Reenable possibility to use an already installed C-Blosc library

README.rst

@@ -79,7 +79,7 @@ Installing via setuptools
 .. code-block:: console
 
     $ python -m pip install -r requirements-dev.txt
-    $ python setup.py build_ext --inplace
+    $ python setup.py build --inplace
 
 Any codec can be enabled (`=1`) or disabled (`=0`) on this build-path with the appropriate
 OS environment variables `INCLUDE_LZ4`, `INCLUDE_SNAPPY`, `INCLUDE_ZLIB`, and
@@ -115,17 +115,15 @@ Using an environment variable:
 
 .. code-block:: console
 
-    $ BLOSC_DIR=/usr/local     (or "set BLOSC_DIR=\blosc" on Win)
-    $ export BLOSC_DIR         (not needed on Win)
-    $ python setup.py build_clib
-    $ python setup.py build_ext --inplace
+    $ export USE_SYSTEM_BLOSC=1                 # or "set USE_SYSTEM_BLOSC=1" on Windows
+    $ export Blosc_ROOT=/usr/local/customprefix # If you installed Blosc into a custom location
+    $ python setup.py build --inplace
 
-Using a flag:
+Using flags:
 
 .. code-block:: console
 
-    $ python setup.py build_clib
-    $ python setup.py build_ext --inplace --blosc=/usr/local
+    $ python setup.py build --inplace -DUSE_SYSTEM_BLOSC:BOOL=YES -DBlosc_ROOT:PATH=/usr/local/customprefix
 
 
 Testing

blosc/CMakeLists.txt

@@ -1,19 +1,24 @@
-# Todo: c-blosc provides a CMake package configuration file that we can build
-# against if blosc is available on the system, etc.
-# find_package(blosc)
-# if(NOT blosc_FOUND)
-set(BUILD_STATIC ON CACHE BOOL "Build a static version of the blosc library.")
-set(BUILD_SHARED ON CACHE BOOL "Build a shared library version of the blosc library.")
-set(BUILD_TESTS OFF CACHE BOOL "Build test programs form the blosc compression library")
-set(BUILD_BENCHMARKS OFF CACHE BOOL "Build benchmark programs form the blosc compression library")
-set(BLOSC_IS_SUBPROJECT OFF CACHE BOOL "Blosc is subproject")
-set(CMAKE_POSITION_INDEPENDENT_CODE ON)
-add_subdirectory(c-blosc)
-include_directories("${CMAKE_CURRENT_SOURCE_DIR}/c-blosc/blosc")
+add_library(blosc_extension MODULE blosc_extension.c)
+
+if(USE_SYSTEM_BLOSC)
+    set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")
+    find_package(Blosc REQUIRED)
+    target_include_directories(blosc_extension PRIVATE ${Blosc_INCLUDE_DIRS})
+    target_link_libraries(blosc_extension ${Blosc_LIBRARIES})
+else()
+    set(BUILD_STATIC ON CACHE BOOL "Build a static version of the blosc library.")
+    set(BUILD_SHARED ON CACHE BOOL "Build a shared library version of the blosc library.")
+    set(BUILD_TESTS OFF CACHE BOOL "Build test programs form the blosc compression library")
+    set(BUILD_BENCHMARKS OFF CACHE BOOL "Build benchmark programs form the blosc compression library")
+    set(BLOSC_IS_SUBPROJECT OFF CACHE BOOL "Blosc is subproject")
+    set(CMAKE_POSITION_INDEPENDENT_CODE ON)
+    add_subdirectory(c-blosc)
+    include_directories("${CMAKE_CURRENT_SOURCE_DIR}/c-blosc/blosc")
+    target_link_libraries(blosc_extension blosc_static)
+endif()
+
 
 
-add_library(blosc_extension MODULE blosc_extension.c)
-target_link_libraries(blosc_extension blosc_static)
 python_extension_module(blosc_extension)
 
 add_custom_command(

cmake/FindBlosc.cmake

@@ -0,0 +1,12 @@
+find_path(Blosc_INCLUDE_DIR blosc.h)
+
+find_library(Blosc_LIBRARY NAMES blosc)
+
+if (Blosc_INCLUDE_DIR AND Blosc_LIBRARY)
+    set(Blosc_FOUND TRUE)
+    set(Blosc_INCLUDE_DIRS ${Blosc_INCLUDE_DIR})
+    set(Blosc_LIBRARIES ${Blosc_LIBRARY})
+    message(STATUS "Found Blosc library: ${Blosc_LIBRARIES}")
+else ()
+    message(STATUS "No Blosc library found.  Using internal sources.")
+endif ()

setup.py

@@ -88,16 +88,18 @@ def cmake_bool(cond):
         url = 'http://github.com/blosc/python-blosc',
         license = 'https://opensource.org/licenses/BSD-3-Clause',
         platforms = ['any'],
-        cmake_args = [
-          '-DBLOSC_DIR:PATH=%s' % os.environ.get('BLOSC_DIR', ''),
-          '-DDEACTIVATE_SSE2:BOOL=%s' % cmake_bool(('DISABLE_BLOSC_SSE2' in os.environ) or (cpu_info is None) or ('flags' not in cpu_info) or ('sse2' not in cpu_info['flags'])),
-          '-DDEACTIVATE_AVX2:BOOL=%s' % cmake_bool(('DISABLE_BLOSC_AVX2' in os.environ) or (cpu_info is None) or ('flags' not in cpu_info) or ('avx2' not in cpu_info['flags'])),
-          '-DDEACTIVATE_LZ4:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_LZ4', '1'))),
-          # Snappy is disabled by default
-          '-DDEACTIVATE_SNAPPY:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_SNAPPY', '0'))),
-          '-DDEACTIVATE_ZLIB:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_ZLIB', '1'))),
-          '-DDEACTIVATE_ZSTD:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_ZSTD', '1'))),
-        ],
+        cmake_args = (
+          ['-DUSE_SYSTEM_BLOSC:BOOL=ON'] if int(os.environ.get('USE_SYSTEM_BLOSC', '0'))
+          else [
+           '-DUSE_SYSTEM_BLOSC:BOOL=OFF',
+           '-DDEACTIVATE_SSE2:BOOL=%s' % cmake_bool(('DISABLE_BLOSC_SSE2' in os.environ) or (cpu_info is None) or ('sse2' not in cpu_info['flags'])),
+           '-DDEACTIVATE_AVX2:BOOL=%s' % cmake_bool(('DISABLE_BLOSC_AVX2' in os.environ) or (cpu_info is None) or ('avx2' not in cpu_info['flags'])),
+           '-DDEACTIVATE_LZ4:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_LZ4', '1'))),
+           # Snappy is disabled by default
+           '-DDEACTIVATE_SNAPPY:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_SNAPPY', '0'))),
+           '-DDEACTIVATE_ZLIB:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_ZLIB', '1'))),
+           '-DDEACTIVATE_ZSTD:BOOL=%s' % cmake_bool(not int(os.environ.get('INCLUDE_ZSTD', '1'))),
+           ]),        
         setup_requires=['scikit-build'],
         tests_require=['numpy', 'psutil'],
         packages = ['blosc'],