[API] changes for Julia bindings (#1016)

This PR brings some changes to the API, in order to facilitate the creation of Julia bindings for SIRIUS in a future SIRIUS.jl package.

Apart from the additions of new functions to sirius_api.cpp (necessary for the DFTK integration), the main addition consists of a header file for the API: sirius_c_headers.h. It turns out that having a header file drastically simplifies the process of creating Julia bindings for a C/C++ library.

As things stand, this header file is generated by a script (generate_c_headers.py), in the same spirit as the Fortran API. As a result, it is not used for compilation, but only as source material for the automatic generation of Julia bindings.

src/CMakeLists.txt

@@ -157,6 +157,8 @@ if(SIRIUS_CREATE_FORTRAN_BINDINGS)
  set_target_properties(sirius PROPERTIES Fortran_MODULE_DIRECTORY mod_files)
  install(FILES "${PROJECT_BINARY_DIR}/src/mod_files/sirius.mod"
  DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/sirius")
+ install(FILES "${PROJECT_SOURCE_DIR}/src/api/sirius_c_headers.h"
+ DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/sirius/src/api")
  install(TARGETS sirius
  EXPORT sirius_targets
  ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"

src/api/generate_c_headers.py

@@ -0,0 +1,48 @@
+# This script generates a basic header file from the sirius_api.cpp file
+# A lot of assumptions are made: all functions are void, we only care about the extern "C",
+# etc. In the end, the idea is to provide an input for Clang.jl wrapping
+
+import re
+import sys
+
+#Only read the file from the extern "C" section beginning
+is_extern = False
+content = ""
+with open("sirius_api.cpp", "r") as myfile:
+ for line in myfile:
+ if not is_extern:
+ if line.startswith("extern"):
+ is_extern = True
+
+ if is_extern:
+ content += line
+
+#We want C-style complex types, not C++
+content = content.replace("std::complex<double>", "double complex")
+
+#A regex that matches all SIRIUS API calls: returns a void,
+#starts with sirius_, and allows for line breaks
+pattern = r'\bvoid\s+(?:\s*\n\s*)?sirius_\w+\s*\([^{]*\{'
+matches = re.findall(pattern, content, re.DOTALL)
+
+signatures = []
+for match in matches:
+ signatures.append(match.strip().replace("\n{", ";\n\n"))
+
+#We also want to carry over the Fortran API info
+pattern = r'@api begin(.*?)@api end'
+matches = re.findall(pattern, content, re.DOTALL)
+docs = []
+for match in matches:
+ docs.append("/*\n"+match.strip()+"\n*/\n")
+
+with open("sirius_c_headers.h", "w") as myfile:
+ myfile.write("#include <stdbool.h>\n")
+ myfile.write("#include <complex.h>\n\n")
+ for doc in docs:
+ fname = doc.split("\n")[1][:-1]
+ for signature in signatures:
+ if fname+"(" in signature:
+ myfile.write(doc)
+ myfile.write(signature)
+ break