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 Written by and Copyright (C) 2001 the SourceForge
 Privoxy team. http://www.privoxy.org/

 Based on the Internet Junkbuster originally written
 by and Copyright (C) 1997 Anonymous Coders and 
 Junkbusters Corporation.  http://www.junkbusters.com
-->

<article id="index">
  <artheader>
    <title>Privoxy Developer Manual</title>

    <pubdate>$Id: developer-manual.sgml,v 1.10 2002/03/24 12:33:01 swa Exp $</pubdate>

    <authorgroup>
      <author>
        <affiliation>
          <orgname>By: Privoxy Developers</orgname>
        </affiliation>
      </author>
    </authorgroup>

    <abstract>
      <para>
The developer manual gives the users information on how to help the developer
team. It provides guidance on coding, testing, documentation and other
issues. <application>Privoxy</application> is a web proxy with advanced
filtering capabilities for protecting privacy, filtering web page content,
managing cookies, controlling access, and removing ads, banners, pop-ups and
other obnoxious Internet Junk. <application>Privoxy</application> has a very
flexible configuration and can be customized to suit individual needs and
tastes. <application>Privoxy</application> has application for both stand-alone
systems and multi-user networks.
 </para>
      <para>
You can find the latest version of the user manual at <ulink
url="http://www.privoxy.org/developer-manual/">http://www.privoxy.org/developer-manual/</ulink>.
Please see the Contact section in the user-manual if you want to contact the developers.
 </para>

<!--        <para> -->
<!--    Feel free to send a note to the developers at <email>ijbswa-developers@lists.sourceforge.net</email>. -->
<!--   </para> -->

    </abstract>
  </artheader>

  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="introduction"><title>Introduction</title>
    <para>To be filled.
</para>
  </sect1>

  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="quickstart"><title>Quickstart to Privoxy Development</title>
    <para>
You'll need an account on Sourceforge to support our development. Mail you ID
to the list and wait until a project manager has added you.

For the time beeing (read, this section is under construction), please note the
following guidelines for changing stuff in the code. If it is
        <orderedlist numeration="arabic">
                <listitem><para>
                A bugfix / clean-up / cosmetic thing: shoot
                </para></listitem>
                <listitem><para>
                A new feature that can be turned off: shoot
                </para></listitem>
                <listitem><para>
                A clear improvement w/o side effects on other parts of the code: shoot
                </para></listitem>
                <listitem><para>
                A matter of taste: ask the list
                </para></listitem>
                <listitem><para>
                A major redesign of some part of the code: ask the list
                </para></listitem>
        </orderedlist>  
</para>         
  </sect1>      
        
  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="documentation"><title>Documentation Guidelines</title>
    <para>
        All docs are in SGML format and located in the <computeroutput>doc/source</computeroutput> directory.
        </para>
        <para>
        How do you update the webserver (i.e. the pages on sourceforge)?
        <orderedlist numeration="arabic">
                <listitem><para>
        Run <computeroutput>make dok</computeroutput> (which uses the documents in <computeroutput>doc/source</computeroutput> to update all
        text files in <computeroutput>doc/text</computeroutput> and to update
all web documents in <computeroutput>doc/webserver</computeroutput>.
                </para></listitem>
                <listitem><para>
        Run <computeroutput>make webserver</computeroutput> which copies all files from
<computeroutput>doc/webserver</computeroutput> to the sourceforge webserver
via scp.
                </para></listitem>
        </orderedlist>
  </para>
 </sect1>

<!--     <listitem><para>be consistent with the redirect script (i.e. the <application>Privoxy</application> program -->
<!--       points via the redirect URL at sf to valid end-points in the document)</para></listitem> -->

  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="coding"><title>Coding Guidelines</title>

    <sect2 id="s1"><title>Introduction</title>

    <para>This set of standards is designed to make our lives easier.  It is
    developed with the simple goal of helping us keep the "new and improved
    <application>Privoxy</application>" consistent and reliable. Thus making
    maintenance easier and increasing chances of success of the
    project.</para>

    <para>And that of course comes back to us as individuals. If we can
    increase our development and product efficiencies then we can solve more
    of the request for changes/improvements and in general feel good about
    ourselves. ;-></para>

