lib/mem: Python utilities to zero, set & copy memory

Like C bzero / memset & memcopy - but work on python buffers. We
leverage NumPy for doing actual work, and this way NumPy becomes a
depenency.

Having NumPy as a dependency is ok - we'll for sure need it later as we
are trying to build out-of-core ndarrays.

lib/mem.py

+# -*- coding: utf-8 -*-
+# Wendelin. Memory helpers
+# Copyright (C) 2014-2015  Nexedi SA and Contributors.
+#                          Kirill Smelkov <kirr@nexedi.com>
+#
+# This program is free software: you can Use, Study, Modify and Redistribute
+# it under the terms of the GNU General Public License version 3, or (at your
+# option) any later version, as published by the Free Software Foundation.
+#
+# You can also Link and Combine this program with other software covered by
+# the terms of any of the Open Source Initiative approved licenses and Convey
+# the resulting work. Corresponding source of such a combination shall include
+# the source code for all other software used.
+#
+# This program is distributed WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See COPYING file for full licensing terms.
+from numpy import ndarray, uint64, copyto
+
+
+# zero buffer memory
+def bzero(buf):
+    assert len(buf)%8 == 0  # XXX for simplicity
+    a = ndarray(len(buf)//8, buffer=buf, dtype=uint64)
+    a[:] = 0
+
+
+# set bytes in memory
+def memset(buf, c):
+    assert 0 <= c <= 0xff
+    assert len(buf)%8 == 0  # XXX for simplicity
+    a = ndarray(len(buf)//8, buffer=buf, dtype=uint64)
+    a[:] = (c * 0x0101010101010101)
+
+
+# copy src buffer memory to dst
+# precondition: len(dst) == len(src)
+def memcpy(dst, src):
+    l = len(src)
+    assert len(dst) == l
+    assert l % 8 == 0    # XXX for simplicity
+    adst = ndarray(l//8, buffer=dst, dtype=uint64)
+    asrc = ndarray(l//8, buffer=src, dtype=uint64)
+    copyto(adst, asrc)

setup.py

@@ -175,6 +175,10 @@ setup(
     package_dir = {'wendelin': ''},
     packages    = ['wendelin'] + ['wendelin.%s' % _ for _ in
                         find_packages(exclude='3rdparty')],
+    install_requires = [
+                   'numpy',     # lib/mem
+                  ],
+
     cmdclass    = {'build_ext':     build_ext,
                    'll_build_ext':  _build_ext, # original build_ext for Makefile
                    'build_py':      build_py,