Doc/Devel/engineering.html - third_party/swig - Git at Google

 <html>
 <head>
 <title>SWIG Engineering Manual</title>
 </head>
 <body bgcolor="#ffffff">
 <center>
 <h1>SWIG Engineering Manual</h1>

 <b>David Beazley <br>
 </b>
 </center>

 <p>
 (Note : This is a work in progress.)

 <h2>Table of Contents</h2>
 <ul>
 <li><a name="i1" href="#1">1. Introduction</a>
 <li><a name="i2" href="#2">2. Programming Languages and Libraries</a>
 <li><a name="i3" href="#3">3. The Source Directory and Module Names</a>
 <li><a name="i4" href="#4">4. Include Files</a>
 <li><a name="i5" href="#5">5. File Structure</a>
 <li><a name="i6" href="#6">6. Bottom-Up Design</a>
 <li><a name="i7" href="#7">7. Functions</a>
 <li><a name="i8" href="#8">8. Naming Conventions</a>
 <li><a name="i9" href="#9">9. Visibility</a>
 <li><a name="i10" href="#10">10. Miscellaneous Coding Guidelines</a>
 <li><a name="i11" href="#11">11. Git Tagging Conventions</a>
 </ul>

 <a name="1" href="#i1">
 <h2>1. Introduction</h2>
 </a>

 The purpose of this document is to describe various coding conventions
 and organizational aspects for SWIG developers. The idea for this
 document is largely borrowed from John Ousterhout's Tcl/Tk Engineering
 Manual.  It is not my intent to overly managerial about matters--rather I'm
 hoping to make life a little less chaotic for everyone.

 <p>
 First a little background: SWIG was started in 1995 as a one-person
 project and continued in this mode of operation until about 1998.
 Most of this development was driven by ideas submitted by early SWIG
 users as opposed to being motivated by a grand design.  As a result,
 the code ended up being a pretty horrible C++ coding disaster.  A
 mostly working disaster perhaps, but a disaster nonetheless.

 <p>
 With that said, the primary goal of future SWIG development is to
 reengineer the original system, fix most of its inherent design flaws,
 and to produce what I hope will become a highly extensible and modular
 interface compiler framework.  To this do this, there are a few
 critical areas of work.  First, I want to restructure SWIG as a
 collection of loosely coupled modules written in either ANSI C or an
 scripting language.  Second, I want the system to be minimalistic in
 its use of data structures and interconnections.  The primary reason
 for this is that the fewer data structures there are, the less users
 will have to remember.  This will also make the system more accessible
 to non-experts.  Finally, I want to reevaluate the whole idea of a
 SWIG module is and expand the definition to include just about
 anything from parsers, preprocessors, optimizers, interface editors,
 and code generators.

 <p>
 The rest of this document outlines a few general rules of how code
 should be developed within the SWIG project.  These rules are
 primarily drawn from my own experience developing software and
 observing the practices of other successful projects.

 <a name="2" href="#i2">
 <h2>2. Programming Languages and Libraries </h2>
 </a>

 All SWIG modules must be written in either ANSI C or one of the
 scripting languages for which SWIG can generate an interface (e.g.,
 Perl, Python, or Tcl).  C++ is currently being used to write
 SWIG modules, but it is only being utilized to avoid working with
 a lot of pointers to functions.  <b>Advanced C++ features like namespaces, templates,
 and overloading should not be used.</b>.

 <p>
 Module writers should make every attempt to use only those functions
 described in the POSIX.1 standard.  This includes most of the
 functions contained the Kernighan and Ritchie C programming book.  Use
 of operating system dependent functionality such as socket libraries
 should always be included inside a conditional compilation block so
 that it can be omitted on problematic platforms.  If you are unsure
 about a library call, check the man page or contact Dave.

 <a name="3" href="#i3">
 <h2>3. The Source Directory and Module Names</h2>
 </a>

 All SWIG modules are contained within the "Source" directory.  Within
 this directory, each module is placed into its own subdirectory.  The
 name of this subdirectory should exactly match the name of the module.
 For example, if you are creating a module called "Tcl", all of your
 files should be placed in a directory "Tcl".

