Enhance openssl recipe and remove lib_version

Several actions done:
  - The openssl recipe has been enhanced by introducing a couple of methods (include_flags and link_flags) which should help us to link other recipes with the openssl libs.
  - Remove lib_version introduced in the last openssl version update, so we don't have to modify all dependant recipes
  - Add a new variable `url_version`, used to download our recipe in the subclassed method versioned_url (this replaces the removed lib_version)
  - Add D__ANDROID_API__ to the configure command (needed to successfully build the libraries and link them with python)
  - Add documentation

Author: opacam

pythonforandroid/recipes/openssl/__init__.py

@@ -1,17 +1,73 @@
+import time
+from os.path import join
 from functools import partial
 
 from pythonforandroid.toolchain import Recipe, shprint, current_directory
 import sh
 
 
 class OpenSSLRecipe(Recipe):
-    version = '1.1.1'
-    lib_version = '1.1'
-    url = 'https://www.openssl.org/source/openssl-{version}.tar.gz'
+    '''
+    The OpenSSL libraries for python-for-android. This recipe will generate the
+    following libraries as shared libraries (*.so):
+
+        - crypto
+        - ssl
+
+    The generated openssl libraries are versioned, where the version is the
+    recipe attribute :attr:`version` e.g.: ``libcrypto1.1.so``,
+    ``libssl1.1.so``...so...to link your recipe with the openssl libs,
+    remember to add the version at the end, e.g.:
+    ``-lcrypto1.1 -lssl1.1``. Or better, you could do it dynamically
+    using the methods: :meth:`include_flags` and :meth:`link_flags`.
+
+    .. warning:: This recipe is very sensitive because is used for our core
+        recipes, the python recipes. The used API should match with the one
+        used in our python build, otherwise we will be unable to build the
+        _ssl.so python module.
+
+    .. versionchanged:: 0.6.0
+
+        - The gcc compiler has been deprecated in favour of clang and libraries
+          updated to version 1.1.1 (LTS - supported until 11th September 2023)
+        - Added two new methods to make easier to link with openssl:
+          :meth:`include_flags` and :meth:`link_flags`
+        - subclassed versioned_url
+        - Adapted method :meth:`select_build_arch` to API 21+
+
+    '''
+
+    version = '1.1'
+    '''the major minor version used to link our recipes'''
+
+    url_version = '1.1.1'
+    '''the version used to download our libraries'''
+
+    url = 'https://www.openssl.org/source/openssl-{url_version}.tar.gz'
+
+    @property
+    def versioned_url(self):
+        if self.url is None:
+            return None
+        return self.url.format(url_version=self.url_version)
+
+    def include_flags(self, arch):
+        '''Returns a string with the include folders'''
+        openssl_includes = join(self.get_build_dir(arch.arch), 'include')
+        return ' -I' + openssl_includes + \
+               ' -I' + join(openssl_includes, 'internal') + \
+               ' -I' + join(openssl_includes, 'openssl')
+
+    def link_flags(self, arch):
+        '''Returns a string with the right link flags to compile against the
+        openssl libraries'''
+        build_dir = self.get_build_dir(arch.arch)
+        return ' -L' + build_dir + \
+               ' -lcrypto{version} -lssl{version}'.format(version=self.version)
 
     def should_build(self, arch):
-        return not self.has_libs(arch, 'libssl' + self.lib_version + '.so',
-                                 'libcrypto' + self.lib_version + '.so')
+        return not self.has_libs(arch, 'libssl' + self.version + '.so',
+                                 'libcrypto' + self.version + '.so')
 
     def check_symbol(self, env, sofile, symbol):
         nm = env.get('NM', 'nm')
@@ -24,7 +80,7 @@ def check_symbol(self, env, sofile, symbol):
 
     def get_recipe_env(self, arch=None):
         env = super(OpenSSLRecipe, self).get_recipe_env(arch, clang=True)
-        env['OPENSSL_VERSION'] = self.lib_version
+        env['OPENSSL_VERSION'] = self.version
         env['MAKE'] = 'make'  # This removes the '-j5', which isn't safe
         env['ANDROID_NDK'] = self.ctx.ndk_dir
         return env
@@ -54,21 +110,22 @@ def build_arch(self, arch):
             #              ^
             # crypto/aes/bsaes-armv7.S:1434:14: error: immediate operand must be in the range [0,4095]
             #  sub r6, r8, #.LREVM0SR-.LSR @ pass constants
-            shprint(perl, 'Configure', 'shared', 'no-dso', 'no-asm', buildarch, _env=env)
+            shprint(perl, 'Configure', 'shared', 'no-dso', 'no-asm', buildarch,
+                    '-D__ANDROID_API__={}'.format(self.ctx.ndk_api),
+                    _env=env)
             self.apply_patch('disable-sover.patch', arch.arch)
 
             # check_ssl = partial(self.check_symbol, env, 'libssl' + self.version + '.so')
-            check_crypto = partial(self.check_symbol, env, 'libcrypto' + self.lib_version + '.so')
+            check_crypto = partial(self.check_symbol, env, 'libcrypto' + self.version + '.so')
             while True:
                 shprint(sh.make, 'build_libs', _env=env)
                 if all(map(check_crypto, ('MD5_Transform', 'MD4_Init'))):
                     break
-                import time
                 time.sleep(3)
                 shprint(sh.make, 'clean', _env=env)
 
-            self.install_libs(arch, 'libssl' + self.lib_version + '.so',
-                              'libcrypto' + self.lib_version + '.so')
+            self.install_libs(arch, 'libssl' + self.version + '.so',
+                              'libcrypto' + self.version + '.so')
 
 
 recipe = OpenSSLRecipe()