Lib/test/test_gzip.py

"""Test script for the gzip module.
"""

import array
import functools
import io
import os
import struct
import sys
import unittest
from subprocess import PIPE, Popen
from test.support import import_helper
from test.support import os_helper
from test.support import _4G, bigmemtest, requires_subprocess
from test.support.script_helper import assert_python_ok, assert_python_failure

gzip = import_helper.import_module('gzip')
zlib = import_helper.import_module('zlib')

data1 = b"""  int length=DEFAULTALLOC, err = Z_OK;
  PyObject *RetVal;
  int flushmode = Z_FINISH;
  unsigned long start_total_out;

"""

data2 = b"""/* zlibmodule.c -- gzip-compatible data compression */
/* See http://www.gzip.org/zlib/
/* See http://www.winimage.com/zLibDll for Windows */
"""


TEMPDIR = os.path.abspath(os_helper.TESTFN) + '-gzdir'


class UnseekableIO(io.BytesIO):
    def seekable(self):
        return False

    def tell(self):
        raise io.UnsupportedOperation

    def seek(self, *args):
        raise io.UnsupportedOperation


class BaseTest(unittest.TestCase):
    filename = os_helper.TESTFN

    def setUp(self):
        os_helper.unlink(self.filename)

    def tearDown(self):
        os_helper.unlink(self.filename)


class TestGzip(BaseTest):
    def write_and_read_back(self, data, mode='b'):
        b_data = bytes(data)
        with gzip.GzipFile(self.filename, 'w'+mode) as f:
            l = f.write(data)
        self.assertEqual(l, len(b_data))
        with gzip.GzipFile(self.filename, 'r'+mode) as f:
            self.assertEqual(f.read(), b_data)

    def test_write(self):
        with gzip.GzipFile(self.filename, 'wb') as f:
            f.write(data1 * 50)

            # Try flush and fileno.
            f.flush()
            f.fileno()
            if hasattr(os, 'fsync'):
                os.fsync(f.fileno())
            f.close()

        # Test multiple close() calls.
        f.close()

    def test_write_read_with_pathlike_file(self):
        filename = os_helper.FakePath(self.filename)
        with gzip.GzipFile(filename, 'w') as f:
            f.write(data1 * 50)
        self.assertIsInstance(f.name, str)
        self.assertEqual(f.name, self.filename)
        with gzip.GzipFile(filename, 'a') as f:
            f.write(data1)
        with gzip.GzipFile(filename) as f:
            d = f.read()
        self.assertEqual(d, data1 * 51)
        self.assertIsInstance(f.name, str)
        self.assertEqual(f.name, self.filename)

    # The following test_write_xy methods test that write accepts
    # the corresponding bytes-like object type as input
    # and that the data written equals bytes(xy) in all cases.
    def test_write_memoryview(self):
        self.write_and_read_back(memoryview(data1 * 50))
        m = memoryview(bytes(range(256)))
        data = m.cast('B', shape=[8,8,4])
        self.write_and_read_back(data)

    def test_write_bytearray(self):
        self.write_and_read_back(bytearray(data1 * 50))

    def test_write_array(self):
        self.write_and_read_back(array.array('I', data1 * 40))

    def test_write_incompatible_type(self):
        # Test that non-bytes-like types raise TypeError.
        # Issue #21560: attempts to write incompatible types
        # should not affect the state of the fileobject
        with gzip.GzipFile(self.filename, 'wb') as f:
            with self.assertRaises(TypeError):
                f.write('')
            with self.assertRaises(TypeError):
                f.write([])
            f.write(data1)
        with gzip.GzipFile(self.filename, 'rb') as f:
            self.assertEqual(f.read(), data1)

    def test_read(self):
        self.test_write()
        # Try reading.
        with gzip.GzipFile(self.filename, 'r') as f:
            d = f.read()
        self.assertEqual(d, data1*50)

    def test_read1(self):
        self.test_write()
        blocks = []
        nread = 0
        with gzip.GzipFile(self.filename, 'r') as f:
            while True:
                d = f.read1()
                if not d:
                    break
                blocks.append(d)
                nread += len(d)
                # Check that position was updated correctly (see issue10791).
                self.assertEqual(f.tell(), nread)
        self.assertEqual(b''.join(blocks), data1 * 50)

    @bigmemtest(size=_4G, memuse=1)
    def test_read_large(self, size):
        # Read chunk size over UINT_MAX should be supported, despite zlib's
        # limitation per low-level call
        compressed = gzip.compress(data1, compresslevel=1)
        f = gzip.GzipFile(fileobj=io.BytesIO(compressed), mode='rb')
        self.assertEqual(f.read(size), data1)

    def test_io_on_closed_object(self):
        # Test 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')
        fileobj = f.fileobj
        self.assertFalse(fileobj.closed)
        f.close()
        self.assertTrue(fileobj.closed)
        with self.assertRaises(ValueError):
            f.read(1)
        with self.assertRaises(ValueError):
            f.seek(0)
        with self.assertRaises(ValueError):
            f.tell()
        # Open the file for writing, then close it.
        f = gzip.GzipFile(self.filename, 'w')
        fileobj = f.fileobj
        self.assertFalse(fileobj.closed)
        f.close()
        self.assertTrue(fileobj.closed)
        with self.assertRaises(ValueError):
            f.write(b'')
        with self.assertRaises(ValueError):
            f.flush()