 <p>
 When choosing a module name, please pick a name that is not
 currently in use.  As a general convention, the first letter of a
 module name is capitalized such as "Perl".  Alternatives such as
 "perl" or "PERL" should be avoided.  In certain instances, the first
 two letters may be capitalized as in "CParse."  The exact usage of
 this is somewhat inconsistent and isn't terribly important--just make
 sure the first letter is capitalized.  Also, module names should not
 start with numbers, include underscores or any other special
 non-alphanumeric characters.

 <a name="5" href="#i5">
 <h2>5. File Structure </h2>
 </a>

 Each file in a module should be given a filename that is all lowercase letters
 such as "parser.c", not "Parser.c" or "PARSER.c".   Please note that filenames
 are case-insensitive on Windows so this convention will prevent you from inadvertently
 creating two files that differ in case-only.

 <p>
 Each file should include a short abstract and license information
 like this:

 <blockquote>
 <pre>
 /* -----------------------------------------------------------------------------
  * This file is part of SWIG, which is licensed as a whole under version 3
  * (or any later version) of the GNU General Public License. Some additional
  * terms also apply to certain portions of SWIG. The full details of the SWIG
  * license and copyrights can be found in the LICENSE and COPYRIGHT files
  * included with the SWIG source code as distributed by the SWIG developers
  * and at http://www.swig.org/legal.html.
  *
  * xxx.c
  *
  * This file defines ...
  * ----------------------------------------------------------------------------- */

 #include "swig.h"

 /* Declarations */
 typedef struct {
    int x, y;
 } Foo;

 ...

 /* Private Declarations (used only in this file) */
 static int  avariable;

 ...

 /* Functions */
 ...

 </pre>
 </blockquote>

 <p>
 As a general rule, files start to get unmanageable once they exceed
 about 2000 lines.  Files larger than this should be broken up into
 multiple files.  Similarly, you should avoid the temptation to create
 many small files as this increases compilation time and makes the
 directory structure too complicated.

 <a name="6" href="#i6">
 <h2>6. Bottom-Up Design </h2>
 </a>

 Within each source file, the preferred organization is to use what is
 known as "bottom-up" design.  Under this scheme, lower-level functions
 appear first and the highest level function appears last.  The easy
 way to remember is that the "main" function of your module should
 always appear last in the source file.  For example:

 <blockquote>
 <pre>
 /* Simple bottom-up program */
 #include &lt;stdio.h&gt;

 int foo(int x, int y) {
     /* Implement foo */
     ...
 }

 int bar() {
     ...
     foo(i,j);
     ...
 }

 ...
 int main(int argc, char **argv) {
     ...
     bar();
     ...
 }
 </pre>
 </blockquote>

 This choice of design is somewhat arbitrary however it has a number of
 benefits particular to C. In particular, a bottom-up design generally
 eliminates the need to include forward references--resulting in
 cleaner code and fewer compilation errors.

 <a name="7" href="#i7">
 <h2>7. Functions</h2>
 </a>

 All functions should have a function header that gives the function name
 and a short description like this:

 <blockquote>
 <pre>
 /* -------------------------------------------------------------------------
  * Swig_add_directory()
  *
  * Adds a directory to the SWIG search path.
  * ------------------------------------------------------------------------- */

 void
 Swig_add_directory(DOH *dirname) {
 ...

 }
 </pre>
 </blockquote>

 In the function declaration, the return type and any specifiers
 (extern or static) should appear on a separate line followed by the
 function name and arguments as shown above.  The left curly brace
 should appear on the same line as the function name.

 <p>
 Function declarations should <b>NOT</b> use the pre-ANSI function
 declaration syntax.   The ANSI standard has been around long enough for
 this to be a non-issue.

 <a name="8" href="#i8">
 <h2>8. Naming Conventions</h2>
 </a>

 The following conventions are used to name various objects throughout SWIG.

 <h4>Functions</h4>

 Functions should consist of the module name and the function name separated by an underscore like this:

 <blockquote>
 <pre>
 Preprocessor_define()
 Swig_add_directory()
 </pre>
 </blockquote>

 In general, the module name should match the name of the module
 subdirectory and the function name should be in all lowercase with
 words separated by underscores.

