Rework using try...except

The previous implementation introduced a behavior change: a field with
truncated data was always kept, while it had been filtered by passed
`field_id`.

Go back to use the try...except to adhere the original behavior as the
original `_Extra.split()`.  Also add a test to explicitly check for
such case.

Benchmark shows this implementation improves performance.

Author: danny0838

Lib/test/test_zipfile/test_core.py

@@ -5884,6 +5884,20 @@ def test_multiples(self):
         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_truncated_data_for_stripped_id(self):
+        s = struct.Struct("<HH")
+        a = s.pack(self.ZIP64_EXTRA, 3) + b"a"
+        b = s.pack(2, 2) + b"bb"
+
+        self.assertEqual(b, self.strip_extra(b+a, (self.ZIP64_EXTRA,)))
+
+    def test_truncated_data_for_nonstripped_id(self):
+        s = struct.Struct("<HH")
+        a = s.pack(self.ZIP64_EXTRA, 3) + b"a"
+        b = s.pack(2, 2) + b"bb"
+
+        self.assertEqual(b+a, self.strip_extra(b+a, (3,)))
+
     def test_too_short(self):
         self.assertEqual(b"", self.strip_extra(b"", (self.ZIP64_EXTRA,)))
         self.assertEqual(b"z", self.strip_extra(b"z", (self.ZIP64_EXTRA,)))

Lib/zipfile/__init__.py

@@ -2718,18 +2718,15 @@ def _strip_extra_fields(data, field_ids):
 
         data_len = len(data)
         pos = 0
-        while pos + 4 <= data_len:
-            xid, xlen = struct.unpack_from('<HH', data, pos)
-            if pos + 4 + xlen > data_len:
-                break
+        while pos < data_len:
+            try:
+                xid, xlen = struct.unpack_from('<HH', data, pos)
+            except struct.error:
+                xid, xlen = None, 0
             if xid not in field_ids:
                 result.extend(data[pos:pos + 4 + xlen])
             pos += 4 + xlen
 
-        # keep remaining trailing bytes (e.g. truncated or malformed data)
-        if pos < data_len:
-            result.extend(data[pos:])
-
         return result
 
     def _fpclose(self, fp):