    def test_append(self):
        self.test_write()
        # Append to the previous file
        with gzip.GzipFile(self.filename, 'ab') as f:
            f.write(data2 * 15)

        with gzip.GzipFile(self.filename, 'rb') as f:
            d = f.read()
        self.assertEqual(d, (data1*50) + (data2*15))

    def test_many_append(self):
        # Bug #1074261 was triggered when reading a file that contained
        # many, many members.  Create such a file and verify that reading it
        # works.
        with gzip.GzipFile(self.filename, 'wb', 9) as f:
            f.write(b'a')
        for i in range(0, 200):
            with gzip.GzipFile(self.filename, "ab", 9) as f: # append
                f.write(b'a')

        # Try reading the file
        with gzip.GzipFile(self.filename, "rb") as zgfile:
            contents = b""
            while 1:
                ztxt = zgfile.read(8192)
                contents += ztxt
                if not ztxt: break
        self.assertEqual(contents, b'a'*201)

    def test_exclusive_write(self):
        with gzip.GzipFile(self.filename, 'xb') as f:
            f.write(data1 * 50)
        with gzip.GzipFile(self.filename, 'rb') as f:
            self.assertEqual(f.read(), data1 * 50)
        with self.assertRaises(FileExistsError):
            gzip.GzipFile(self.filename, 'xb')

    def test_buffered_reader(self):
        # Issue #7471: a GzipFile can be wrapped in a BufferedReader for
        # performance.
        self.test_write()

        with gzip.GzipFile(self.filename, 'rb') as f:
            with io.BufferedReader(f) as r:
                lines = [line for line in r]

        self.assertEqual(lines, 50 * data1.splitlines(keepends=True))

    def test_readline(self):
        self.test_write()
        # Try .readline() with varying line lengths

        with gzip.GzipFile(self.filename, 'rb') as f:
            line_length = 0
            while 1:
                L = f.readline(line_length)
                if not L and line_length != 0: break
                self.assertTrue(len(L) <= line_length)
                line_length = (line_length + 1) % 50

    def test_readlines(self):
        self.test_write()
        # Try .readlines()

        with gzip.GzipFile(self.filename, 'rb') as f:
            L = f.readlines()

        with gzip.GzipFile(self.filename, 'rb') as f:
            while 1:
                L = f.readlines(150)
                if L == []: break

    def test_seek_read(self):
        self.test_write()
        # Try seek, read test

        with gzip.GzipFile(self.filename) as f:
            while 1:
                oldpos = f.tell()
                line1 = f.readline()
                if not line1: break
                newpos = f.tell()
                f.seek(oldpos)  # negative seek
                if len(line1)>10:
                    amount = 10
                else:
                    amount = len(line1)
                line2 = f.read(amount)
                self.assertEqual(line1[:amount], line2)
                f.seek(newpos)  # positive seek

    def test_seek_whence(self):
        self.test_write()
        # Try seek(whence=1), read test

        with gzip.GzipFile(self.filename) as f:
            f.read(10)
            f.seek(10, whence=1)
            y = f.read(10)
        self.assertEqual(y, data1[20:30])

    def test_seek_write(self):
        # Try seek, write test
        with gzip.GzipFile(self.filename, 'w') as f:
            for pos in range(0, 256, 16):
                f.seek(pos)
                f.write(b'GZ\n')

    def test_mode(self):
        self.test_write()
        with gzip.GzipFile(self.filename, 'r') as f:
            self.assertEqual(f.myfileobj.mode, 'rb')
        os_helper.unlink(self.filename)
        with gzip.GzipFile(self.filename, 'x') as f:
            self.assertEqual(f.myfileobj.mode, 'xb')

    def test_1647484(self):
        for mode in ('wb', 'rb'):
            with gzip.GzipFile(self.filename, mode) as f:
                self.assertTrue(hasattr(f, "name"))
                self.assertEqual(f.name, self.filename)

    def test_paddedfile_getattr(self):
        self.test_write()
        with gzip.GzipFile(self.filename, 'rb') as f:
            self.assertTrue(hasattr(f.fileobj, "name"))
            self.assertEqual(f.fileobj.name, self.filename)

    def test_mtime(self):
        mtime = 123456789
        with gzip.GzipFile(self.filename, 'w', mtime = mtime) as fWrite:
            fWrite.write(data1)
        with gzip.GzipFile(self.filename) as fRead:
            self.assertTrue(hasattr(fRead, 'mtime'))
            self.assertIsNone(fRead.mtime)
            dataRead = fRead.read()
            self.assertEqual(dataRead, data1)
            self.assertEqual(fRead.mtime, mtime)

    def test_metadata(self):
        mtime = 123456789

        with gzip.GzipFile(self.filename, 'w', mtime = mtime) as fWrite:
            fWrite.write(data1)