 <h4>Structures and Types</h4>

 If your module defines new structures, the structure name should include the name of the
 module and the name of the structure appended together like this:

 <blockquote>
 <pre>
 typedef struct SwigScanner {
    ...
 } SwigScanner;

 typedef struct LParseType {
    ...
 } LParseType;
 </pre>
 </blockquote>

 In this case, both the name of the module and the type should be capitalized.  Also, whenever
 possible, you should use the "typedef struct Name { ... } Name" form when defining new
 data structures.

 <h4>Global Variables</h4>

 Global variables should be avoided if at all possible.  However, if you must use a global
 variable, please prepend the module name and use the same naming scheme as for functions.

 <h4>Constants</h4>

 Constants should be created using #define and should be in all caps like this:

 <blockquote>
 <pre>
 #define   SWIG_TOKEN_LPAREN  1
 </pre>
 </blockquote>

 Separate words in a constant should be separated by underscores as with functions.

 <h4>Structure members</h4>

 Structure members should be in all lower-case and follow the same word-separation convention
 as for function names.  However, the module name does not have to be included.
 For example:

 <blockquote>
 <pre>
 typedef struct SwigScanner {
   DOH           *text;           /* Current token value */
   DOH           *scanobjs;       /* Objects being scanned */
   DOH           *str;            /* Current object being scanned */
   char          *idstart;        /* Optional identifier start characters */
   int            next_token;     /* Next token to be returned */
   int            start_line;     /* Starting line of certain declarations */
   int            yylen;          /* Length of text pushed into text */
   DOH           *file;           /* Current file name */
 } SwigScanner;
 </pre>
 </blockquote>

 <h4>Static Functions and Variables </h4>

 Static declarations are free to use any naming convention that is appropriate. However, most
 existing parts of SWIG use lower-case names and follow the same convention as described for functions.

 <a name="9" href="#i9">
 <h2>9. Visibility</h2>
 </a>

 Modules should keep the following rules in mind when exposing their internals:

 <ul>
 <li>Only publicly accessible functions should be included in the module header file.
 <li>All non-static declarations must be prepended with some form of the module name
 to avoid potential linker namespace conflicts with other modules.
 <li>Modules should not expose global variables or use global variables in their
 public interface.
 <li>Similarly, modules should discourage the direct manipulation of data contained
 within data structures in favor of using function calls instead.  For example,
 instead of providing a user with a structure like this:

 <blockquote>
 <pre>
 typedef struct Foo {
    int line;
 } Foo;
 </pre>
 </blockquote>

 It is better to hide the implementation of Foo and provide an
 function-call interface like this:

 <blockquote>
 <pre>
 typedef struct Foo Foo;
 extern int  Foo_getline(Foo *f);
 extern void Foo_setline(Foo *f, int line);
 </pre>
 </blockquote>

 Although this results in worse performance, there are many practical
 reasons for doing this.  The most important reason is that it allows
 you to change the internal representation of Foo without breaking all
 of the other modules or having to recompile the entire universe after
 making your changes.

 </ul>

 <a name="10" href="#i10">
 <h2>10. Miscellaneous Coding Guidelines</h2>
 </a>
 These are largely covered in the main documentation in the Extending.html file.

 <a name="11" href="#i11">
 <h2>11. Git Tagging Conventions</h2>
 </a>

 Use <tt>git tag</tt> to declare some set of file revisions as related in some
 symbolic way.  This eases reference, retrieval and manipulation of these files
 later.  At the moment (2001/01/16 14:02:53), the conventions are very simple;
 let's hope they stay that way!

 <p>
 There are two types of tags, internal (aka personal) and external.
 Internal tags are used by SWIG developers primarily, whereas external
 tags are used when communicating with people w/ anonymous git access.
 <ul>
 <li> Internal tags should start with the developer name and a hyphen.
 <li> External tags should start with "rel-".
 </ul>

 That's all there is to it.  Some example tags:

 <ul>
 <li> ttn-pre-xml-patch
 <li> ttn-post-xml-patch
 <li> ttn-going-on-vacation-so-dutifully-tagging-now
 <li> rel-1.3.40
 <li> rel-2.0.9
 </ul>

 <hr>
 Copyright (C) 1999-2004 SWIG Development Team.
 </body>
 </html>
	<html>
	<head>
	<title>SWIG Engineering Manual</title>
	</head>
	<body bgcolor="#ffffff">
	<center>
	<h1>SWIG Engineering Manual</h1>

	<b>David Beazley <br>
	</b>
	</center>

	<p>
	(Note : This is a work in progress.)

