use _ffi.from_buffer() to support bytearray (#852)

* use _ffi.from_buffer(buf) in send, to support bytearray

* add bytearray test

* update CHANGELOG.rst

* move from_buffer before 'buffer too long' check

* context-managed from_buffer + black

* don't shadow buf in send()

* test return count for sendall

* test sending an array

* fix test

* also use from_buffer in bio_write

* de-format _util.py

* formatting

* add simple bio_write tests

* wrap line

1 files changed, 14 insertions, 0 deletions

diff --git a/src/OpenSSL/_util.py b/src/OpenSSL/_util.py
index cdcacc8..d8e3f66 100644
--- a/src/OpenSSL/_util.py
+++ b/src/OpenSSL/_util.py
@@ -145,3 +145,17 @@ def text_to_bytes_and_warn(label, obj):
         )
         return obj.encode('utf-8')
     return obj
+
+
+try:
+    # newer versions of cffi free the buffer deterministically
+    with ffi.from_buffer(b""):
+        pass
+    from_buffer = ffi.from_buffer
+except AttributeError:
+    # cffi < 0.12 frees the buffer with refcounting gc
+    from contextlib import contextmanager
+
+    @contextmanager
+    def from_buffer(*args):
+        yield ffi.from_buffer(*args)