Add readinto method for MemoryFS and FTPFS file objects

CHANGELOG.md

@@ -10,6 +10,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - Missing `mode` attribute to `_MemoryFile` objects returned by `MemoryFS.openbin`.
+- Missing `readinto` method for `MemoryFS` and `FTPFS` file objects. Closes
+  [#380](https://github.com/PyFilesystem/pyfilesystem2/issues/380).
 
 ### Changed
 

CONTRIBUTORS.md

@@ -9,6 +9,7 @@ Many thanks to the following developers for contributing to this project:
 - [Justin Charlong](https://github.com/jcharlong)
 - [Louis Sautier](https://github.com/sbraz)
 - [Martin Larralde](https://github.com/althonos)
+- [Nick Henderson](https://github.com/nwh)
 - [Will McGugan](https://github.com/willmcgugan)
 - [Zmej Serow](https://github.com/zmej-serow)
 - [Morten Engelhardt Olsen](https://github.com/xoriath)

fs/ftpfs.py

@@ -235,6 +235,13 @@ def read(self, size=-1):
                 remaining -= len(chunk)
         return b"".join(chunks)
 
+    def readinto(self, buffer):
+        # type: (bytearray) -> int
+        data = self.read(len(buffer))
+        bytes_read = len(data)
+        buffer[:bytes_read] = data
+        return bytes_read
+
     def readline(self, size=-1):
         # type: (int) -> bytes
         return next(line_iterator(self, size))  # type: ignore

fs/iotools.py

@@ -117,7 +117,7 @@ def readinto(self, b):
         except AttributeError:
             data = self._f.read(len(b))
             bytes_read = len(data)
-            b[: len(data)] = data
+            b[:bytes_read] = data
             return bytes_read
 
     @typing.no_type_check
@@ -128,7 +128,7 @@ def readinto1(self, b):
         except AttributeError:
             data = self._f.read1(len(b))
             bytes_read = len(data)
-            b[: len(data)] = data
+            b[:bytes_read] = data
             return bytes_read
 
     def readline(self, limit=-1):

fs/memoryfs.py

@@ -113,12 +113,15 @@ def __iter__(self):
     def next(self):
         # type: () -> bytes
         with self._seek_lock():
+            self.on_access()
             return next(self._bytes_io)
 
     __next__ = next
 
     def readline(self, size=-1):
         # type: (int) -> bytes
+        if not self._mode.reading:
+            raise IOError("File not open for reading")
         with self._seek_lock():
             self.on_access()
             return self._bytes_io.readline(size)
@@ -142,9 +145,20 @@ def readable(self):
         # type: () -> bool
         return self._mode.reading
 
+    def readinto(self, buffer):
+        # type (bytearray) -> Optional[int]
+        if not self._mode.reading:
+            raise IOError("File not open for reading")
+        with self._seek_lock():
+            self.on_access()
+            return self._bytes_io.readinto(buffer)
+
     def readlines(self, hint=-1):
         # type: (int) -> List[bytes]
+        if not self._mode.reading:
+            raise IOError("File not open for reading")
         with self._seek_lock():
+            self.on_access()
             return self._bytes_io.readlines(hint)
 
     def seekable(self):

fs/test.py

@@ -870,6 +870,11 @@ def test_open_files(self):
             self.assertTrue(f.readable())
             self.assertFalse(f.closed)
             self.assertEqual(f.readlines(8), [b"Hello\n", b"World\n"])
+            self.assertEqual(f.tell(), 12)
+            buffer = bytearray(4)
+            self.assertEqual(f.readinto(buffer), 4)
+            self.assertEqual(f.tell(), 16)
+            self.assertEqual(buffer, b"foo\n")
             with self.assertRaises(IOError):
                 f.write(b"no")
         self.assertTrue(f.closed)