        # use memoryview for zero-copy slices
-        rest = memoryview(data)
-        while rest:
-            extra, rest = _Extra.read_one(rest)
-            yield extra
-
-    @classmethod
-    def strip(cls, data, xids):
-        """Remove Extra fields with specified IDs."""
-        return b''.join(
-            ex
-            for ex in cls.split(data)
-            if ex.id not in xids
-        )
-
-
 def _check_zipfile(fp):
     try:
         endrec = _EndRecData(fp)
@@ -2670,11 +2633,11 @@ def _write_end_record(self):
             extra_data = zinfo.extra
             min_version = 0
             if extra:
-                # Append a ZIP64 field to the extra's
-                extra_data = _Extra.strip(extra_data, (1,))
+                # Prepend a ZIP64 field to the extra's
                 extra_data = struct.pack(
                     '<HH' + 'Q'*len(extra),
-                    1, 8*len(extra), *extra) + extra_data
+                    1, 8*len(extra), *extra
+                ) + self._strip_extra_fields(extra_data, (1,))
 
                 min_version = ZIP64_VERSION
 
@@ -2741,6 +2704,36 @@ def _write_end_record(self):
             self.fp.truncate()
         self.fp.flush()
 
+    @staticmethod
+    def _strip_extra_fields(data, field_ids):
+        """Remove Extra fields with specified IDs and return a bytearray.
+
+        data should be bytes or bytearray.
+        """
+        result = bytearray()
+
+        # early return for empty extra data
+        if not data:
+            return result
+
+        # use memoryview for zero-copy slices
+        mv = memoryview(data)
+        mv_len = len(mv)
+        pos = 0
+        while pos + 4 <= mv_len:
+            xid, xlen = struct.unpack_from('<HH', mv, pos)
+            if pos + 4 + xlen > mv_len:
+                break
+            if xid not in field_ids:
+                result.extend(mv[pos:pos + 4 + xlen])
+            pos += 4 + xlen
+
+        # keep remaining trailing bytes (e.g. truncated or malformed data)
+        if pos < mv_len:
+            result.extend(mv[pos:])
+
+        return result
+
     def _fpclose(self, fp):
         assert self._fileRefCnt > 0
         self._fileRefCnt -= 1

From f334193f92d96a2294fcc0764bb3f5779b245f66 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Thu, 25 Jun 2026 00:42:00 +0000
Subject: [PATCH 2/4] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../2026-06-25-00-41-52.gh-issue-152140.u0phBe.rst               | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-25-00-41-52.gh-issue-152140.u0phBe.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-25-00-41-52.gh-issue-152140.u0phBe.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-25-00-41-52.gh-issue-152140.u0phBe.rst
new file mode 100644
index 00000000000000..958c00b7e53eec
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-25-00-41-52.gh-issue-152140.u0phBe.rst
@@ -0,0 +1 @@
+Replace :class:`!_Extra` with :meth:`!ZipFile._strip_extra_fields` in the :mod:`zipfile` module.

From 4eae06b019d35646597015ba545bcf6bac35eda1 Mon Sep 17 00:00:00 2001
From: Danny Lin <danny0838@gmail.com>
Date: Thu, 25 Jun 2026 08:47:41 +0800
Subject: [PATCH 3/4] Make `strip_extra` a direct class property in the test

---
 Lib/test/test_zipfile/test_core.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/Lib/test/test_zipfile/test_core.py b/Lib/test/test_zipfile/test_core.py
index 43a2fddfd4e173..3db85d0df275cf 100644
--- a/Lib/test/test_zipfile/test_core.py
+++ b/Lib/test/test_zipfile/test_core.py
@@ -5840,9 +5840,7 @@ class StripExtraTests(unittest.TestCase):
 
     ZIP64_EXTRA = 1
 
-    @classmethod
-    def setUpClass(cls):
-        cls.strip_extra = staticmethod(zipfile.ZipFile._strip_extra_fields)
+    strip_extra = staticmethod(zipfile.ZipFile._strip_extra_fields)
 
     def test_no_data(self):
         s = struct.Struct("<HH")

From 4551fe385021589708b5247ecc39dff2f4e7a050 Mon Sep 17 00:00:00 2001
From: Danny Lin <danny0838@gmail.com>
Date: Thu, 25 Jun 2026 18:55:57 +0800
Subject: [PATCH 4/4] Remove `memoryview` usage

Since `struct.unpack_from` is already an offset-based approach at the
C level, and `result.extend` requires data copy anyway, avoiding a
`memoryview` wrapper prevents redundant Python object allocation and
pointer-shifting overhead, yielding optimal runtime memory footprint
and CPU performance.
---
 Lib/zipfile/__init__.py | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/Lib/zipfile/__init__.py b/Lib/zipfile/__init__.py
index de57ff9c40ede9..7e89f47d7722ff 100644
--- a/Lib/zipfile/__init__.py
+++ b/Lib/zipfile/__init__.py
@@ -2717,20 +2717,19 @@ def _strip_extra_fields(data, field_ids):
             return result
 
         # use memoryview for zero-copy slices
-        mv = memoryview(data)
-        mv_len = len(mv)
+        data_len = len(data)
         pos = 0
-        while pos + 4 <= mv_len:
-            xid, xlen = struct.unpack_from('<HH', mv, pos)
-            if pos + 4 + xlen > mv_len:
+        while pos + 4 <= data_len:
+            xid, xlen = struct.unpack_from('<HH', data, pos)
+            if pos + 4 + xlen > data_len:
                 break
             if xid not in field_ids:
-                result.extend(mv[pos:pos + 4 + xlen])
+                result.extend(data[pos:pos + 4 + xlen])
             pos += 4 + xlen
 
         # keep remaining trailing bytes (e.g. truncated or malformed data)
-        if pos < mv_len:
-            result.extend(mv[pos:])
+        if pos < data_len:
+            result.extend(data[pos:])
 
         return result