  </sect2>

    <sect2 id="s2"><title>Using Comments</title>
 

    <sect3 id="s3"><title>Comment, Comment, Comment</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Comment as much as possible without commenting the obvious.
    For example do not comment "aVariable is equal to bVariable".
    Instead explain why aVariable should be equal to the bVariable.
    Just because a person can read code does not mean they will
    understand why or what is being done. A reader may spend a lot
    more time figuring out what is going on when a simple comment
    or explanation would have prevented the extra research. Please
    help your brother IJB'ers out!</para>

    <para>The comments will also help justify the intent of the code.
    If the comment describes something different than what the code
    is doing then maybe a programming error is occurring.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
/* if page size greater than 1k ... */
if ( PageLength() > 1024 )
{
    ... "block" the page up ...
}

/* if page size is small, send it in blocks */
if ( PageLength() > 1024 )
{
    ... "block" the page up ...
}

This demonstrates 2 cases of "what not to do".  The first is a
"syntax comment".  The second is a comment that does not fit what
is actually being done.
</programlisting>
  </sect3>

    

    <sect3 id="s4"><title>Use blocks for comments</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Comments can help or they can clutter. They help when they
    are differentiated from the code they describe. One line
    comments do not offer effective separation between the comment
    and the code. Block identifiers do, by surrounding the code
    with a clear, definable pattern.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
/*********************************************************************
 * This will stand out clearly in your code!
 *********************************************************************/
if ( thisVariable == thatVariable )
{
   DoSomethingVeryImportant();
}


/* unfortunately, this may not */
if ( thisVariable == thatVariable )
{
   DoSomethingVeryImportant();
}


if ( thisVariable == thatVariable ) /* this may not either */
{
   DoSomethingVeryImportant();
}</programlisting>

    <para><emphasis>Exception:</emphasis></para>

    <para>If you are trying to add a small logic comment and do not
    wish to "disrubt" the flow of the code, feel free to use a 1
    line comment which is NOT on the same line as the code.</para>

    
  </sect3>
    

    <sect3 id="s5"><title>Keep Comments on their own line</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>It goes back to the question of readability. If the comment
    is on the same line as the code it will be harder to read than
    the comment that is on its own line.</para>

    <para>There are three exceptions to this rule, which should be
    violated freely and often: during the definition of variables,
    at the end of closing braces, when used to comment
    parameters.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
/*********************************************************************
 * This will stand out clearly in your code,
 * But the second example won't.
 *********************************************************************/
if ( thisVariable == thatVariable )
{
   DoSomethingVeryImportant();
}

if ( thisVariable == thatVariable ) /*can you see me?*/
{
   DoSomethingVeryImportant(); /*not easily*/
}


/*********************************************************************
 * But, the encouraged exceptions:
 *********************************************************************/
int urls_read     = 0;     /* # of urls read + rejected */
int urls_rejected = 0;     /* # of urls rejected */

if ( 1 == X )
{
   DoSomethingVeryImportant();
}


short DoSomethingVeryImportant(
   short firstparam,   /* represents something */
   short nextparam     /* represents something else */ )
{
   ...code here...

}   /* -END- DoSomethingVeryImportant */
</programlisting>
  </sect3>
    

    <sect3 id="s6"><title>Comment each logical step</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Logical steps should be commented to help others follow the
    intent of the written code and comments will make the code more
    readable.</para>

    <para>If you have 25 lines of code without a comment, you should
    probably go back into it to see where you forgot to put
    one.</para>

    <para>Most "for", "while", "do", etc... loops _probably_ need a
    comment. After all, these are usually major logic
    containers.</para>

    
  </sect3>
    

    <sect3 id="s7"><title>Comment All Functions Thoroughly</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>A reader of the code should be able to look at the comments
    just prior to the beginning of a function and discern the
    reason for its existence and the consequences of using it. The
    reader should not have to read through the code to determine if
    a given function is safe for a desired use. The proper
    information thoroughly presented at the introduction of a
    function not only saves time for subsequent maintenance or
    debugging, it more importantly aids in code reuse by allowing a
    user to determine the safety and applicability of any function
    for the problem at hand. As a result of such benefits, all
    functions should contain the information presented in the
    addendum section of this document.</para>