	<h2>Table of Contents</h2>
	<ul>
	<li><a name="i1" href="#1">1. Introduction</a>
	<li><a name="i2" href="#2">2. Programming Languages and Libraries</a>
	<li><a name="i3" href="#3">3. The Source Directory and Module Names</a>
	<li><a name="i4" href="#4">4. Include Files</a>
	<li><a name="i5" href="#5">5. File Structure</a>
	<li><a name="i6" href="#6">6. Bottom-Up Design</a>
	<li><a name="i7" href="#7">7. Functions</a>
	<li><a name="i8" href="#8">8. Naming Conventions</a>
	<li><a name="i9" href="#9">9. Visibility</a>
	<li><a name="i10" href="#10">10. Miscellaneous Coding Guidelines</a>
	<li><a name="i11" href="#11">11. Git Tagging Conventions</a>
	</ul>

	<a name="1" href="#i1">
	<h2>1. Introduction</h2>
	</a>

	The purpose of this document is to describe various coding conventions
	and organizational aspects for SWIG developers. The idea for this
	document is largely borrowed from John Ousterhout's Tcl/Tk Engineering
	Manual. It is not my intent to overly managerial about matters--rather I'm
	hoping to make life a little less chaotic for everyone.

	<p>
	First a little background: SWIG was started in 1995 as a one-person
	project and continued in this mode of operation until about 1998.
	Most of this development was driven by ideas submitted by early SWIG
	users as opposed to being motivated by a grand design. As a result,
	the code ended up being a pretty horrible C++ coding disaster. A
	mostly working disaster perhaps, but a disaster nonetheless.

	<p>
	With that said, the primary goal of future SWIG development is to
	reengineer the original system, fix most of its inherent design flaws,
	and to produce what I hope will become a highly extensible and modular
	interface compiler framework. To this do this, there are a few
	critical areas of work. First, I want to restructure SWIG as a
	collection of loosely coupled modules written in either ANSI C or an
	scripting language. Second, I want the system to be minimalistic in
	its use of data structures and interconnections. The primary reason
	for this is that the fewer data structures there are, the less users
	will have to remember. This will also make the system more accessible
	to non-experts. Finally, I want to reevaluate the whole idea of a
	SWIG module is and expand the definition to include just about
	anything from parsers, preprocessors, optimizers, interface editors,
	and code generators.

	<p>
	The rest of this document outlines a few general rules of how code
	should be developed within the SWIG project. These rules are
	primarily drawn from my own experience developing software and
	observing the practices of other successful projects.

	<a name="2" href="#i2">
	<h2>2. Programming Languages and Libraries </h2>
	</a>

	All SWIG modules must be written in either ANSI C or one of the
	scripting languages for which SWIG can generate an interface (e.g.,
	Perl, Python, or Tcl). C++ is currently being used to write
	SWIG modules, but it is only being utilized to avoid working with
	a lot of pointers to functions. <b>Advanced C++ features like namespaces, templates,
	and overloading should not be used.</b>.

	<p>
	Module writers should make every attempt to use only those functions
	described in the POSIX.1 standard. This includes most of the
	functions contained the Kernighan and Ritchie C programming book. Use
	of operating system dependent functionality such as socket libraries
	should always be included inside a conditional compilation block so
	that it can be omitted on problematic platforms. If you are unsure
	about a library call, check the man page or contact Dave.

	<a name="3" href="#i3">
	<h2>3. The Source Directory and Module Names</h2>
	</a>

	All SWIG modules are contained within the "Source" directory. Within
	this directory, each module is placed into its own subdirectory. The
	name of this subdirectory should exactly match the name of the module.
	For example, if you are creating a module called "Tcl", all of your
	files should be placed in a directory "Tcl".

