# HG changeset patch
# User Jeffrey Finkelstein <jeffrey.finkelstein@gmail.com>
# Date 1284569399 14400
# Branch py3k
# Node ID 42b46e64900d38ec56bdfa0f45237d322e633206
# Parent  4ea5a13762e53b439a6f86833f6d5b36167acac1
fix for issue #9759: adds a check to GzipFile.read(), GzipFile.write(), and GzipFile.flush() which raises a ValueError if I/O operations are performed on a closed file

diff -r 4ea5a13762e5 -r 42b46e64900d Lib/gzip.py
--- a/Lib/gzip.py	Wed Sep 15 17:13:17 2010 +0200
+++ b/Lib/gzip.py	Wed Sep 15 12:49:59 2010 -0400
@@ -150,6 +150,13 @@
         s = repr(self.fileobj)
         return '<gzip ' + s[1:-1] + ' ' + hex(id(self)) + '>'
 
+    def _check_closed(self):
+        """Raises a ValueError if the underlying file object has been closed.
+
+        """
+        if self.closed:
+            raise ValueError('I/O operation on closed file.')
+
     def _init_write(self, filename):
         self.name = filename
         self.crc = zlib.crc32(b"") & 0xffffffff
@@ -220,6 +227,7 @@
             self.fileobj.read(2)     # Read & discard the 16-bit header CRC
 
     def write(self,data):
+        self._check_closed()
         if self.mode != WRITE:
             import errno
             raise IOError(errno.EBADF, "write() on read-only GzipFile object")
@@ -240,6 +248,7 @@
         return len(data)
 
     def read(self, size=-1):
+        self._check_closed()
         if self.mode != READ:
             import errno
             raise IOError(errno.EBADF, "read() on write-only GzipFile object")
@@ -377,6 +386,7 @@
             self.myfileobj = None
 
     def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
+        self._check_closed()
         if self.mode == WRITE:
             # Ensure the compressor's buffer is flushed
             self.fileobj.write(self.compress.flush(zlib_mode))
diff -r 4ea5a13762e5 -r 42b46e64900d Lib/test/test_gzip.py
--- a/Lib/test/test_gzip.py	Wed Sep 15 17:13:17 2010 +0200
+++ b/Lib/test/test_gzip.py	Wed Sep 15 12:49:59 2010 -0400
@@ -51,6 +51,29 @@
         f = gzip.GzipFile(self.filename, 'r') ; d = f.read() ; f.close()
         self.assertEqual(d, data1*50)
 
+    def test_io_on_closed_object(self):
+        """Tests that I/O operations on closed GzipFile objects raise a
+        ValueError, just like the corresponding functions on file objects.
+
+        """
+        # Write to a file, open it for reading, then close it.
+        self.test_write()
+        f = gzip.GzipFile(self.filename, 'r')
+        f.close()
+
+        with self.assertRaises(ValueError):
+            f.read()
+
+        # Open the file for writing, then close it.
+        f = gzip.GzipFile(self.filename, 'w')
+        f.close()
+
+        with self.assertRaises(ValueError):
+            f.write('')
+
+        with self.assertRaises(ValueError):
+            f.flush()
+
     def test_append(self):
         self.test_write()
         # Append to the previous file