gh-138013: Move buffered tests to test_bufferedio

This moves test support code to `test_io._support` and buffered test
cases to `test_io.test_bufferedio` via copy/paste code movement then
adjusts imports as needed (remove unneded + add all required).

Author: cmaloney

Lib/test/test_io/_support.py

@@ -0,0 +1,317 @@
+import array
+import threading
+import time
+import unittest
+
+import io  # C implementation of io
+import _pyio as pyio # Python implementation of io
+
+
+try:
+    import ctypes
+except ImportError:
+    def byteslike(*pos, **kw):
+        return array.array("b", bytes(*pos, **kw))
+else:
+    def byteslike(*pos, **kw):
+        """Create a bytes-like object having no string or sequence methods"""
+        data = bytes(*pos, **kw)
+        obj = EmptyStruct()
+        ctypes.resize(obj, len(data))
+        memoryview(obj).cast("B")[:] = data
+        return obj
+    class EmptyStruct(ctypes.Structure):
+        pass
+
+
+class MockRawIOWithoutRead:
+    """A RawIO implementation without read(), so as to exercise the default
+    RawIO.read() which calls readinto()."""
+
+    def __init__(self, read_stack=()):
+        self._read_stack = list(read_stack)
+        self._write_stack = []
+        self._reads = 0
+        self._extraneous_reads = 0
+
+    def write(self, b):
+        self._write_stack.append(bytes(b))
+        return len(b)
+
+    def writable(self):
+        return True
+
+    def fileno(self):
+        return 42
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def seek(self, pos, whence):
+        return 0   # wrong but we gotta return something
+
+    def tell(self):
+        return 0   # same comment as above
+
+    def readinto(self, buf):
+        self._reads += 1
+        max_len = len(buf)
+        try:
+            data = self._read_stack[0]
+        except IndexError:
+            self._extraneous_reads += 1
+            return 0
+        if data is None:
+            del self._read_stack[0]
+            return None
+        n = len(data)
+        if len(data) <= max_len:
+            del self._read_stack[0]
+            buf[:n] = data
+            return n
+        else:
+            buf[:] = data[:max_len]
+            self._read_stack[0] = data[max_len:]
+            return max_len
+
+    def truncate(self, pos=None):
+        return pos
+
+class CMockRawIOWithoutRead(MockRawIOWithoutRead, io.RawIOBase):
+    pass
+
+class PyMockRawIOWithoutRead(MockRawIOWithoutRead, pyio.RawIOBase):
+    pass
+
+
+class MockRawIO(MockRawIOWithoutRead):
+
+    def read(self, n=None):
+        self._reads += 1
+        try:
+            return self._read_stack.pop(0)
+        except:
+            self._extraneous_reads += 1
+            return b""
+
+class CMockRawIO(MockRawIO, io.RawIOBase):
+    pass
+
+class PyMockRawIO(MockRawIO, pyio.RawIOBase):
+    pass
+
+
+class MisbehavedRawIO(MockRawIO):
+    def write(self, b):
+        return super().write(b) * 2
+
+    def read(self, n=None):
+        return super().read(n) * 2
+
+    def seek(self, pos, whence):
+        return -123
+
+    def tell(self):
+        return -456
+
+    def readinto(self, buf):
+        super().readinto(buf)
+        return len(buf) * 5
+
+class CMisbehavedRawIO(MisbehavedRawIO, io.RawIOBase):
+    pass
+
+class PyMisbehavedRawIO(MisbehavedRawIO, pyio.RawIOBase):
+    pass
+
+
+class SlowFlushRawIO(MockRawIO):
+    def __init__(self):
+        super().__init__()
+        self.in_flush = threading.Event()
+
+    def flush(self):
+        self.in_flush.set()
+        time.sleep(0.25)
+
+class CSlowFlushRawIO(SlowFlushRawIO, io.RawIOBase):
+    pass
+
+class PySlowFlushRawIO(SlowFlushRawIO, pyio.RawIOBase):
+    pass
+
+
+class CloseFailureIO(MockRawIO):
+    closed = 0
+
+    def close(self):
+        if not self.closed:
+            self.closed = 1
+            raise OSError
+
+class CCloseFailureIO(CloseFailureIO, io.RawIOBase):
+    pass
+
+class PyCloseFailureIO(CloseFailureIO, pyio.RawIOBase):
+    pass
+
+
+class MockFileIO:
+
+    def __init__(self, data):
+        self.read_history = []
+        super().__init__(data)
+
+    def read(self, n=None):