	<p>
	When choosing a module name, please pick a name that is not
	currently in use. As a general convention, the first letter of a
	module name is capitalized such as "Perl". Alternatives such as
	"perl" or "PERL" should be avoided. In certain instances, the first
	two letters may be capitalized as in "CParse." The exact usage of
	this is somewhat inconsistent and isn't terribly important--just make
	sure the first letter is capitalized. Also, module names should not
	start with numbers, include underscores or any other special
	non-alphanumeric characters.

	<a name="5" href="#i5">
	<h2>5. File Structure </h2>
	</a>

	Each file in a module should be given a filename that is all lowercase letters
	such as "parser.c", not "Parser.c" or "PARSER.c". Please note that filenames
	are case-insensitive on Windows so this convention will prevent you from inadvertently
	creating two files that differ in case-only.

	<p>
	Each file should include a short abstract and license information
	like this:

	<blockquote>
	<pre>
	/* -----------------------------------------------------------------------------
	* This file is part of SWIG, which is licensed as a whole under version 3
	* (or any later version) of the GNU General Public License. Some additional
	* terms also apply to certain portions of SWIG. The full details of the SWIG
	* license and copyrights can be found in the LICENSE and COPYRIGHT files
	* included with the SWIG source code as distributed by the SWIG developers
	* and at http://www.swig.org/legal.html.
	*
	* xxx.c
	*
	* This file defines ...
	* ----------------------------------------------------------------------------- */

	#include "swig.h"

	/* Declarations */
	typedef struct {
	int x, y;
	} Foo;

	...

	/* Private Declarations (used only in this file) */
	static int avariable;

	...

	/* Functions */
	...

	</pre>
	</blockquote>

	<p>
	As a general rule, files start to get unmanageable once they exceed
	about 2000 lines. Files larger than this should be broken up into
	multiple files. Similarly, you should avoid the temptation to create
	many small files as this increases compilation time and makes the
	directory structure too complicated.

	<a name="6" href="#i6">
	<h2>6. Bottom-Up Design </h2>
	</a>

	Within each source file, the preferred organization is to use what is
	known as "bottom-up" design. Under this scheme, lower-level functions
	appear first and the highest level function appears last. The easy
	way to remember is that the "main" function of your module should
	always appear last in the source file. For example:

	<blockquote>
	<pre>
	/* Simple bottom-up program */
	#include <stdio.h>

	int foo(int x, int y) {
	/* Implement foo */
	...
	}

	int bar() {
	...
	foo(i,j);
	...
	}

	...
	int main(int argc, char **argv) {
	...
	bar();
	...
	}
	</pre>
	</blockquote>

	This choice of design is somewhat arbitrary however it has a number of
	benefits particular to C. In particular, a bottom-up design generally
	eliminates the need to include forward references--resulting in
	cleaner code and fewer compilation errors.

	<a name="7" href="#i7">
	<h2>7. Functions</h2>
	</a>

	All functions should have a function header that gives the function name
	and a short description like this:

	<blockquote>
	<pre>
	/* -------------------------------------------------------------------------
	* Swig_add_directory()
	*
	* Adds a directory to the SWIG search path.
	* ------------------------------------------------------------------------- */

	void
	Swig_add_directory(DOH *dirname) {
	...

	}
	</pre>
	</blockquote>

	In the function declaration, the return type and any specifiers
	(extern or static) should appear on a separate line followed by the
	function name and arguments as shown above. The left curly brace
	should appear on the same line as the function name.

	<p>
	Function declarations should <b>NOT</b> use the pre-ANSI function
	declaration syntax. The ANSI standard has been around long enough for
	this to be a non-issue.

	<a name="8" href="#i8">
	<h2>8. Naming Conventions</h2>
	</a>

	The following conventions are used to name various objects throughout SWIG.

	<h4>Functions</h4>

	Functions should consist of the module name and the function name separated by an underscore like this:

	<blockquote>
	<pre>
	Preprocessor_define()
	Swig_add_directory()
	</pre>
	</blockquote>

	In general, the module name should match the name of the module
	subdirectory and the function name should be in all lowercase with
	words separated by underscores.

