numpy · charris · Nov 27, 2019 · Nov 21, 2019 · Nov 21, 2019 · Nov 22, 2019
diff --git a/doc/source/reference/random/examples/cffi.rst b/doc/source/reference/random/examples/cffi.rst
@@ -0,0 +1,5 @@
+Extending via CFFI
+------------------
+
+.. literalinclude:: ../../../../../numpy/random/_examples/cffi/extending.py
+    :language: python
diff --git a/doc/source/reference/random/extending.rst b/doc/source/reference/random/extending.rst
@@ -49,6 +49,25 @@ RNG structure.
 These functions along with a minimal setup file are included in the
 `examples` folder, ``numpy.random.examples``.
 
+CFFI
+====
+
+CFFI can be used to directly access the functions in
+``include/numpy/random/distributions.h``. Some "massaging" of the header
+file is required:
+
+.. literalinclude:: ../../../../numpy/random/_examples/cffi/extending.py
+    :language: python
+    :end-before: dlopen
+
+Once the header is parsed by ``ffi.cdef``, the functions can be accessed
+directly from the ``_generator`` shared object, using the `BitGenerator.cffi` interface.
+
+.. literalinclude:: ../../../../numpy/random/_examples/cffi/extending.py
+    :language: python
+    :start-after: dlopen
+
+
 New Basic RNGs
 ==============
 `~Generator` can be used with other user-provided BitGenerators. The simplest
@@ -85,3 +104,4 @@ Examples
     Numba <examples/numba>
     CFFI + Numba <examples/numba_cffi> 
     Cython <examples/cython/index>
+    CFFI <examples/cffi>
diff --git a/numpy/core/include/numpy/random/distributions.h b/numpy/core/include/numpy/random/distributions.h
@@ -24,7 +24,7 @@
 #define RAND_INT_MAX INT64_MAX
 #endif
 
-#ifdef DLL_EXPORT
+#ifdef _MSC_VER
 #define DECLDIR __declspec(dllexport)
 #else
 #define DECLDIR extern

diff --git a/numpy/random/_examples/cffi/extending.py b/numpy/random/_examples/cffi/extending.py
@@ -0,0 +1,72 @@
+"""
+Use cffi to access the underlying C functions from distributions.h
+"""
+import os
+import numpy as np
+import cffi
+ffi = cffi.FFI()
+
+inc_dir = os.path.join(np.get_include(), 'numpy')
+
+# Basic numpy types
+ffi.cdef('''
+    typedef intptr_t npy_intp;
+    typedef unsigned char npy_bool;
+
+''')
+
+with open(os.path.join(inc_dir, 'random', 'bitgen.h')) as fid:
+    s = []
+    for line in fid:
+        # massage the include file
+        if line.strip().startswith('#'):
+            continue
+        s.append(line)
+    ffi.cdef('\n'.join(s))
+
+with open(os.path.join(inc_dir, 'random', 'distributions.h')) as fid:
+    s = []
+    in_skip = 0
+    for line in fid:
+        # massage the include file
+        if line.strip().startswith('#'):
+            continue
+
+        # skip any inlined function definition
+        # which starts with 'static NPY_INLINE xxx(...) {'
+        # and ends with a closing '}'
+        if line.strip().startswith('static NPY_INLINE'):
+            in_skip += line.count('{')
+            continue
+        elif in_skip > 0:
+            in_skip += line.count('{')
+            in_skip -= line.count('}')
+            continue
+
+        # replace defines with their value or remove them
+        line = line.replace('DECLDIR', '')
+        line = line.replace('NPY_INLINE', '')
+        line = line.replace('RAND_INT_TYPE', 'int64_t')
+        s.append(line)
+    ffi.cdef('\n'.join(s))
+
+lib = ffi.dlopen(np.random._generator.__file__)
+
+# Compare the distributions.h random_standard_normal_fill to
+# Generator.standard_random
+bit_gen = np.random.PCG64()
+rng = np.random.Generator(bit_gen)
+state = bit_gen.state
+
+interface = rng.bit_generator.cffi
+n = 100
+vals_cffi = ffi.new('double[%d]' % n)
+lib.random_standard_normal_fill(interface.bit_generator, n, vals_cffi)
+
+# reset the state
+bit_gen.state = state
+
+vals = rng.standard_normal(n)
+
+for i in range(n):
+    assert vals[i] == vals_cffi[i]
diff --git a/numpy/random/setup.py b/numpy/random/setup.py
@@ -78,8 +78,8 @@ def generate_libraries(ext, build_dir):
                              libraries=EXTRA_LIBRARIES,
                              extra_compile_args=EXTRA_COMPILE_ARGS,
                              extra_link_args=EXTRA_LINK_ARGS,
-                             depends=['_%s.pyx' % gen, 'bit_generator.pyx',
-                                      'bit_generator.pxd'],
+                             depends=['_%s.pyx' % gen, '_bit_generator.pyx',
+                                      '_bit_generator.pxd'],
                              define_macros=_defs,
                              )
     for gen in ['_common', '_bit_generator']:
@@ -112,7 +112,7 @@ def generate_libraries(ext, build_dir):
                              depends=['%s.pyx' % gen],
                              define_macros=defs,
                              )
-    config.add_data_files('_bounded_inteters.pxd')
+    config.add_data_files('_bounded_integers.pxd')
     config.add_extension('mtrand',
                          sources=['mtrand.c',
                                   'src/legacy/legacy-distributions.c',

diff --git a/numpy/random/tests/test_direct.py b/numpy/random/tests/test_direct.py
@@ -1,5 +1,6 @@
 import os
 from os.path import join
+import sys
 
 import numpy as np
 from numpy.testing import (assert_equal, assert_allclose, assert_array_equal,
@@ -26,6 +27,12 @@
 except ImportError:
     MISSING_CTYPES = False
 
+if sys.flags.optimize > 1:
+    # no docstrings present to inspect when PYTHONOPTIMIZE/Py_OptimizeFlag > 1
+    # cffi cannot succeed
+    MISSING_CFFI = True
+
+
 pwd = os.path.dirname(os.path.abspath(__file__))
 
 

diff --git a/numpy/random/tests/test_extending.py b/numpy/random/tests/test_extending.py
@@ -2,12 +2,21 @@
 import pytest
 import warnings
 
+try:
+    import cffi
+except ImportError:
+    cffi = None
+
+if sys.flags.optimize > 1:
+    # no docstrings present to inspect when PYTHONOPTIMIZE/Py_OptimizeFlag > 1
+    # cffi cannot succeed
+    cffi = None
+
 try:
     with warnings.catch_warnings(record=True) as w:
         # numba issue gh-4733
         warnings.filterwarnings('always', '', DeprecationWarning)
         import numba
-    import cffi
 except ImportError:
     numba = None
 
@@ -26,7 +35,11 @@ def test_cython():
         sys.argv = argv
         os.chdir(curdir)
 
-@pytest.mark.skipif(numba is None, reason="requires numba")
+@pytest.mark.skipif(numba is None or cffi is None,
+                    reason="requires numba and cffi")
 def test_numba():
         from numpy.random._examples.numba import extending
 
+@pytest.mark.skipif(cffi is None, reason="requires cffi")
+def test_cffi():
+        from numpy.random._examples.cffi import extending
diff --git a/test_requirements.txt b/test_requirements.txt
@@ -5,3 +5,5 @@ pytest-cov==2.8.1
 pickle5; python_version == '3.7'
 pickle5; python_version == '3.6' and platform_python_implementation != 'PyPy'
 nose
+# for numpy.random.test.test_extending
+cffi