    
  </sect3>
    

    <sect3 id="s8"><title>Comment at the end of braces if the
    content is more than one screen length</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Each closing brace should be followed on the same line by a
    comment that describes the origination of the brace if the
    original brace is off of the screen, or otherwise far away from
    the closing brace. This will simplify the debugging,
    maintenance, and readability of the code.</para>

    <para>As a suggestion , use the following flags to make the
    comment and its brace more readable:</para>

    <para>use following a closing brace: } /* -END- if() or while ()
    or etc... */</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
if ( 1 == X )
{
   DoSomethingVeryImportant();
   ...some long list of commands...
} /* -END- if x is 1 */

or:

if ( 1 == X )
{
   DoSomethingVeryImportant();
   ...some long list of commands...
} /* -END- if ( 1 == X ) */
</programlisting>
  </sect3>
    
  </sect2>

    <sect2 id="s9"><title>Naming Conventions</title>

    

    <sect3 id="s10"><title>Variable Names</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Use all lowercase, and seperate words via an underscore
    ('_'). Do not start an identifier with an underscore. (ANSI C
    reserves these for use by the compiler and system headers.) Do
    not use identifiers which are reserved in ANSI C++. (E.g.
    template, class, true, false, ...). This is in case we ever
    decide to port Privoxy to C++.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
int ms_iis5_hack = 0;</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>
<programlisting>
int msiis5hack = 0; int msIis5Hack = 0;
</programlisting>
</para>

    

  </sect3>    

    <sect3 id="s11"><title>Function Names</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Use all lowercase, and seperate words via an underscore
    ('_'). Do not start an identifier with an underscore. (ANSI C
    reserves these for use by the compiler and system headers.) Do
    not use identifiers which are reserved in ANSI C++. (E.g.
    template, class, true, false, ...). This is in case we ever
    decide to port Privoxy to C++.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
int load_some_file( struct client_state *csp )</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>
<programlisting>
int loadsomefile( struct client_state *csp )
int loadSomeFile( struct client_state *csp )
</programlisting>
</para>

    
  </sect3>
    

    <sect3 id="s12"><title>Header file prototypes</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Use a descriptive parameter name in the function prototype
    in header files. Use the same parameter name in the header file
    that you use in the c file.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
(.h) extern int load_aclfile( struct client_state *csp );
(.c) int load_aclfile( struct client_state *csp )</programlisting>

    <para><emphasis>Instead of:</emphasis>
<programlisting>
(.h) extern int load_aclfile( struct client_state * ); or 
(.h) extern int load_aclfile(); 
(.c) int load_aclfile( struct client_state *csp )
</programlisting>
</para>

    
  </sect3>
    

    <sect3 id="s13"><title>Enumerations, and #defines</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Use all capital letters, with underscores between words. Do
    not start an identifier with an underscore. (ANSI C reserves
    these for use by the compiler and system headers.)</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
(enumeration) : enum Boolean { FALSE, TRUE };
(#define) : #define DEFAULT_SIZE 100;</programlisting>

    <para><emphasis>Note:</emphasis> We have a standard naming scheme for #defines
    that toggle a feature in the preprocessor: FEATURE_>, where
    > is a short (preferably 1 or 2 word) description.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
#define FEATURE_FORCE 1

#ifdef FEATURE_FORCE
#define FORCE_PREFIX blah
#endif /* def FEATURE_FORCE */
</programlisting>
  </sect3>
    

    <sect3 id="s14"><title>Constants</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Spell common words out entirely (do not remove vowels).</para>

    <para>Use only widely-known domain acronyms and abbreviations.
    Capitalize all letters of an acronym.</para>

    <para>Use underscore (_) to separate adjacent acronyms and
    abbreviations. Never terminate a name with an underscore.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
#define USE_IMAGE_LIST 1</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>
<programlisting>
#define USE_IMG_LST 1 or 
#define _USE_IMAGE_LIST 1 or
#define USE_IMAGE_LIST_ 1 or 
#define use_image_list 1 or
#define UseImageList 1
</programlisting>
</para>

    
  </sect3>

  </sect2>
    

    <sect2 id="s15"><title>Using Space</title>

    