        with open(self.filename, 'rb') as fRead:
            # see RFC 1952: http://www.faqs.org/rfcs/rfc1952.html

            idBytes = fRead.read(2)
            self.assertEqual(idBytes, b'\x1f\x8b') # gzip ID

            cmByte = fRead.read(1)
            self.assertEqual(cmByte, b'\x08') # deflate

            try:
                expectedname = self.filename.encode('Latin-1') + b'\x00'
                expectedflags = b'\x08' # only the FNAME flag is set
            except UnicodeEncodeError:
                expectedname = b''
                expectedflags = b'\x00'

            flagsByte = fRead.read(1)
            self.assertEqual(flagsByte, expectedflags)

            mtimeBytes = fRead.read(4)
            self.assertEqual(mtimeBytes, struct.pack('<i', mtime)) # little-endian

            xflByte = fRead.read(1)
            self.assertEqual(xflByte, b'\x02') # maximum compression

            osByte = fRead.read(1)
            self.assertEqual(osByte, b'\xff') # OS "unknown" (OS-independent)

            # Since the FNAME flag is set, the zero-terminated filename follows.
            # RFC 1952 specifies that this is the name of the input file, if any.
            # However, the gzip module defaults to storing the name of the output
            # file in this field.
            nameBytes = fRead.read(len(expectedname))
            self.assertEqual(nameBytes, expectedname)

            # Since no other flags were set, the header ends here.
            # Rather than process the compressed data, let's seek to the trailer.
            fRead.seek(os.stat(self.filename).st_size - 8)

            crc32Bytes = fRead.read(4) # CRC32 of uncompressed data [data1]
            self.assertEqual(crc32Bytes, b'\xaf\xd7d\x83')

            isizeBytes = fRead.read(4)
            self.assertEqual(isizeBytes, struct.pack('<i', len(data1)))

    def test_metadata_ascii_name(self):
        self.filename = os_helper.TESTFN_ASCII
        self.test_metadata()

    def test_compresslevel_metadata(self):
        # see RFC 1952: http://www.faqs.org/rfcs/rfc1952.html
        # specifically, discussion of XFL in section 2.3.1
        cases = [
            ('fast', 1, b'\x04'),
            ('best', 9, b'\x02'),
            ('tradeoff', 6, b'\x00'),
        ]
        xflOffset = 8

        for (name, level, expectedXflByte) in cases:
            with self.subTest(name):
                fWrite = gzip.GzipFile(self.filename, 'w', compresslevel=level)
                with fWrite:
                    fWrite.write(data1)
                with open(self.filename, 'rb') as fRead:
                    fRead.seek(xflOffset)
                    xflByte = fRead.read(1)
                    self.assertEqual(xflByte, expectedXflByte)

    def test_with_open(self):
        # GzipFile supports the context management protocol
        with gzip.GzipFile(self.filename, "wb") as f:
            f.write(b"xxx")
        f = gzip.GzipFile(self.filename, "rb")
        f.close()
        try:
            with f:
                pass
        except ValueError:
            pass
        else:
            self.fail("__enter__ on a closed file didn't raise an exception")
        try:
            with gzip.GzipFile(self.filename, "wb") as f:
                1/0
        except ZeroDivisionError:
            pass
        else:
            self.fail("1/0 didn't raise an exception")

    def test_zero_padded_file(self):
        with gzip.GzipFile(self.filename, "wb") as f:
            f.write(data1 * 50)

        # Pad the file with zeroes
        with open(self.filename, "ab") as f:
            f.write(b"\x00" * 50)

        with gzip.GzipFile(self.filename, "rb") as f:
            d = f.read()
            self.assertEqual(d, data1 * 50, "Incorrect data in file")

    def test_gzip_BadGzipFile_exception(self):
        self.assertTrue(issubclass(gzip.BadGzipFile, OSError))

    def test_bad_gzip_file(self):
        with open(self.filename, 'wb') as file:
            file.write(data1 * 50)
        with gzip.GzipFile(self.filename, 'r') as file:
            self.assertRaises(gzip.BadGzipFile, file.readlines)

    def test_non_seekable_file(self):
        uncompressed = data1 * 50
        buf = UnseekableIO()
        with gzip.GzipFile(fileobj=buf, mode="wb") as f:
            f.write(uncompressed)
        compressed = buf.getvalue()
        buf = UnseekableIO(compressed)
        with gzip.GzipFile(fileobj=buf, mode="rb") as f:
            self.assertEqual(f.read(), uncompressed)

    def test_peek(self):
        uncompressed = data1 * 200
        with gzip.GzipFile(self.filename, "wb") as f:
            f.write(uncompressed)

        def sizes():
            while True:
                for n in range(5, 50, 10):
                    yield n

        with gzip.GzipFile(self.filename, "rb") as f:
            f.max_read_chunk = 33
            nread = 0
            for n in sizes():
                s = f.peek(n)
                if s == b'':
                    break
                self.assertEqual(f.read(len(s)), s)
                nread += len(s)
            self.assertEqual(f.read(100), b'')
            self.assertEqual(nread, len(uncompressed))

