(#18) Moved compress from lambda to named func

`compress` was implemented inlined as a lambda in the module
initialization.

Since it wasn't a "trivial" implementation, I think it's better for it
to be a "real" function.

src/papi/lz4/module.cpp

@@ -11,33 +11,33 @@
 
 static test_initializer modules([](py::module &m) {
 
-    using namespace gsl;
     using namespace lz4;
 
     m.def_submodule("lz4")
         .def("VERSION_NUMBER", VERSION_NUMBER)
         .def("VERSION", [](){
-            return py::make_tuple(VERSION_MAJOR(), VERSION_MINOR(), VERSION_RELEASE());
-        })
+                return py::make_tuple(VERSION_MAJOR(), VERSION_MINOR(), VERSION_RELEASE());
+            })
         .def("__version__", [](){
-            return py::str(VERSION_STRING());
-        })
-        .def("compress", [](const py::bytes& buffer){
-
-            std::string source{buffer};
-            auto size = lz4::api::compressBound(source.length());
+                return py::str(VERSION_STRING());
+            })
+        .def("compress", compress)
+    ;
+});
 
+py::bytes lz4::compress(const py::bytes& buffer) 
+{
+    std::string source{buffer};
+    auto size = api::compressBound(source.length());
 
-            std::vector<char> dest(size);
 
-            auto res = lz4::api::compress_default(source, dest);
+    std::vector<char> dest(size);
 
-            if (res == 0) {
-                throw std::exception("compression failed");
-            }
+    auto res = api::compress_default(source, dest);
 
+    if (res == 0) {
+        throw std::exception("compression failed");
+    }
 
-            return py::bytes(dest.data(), res);
-        })
-    ;
-});
+    return py::bytes(dest.data(), res);
+};

src/papi/lz4/module.h

@@ -6,12 +6,18 @@
 
 #include "api.h"    
 
+namespace py = pybind11;
+using namespace pybind11::literals;
+
 namespace lz4 {
 
+
     class context {
         context();
         ~context();
     };
 
+
+    py::bytes compress(const py::bytes& buffer);
 };
 #endif // __CINT_LZ4_MODULE__