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CodeConvention

Neon Code Convention

General rules:

  • Use doxgen for documentation with Javadoc style comment block i.e., 
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    /**
 * ... text ...
 */

  • Use inline documentation of the function input variables and class members variables e.g., 

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    void foo(int v /**< [in] docs for input parameter v */);

  • using namespace is only allowed inside .cpp/.cu files. It’s disallowed in headers.

  • using namespace std is disallowed even in .cpp/.cu files. If you want to save some work, just typedef the type you need from the std namespace, or use auto.

  • For consistency reasons, use using declaration instead of typedef e.g., 

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    using UintVector = std::vector<uint32_t>;

  • Use only sized types (e.g., int32_t, uint32_t, int16_t). Conceptually, bool has unknown size, so no size equivalent. char is special and can be used only for C strings (use int8_t otherwise).

  • Don’t use NULL or 0 to initialize pointers. nullptr is part of the language now.

  • Preprocessor definitions are all capitals and may contain _ e.g., c++ #define SOME_DEFINE

  • Don’t use long line comment separator e.g., ///////////// or /*****************/

  • We use NEON_TRACE, NEON_INFO, NEON_WARNING, NEON_ERROR, and NEON_CRITICAL for logging. Using printf or std::cout is prohibited. NEON_* logging macro rely on spdlog with easy python-like string formatting e.g., 

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    NEON_INFO("Welcome to spdlog!");
NEON_ERROR("Some error message with arg: {}", 1);

NEON_WARNING("Easy padding in numbers like {:08d}", 12);
NEON_CRITICAL("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
NEON_INFO("Support for floats {:03.2f}", 1.23456);
NEON_INFO("Positional args are {1} {0}..", "too", "supported");
NEON_INFO("{:<30}", "left aligned");

Variable prefixes:

Use the following prefixes for variable names based on the scope s, m, g, and k. These are mutually exclusive prefixes, where k takes precedence above the rest. - k for compile-time const variables. - g for global variables, including static global variables. - s for class static variables. - m for member variables in classes (not in structs).

In addition p is used for pointers e.g.,

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//Global Variables:
const uint32_t kConstGlobal; // compile-time-const, so 'k' takes precedence
int32_t gSomeGlobal;         // global start with 'g'
static int gStaticGlobal;    // Static globals start with 'g'
void* gpSomePointer;         // Global variables which is a pointer is prefixed with 'gp'
const void* gpPointer2;      // Not compile-time constant.

Functions:

  • Use auto style for function but explicitly defining the return type using trailing arrow e.g., 

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    auto getGirdSize() -> int;

  • Function names should be descriptive:

  • Functions that perform an action should be named after the action it performs e.g., Fbo::clear(), createTextureFromFile().
  • Getters/Setters should start with get and set

  • Functions names that return a bool should be phrased as a question e.g., isWhite(), doesFileExist(), hasTexture()

  • Function names are lower-camel-case e.g., 

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    void someFunction()

Classes:

  • Classes should hide their internal data as much as possible.

  • Class names should be Upper Camel case (UpperCamelClass) or Lower Camel case (lowerCamelClass)

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class UpperCamelClass
{

    bool isValid();                // Function names are lower-camel-case
    static uint32_t sInt;          // Static variables start with 's'
    static const uint32_t kValue;  // Const static is prefixed with 'k'
    int32_t mMemberVar;           // Member variables start with 'm'
    int16_t* mpSomePointer;       // Note that with a pointer variable, "p" counts as the first word, so the next letter *is* capitalized
};

  • Header file must be a .h containing only the class declaration i.e., class name, methods’ signature and variables

  • Source file must be a .cpp or .cu and it contains the definition of all methods

  • Templated methods definition must be in separate .h file that is included by the corresponding .h. File name should end with _imp.h

  • File names only contain dot (“.”) before the file extension suffix

  • Each class has it’s own files with same name e.g., Grid class goes into Grid.h, Grid.cpp, and Grid_imp.h

  • The order of public/private members and methods as they appear in the class .h file is:

    1. public members
    2. public methods
    3. private methods
    4. private members
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// Grid.h
#pragma once
namespace Neon::grid {
/**
 * Grid is the blueprint of creating physical domains 
*/
class Grid
{
   private:   
    int mNumCells = 0 /**< number of cells */;

   public:
    /**
     * default constructor 
    */
    Grid() = default;

    /**
     * Grid constructor      
    */
    Grid(int& const bool padding /**< [in] Enable memory padding if true */);

    /**
     * Create new field      
     * @return the new field 
    */
    template <typename T /**< Field type */>
    auto newField() -> Grid::Field<T>;


};
}  // namespace Neon::grid
#include "Neon/domain/Grid_imp.h"

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// Grid.cpp
#pragma once
#include "Neon/domain/Grid.h"
namspeace Neon::grid {
    Grid::Grid(int& const bool padding){
        // ....
    }
} // namspeace Neon::grid 

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//Grid_imp.h
#pragma once
#include "Neon/domain/Grid.h"
namspeace Neon::grid {
    template<typename T>
    auto Grid::newField() -> Grid::Field<T>{        
        //...        
    }
} // namspeace Neon::grid

Structs:

Use struct only as a data-container. All fields must be public. No member functions are allowed. In-class initialization is allowed.

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//UpperCamelStruct.h
struct UpperCamelStruct
{
    int32_t someVar;               // Struct members are lower-camel-case    
    int32_t** pDoublePointer;      // Double pointer is just a pointer
    std::smart_ptr<int> pSmartPtr; // Smart pointer is a pointer
    char charArray[];              // Array is not a pointer
    std::string myString;          // String is a string
    bool isBoolean;                // bool name implies that it's a bool. 'enable', 'is*', 'has*', etc. Don't use negative meaning (use 'enable' instead of 'disable')
    uint32_t& refVal;              // Reference is not a pointer
};

Enums:

Use typed enums (i.e, enum class) as they are type safe and they automatically define their namespace. When approperiate, each enum class should be followed by utility class with static methods. These utility method provide a toString() funtionality as well as toInt() for easy conversions.

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//DataView.h
enum class DataView : char {
    standard,
    internal, 
    boundary
};
class DataViewUtils {
    static auto toString(DataView d) -> std::string;
    static auto toInt(DataView d) -> int;
}