    def test_textio_readlines(self):
        # Issue #10791: TextIOWrapper.readlines() fails when wrapping GzipFile.
        lines = (data1 * 50).decode("ascii").splitlines(keepends=True)
        self.test_write()
        with gzip.GzipFile(self.filename, 'r') as f:
            with io.TextIOWrapper(f, encoding="ascii") as t:
                self.assertEqual(t.readlines(), lines)

    def test_fileobj_with_name(self):
        with open(self.filename, "xb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="x") as f:
                f.write(b'one')
                self.assertEqual(f.name, raw.name)
                self.assertEqual(f.fileno(), raw.fileno())
                self.assertEqual(f.mode, gzip.WRITE)
                self.assertIs(f.readable(), False)
                self.assertIs(f.writable(), True)
                self.assertIs(f.seekable(), True)
                self.assertIs(f.closed, False)
            self.assertIs(f.closed, True)
            self.assertEqual(f.name, raw.name)
            self.assertRaises(AttributeError, f.fileno)
            self.assertEqual(f.mode, gzip.WRITE)
            self.assertIs(f.readable(), False)
            self.assertIs(f.writable(), True)
            self.assertIs(f.seekable(), True)

        with open(self.filename, "wb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="w") as f:
                f.write(b'two')
                self.assertEqual(f.name, raw.name)
                self.assertEqual(f.fileno(), raw.fileno())
                self.assertEqual(f.mode, gzip.WRITE)
                self.assertIs(f.readable(), False)
                self.assertIs(f.writable(), True)
                self.assertIs(f.seekable(), True)
                self.assertIs(f.closed, False)
            self.assertIs(f.closed, True)
            self.assertEqual(f.name, raw.name)
            self.assertRaises(AttributeError, f.fileno)
            self.assertEqual(f.mode, gzip.WRITE)
            self.assertIs(f.readable(), False)
            self.assertIs(f.writable(), True)
            self.assertIs(f.seekable(), True)

        with open(self.filename, "ab") as raw:
            with gzip.GzipFile(fileobj=raw, mode="a") as f:
                f.write(b'three')
                self.assertEqual(f.name, raw.name)
                self.assertEqual(f.fileno(), raw.fileno())
                self.assertEqual(f.mode, gzip.WRITE)
                self.assertIs(f.readable(), False)
                self.assertIs(f.writable(), True)
                self.assertIs(f.seekable(), True)
                self.assertIs(f.closed, False)
            self.assertIs(f.closed, True)
            self.assertEqual(f.name, raw.name)
            self.assertRaises(AttributeError, f.fileno)
            self.assertEqual(f.mode, gzip.WRITE)
            self.assertIs(f.readable(), False)
            self.assertIs(f.writable(), True)
            self.assertIs(f.seekable(), True)

        with open(self.filename, "rb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="r") as f:
                self.assertEqual(f.read(), b'twothree')
                self.assertEqual(f.name, raw.name)
                self.assertEqual(f.fileno(), raw.fileno())
                self.assertEqual(f.mode, gzip.READ)
                self.assertIs(f.readable(), True)
                self.assertIs(f.writable(), False)
                self.assertIs(f.seekable(), True)
                self.assertIs(f.closed, False)
            self.assertIs(f.closed, True)
            self.assertEqual(f.name, raw.name)
            self.assertRaises(AttributeError, f.fileno)
            self.assertEqual(f.mode, gzip.READ)
            self.assertIs(f.readable(), True)
            self.assertIs(f.writable(), False)
            self.assertIs(f.seekable(), True)

    def test_fileobj_from_fdopen(self):
        # Issue #13781: Opening a GzipFile for writing fails when using a
        # fileobj created with os.fdopen().
        fd = os.open(self.filename, os.O_WRONLY | os.O_CREAT | os.O_EXCL)
        with os.fdopen(fd, "xb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="x") as f:
                f.write(b'one')
                self.assertEqual(f.name, '')
                self.assertEqual(f.fileno(), raw.fileno())
            self.assertIs(f.closed, True)
            self.assertEqual(f.name, '')
            self.assertRaises(AttributeError, f.fileno)

        fd = os.open(self.filename, os.O_WRONLY | os.O_CREAT | os.O_TRUNC)
        with os.fdopen(fd, "wb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="w") as f:
                f.write(b'two')
                self.assertEqual(f.name, '')
                self.assertEqual(f.fileno(), raw.fileno())
            self.assertEqual(f.name, '')
            self.assertRaises(AttributeError, f.fileno)

        fd = os.open(self.filename, os.O_WRONLY | os.O_CREAT | os.O_APPEND)
        with os.fdopen(fd, "ab") as raw:
            with gzip.GzipFile(fileobj=raw, mode="a") as f:
                f.write(b'three')
                self.assertEqual(f.name, '')
                self.assertEqual(f.fileno(), raw.fileno())
            self.assertEqual(f.name, '')
            self.assertRaises(AttributeError, f.fileno)

        fd = os.open(self.filename, os.O_RDONLY)
        with os.fdopen(fd, "rb") as raw:
            with gzip.GzipFile(fileobj=raw, mode="r") as f:
                self.assertEqual(f.read(), b'twothree')
                self.assertEqual(f.name, '')
                self.assertEqual(f.fileno(), raw.fileno())
            self.assertEqual(f.name, '')
            self.assertRaises(AttributeError, f.fileno)

