From e5e75c64f24dc8c7e5ee17bfa46d7f3222ebc0fc Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Tue, 14 Sep 2010 18:53:07 +0000
Subject: [PATCH] Merged revisions 84814 via svnmerge from
 svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r84814 | antoine.pitrou | 2010-09-14 20:37:24 +0200 (mar., 14 sept. 2010) | 4 lines

  Issue #9854: The default read() implementation in io.RawIOBase now
  handles non-blocking readinto() returning None correctly.
........
---
 Doc/library/io.rst   |  5 +++--
 Lib/_pyio.py         |  4 +++-
 Lib/test/test_io.py  | 44 ++++++++++++++++++++++++++++++++++----------
 Misc/NEWS            |  3 +++
 Modules/_io/iobase.c |  4 ++--
 5 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index b2e586aa0f..faf1aeaed2 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -361,8 +361,9 @@ I/O Base Classes
 
    .. method:: readinto(b)
 
-      Read up to len(b) bytes into bytearray *b* and return the number of bytes
-      read.
+      Read up to len(b) bytes into bytearray *b* and return the number ofbytes
+      read.  If the object is in non-blocking mode and no bytes are available,
+      ``None`` is returned.
 
    .. method:: write(b)
 
diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index ffbfda1911..4485233b9a 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -542,6 +542,8 @@ class RawIOBase(IOBase):
             return self.readall()
         b = bytearray(n.__index__())
         n = self.readinto(b)
+        if n is None:
+            return None
         del b[n:]
         return bytes(b)
 
@@ -559,7 +561,7 @@ class RawIOBase(IOBase):
         """Read up to len(b) bytes into b.
 
         Returns number of bytes read (0 for EOF), or None if the object
-        is set not to block as has no data to read.
+        is set not to block and has no data to read.
         """
         self._unsupported("readinto")
 
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 3a3e074ba6..4c7ce31141 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -47,7 +47,9 @@ def _default_chunk_size():
         return f._CHUNK_SIZE
 
 
-class MockRawIO:
+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)
@@ -55,14 +57,6 @@ class MockRawIO:
         self._reads = 0
         self._extraneous_reads = 0
 
-    def read(self, n=None):
-        self._reads += 1
-        try:
-            return self._read_stack.pop(0)
-        except:
-            self._extraneous_reads += 1
-            return b""
-
     def write(self, b):
         self._write_stack.append(bytes(b))
         return len(b)
@@ -109,6 +103,23 @@ class MockRawIO:
     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
 
@@ -554,6 +565,19 @@ class IOTest(unittest.TestCase):
         f.close()
         self.assertRaises(ValueError, f.flush)
 
+    def test_RawIOBase_read(self):
+        # Exercise the default RawIOBase.read() 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")
+        self.assertEqual(rawio.read(2), b"d")
+        self.assertEqual(rawio.read(2), None)
+        self.assertEqual(rawio.read(2), b"ef")
+        self.assertEqual(rawio.read(2), b"g")
+        self.assertEqual(rawio.read(2), None)
+        self.assertEqual(rawio.read(2), b"")
+
 class CIOTest(IOTest):
     pass
 
@@ -2557,7 +2581,7 @@ def test_main():
     # Put the namespaces of the IO module we are testing and some useful mock
     # classes in the __dict__ of each test.
     mocks = (MockRawIO, MisbehavedRawIO, MockFileIO, CloseFailureIO,
-             MockNonBlockWriterIO)
+             MockNonBlockWriterIO, MockRawIOWithoutRead)
     all_members = io.__all__ + ["IncrementalNewlineDecoder"]
     c_io_ns = {name : getattr(io, name) for name in all_members}
     py_io_ns = {name : getattr(pyio, name) for name in all_members}
diff --git a/Misc/NEWS b/Misc/NEWS
index 55160ca4ce..2932280640 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -117,6 +117,9 @@ C-API
 Library
 -------
 
+- Issue #9854: The default read() implementation in io.RawIOBase now
+  handles non-blocking readinto() returning None correctly.
+
 - Issue #9853: Fix the signature of SSLSocket.recvfrom() and
   SSLSocket.sendto() to match the corresponding socket methods.
 
diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
index 2d664ab48c..dfc1a3ad5d 100644
--- a/Modules/_io/iobase.c
+++ b/Modules/_io/iobase.c
@@ -776,9 +776,9 @@ rawiobase_read(PyObject *self, PyObject *args)
         return NULL;
 
     res = PyObject_CallMethodObjArgs(self, _PyIO_str_readinto, b, NULL);
-    if (res == NULL) {
+    if (res == NULL || res == Py_None) {
         Py_DECREF(b);
-        return NULL;
+        return res;
     }
 
     n = PyNumber_AsSsize_t(res, PyExc_ValueError);
-- 
2.40.0