02_CodingConventions.dox

/*
 * Copyright (C) 1996-2023 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */

/**
\page Conventions Coding and Other Conventions used in Squid

\section Coding Code Conventions
\par
        Most custom types and tools are documented in the code or the relevant
        portions of this manual. Some key points apply globally however.

\section FWT Fixed Width types

\par
        If you need to use specific width types - such as
        a 16 bit unsigned integer, use one of the following types. To access
        them simply include "squid.h".

\verbatim
        int16_t    -  16 bit signed.
        uint16_t  -  16 bit unsigned.
        int32_t    -  32 bit signed.
        uint32_t  -  32 bit unsigned.
        int64_t    -  64 bit signed.
        uint64_t  -  64 bit unsigned.
\endverbatim

\section Documentation Documentation Conventions
\par
	Now that documentation is generated automatically from the sources
	some common comment conventions need to be adopted.


\subsection CommentComponents	API vs Internal Component Commenting

\par
	First among these is a definition separation between component API
	and Internal operations. API functions and objects should always be
	commented and in the *.h file for the component. Internal logic and
	objects should be commented in the *.cc file where they are defined.
        The group is to be defined in the components main files with the
	overview paragraphs about the API usage or component structure.

\par
	With C++ classes it is easy to separate API and Internals with the C++
	public: and private: distinctions on whichever class defines the
	component API. An Internal group may not be required if there are no
	additional items in the Internals (rare as globals are common in squid).

\par
	With unconverted modules still coded in Objective-C, the task is harder.
	In these cases two sub-groups must be defined *API and *Internal into
	which naturally individual functions, variables, etc. are grouped using
	the \b \\ingroup tag. The API group is usually a sub-group of Components
	and the Internal is always a sub-group of the API.

\par	Rule of thumb:
	For both items, if its referenced from elsewhere in the code or
	defined in the .h file it should be part of the API.
	Everything else should be in the Internals group and kept out of the .h file.

\subsection FunctionComments	Function/Method Comments

\par
	All descriptions may be more than one line, and while whitespace formatting is
	ignored by doxygen, it is good to keep it clear for manual reading of the code.

\par
	Any text directly following a \b \\par tag will be highlighted in bold
	automatically (like all the 'For Examples' below) so be careful what is placed
	there.


\subsubsection PARAM    Function Parameters

\par
	Function and Method parameters MUST be named in both the definition and in
	the declaration, and they also MUST be the same text. The doxygen parser
	needs them to be identical to accurately link the two with documentation.
	Particularly linking function with documentation of the label itself.

\par
	Each function that takes parameters should have the possible range of values
	commented in the pre-function descriptor. For API function this is as usual
	in the .h file, for Internal functions it is i the .(cc|cci) file.

\par
	The \b \\param tag is used to describe these. It takes two required parameters;
	the name of the function parameter being documented followed immediately by
	either [in], [out], or [in,out].
	Followed by an optional description of what the parameter represents.

\par	For Example:
\verbatim
/**
 \param g[out]		Buffer to receive something
 \param glen[in]	Length of buffer available to write
 */
void
X::getFubar(char *g, int glen)
...
\endverbatim


\subsubsection RETVAL   Return Values

\par
	Each function that returns a value should have the possible range of values
	commented in the pre-function descriptor.
\par
	The \b \\retval tag is used to describe these. It takes one required parameter;
	the value or range of values returned.
	Followed by an optional description of what/why of that value.

\par	For Example:
\verbatim
/**
 \retval 0	when FUBAR does not start with 'F'
 \retval 1	when FUBAR starts with F
 */
int
X::saidFubar()
...
\endverbatim

\par	Alternatively
	when a state or other context-dependent object is returned the \b \\return
	tag is used. It is followed by a description of the object and ideally its
	content.


\subsubsection FLOW     Function Actions / Internal Flows

\par	Simple functions
	do not exactly need a detailed description of their operation.
	The \ref PARAM and \ref RETVAL
	should be enough for any developer to understand the function.

\par	Long or Complex Functions
	do however need some commenting.
	A well-designed function does all its operations in distinct blocks;
	\arg Input validation
	\arg Processing on some state
	\arg Processing on the output of that earlier processing
	\arg etc, etc.

\par
	Each of these design blocks inside the function should be given a comment
	indicating what they do. The comments should begin with
	\verbatim /** \\par \endverbatim
	The resulting function description will then contain a paragraph on each of the
	blocks in the order they occur in the function.

\par	For example:
\verbatim
/**
 \param g	The buffer to be used
 \param glen	Length of buffer provided
 \param state	Object of type X storing foo
 */
void
fubar(char *g, int glen, void *state) {
\endverbatim
	Designed validation part of the function
\verbatim
    /** \par
     * When g is NULL or gen is 0 nothing is done */
    if(g == NULL || glen < 1)
        return;

   /** \par
     * When glen is longer than the accepted length it gets truncated */
   if(glen > MAX_FOO) glen = MAX_FOO;
\endverbatim
	now we get on to the active part of the function
\verbatim
   /** \par
     * Appends up to MAX_FOO bytes from g onto the end of state->foo
     * then passes the state off to FUBAR.
     * No check for null-termination is done.
     */
   memcpy(g, glen, state->foo_end_ptr );
   state->foo_end_ptr += glen;
   fubar(state);
}
\endverbatim

\par
	Of course, this is a very simple example. This type of comment should only be
	needed in the larger functions with many side effects.
	A function this small could reasonably have all its commenting done just ahead of
	the parameter description.

 */