    def test_fileobj_mode(self):
        self.assertEqual(gzip.READ, 'rb')
        self.assertEqual(gzip.WRITE, 'wb')
        gzip.GzipFile(self.filename, "wb").close()
        with open(self.filename, "r+b") as f:
            with gzip.GzipFile(fileobj=f, mode='r') as g:
                self.assertEqual(g.mode, gzip.READ)
            with gzip.GzipFile(fileobj=f, mode='w') as g:
                self.assertEqual(g.mode, gzip.WRITE)
            with gzip.GzipFile(fileobj=f, mode='a') as g:
                self.assertEqual(g.mode, gzip.WRITE)
            with gzip.GzipFile(fileobj=f, mode='x') as g:
                self.assertEqual(g.mode, gzip.WRITE)
            with self.assertRaises(ValueError):
                gzip.GzipFile(fileobj=f, mode='z')
        for mode in "rb", "r+b":
            with open(self.filename, mode) as f:
                with gzip.GzipFile(fileobj=f) as g:
                    self.assertEqual(g.mode, gzip.READ)
        for mode in "wb", "ab", "xb":
            if "x" in mode:
                os_helper.unlink(self.filename)
            with open(self.filename, mode) as f:
                with self.assertWarns(FutureWarning):
                    g = gzip.GzipFile(fileobj=f)
                with g:
                    self.assertEqual(g.mode, gzip.WRITE)

    def test_bytes_filename(self):
        str_filename = self.filename
        bytes_filename = os.fsencode(str_filename)
        with gzip.GzipFile(bytes_filename, "wb") as f:
            f.write(data1 * 50)
        self.assertEqual(f.name, bytes_filename)
        with gzip.GzipFile(bytes_filename, "rb") as f:
            self.assertEqual(f.read(), data1 * 50)
        self.assertEqual(f.name, bytes_filename)
        # Sanity check that we are actually operating on the right file.
        with gzip.GzipFile(str_filename, "rb") as f:
            self.assertEqual(f.read(), data1 * 50)
        self.assertEqual(f.name, str_filename)

    def test_fileobj_without_name(self):
        bio = io.BytesIO()
        with gzip.GzipFile(fileobj=bio, mode='wb') as f:
            f.write(data1 * 50)
            self.assertEqual(f.name, '')
            self.assertRaises(io.UnsupportedOperation, f.fileno)
            self.assertEqual(f.mode, gzip.WRITE)
            self.assertIs(f.readable(), False)
            self.assertIs(f.writable(), True)
            self.assertIs(f.seekable(), True)
            self.assertIs(f.closed, False)
        self.assertIs(f.closed, True)
        self.assertEqual(f.name, '')
        self.assertRaises(AttributeError, f.fileno)
        self.assertEqual(f.mode, gzip.WRITE)
        self.assertIs(f.readable(), False)
        self.assertIs(f.writable(), True)
        self.assertIs(f.seekable(), True)

        bio.seek(0)
        with gzip.GzipFile(fileobj=bio, mode='rb') as f:
            self.assertEqual(f.read(), data1 * 50)
            self.assertEqual(f.name, '')
            self.assertRaises(io.UnsupportedOperation, f.fileno)
            self.assertEqual(f.mode, gzip.READ)
            self.assertIs(f.readable(), True)
            self.assertIs(f.writable(), False)
            self.assertIs(f.seekable(), True)
            self.assertIs(f.closed, False)
        self.assertIs(f.closed, True)
        self.assertEqual(f.name, '')
        self.assertRaises(AttributeError, f.fileno)
        self.assertEqual(f.mode, gzip.READ)
        self.assertIs(f.readable(), True)
        self.assertIs(f.writable(), False)
        self.assertIs(f.seekable(), True)

    def test_fileobj_and_filename(self):
        filename2 = self.filename + 'new'
        with (open(self.filename, 'wb') as fileobj,
              gzip.GzipFile(fileobj=fileobj, filename=filename2, mode='wb') as f):
            f.write(data1 * 50)
            self.assertEqual(f.name, filename2)
        with (open(self.filename, 'rb') as fileobj,
              gzip.GzipFile(fileobj=fileobj, filename=filename2, mode='rb') as f):
            self.assertEqual(f.read(), data1 * 50)
            self.assertEqual(f.name, filename2)
        # Sanity check that we are actually operating on the right file.
        with gzip.GzipFile(self.filename, 'rb') as f:
            self.assertEqual(f.read(), data1 * 50)
            self.assertEqual(f.name, self.filename)

    def test_decompress_limited(self):
        """Decompressed data buffering should be limited"""
        bomb = gzip.compress(b'\0' * int(2e6), compresslevel=9)
        self.assertLess(len(bomb), io.DEFAULT_BUFFER_SIZE)

        bomb = io.BytesIO(bomb)
        decomp = gzip.GzipFile(fileobj=bomb)
        self.assertEqual(decomp.read(1), b'\0')
        max_decomp = 1 + io.DEFAULT_BUFFER_SIZE
        self.assertLessEqual(decomp._buffer.raw.tell(), max_decomp,
            "Excessive amount of data was decompressed")