+        res = super().read(n)
+        self.read_history.append(None if res is None else len(res))
+        return res
+
+    def readinto(self, b):
+        res = super().readinto(b)
+        self.read_history.append(res)
+        return res
+
+class CMockFileIO(MockFileIO, io.BytesIO):
+    pass
+
+class PyMockFileIO(MockFileIO, pyio.BytesIO):
+    pass
+
+
+class MockUnseekableIO:
+    def seekable(self):
+        return False
+
+    def seek(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+    def tell(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+    def truncate(self, *args):
+        raise self.UnsupportedOperation("not seekable")
+
+class CMockUnseekableIO(MockUnseekableIO, io.BytesIO):
+    UnsupportedOperation = io.UnsupportedOperation
+
+class PyMockUnseekableIO(MockUnseekableIO, pyio.BytesIO):
+    UnsupportedOperation = pyio.UnsupportedOperation
+
+
+class MockCharPseudoDevFileIO(MockFileIO):
+    # GH-95782
+    # ftruncate() does not work on these special files (and CPython then raises
+    # appropriate exceptions), so truncate() does not have to be accounted for
+    # here.
+    def __init__(self, data):
+        super().__init__(data)
+
+    def seek(self, *args):
+        return 0
+
+    def tell(self, *args):
+        return 0
+
+class CMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, io.BytesIO):
+    pass
+
+class PyMockCharPseudoDevFileIO(MockCharPseudoDevFileIO, pyio.BytesIO):
+    pass
+
+
+class MockNonBlockWriterIO:
+
+    def __init__(self):
+        self._write_stack = []
+        self._blocker_char = None
+
+    def pop_written(self):
+        s = b"".join(self._write_stack)
+        self._write_stack[:] = []
+        return s
+
+    def block_on(self, char):
+        """Block when a given char is encountered."""
+        self._blocker_char = char
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def seek(self, pos, whence=0):
+        # naive implementation, enough for tests
+        return 0
+
+    def writable(self):
+        return True
+
+    def write(self, b):
+        b = bytes(b)
+        n = -1
+        if self._blocker_char:
+            try:
+                n = b.index(self._blocker_char)
+            except ValueError:
+                pass
+            else:
+                if n > 0:
+                    # write data up to the first blocker
+                    self._write_stack.append(b[:n])
+                    return n
+                else:
+                    # cancel blocker and indicate would block
+                    self._blocker_char = None
+                    return None
+        self._write_stack.append(b)
+        return len(b)
+
+class CMockNonBlockWriterIO(MockNonBlockWriterIO, io.RawIOBase):
+    BlockingIOError = io.BlockingIOError
+
+class PyMockNonBlockWriterIO(MockNonBlockWriterIO, pyio.RawIOBase):
+    BlockingIOError = pyio.BlockingIOError
+
+
+# Build classes which point to all the right mocks per io implementation
+class CTestCase(unittest.TestCase):
+    io = io
+    is_C = True
+
+    MockRawIO = CMockRawIO
+    MisbehavedRawIO = CMisbehavedRawIO
+    MockFileIO = CMockFileIO
+    CloseFailureIO = CCloseFailureIO
+    MockNonBlockWriterIO = CMockNonBlockWriterIO
+    MockUnseekableIO = CMockUnseekableIO
+    MockRawIOWithoutRead = CMockRawIOWithoutRead
+    SlowFlushRawIO = CSlowFlushRawIO
+    MockCharPseudoDevFileIO = CMockCharPseudoDevFileIO
+
+    # Use the class as a proxy to the io module members.
+    def __getattr__(self, name):
+        return getattr(io, name)
+
+
+class PyTestCase(unittest.TestCase):
+    io = pyio
+    is_C = False
+
+    MockRawIO = PyMockRawIO
+    MisbehavedRawIO = PyMisbehavedRawIO
+    MockFileIO = PyMockFileIO
+    CloseFailureIO = PyCloseFailureIO
+    MockNonBlockWriterIO = PyMockNonBlockWriterIO
+    MockUnseekableIO = PyMockUnseekableIO
+    MockRawIOWithoutRead = PyMockRawIOWithoutRead
+    SlowFlushRawIO = PySlowFlushRawIO
+    MockCharPseudoDevFileIO = PyMockCharPseudoDevFileIO
+
+    # Use the class as a proxy to the _pyio module members.
+    def __getattr__(self, name):
+        return getattr(pyio, name)