Revision as of 00:36, 4 June 2008

Overview

Odamex relies on a coding standard to ensure continuity, this reduces bugs and provides easy readability of the code.

Requirements

• Make logical changes in separate patches
• Minimise the number of changes in each patch
• Provide an off switch for every new feature
• Do not submit things you cannot test (e.g. code for alternative platforms)

Code guidelines

General

• Add a test for every change (or an explanation of why this is impossible)

Things you should definitely AVOID in your code:

• Changing code that already works
• Precompiler macros
• Global variables (they can create problems elsewhere in code)
• Variants (tagged unions) - they can present a performance problem
• Magic numbers (use #define or const in your code for fixed numbers, at the top of files)
• Hungarian notation (just plan evil)
• C style strings. (replace them with C++ types where it is safe to do so)
• goto

File Operations

When using file i/o based functions, such as fopen() etc or filename string functions, there are some that are not provided, ie retrieving the length of a file, checking if a file exists or not.

Thankfully, Odamex provides some internal functions for doing such. Be sure to check out m_fileio.h before writing your own, it may have already been implemented! If it isn't, write us a patch and send it in.

Some of the useful functions included are:

• SDWORD M_FileLength(FILE *) - Returns the length of an open file handle

Filename operations:

• BOOL M_FileExists(std::string Filename) - Checks if a file exists or not
• BOOL M_AppendExtension(std::string &Filename, std::string Extension, bool If_Needed = true) - Add an extension on to the end of a filename, If_Needed detects if Extension is in the path, if it isn't, it is added
• void M_ExtractFilePath(std::string Path, std::string &Destination) - Returns the path of a filename in Destination
• BOOL M_ExtractFileExtension(std::string Filename, std::string &Destination) - Returns the extension of Filename in Destination
• void M_ExtractFileBase(std::string Path, std::string &Destination) - Returns the base name of Path in Destination
• void M_ExtractFileName(std::string Path, std::string &Destination) - Returns the complete filename of Path in Destination

Others include:

• BOOL M_WriteFile(std::string Filename, void *Buffer, QWORD Length) - Creates/overwrites a file and writes a block of data to it.
• QWORD M_ReadFile(std::string Filename, BYTE **Buffer) - Allocates a buffer using Z_Malloc and reads the data into it from a file, lifetime is PU_STATIC.

Memory Management

If you need to use malloc(), calloc(), realloc(), free() functions. Use the macros located in m_alloc.h, these are provided because they are much better when it comes to debugging code and such:

• M_Malloc(size_t Size)
• M_Calloc(size_t Items, size_t Size)
• M_Realloc(void *Pointer, size_t Size)
• M_Free(uintptr_t &Reference)

A list of features these functions offer:

• The Size value can NEVER be 0, this prevents platform-specific behaviour.
• M_Free uses a reference instead of a pointer, it still does the same as normal free(), but will NULL the address on return.
• They will abort the program if their operation fails.

Z_Zone Memory Management

• Be aware that the all Z_Zone allocated memory is freed when the WAD changes

Formatting

• If creating a new file, include a GPL header at the top of it, as seen in other files.
• Descriptive comments
• Comments of reasonable size. (not too big and not too small)
• Comment formatting. (in c/c++, either // for 1 liners or /* */ for multiple lines)
• Indentations to be of 1 tab character, using 4 space width tabs
• Be sure your editor/IDE's EOL mode is LF, not CRLF or CR
• 80 line character limit, for devs with text-based editors
• if you can, limit functions to a maximum size (like the amount that would fit on a monitor with a reasonable screen resolution)

What you should strive for:

• Clarity of code
• Defensive and secure coding practices
• Maintain traditional naming conventions, for consistency

External Links

• tabs-vs-spaces