From 7c3095f984dd1f05e0596d243e0aeea642c7ebc7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A9n=C3=A9dikt=20Tran?=
 <10796600+picnixz@users.noreply.github.com>
Date: Thu, 20 Jun 2024 15:13:03 +0200
Subject: [PATCH] drop reverse read support for BufferedRWPair objects

---
 Lib/_pyio.py             | 14 --------------
 Lib/test/test_io.py      | 25 ++++++++-----------------
 Modules/_io/bufferedio.c | 28 ----------------------------
 3 files changed, 8 insertions(+), 59 deletions(-)

diff --git a/Lib/_pyio.py b/Lib/_pyio.py
index 414d4957a7ed4a..959327ecfd967a 100644
--- a/Lib/_pyio.py
+++ b/Lib/_pyio.py
@@ -1578,9 +1578,6 @@ def readinto(self, b):
     def write(self, b):
         return self.writer.write(b)
 
-    def seek(self, pos, whence=0):
-        return self.reader.seek(0, 2)
-
     def peek(self, size=0):
         return self.reader.peek(size)
 
@@ -1590,17 +1587,6 @@ def read1(self, size=-1):
     def readinto1(self, b):
         return self.reader.readinto1(b)
 
-    def backread(self, size=-1):
-        if size is None:
-            size = -1
-        return self.reader.backread(size)
-
-    def backreadinto(self, b):
-        return self.reader.backreadinto(b)
-
-    def seekable(self):
-        return self.reader.seekable()
-
     def readable(self):
         return self.reader.readable()
 
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 5c36bda82f60fc..4d3fbee6b6b764 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2278,25 +2278,16 @@ def test_readinto(self):
                 self.assertEqual(getattr(pair, method)(data), 5)
                 self.assertEqual(bytes(data), b"abcde")
 
-    def test_backread(self):
-        self.skipTest("TODO C (all interfaces)")
-        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
-        pair.seek(0, 2)
-        self.assertEqual(pair.backread(3), b"fed")
-        self.assertEqual(pair.backread(1), b"c")
-        self.assertEqual(pair.backread(), b"ba")
-
-        pair = self.tp(self.BytesIO(b"abc"), self.MockRawIO())
-        pair.seek(0, 2)
-        self.assertEqual(pair.backread(None), b"cba")
+    def test_no_backread_support(self):
+        # Because of the non-seekability of BufferedRWPair, it does
+        # not make sense to support backread() or backreadinto() even
+        # for seekable buffers.
+        pair = self.tp(self.BytesIO(b"1234567890"), self.MockRawIO())
+        self.assertRaises(io.UnsupportedOperation, pair.backread)
+        self.assertRaises(io.UnsupportedOperation, pair.backread, 2)
 
-    def test_backreadinto(self):
-        self.skipTest("TODO C (backreadinto of buffered)")
         pair = self.tp(self.BytesIO(b"1234567890"), self.MockRawIO())
-        data = byteslike(b'\0' * 5)
-        pair.seek(0, 2)
-        self.assertEqual(pair.backreadinto(data), 5)
-        self.assertEqual(bytes(data), b"09876")
+        self.assertRaises(io.UnsupportedOperation, pair.backreadinto, bytearray())
 
     def test_write(self):
         w = self.MockRawIO()
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 0da0ed92eca3b2..aaa4bca5d69da9 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -2498,42 +2498,18 @@ bufferedrwpair_readinto1(rwpair *self, PyObject *args)
     return _forward_call(self->reader, &_Py_ID(readinto1), args);
 }
 
-static PyObject *
-bufferedrwpair_backread(rwpair *self, PyObject *args)
-{
-    return _forward_call(self->reader, &_Py_ID(backread), args);
-}
-
-static PyObject *
-bufferedrwpair_backreadinto(rwpair *self, PyObject *args)
-{
-    return _forward_call(self->reader, &_Py_ID(backreadinto), args);
-}
-
 static PyObject *
 bufferedrwpair_write(rwpair *self, PyObject *args)
 {
     return _forward_call(self->writer, &_Py_ID(write), args);
 }
 
-static PyObject *
-bufferedrwpair_seek(rwpair *self, PyObject *args)
-{
-    return _forward_call(self->reader, &_Py_ID(seek), args);
-}
-
 static PyObject *
 bufferedrwpair_flush(rwpair *self, PyObject *Py_UNUSED(ignored))
 {
     return _forward_call(self->writer, &_Py_ID(flush), NULL);
 }
 
-static PyObject *
-bufferedrwpair_seekable(rwpair *self, PyObject *Py_UNUSED(ignored))
-{
-    return _forward_call(self->reader, &_Py_ID(seekable), NULL);
-}
-
 static PyObject *
 bufferedrwpair_readable(rwpair *self, PyObject *Py_UNUSED(ignored))
 {
@@ -2808,14 +2784,10 @@ static PyMethodDef bufferedrwpair_methods[] = {
     {"read1", (PyCFunction)bufferedrwpair_read1, METH_VARARGS},
     {"readinto", (PyCFunction)bufferedrwpair_readinto, METH_VARARGS},
     {"readinto1", (PyCFunction)bufferedrwpair_readinto1, METH_VARARGS},
-    {"backread", (PyCFunction)bufferedrwpair_backread, METH_VARARGS},
-    {"backreadinto", (PyCFunction)bufferedrwpair_backreadinto, METH_VARARGS},
-    {"seek", (PyCFunction)bufferedrwpair_seek, METH_VARARGS},
 
     {"write", (PyCFunction)bufferedrwpair_write, METH_VARARGS},
     {"flush", (PyCFunction)bufferedrwpair_flush, METH_NOARGS},
 
-    {"seekable", (PyCFunction)bufferedrwpair_seekable, METH_NOARGS},
     {"readable", (PyCFunction)bufferedrwpair_readable, METH_NOARGS},
     {"writable", (PyCFunction)bufferedrwpair_writable, METH_NOARGS},