Add buffer types to struct module. (#1125)

* Add buffer types to struct module.

I noticed these were missing and I made the version look alike for an easy rename into 2and3.

* Add array to WriteBuffer, add iter_unpack

* Code review comments

stdlib/2/struct.pyi

@@ -1,28 +1,40 @@
-# Stubs for struct for Python 2.7
-# Based on https://docs.python.org/2/library/struct.html
+# Stubs for struct
 
-from typing import Any, Tuple
+# Based on http://docs.python.org/3.2/library/struct.html
+# Based on http://docs.python.org/2/library/struct.html
+
+import sys
+from typing import Any, Tuple, Text, Union, Iterator
+from array import array
 
 class error(Exception): ...
 
-def pack(fmt: str, *v: Any) -> str: ...
-# TODO buffer type
-def pack_into(fmt: str, buffer: Any, offset: int, *v: Any) -> None: ...
+_FmtType = Union[bytes, Text]
+if sys.version_info >= (3,):
+    _BufferType = Union[bytes, bytearray, memoryview]
+    _WriteBufferType = Union[array, bytearray, memoryview]
+else:
+    _BufferType = Union[bytes, bytearray, buffer, memoryview]
+    _WriteBufferType = Union[array[Any], bytearray, buffer, memoryview]
 
-# TODO buffer type
-def unpack(fmt: str, buffer: Any) -> Tuple[Any, ...]: ...
-def unpack_from(fmt: str, buffer: Any, offset: int = ...) -> Tuple[Any, ...]: ...
+def pack(fmt: _FmtType, *v: Any) -> bytes: ...
+def pack_into(fmt: _FmtType, buffer: _WriteBufferType, offset: int, *v: Any) -> None: ...
+def unpack(fmt: _FmtType, buffer: _BufferType) -> Tuple[Any, ...]: ...
+def unpack_from(fmt: _FmtType, buffer: _BufferType, offset: int = ...) -> Tuple[Any, ...]: ...
+if sys.version_info >= (3, 4):
+    def iter_unpack(fmt: _FmtType, buffer: _BufferType) -> Iterator[Tuple[Any, ...]]: ...
 
-def calcsize(fmt: str) -> int: ...
+def calcsize(fmt: _FmtType) -> int: ...
 
 class Struct:
-    format = ...  # type: str
+    format = ...  # type: bytes
     size = ...  # type: int
 
-    def __init__(self, format: str) -> None: ...
+    def __init__(self, format: _FmtType) -> None: ...
 
-    def pack(self, *v: Any) -> str: ...
-    # TODO buffer type
-    def pack_into(self, buffer: Any, offset: int, *v: Any) -> None: ...
-    def unpack(self, buffer: Any) -> Tuple[Any, ...]: ...
-    def unpack_from(self, buffer: Any, offset: int = ...) -> Tuple[Any, ...]: ...
+    def pack(self, *v: Any) -> bytes: ...
+    def pack_into(self, buffer: _WriteBufferType, offset: int, *v: Any) -> None: ...
+    def unpack(self, buffer: _BufferType) -> Tuple[Any, ...]: ...
+    def unpack_from(self, buffer: _BufferType, offset: int = ...) -> Tuple[Any, ...]: ...
+    if sys.version_info >= (3, 4):
+        def iter_unpack(self, buffer: _BufferType) -> Iterator[Tuple[Any, ...]]: ...

stdlib/3/struct.pyi

@@ -1,30 +1,40 @@
 # Stubs for struct
 
 # Based on http://docs.python.org/3.2/library/struct.html
+# Based on http://docs.python.org/2/library/struct.html
 
-from typing import overload, Any, Tuple
+import sys
+from typing import Any, Tuple, Text, Union, Iterator
+from array import array
 
 class error(Exception): ...
 
-def pack(fmt: str, *v: Any) -> bytes: ...
-# TODO buffer type
-def pack_into(fmt: str, buffer: Any, offset: int, *v: Any) -> None: ...
+_FmtType = Union[bytes, Text]
+if sys.version_info >= (3,):
+    _BufferType = Union[bytes, bytearray, memoryview]
+    _WriteBufferType = Union[array, bytearray, memoryview]
+else:
+    _BufferType = Union[bytes, bytearray, buffer, memoryview]
+    _WriteBufferType = Union[array[Any], bytearray, buffer, memoryview]
 
-# TODO buffer type
-def unpack(fmt: str, buffer: Any) -> Tuple[Any, ...]: ...
-def unpack_from(fmt: str, buffer: Any, offset: int = ...) -> Tuple[Any, ...]: ...
+def pack(fmt: _FmtType, *v: Any) -> bytes: ...
+def pack_into(fmt: _FmtType, buffer: _WriteBufferType, offset: int, *v: Any) -> None: ...
+def unpack(fmt: _FmtType, buffer: _BufferType) -> Tuple[Any, ...]: ...
+def unpack_from(fmt: _FmtType, buffer: _BufferType, offset: int = ...) -> Tuple[Any, ...]: ...
+if sys.version_info >= (3, 4):
+    def iter_unpack(fmt: _FmtType, buffer: _BufferType) -> Iterator[Tuple[Any, ...]]: ...
 
-def calcsize(fmt: str) -> int: ...
+def calcsize(fmt: _FmtType) -> int: ...
 
 class Struct:
-    format = b''
-    size = 0
+    format = ...  # type: bytes
+    size = ...  # type: int
 
-    def __init__(self, format: str) -> None: ...
+    def __init__(self, format: _FmtType) -> None: ...
 
     def pack(self, *v: Any) -> bytes: ...
-    # TODO buffer type
-    def pack_into(self, buffer: Any, offset: int, *v: Any) -> None: ...
-    # TODO buffer type
-    def unpack(self, buffer: Any) -> Tuple[Any, ...]: ...
-    def unpack_from(self, buffer: Any, offset: int = ...) -> Tuple[Any, ...]: ...
+    def pack_into(self, buffer: _WriteBufferType, offset: int, *v: Any) -> None: ...
+    def unpack(self, buffer: _BufferType) -> Tuple[Any, ...]: ...
+    def unpack_from(self, buffer: _BufferType, offset: int = ...) -> Tuple[Any, ...]: ...
+    if sys.version_info >= (3, 4):
+        def iter_unpack(self, buffer: _BufferType) -> Iterator[Tuple[Any, ...]]: ...