crypto.low_level extension: build blake2 like zstd, see #3415

(cherry picked from commit 4a2fec32b6)

setup.py

@@ -14,6 +14,7 @@
 
 import setup_lz4
 import setup_zstd
+import setup_b2
 
 # True: use the shared liblz4 (>= 1.7.0 / r129) from the system, False: use the bundled lz4 code
 prefer_system_liblz4 = True
@@ -21,6 +22,9 @@
 # True: use the shared libzstd (>= 1.3.0) from the system, False: use the bundled zstd code
 prefer_system_libzstd = True
 
+# True: use the shared libb2 from the system, False: use the bundled blake2 code
+prefer_system_libb2 = True
+
 min_python = (3, 4)
 my_python = sys.version_info
 
@@ -146,19 +150,9 @@ def detect_openssl(prefixes):
                     return prefix
 
 
-def detect_libb2(prefixes):
-    for prefix in prefixes:
-        filename = os.path.join(prefix, 'include', 'blake2.h')
-        if os.path.exists(filename):
-            with open(filename, 'r') as fd:
-                if 'blake2b_init' in fd.read():
-                    return prefix
-
-
 include_dirs = []
 library_dirs = []
 define_macros = []
-crypto_libraries = ['crypto']
 
 possible_openssl_prefixes = ['/usr', '/usr/local', '/usr/local/opt/openssl', '/usr/local/ssl', '/usr/local/openssl',
                              '/usr/local/borg', '/opt/local', '/opt/pkg', ]
@@ -187,13 +181,13 @@ def detect_libb2(prefixes):
                            '/usr/local/borg', '/opt/local', '/opt/pkg', ]
 if os.environ.get('BORG_LIBB2_PREFIX'):
     possible_libb2_prefixes.insert(0, os.environ.get('BORG_LIBB2_PREFIX'))
-libb2_prefix = detect_libb2(possible_libb2_prefixes)
-if libb2_prefix:
+libb2_prefix = setup_b2.b2_system_prefix(possible_libb2_prefixes)
+if prefer_system_libb2 and libb2_prefix:
     print('Detected and preferring libb2 over bundled BLAKE2')
-    include_dirs.append(os.path.join(libb2_prefix, 'include'))
-    library_dirs.append(os.path.join(libb2_prefix, 'lib'))
-    crypto_libraries.append('b2')
     define_macros.append(('BORG_USE_LIBB2', 'YES'))
+    libb2_system = True
+else:
+    libb2_system = False
 
 possible_libzstd_prefixes = ['/usr', '/usr/local', '/usr/local/opt/libzstd', '/usr/local/libzstd',
                              '/usr/local/borg', '/opt/local', '/opt/pkg', ]
@@ -774,9 +768,14 @@ def run(self):
     compress_ext_kwargs = setup_zstd.zstd_ext_kwargs(bundled_path='src/borg/algorithms/zstd',
                                                      system_prefix=libzstd_prefix, system=libzstd_system,
                                                      multithreaded=False, legacy=False, **compress_ext_kwargs)
+    crypto_ext_kwargs = dict(sources=[crypto_ll_source], libraries=['crypto'],
+                             include_dirs=include_dirs, library_dirs=library_dirs, define_macros=define_macros)
+    crypto_ext_kwargs = setup_b2.b2_ext_kwargs(bundled_path='src/borg/algorithms/blake2',
+                                               system_prefix=libb2_prefix, system=libb2_system,
+                                               **crypto_ext_kwargs)
     ext_modules += [
         Extension('borg.compress', **compress_ext_kwargs),
-        Extension('borg.crypto.low_level', [crypto_ll_source], libraries=crypto_libraries, include_dirs=include_dirs, library_dirs=library_dirs, define_macros=define_macros),
+        Extension('borg.crypto.low_level', **crypto_ext_kwargs),
         Extension('borg.hashindex', [hashindex_source]),
         Extension('borg.item', [item_source]),
         Extension('borg.chunker', [chunker_source]),

setup_b2.py

@@ -0,0 +1,72 @@
+# Support code for building a C extension with blake2 files
+#
+# Copyright (c) 2016-present, Gregory Szorc (original code for zstd)
+#               2017-present, Thomas Waldmann (mods to make it more generic, code for blake2)
+# All rights reserved.
+#
+# This software may be modified and distributed under the terms
+# of the BSD license. See the LICENSE file for details.
+
+import os
+
+# b2 files, structure as seen in BLAKE2 (reference implementation) project repository:
+
+b2_sources = [
+    'ref/blake2b-ref.c',
+]
+
+b2_includes = [
+    'ref',
+]
+
+
+def b2_system_prefix(prefixes):
+    for prefix in prefixes:
+        filename = os.path.join(prefix, 'include', 'blake2.h')
+        if os.path.exists(filename):
+            with open(filename, 'r') as fd:
+                if 'blake2b_init' in fd.read():
+                    return prefix
+
+
+def b2_ext_kwargs(bundled_path, system_prefix=None, system=False, **kwargs):
+    """amend kwargs with b2 stuff for a distutils.extension.Extension initialization.
+
+    bundled_path: relative (to this file) path to the bundled library source code files
+    system_prefix: where the system-installed library can be found
+    system: True: use the system-installed shared library, False: use the bundled library code
+    kwargs: distutils.extension.Extension kwargs that should be amended
+    returns: amended kwargs
+    """
+    def multi_join(paths, *path_segments):
+        """apply os.path.join on a list of paths"""
+        return [os.path.join(*(path_segments + (path, ))) for path in paths]
+
+    use_system = system and system_prefix is not None
+
+    sources = kwargs.get('sources', [])
+    if not use_system:
+        sources += multi_join(b2_sources, bundled_path)
+
+    include_dirs = kwargs.get('include_dirs', [])
+    if use_system:
+        include_dirs += multi_join(['include'], system_prefix)
+    else:
+        include_dirs += multi_join(b2_includes, bundled_path)
+
+    library_dirs = kwargs.get('library_dirs', [])
+    if use_system:
+        library_dirs += multi_join(['lib'], system_prefix)
+
+    libraries = kwargs.get('libraries', [])
+    if use_system:
+        libraries += ['b2', ]
+
+    extra_compile_args = kwargs.get('extra_compile_args', [])
+    if not use_system:
+        extra_compile_args += []  # not used yet
+
+    ret = dict(**kwargs)
+    ret.update(dict(sources=sources, extra_compile_args=extra_compile_args,
+                    include_dirs=include_dirs, library_dirs=library_dirs, libraries=libraries))
+    return ret

src/borg/algorithms/blake2-libselect.h

@@ -1,5 +1,5 @@
 #ifdef BORG_USE_LIBB2
 #include <blake2.h>
 #else
-#include "blake2/ref/blake2b-ref.c"
+#include "blake2/ref/blake2.h"
 #endif