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# CPACSGen

CPACSGen (short for CPACS generator) creates source code for classes and enums from the types defined in a CPACS XML schema file for the TiGL library.

## GitHub

CPACSGen is hosted on Github:
https://github.com/RISCSoftware/cpacs_tigl_gen

## Dependencies
The following components are required to build and run CPACSGen
* A working copy of CPACSGen
* CMake
* C\++11/C++14 compliant compiler (VS2017 is currently used and tested)
* TIXI library (https://github.com/DLR-SC/tixi)
* Boost libraries (v1.55 or higher)
* A working copy of TiGL with CPACSGen input files (https://github.com/DLR-SC/tigl)

## Input files
Given an input directory, CPACSGen searches for the following input files:
* *.xsd _(any number of XML schema files)_
* CustomTypes.txt
* ParentPointer.txt
* PrefixedEnums.txt
* PruneList.txt
* TypeSubstitution.txt

These files are typically part of the TiGL distribution and do not have to be created.
Altering these files influences CPACSGen’s output and may require further adaption of the TiGL code depending on the generated code.

In addition to these files, three more files have existed with are now compiled into CPACSGen and inside Tables.cpp:
* FundamentalTypes.txt
* ReservedNames.txt
* XsdTypes.txt

Furthermore, in addition to the discussed input files, subdirectories may be present containing the same input files as listed above.
For each subdirectory, CPACSGen runs an additional pass, putting the generated files into an equally named subfolder in the output directory and generating an equally named additional namespace in the generated code.

## Workflow
1. Clone the CPACSGen repository from Github
2. Clone the TiGL repository Github
3. Use CMake to configure CPACSGen
    1. Set BOOST_ROOT
    2. Set TIXI_PATH
    3. Set TIGL_PATH to the directory of your TiGL clone
4. Build CPACSGen
5. Build target generate  
   executes CPACSGen.exe $\{TIGL_DIR}/cpacs_gen_input $\{CPACSGEN_DIR}/src $\{TIGL_DIR}/src/generated
6. Use CMake to configure TiGL (which picks up generated files)
7. Build TiGL

## Command line options
The CPACSGen executable takes the following positional command line options:
1. Input directory  
   The directory containing the CPACS schema and the table files
2. runtime src directory  
   The directory of the runtime source code copied to the output directory, typically src/lib/runtime inside your working copy
3. Output directory  
   The directory to which the CPACSGen output files are written
4. (optional) output Graphviz file  
   If a filename is specified, writes a Graphviz dot file containing a directed graph of the created CPACS types. This is especially useful when optimizing PruneList.txt

## Table details
* CustomTypes.txt  
  Types which will be sub-classed in TIGL, e.g. for implementing additional behavior or fixing issues with the generated code.
  Types for which a custom type has been specified will never be instantiated by the generated code.
  Instead, their customized derived classes are instantiated.
  Customized types are still outputted.  
  e.g. tigl\::generated\::CPACSFuselage -> tigl::CCPACSFuselage

* ParentPointer.txt  
  e.g. CPACSWing, CPACSFuselageSegment  
  List of types which should hold a pointer to their parent element in CPACS.
  Causes all parent classes to pass themselves to their child classes on child instantiation.

* PruneList.txt  
  List of CPACS types which (including their child types in the CPACS schema tree) should be removed from the type system built by CPACSGen.
  Pruned types are not outputted.
  A graphical representation of the type system after pruning can be obtained using the optional Graphviz file command line argument.

* TypeSubstitution.txt  
  e.g. stringUIDBaseType -> std::string, integerBaseType -> int  
  Types of the CPACS schema which should simply be replaced without further logic.
  Replaced types are not outputted.



* FundamentalTypes.txt  
  std::string, double, bool, int, time_t  
  Fundamental data types for which XML element and attribute IO functions exist in the TIXI wrapper.

* ReservedNames.txt  
  e.g. int, inline, break, false  
  List of identifiers which are reserved in C++.
  Members of generated enums are checked against this table and altered.

* XsdTypes.txt  
  e.g. xsd:unsignedLong -> uint64_t  
  Same functionality as TypeSubstitution.txt. Maps XSD to C++ types.

## Generated code dependencies
The classes generated by CPACSGen depend upon the following helper files, which are part of CPACSGen and will be written to the output directory when CPACSGen is invoked:

* TixiHelper.h  
  Wrappers over TIXI functions providing a C++ friendly interface (references, std::string, exceptions, ...).
  Is used by the ReadCPACS and WriteCPACS implementation.

* UniquePtr.hpp  
  Contains tigl\::unique_ptr\<T> which defaults to std\::unique_ptr\<T> if C++11 is available, otherwise provides a custom type based on std\::auto_ptr\<T>.
  Furthermore, the generated classes may require boost::optional\<T>, which is part of TiGL, and some internal TiGL files.