NFD code style guidelines¶

NFD adopts NDN Platform C++, C, C#, Java and JavaScript Code Guidelines, with the following exceptions:

• (amended 8) Names representing generic template types should be a single uppercase letter

  template<class T> ...
  template<class C, class D> ...
  

  However, when template parameter represents a certain concept and expected to have a certain interface, the name should be explicitly spelled out:

  template<class FaceBase> ...
  template<class Packet> ...
  

• (amended 10)
  Global variables should have g_ prefix

• (amended 11)
  Private class variables should have m_ prefix.
  Static class variables should have s_ prefix.

• (amended 26)
  Allow commonly used abbreviated next/prev pair in addition to next/previous

  Pair insert/erase should be used for any new code, already implemented code can keep insert/delete if it does not conflict with C++ delete keyword.

• (amended 27)
  In cases when full word is too long, a commonly accepted abbreviation can be used. For example, dest instead of destination.

• (amended 31)
  Exceptions can be used in the code, but should be used only in exceptional cases and not in the primary processing path.

  Exceptions can be suffixed with either Exception (eg. SecurityException) or Error (eg. SecurityError). Alternatively (and it is a recommended method), one should declare exception class Exception or Error as an inner class, from which the exception is thrown. For example, when declaring class Foo that can throw errors, one can write the following:

  #include <stdexcept>
  
  class Foo
  {
    class Error : public std::runtime_error
    {
    public:
      explicit
      Error(const std::string& what)
        : std::runtime_error(what)
      {
      }
    };
  };  
  

  In addition to that, if class Foo is a base class or interface for some class hierarchy, then child classes should should define their own Error or Exception classes that are inherited from the parent's Error class.

• (amended 33)
  We will use only .cpp and .hpp extensions

• (removed 35)
  Lines should be within a reasonable range. Lines longer than 100 columns should generally be avoided.

• (updated 37)
  Exceptions:

  • The following is the standard practice with operator<<:

    std::cout << "Something here "
              << "Something there" << std::endl;
    

• (removed 44)
  Implicit conversion is generally allowed.

  Implicit conversion between integer and floating point numbers can cause problems and should be avoided.

  Implicit conversion in single-argument constructor is usually undesirable. Therefore, all single-argument constructors should be marked 'explicit', unless implicit conversion is desirable. In that case, a comment should document the reason.

  Avoid C-style casts. Use static_cast, dynamic_cast, reinterpret_cast, const_cast instead where appropriate. Use static_pointer_cast, dynamic_pointer_cast, const_pointer_cast when dealing with shared_ptr.

• (replaced 48)
  In most cases, class instance variables should never be declared public.

  The concepts of information hiding and encapsulation are violated by public variables. Use private variables and access methods instead. One exception to this rule is when the class is essentially a dumb data structure with no behavior (equivalent to a C struct, also known as PODS). In this case it is appropriate to make the instance variables public by using struct.

• (amended 68)
  All three presented styles ARE acceptable. First and third ARE recommended (these are actually GNU styles).

• (amended 69)
  The class declarations should have the following form:

  class SomeClass : public BaseClass 
  { 
  public: 
    ... <public methods> ...
  protected: 
    ... <protected methods> ...
  private: 
    ... <private methods> ...
  
  public: 
    ... <public data> ...
  protected: 
    ... <protected data> ...
  private: 
    ... <private data> ...
  };
  

  public, protected, private may be repeated several times without interleaving (e.g. public, public, public, private, private) if this allows better readability of the code.

• (amended 70)
  When declaring/defining function/method, the return type should be put on a separate line before function/method name.

  Method and function definitions should have the following form:

  void
  someMethod() 
  { 
    ... 
  }
  

• (changed 76) switch statement should have one of the two of following forms:

  switch (condition) {
  case ABC:
    statements;
    // Fallthrough
  
  case DEF:
    statements;
    break;
  
  case XYZ:
    statements;
    break;
  
  default:
    statements;
    break;
  }
  

  or

  switch (condition)
    {
    case ABC:
      statements;
      // Fallthrough
  
    case DEF:
      statements;
      break;
  
    case XYZ:
      statements;
      break;
  
    default:
      statements;
      break;
    }
  

Python addition¶

Most of the provisions in the above style guidance apply to Python as well. For python-specific elements, PEP 8 can be used as a reference coding style.

The following is few rules directly adopted from PEP 8:

• P1 Always surround these binary operators with a single space on either side: assignment (=), augmented assignment (+=, -= etc.), comparisons (==, <, >, !=, <>, <=, >=, in, not in, is, is not), Booleans (and, or, not).

  def complex(real, imag=0.0):
      value = 1.1
      return magic(r=real + value, i=imag)
  

• P2 Don't use spaces around the = sign when used to indicate a keyword argument or a default parameter value.

  def complex(real, imag=0.0):
      return magic(r=real, i=imag)