    # Testing compress/decompress shortcut functions

    def test_compress(self):
        for data in [data1, data2]:
            for args in [(), (1,), (6,), (9,)]:
                datac = gzip.compress(data, *args)
                self.assertEqual(type(datac), bytes)
                with gzip.GzipFile(fileobj=io.BytesIO(datac), mode="rb") as f:
                    self.assertEqual(f.read(), data)

    def test_compress_mtime(self):
        mtime = 123456789
        for data in [data1, data2]:
            for args in [(), (1,), (6,), (9,)]:
                with self.subTest(data=data, args=args):
                    datac = gzip.compress(data, *args, mtime=mtime)
                    self.assertEqual(type(datac), bytes)
                    with gzip.GzipFile(fileobj=io.BytesIO(datac), mode="rb") as f:
                        f.read(1) # to set mtime attribute
                        self.assertEqual(f.mtime, mtime)

    def test_compress_correct_level(self):
        for mtime in (0, 42):
            with self.subTest(mtime=mtime):
                nocompress = gzip.compress(data1, compresslevel=0, mtime=mtime)
                yescompress = gzip.compress(data1, compresslevel=1, mtime=mtime)
                self.assertIn(data1, nocompress)
                self.assertNotIn(data1, yescompress)

    def test_issue112346(self):
        # The OS byte should be 255, this should not change between Python versions.
        for mtime in (0, 42):
            with self.subTest(mtime=mtime):
                compress = gzip.compress(data1, compresslevel=1, mtime=mtime)
                self.assertEqual(
                    struct.unpack("<IxB", compress[4:10]),
                    (mtime, 255),
                    "Gzip header does not properly set either mtime or OS byte."
                )

    def test_decompress(self):
        for data in (data1, data2):
            buf = io.BytesIO()
            with gzip.GzipFile(fileobj=buf, mode="wb") as f:
                f.write(data)
            self.assertEqual(gzip.decompress(buf.getvalue()), data)
            # Roundtrip with compress
            datac = gzip.compress(data)
            self.assertEqual(gzip.decompress(datac), data)

    def test_decompress_truncated_trailer(self):
        compressed_data = gzip.compress(data1)
        self.assertRaises(EOFError, gzip.decompress, compressed_data[:-4])

    def test_decompress_missing_trailer(self):
        compressed_data = gzip.compress(data1)
        self.assertRaises(EOFError, gzip.decompress, compressed_data[:-8])

    def test_read_truncated(self):
        data = data1*50
        # Drop the CRC (4 bytes) and file size (4 bytes).
        truncated = gzip.compress(data)[:-8]
        with gzip.GzipFile(fileobj=io.BytesIO(truncated)) as f:
            self.assertRaises(EOFError, f.read)
        with gzip.GzipFile(fileobj=io.BytesIO(truncated)) as f:
            self.assertEqual(f.read(len(data)), data)
            self.assertRaises(EOFError, f.read, 1)
        # Incomplete 10-byte header.
        for i in range(2, 10):
            with gzip.GzipFile(fileobj=io.BytesIO(truncated[:i])) as f:
                self.assertRaises(EOFError, f.read, 1)

    def test_read_with_extra(self):
        # Gzip data with an extra field
        gzdata = (b'\x1f\x8b\x08\x04\xb2\x17cQ\x02\xff'
                  b'\x05\x00Extra'
                  b'\x0bI-.\x01\x002\xd1Mx\x04\x00\x00\x00')
        with gzip.GzipFile(fileobj=io.BytesIO(gzdata)) as f:
            self.assertEqual(f.read(), b'Test')

    def test_prepend_error(self):
        # See issue #20875
        with gzip.open(self.filename, "wb") as f:
            f.write(data1)
        with gzip.open(self.filename, "rb") as f:
            f._buffer.raw._fp.prepend()

    def test_issue44439(self):
        q = array.array('Q', [1, 2, 3, 4, 5])
        LENGTH = len(q) * q.itemsize

        with gzip.GzipFile(fileobj=io.BytesIO(), mode='w') as f:
            self.assertEqual(f.write(q), LENGTH)
            self.assertEqual(f.tell(), LENGTH)

    def test_flush_flushes_compressor(self):
        # See issue GH-105808.
        b = io.BytesIO()
        message = b"important message here."
        with gzip.GzipFile(fileobj=b, mode='w') as f:
            f.write(message)
            f.flush()
            partial_data = b.getvalue()
        full_data = b.getvalue()
        self.assertEqual(gzip.decompress(full_data), message)
        # The partial data should contain the gzip header and the complete
        # message, but not the end-of-stream markers (so we can't just
        # decompress it directly).
        with self.assertRaises(EOFError):
            gzip.decompress(partial_data)
        d = zlib.decompressobj(wbits=-zlib.MAX_WBITS)
        f = io.BytesIO(partial_data)
        gzip._read_gzip_header(f)
        read_message = d.decompress(f.read())
        self.assertEqual(read_message, message)