    <sect3 id="s16"><title>Put braces on a line by themselves.</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>The brace needs to be on a line all by itself, not at the
    end of the statement. Curly braces should line up with the
    construct that they're associated with. This practice makes it
    easier to identify the opening and closing braces for a
    block.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
if ( this == that )
{
   ...
}</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>if ( this == that ) { ... }</para>

    <para>or</para>

    <para>if ( this == that ) { ... }</para>

    <para><emphasis>Note:</emphasis> In the special case that the if-statement is
    inside a loop, and it is trivial, i.e. it tests for a
    condidtion that is obvious from the purpose of the block,
    one-liners as above may optically preserve the loop structure
    and make it easier to read.</para>

    <para><emphasis>Status:</emphasis> developer-discrection.</para>

    <para><emphasis>Example exception:</emphasis></para>
<programlisting>
while ( more lines are read )
{
   /* Please document what is/is not a comment line here */
   if ( it's a comment ) continue;

   do_something( line );
}
</programlisting>
  </sect3>
    

    <sect3 id="s17"><title>ALL control statements should have a
    block</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Using braces to make a block will make your code more
    readable and less prone to error. All control statements should
    have a block defined.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
if ( this == that )
{
   DoSomething();
   DoSomethingElse();
}</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>if ( this == that ) DoSomething(); DoSomethingElse();</para>

    <para>or</para>

    <para>if ( this == that ) DoSomething();</para>

    <para><emphasis>Note:</emphasis> The first example in "Instead of" will execute
    in a manner other than that which the developer desired (per
    indentation). Using code braces would have prevented this
    "feature". The "explanation" and "exception" from the point
    above also applies.</para>

    
  </sect3>
    

    <sect3 id="s18"><title>Do not belabor/blow-up boolean
    expressions</title>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
structure->flag = ( condition );</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>if ( condition ) { structure->flag = 1; } else {
    structure->flag = 0; }</para>

    <para><emphasis>Note:</emphasis> The former is readable and consice. The later
    is wordy and inefficient. Please assume that any developer new
    to the project has at least a "good" knowledge of C/C++. (Hope
    I do not offend by that last comment ... 8-)</para>

    
  </sect3>
    

    <sect3 id="s19"><title>Use white space freely because it is
    free</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Make it readable. The notable exception to using white space
    freely is listed in the next guideline.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
int firstValue   = 0;
int someValue    = 0;
int anotherValue = 0;
int thisVariable = 0;

if ( thisVariable == thatVariable )

firstValue = oldValue + ( ( someValue - anotherValue ) - whatever )
</programlisting>
  </sect3>
    

    <sect3 id="s20"><title>Don't use white space around structure
    operators</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>- structure pointer operator ( "->" ) - member operator (
    "." ) - functions and parentheses</para>

    <para>It is a general coding practice to put pointers, references,
    and function parentheses next to names. With spaces, the
    connection between the object and variable/function name is not
    as clear.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
aStruct->aMember;
aStruct.aMember;
FunctionName();</programlisting>

    <para><emphasis>Instead of:</emphasis> aStruct -> aMember; aStruct . aMember;
    FunctionName ();</para>

    
  </sect3>
    

    <sect3 id="s21"><title>Make the last brace of a function stand
    out</title>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
int function1( ... )
{
   ...code...
   return( retCode );

}   /* -END- function1 */


int function2( ... )
{
}   /* -END- function2 */
</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>int function1( ... ) { ...code... return( retCode ); } int
    function2( ... ) { }</para>

    <para><emphasis>Note:</emphasis> Use 1 blank line before the closing brace and 2
    lines afterwards. This makes the end of function standout to
    the most casual viewer. Although function comments help
    seperate functions, this is still a good coding practice. In
    fact, I follow these rules when using blocks in "for", "while",
    "do" loops, and long if {} statements too. After all whitespace
    is free!</para>

    <para><emphasis>Status:</emphasis> developer-discrection on the number of blank
    lines. Enforced is the end of function comments.</para>

    
  </sect3>
    

    <sect3 id="s22"><title>Use 3 character indentions</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>If some use 8 character TABs and some use 3 character TABs,
    the code can look *very* ragged. So use 3 character indentions
    only. If you like to use TABs, pass your code through a filter
    such as "expand -t3" before checking in your code.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
static const char * const url_code_map[256] =
{
   NULL, ...
};


int function1( ... )
{
   if ( 1 )
   {
      return( ALWAYS_TRUE );
   }
   else
   {
      return( HOW_DID_YOU_GET_HERE );
   }

   return( NEVER_GETS_HERE );

