Revert "Use new buffer interface."

This reverts commit 085db7f.

Conflicts:
	msgpack/_unpacker.pyx

Author: methane

msgpack/_unpacker.pyx

@@ -2,6 +2,10 @@
 #cython: embedsignature=True
 
 from cpython cimport *
+cdef extern from "Python.h":
+    ctypedef char* const_void_ptr "const void*"
+    ctypedef struct PyObject
+    cdef int PyObject_AsReadBuffer(object o, const_void_ptr* buff, Py_ssize_t* buf_len) except -1
 
 from libc.stdlib cimport *
 from libc.string cimport *
@@ -15,8 +19,8 @@ from msgpack.exceptions import (
         )
 
 
+
 cdef extern from "unpack.h":
-    ctypedef struct PyObject
     ctypedef struct msgpack_user:
         bint use_list
         PyObject* object_hook
@@ -87,33 +91,32 @@ def unpackb(object packed, object object_hook=None, object list_hook=None,
     cdef size_t off = 0
     cdef int ret
 
-    cdef Py_buffer buff
+    cdef char* buf
+    cdef Py_ssize_t buf_len
     cdef char* cenc = NULL
     cdef char* cerr = NULL
 
-    PyObject_GetBuffer(packed, &buff, PyBUF_SIMPLE)
-    try:
-        if encoding is not None:
-            if isinstance(encoding, unicode):
-                encoding = encoding.encode('ascii')
-            cenc = PyBytes_AsString(encoding)
-
-        if unicode_errors is not None:
-            if isinstance(unicode_errors, unicode):
-                unicode_errors = unicode_errors.encode('ascii')
-            cerr = PyBytes_AsString(unicode_errors)
-
-        init_ctx(&ctx, object_hook, object_pairs_hook, list_hook, use_list, cenc, cerr)
-        ret = unpack_construct(&ctx, <char*>buff.buf, buff.len, &off)
-        if ret == 1:
-            obj = unpack_data(&ctx)
-            if off < buff.len:
-                raise ExtraData(obj, PyBytes_FromStringAndSize(<char*>buff.buf+off, buff.len-off))
-            return obj
-        else:
-            raise UnpackValueError("Unpack failed: error = %d" % (ret,))
-    finally:
-        PyBuffer_Release(&buff)
+    PyObject_AsReadBuffer(packed, <const_void_ptr*>&buf, &buf_len)
+
+    if encoding is not None:
+        if isinstance(encoding, unicode):
+            encoding = encoding.encode('ascii')
+        cenc = PyBytes_AsString(encoding)
+
+    if unicode_errors is not None:
+        if isinstance(unicode_errors, unicode):
+            unicode_errors = unicode_errors.encode('ascii')
+        cerr = PyBytes_AsString(unicode_errors)
+
+    init_ctx(&ctx, object_hook, object_pairs_hook, list_hook, use_list, cenc, cerr)
+    ret = unpack_construct(&ctx, buf, buf_len, &off)
+    if ret == 1:
+        obj = unpack_data(&ctx)
+        if off < buf_len:
+            raise ExtraData(obj, PyBytes_FromStringAndSize(buf+off, buf_len-off))
+        return obj
+    else:
+        raise UnpackValueError("Unpack failed: error = %d" % (ret,))
 
 
 def unpack(object stream, object object_hook=None, object list_hook=None,