    def test_flush_modes(self):
        # Make sure the argument to flush is properly passed to the
        # zlib.compressobj; see issue GH-105808.
        class FakeCompressor:
            def __init__(self):
                self.modes = []
            def compress(self, data):
                return b''
            def flush(self, mode=-1):
                self.modes.append(mode)
                return b''
        b = io.BytesIO()
        fc = FakeCompressor()
        with gzip.GzipFile(fileobj=b, mode='w') as f:
            f.compress = fc
            f.flush()
            f.flush(50)
            f.flush(zlib_mode=100)
        # The implicit close will also flush the compressor.
        expected_modes = [
            zlib.Z_SYNC_FLUSH,
            50,
            100,
            -1,
        ]
        self.assertEqual(fc.modes, expected_modes)

    def test_write_seek_write(self):
        # Make sure that offset is up-to-date before seeking
        # See issue GH-108111
        b = io.BytesIO()
        message = b"important message here."
        with gzip.GzipFile(fileobj=b, mode='w') as f:
            f.write(message)
            f.seek(len(message))
            f.write(message)
        data = b.getvalue()
        self.assertEqual(gzip.decompress(data), message * 2)


class TestOpen(BaseTest):
    def test_binary_modes(self):
        uncompressed = data1 * 50

        with gzip.open(self.filename, "wb") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed)

        with gzip.open(self.filename, "rb") as f:
            self.assertEqual(f.read(), uncompressed)

        with gzip.open(self.filename, "ab") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed * 2)

        with self.assertRaises(FileExistsError):
            gzip.open(self.filename, "xb")
        os_helper.unlink(self.filename)
        with gzip.open(self.filename, "xb") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed)

    def test_pathlike_file(self):
        filename = os_helper.FakePath(self.filename)
        with gzip.open(filename, "wb") as f:
            f.write(data1 * 50)
        self.assertEqual(f.name, self.filename)
        with gzip.open(filename, "ab") as f:
            f.write(data1)
        self.assertEqual(f.name, self.filename)
        with gzip.open(filename) as f:
            self.assertEqual(f.read(), data1 * 51)
        self.assertEqual(f.name, self.filename)

    def test_implicit_binary_modes(self):
        # Test implicit binary modes (no "b" or "t" in mode string).
        uncompressed = data1 * 50

        with gzip.open(self.filename, "w") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed)

        with gzip.open(self.filename, "r") as f:
            self.assertEqual(f.read(), uncompressed)

        with gzip.open(self.filename, "a") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed * 2)

        with self.assertRaises(FileExistsError):
            gzip.open(self.filename, "x")
        os_helper.unlink(self.filename)
        with gzip.open(self.filename, "x") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read())
            self.assertEqual(file_data, uncompressed)

    def test_text_modes(self):
        uncompressed = data1.decode("ascii") * 50
        uncompressed_raw = uncompressed.replace("\n", os.linesep)
        with gzip.open(self.filename, "wt", encoding="ascii") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read()).decode("ascii")
            self.assertEqual(file_data, uncompressed_raw)
        with gzip.open(self.filename, "rt", encoding="ascii") as f:
            self.assertEqual(f.read(), uncompressed)
        with gzip.open(self.filename, "at", encoding="ascii") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read()).decode("ascii")
            self.assertEqual(file_data, uncompressed_raw * 2)

    def test_fileobj(self):
        uncompressed_bytes = data1 * 50
        uncompressed_str = uncompressed_bytes.decode("ascii")
        compressed = gzip.compress(uncompressed_bytes)
        with gzip.open(io.BytesIO(compressed), "r") as f:
            self.assertEqual(f.read(), uncompressed_bytes)
        with gzip.open(io.BytesIO(compressed), "rb") as f:
            self.assertEqual(f.read(), uncompressed_bytes)
        with gzip.open(io.BytesIO(compressed), "rt", encoding="ascii") as f:
            self.assertEqual(f.read(), uncompressed_str)

    def test_bad_params(self):
        # Test invalid parameter combinations.
        with self.assertRaises(TypeError):
            gzip.open(123.456)
        with self.assertRaises(ValueError):
            gzip.open(self.filename, "wbt")
        with self.assertRaises(ValueError):
            gzip.open(self.filename, "xbt")
        with self.assertRaises(ValueError):
            gzip.open(self.filename, "rb", encoding="utf-8")
        with self.assertRaises(ValueError):
            gzip.open(self.filename, "rb", errors="ignore")
        with self.assertRaises(ValueError):
            gzip.open(self.filename, "rb", newline="\n")

    def test_encoding(self):
        # Test non-default encoding.
        uncompressed = data1.decode("ascii") * 50
        uncompressed_raw = uncompressed.replace("\n", os.linesep)
        with gzip.open(self.filename, "wt", encoding="utf-16") as f:
            f.write(uncompressed)
        with open(self.filename, "rb") as f:
            file_data = gzip.decompress(f.read()).decode("utf-16")
            self.assertEqual(file_data, uncompressed_raw)
        with gzip.open(self.filename, "rt", encoding="utf-16") as f:
            self.assertEqual(f.read(), uncompressed)