	<h4>Structures and Types</h4>

	If your module defines new structures, the structure name should include the name of the
	module and the name of the structure appended together like this:

	<blockquote>
	<pre>
	typedef struct SwigScanner {
	...
	} SwigScanner;

	typedef struct LParseType {
	...
	} LParseType;
	</pre>
	</blockquote>

	In this case, both the name of the module and the type should be capitalized. Also, whenever
	possible, you should use the "typedef struct Name { ... } Name" form when defining new
	data structures.

	<h4>Global Variables</h4>

	Global variables should be avoided if at all possible. However, if you must use a global
	variable, please prepend the module name and use the same naming scheme as for functions.

	<h4>Constants</h4>

	Constants should be created using #define and should be in all caps like this:

	<blockquote>
	<pre>
	#define SWIG_TOKEN_LPAREN 1
	</pre>
	</blockquote>

	Separate words in a constant should be separated by underscores as with functions.

	<h4>Structure members</h4>

	Structure members should be in all lower-case and follow the same word-separation convention
	as for function names. However, the module name does not have to be included.
	For example:

	<blockquote>
	<pre>
	typedef struct SwigScanner {
	DOH text; / Current token value */
	DOH scanobjs; / Objects being scanned */
	DOH str; / Current object being scanned */
	char idstart; / Optional identifier start characters */
	int next_token; /* Next token to be returned */
	int start_line; /* Starting line of certain declarations */
	int yylen; /* Length of text pushed into text */
	DOH file; / Current file name */
	} SwigScanner;
	</pre>
	</blockquote>

	<h4>Static Functions and Variables </h4>

	Static declarations are free to use any naming convention that is appropriate. However, most
	existing parts of SWIG use lower-case names and follow the same convention as described for functions.

	<a name="9" href="#i9">
	<h2>9. Visibility</h2>
	</a>

	Modules should keep the following rules in mind when exposing their internals:

	<ul>
	<li>Only publicly accessible functions should be included in the module header file.
	<li>All non-static declarations must be prepended with some form of the module name
	to avoid potential linker namespace conflicts with other modules.
	<li>Modules should not expose global variables or use global variables in their
	public interface.
	<li>Similarly, modules should discourage the direct manipulation of data contained
	within data structures in favor of using function calls instead. For example,
	instead of providing a user with a structure like this:

	<blockquote>
	<pre>
	typedef struct Foo {
	int line;
	} Foo;
	</pre>
	</blockquote>

	It is better to hide the implementation of Foo and provide an
	function-call interface like this:

	<blockquote>
	<pre>
	typedef struct Foo Foo;
	extern int Foo_getline(Foo *f);
	extern void Foo_setline(Foo *f, int line);
	</pre>
	</blockquote>

	Although this results in worse performance, there are many practical
	reasons for doing this. The most important reason is that it allows
	you to change the internal representation of Foo without breaking all
	of the other modules or having to recompile the entire universe after
	making your changes.

	</ul>

	<a name="10" href="#i10">
	<h2>10. Miscellaneous Coding Guidelines</h2>
	</a>
	These are largely covered in the main documentation in the Extending.html file.

	<a name="11" href="#i11">
	<h2>11. Git Tagging Conventions</h2>
	</a>

	Use <tt>git tag</tt> to declare some set of file revisions as related in some
	symbolic way. This eases reference, retrieval and manipulation of these files
	later. At the moment (2001/01/16 14:02:53), the conventions are very simple;
	let's hope they stay that way!

	<p>
	There are two types of tags, internal (aka personal) and external.
	Internal tags are used by SWIG developers primarily, whereas external
	tags are used when communicating with people w/ anonymous git access.
	<ul>
	<li> Internal tags should start with the developer name and a hyphen.
	<li> External tags should start with "rel-".
	</ul>

	That's all there is to it. Some example tags:

	<ul>
	<li> ttn-pre-xml-patch
	<li> ttn-post-xml-patch
	<li> ttn-going-on-vacation-so-dutifully-tagging-now
	<li> rel-1.3.40
	<li> rel-2.0.9
	</ul>

	<hr>
	Copyright (C) 1999-2004 SWIG Development Team.
	</body>
	</html>