Skip to content

[3.6] bpo-22671: Clarify and test default read method implementations (GH-4568) #4796

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
vstinner merged 1 commit into from
Dec 11, 2017
Merged

[3.6] bpo-22671: Clarify and test default read method implementations (GH-4568) #4796

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 8 additions & 5 deletions Doc/library/io.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -205,8 +205,8 @@ ABC Inherits Stub Methods Mixin M
``writable``, and ``writelines``
:class:`RawIOBase` :class:`IOBase` ``readinto`` and Inherited :class:`IOBase` methods, ``read``,
``write`` and ``readall``
:class:`BufferedIOBase` :class:`IOBase` ``detach``, ``read``, Inherited :class:`IOBase` methods, ``readinto``
``read1``, and ``write``
:class:`BufferedIOBase` :class:`IOBase` ``detach``, ``read``, Inherited :class:`IOBase` methods, ``readinto``,
``read1``, and ``write`` and ``readinto1``
:class:`TextIOBase` :class:`IOBase` ``detach``, ``read``, Inherited :class:`IOBase` methods, ``encoding``,
``readline``, and ``errors``, and ``newlines``
``write``
Expand Down Expand Up @@ -385,14 +385,17 @@ I/O Base Classes
.. method:: read(size=-1)

Read up to *size* bytes from the object and return them. As a convenience,
if *size* is unspecified or -1, :meth:`readall` is called. Otherwise,
only one system call is ever made. Fewer than *size* bytes may be
returned if the operating system call returns fewer than *size* bytes.
if *size* is unspecified or -1, all bytes until EOF are returned.
Otherwise, only one system call is ever made. Fewer than *size* bytes may
be returned if the operating system call returns fewer than *size* bytes.

If 0 bytes are returned, and *size* was not 0, this indicates end of file.
If the object is in non-blocking mode and no bytes are available,
``None`` is returned.

The default implementation defers to :meth:`readall` and
:meth:`readinto`.

.. method:: readall()

Read and return all the bytes from the stream until EOF, using multiple
Expand Down
53 changes: 51 additions & 2 deletions Lib/test/test_io.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -796,8 +796,8 @@ def test_multi_close(self):
self.assertRaises(ValueError, f.flush)

def test_RawIOBase_read(self):
# Exercise the default RawIOBase.read() implementation (which calls
# readinto() internally).
# Exercise the default limited RawIOBase.read(n) implementation (which
# calls readinto() internally).
rawio = self.MockRawIOWithoutRead((b"abc", b"d", None, b"efg", None))
self.assertEqual(rawio.read(2), b"ab")
self.assertEqual(rawio.read(2), b"c")
Expand Down Expand Up @@ -905,6 +905,55 @@ def check_path_succeeds(path):
with self.assertRaisesRegex(ValueError, 'read/write/append mode'):
self.open(PathLike(support.TESTFN), 'rwxa')

def test_RawIOBase_readall(self):
# Exercise the default unlimited RawIOBase.read() and readall()
# implementations.
rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
self.assertEqual(rawio.read(), b"abcdefg")
rawio = self.MockRawIOWithoutRead((b"abc", b"d", b"efg"))
self.assertEqual(rawio.readall(), b"abcdefg")

def test_BufferedIOBase_readinto(self):
# Exercise the default BufferedIOBase.readinto() and readinto1()
# implementations (which call read() or read1() internally).
class Reader(self.BufferedIOBase):
def __init__(self, avail):
self.avail = avail
def read(self, size):
result = self.avail[:size]
self.avail = self.avail[size:]
return result
def read1(self, size):
"""Returns no more than 5 bytes at once"""
return self.read(min(size, 5))
tests = (
# (test method, total data available, read buffer size, expected
# read size)
("readinto", 10, 5, 5),
("readinto", 10, 6, 6), # More than read1() can return
("readinto", 5, 6, 5), # Buffer larger than total available
("readinto", 6, 7, 6),
("readinto", 10, 0, 0), # Empty buffer
("readinto1", 10, 5, 5), # Result limited to single read1() call
("readinto1", 10, 6, 5), # Buffer larger than read1() can return
("readinto1", 5, 6, 5), # Buffer larger than total available
("readinto1", 6, 7, 5),
("readinto1", 10, 0, 0), # Empty buffer
)
UNUSED_BYTE = 0x81
for test in tests:
with self.subTest(test):
method, avail, request, result = test
reader = Reader(bytes(range(avail)))
buffer = bytearray((UNUSED_BYTE,) * request)
method = getattr(reader, method)
self.assertEqual(method(buffer), result)
self.assertEqual(len(buffer), request)
self.assertSequenceEqual(buffer[:result], range(result))
unused = (UNUSED_BYTE,) * (request - result)
self.assertSequenceEqual(buffer[result:], unused)
self.assertEqual(len(reader.avail), avail - result)


class CIOTest(IOTest):

Expand Down