    def test_encoding_error_handler(self):
        # Test with non-default encoding error handler.
        with gzip.open(self.filename, "wb") as f:
            f.write(b"foo\xffbar")
        with gzip.open(self.filename, "rt", encoding="ascii", errors="ignore") \
                as f:
            self.assertEqual(f.read(), "foobar")

    def test_newline(self):
        # Test with explicit newline (universal newline mode disabled).
        uncompressed = data1.decode("ascii") * 50
        with gzip.open(self.filename, "wt", encoding="ascii", newline="\n") as f:
            f.write(uncompressed)
        with gzip.open(self.filename, "rt", encoding="ascii", newline="\r") as f:
            self.assertEqual(f.readlines(), [uncompressed])


def create_and_remove_directory(directory):
    def decorator(function):
        @functools.wraps(function)
        def wrapper(*args, **kwargs):
            os.makedirs(directory)
            try:
                return function(*args, **kwargs)
            finally:
                os_helper.rmtree(directory)
        return wrapper
    return decorator


class TestCommandLine(unittest.TestCase):
    data = b'This is a simple test with gzip'

    @requires_subprocess()
    def test_decompress_stdin_stdout(self):
        with io.BytesIO() as bytes_io:
            with gzip.GzipFile(fileobj=bytes_io, mode='wb') as gzip_file:
                gzip_file.write(self.data)

            args = sys.executable, '-m', 'gzip', '-d'
            with Popen(args, stdin=PIPE, stdout=PIPE, stderr=PIPE) as proc:
                out, err = proc.communicate(bytes_io.getvalue())

        self.assertEqual(err, b'')
        self.assertEqual(out, self.data)

    @create_and_remove_directory(TEMPDIR)
    def test_decompress_infile_outfile(self):
        gzipname = os.path.join(TEMPDIR, 'testgzip.gz')
        self.assertFalse(os.path.exists(gzipname))

        with gzip.open(gzipname, mode='wb') as fp:
            fp.write(self.data)
        rc, out, err = assert_python_ok('-m', 'gzip', '-d', gzipname)

        with open(os.path.join(TEMPDIR, "testgzip"), "rb") as gunziped:
            self.assertEqual(gunziped.read(), self.data)

        self.assertTrue(os.path.exists(gzipname))
        self.assertEqual(rc, 0)
        self.assertEqual(out, b'')
        self.assertEqual(err, b'')

    def test_decompress_infile_outfile_error(self):
        rc, out, err = assert_python_failure('-m', 'gzip', '-d', 'thisisatest.out')
        self.assertEqual(b"filename doesn't end in .gz: 'thisisatest.out'", err.strip())
        self.assertEqual(rc, 1)
        self.assertEqual(out, b'')

    @requires_subprocess()
    @create_and_remove_directory(TEMPDIR)
    def test_compress_stdin_outfile(self):
        args = sys.executable, '-m', 'gzip'
        with Popen(args, stdin=PIPE, stdout=PIPE, stderr=PIPE) as proc:
            out, err = proc.communicate(self.data)

        self.assertEqual(err, b'')
        self.assertEqual(out[:2], b"\x1f\x8b")

    @create_and_remove_directory(TEMPDIR)
    def test_compress_infile_outfile_default(self):
        local_testgzip = os.path.join(TEMPDIR, 'testgzip')
        gzipname = local_testgzip + '.gz'
        self.assertFalse(os.path.exists(gzipname))

        with open(local_testgzip, 'wb') as fp:
            fp.write(self.data)

        rc, out, err = assert_python_ok('-m', 'gzip', local_testgzip)

        self.assertTrue(os.path.exists(gzipname))
        self.assertEqual(out, b'')
        self.assertEqual(err, b'')

    @create_and_remove_directory(TEMPDIR)
    def test_compress_infile_outfile(self):
        for compress_level in ('--fast', '--best'):
            with self.subTest(compress_level=compress_level):
                local_testgzip = os.path.join(TEMPDIR, 'testgzip')
                gzipname = local_testgzip + '.gz'
                self.assertFalse(os.path.exists(gzipname))

                with open(local_testgzip, 'wb') as fp:
                    fp.write(self.data)

                rc, out, err = assert_python_ok('-m', 'gzip', compress_level, local_testgzip)

                self.assertTrue(os.path.exists(gzipname))
                self.assertEqual(out, b'')
                self.assertEqual(err, b'')
                os.remove(gzipname)
                self.assertFalse(os.path.exists(gzipname))

    def test_compress_fast_best_are_exclusive(self):
        rc, out, err = assert_python_failure('-m', 'gzip', '--fast', '--best')
        self.assertIn(b"error: argument --best: not allowed with argument --fast", err)
        self.assertEqual(out, b'')

    def test_decompress_cannot_have_flags_compression(self):
        rc, out, err = assert_python_failure('-m', 'gzip', '--fast', '-d')
        self.assertIn(b'error: argument -d/--decompress: not allowed with argument --fast', err)
        self.assertEqual(out, b'')


if __name__ == "__main__":
    unittest.main()