}
</programlisting>
  </sect3>

  </sect2>
    

    <sect2 id="s23"><title>Initializing</title>

    

    <sect3 id="s24"><title>Initialize all variables</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Do not assume that the variables declared will not be used
    until after they have been assigned a value somewhere else in
    the code. Remove the chance of accidentally using an unassigned
    variable.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
short anShort = 0;
float aFloat  = 0;
struct *ptr = NULL;</programlisting>

    <para><emphasis>Note:</emphasis> It is much easier to debug a SIGSEGV if the
    message says you are trying to access memory address 00000000
    and not 129FA012; or arrayPtr[20] causes a SIGSEV vs.
    arrayPtr[0].</para>

    <para><emphasis>Status:</emphasis> developer-discrection if and only if the
    variable is assigned a value "shortly after" declaration.</para>

  </sect3>
  </sect2>
    

    <sect2 id="s25"><title>Functions</title>

    

    <sect3 id="s26"><title>Name functions that return a boolean as a
    question.</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Value should be phrased as a question that would logically
    be answered as a true or false statement</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
ShouldWeBlockThis();
ContainsAnImage();
IsWebPageBlank();
</programlisting>
  </sect3>
    

    <sect3 id="s27"><title>Always specify a return type for a
    function.</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>The default return for a function is an int. To avoid
    ambiguity, create a return for a function when the return has a
    purpose, and create a void return type if the function does not
    need to return anything.</para>

    
  </sect3>
    

    <sect3 id="s28"><title>Minimize function calls when iterating by
    using variables</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>It is easy to write the following code, and a clear argument
    can be made that the code is easy to understand:</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
for ( size_t cnt = 0; cnt &lt; blockListLength(); cnt ++ )
{
   ....
}</programlisting>

    <para><emphasis>Note:</emphasis> Unfortunately, this makes a function call for
    each and every iteration. This increases the overhead in the
    program, because the compiler has to look up the function each
    time, call it, and return a value. Depending on what occurs in
    the blockListLength() call, it might even be creating and
    destroying structures with each iteration, even though in each
    case it is comparing "cnt" to the same value, over and over.
    Remember too - even a call to blockListLength() is a function
    call, with the same overhead.</para>

    <para>Instead of using a function call during the iterations,
    assign the value to a variable, and evaluate using the
    variable.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
size_t len = blockListLength();

for ( size_t cnt = 0; cnt &lt; len; cnt ++ )
{
   ....
}</programlisting>

    <para><emphasis>Exceptions:</emphasis> if the value of blockListLength() *may*
    change or could *potentially* change, then you must code the
    function call in the for/while loop.</para>

    
  </sect3>
    

    <sect3 id="s29"><title>Pass and Return by Const Reference</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>This allows a developer to define a const pointer and call
    your function. If your function does not have the const
    keyword, we may not be able to use your function. Consider
    strcmp, if it were defined as: extern int strcmp( char *s1,
    char *s2 );</para>

    <para>I could then not use it to compare argv's in main: int main(
    int argc, const char *argv[] ) { strcmp( argv[0], "privoxy"
    ); }</para>

    <para>Both these pointers are *const*! If the c runtime library
    maintainers do it, we should too.</para>

    
  </sect3>
    

    <sect3 id="s30"><title>Pass and Return by Value</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Most structures cannot fit onto a normal stack entry (i.e.
    they are not 4 bytes or less). Aka, a function declaration
    like: int load_aclfile( struct client_state csp )</para>

    <para>would not work. So, to be consistent, we should declare all
    prototypes with "pass by value": int load_aclfile( struct
    client_state *csp )</para>

    
  </sect3>
    

    <sect3 id="s31"><title>Names of include files</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Your include statements should contain the file name without
    a path. The path should be listed in the Makefile, using -I as
    processor directive to search the indicated paths. An exception
    to this would be for some proprietary software that utilizes a
    partial path to distinguish their header files from system or
    other header files.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
#include &lt;iostream.h&gt;     /* This is not a local include */
#include "config.h"       /* This IS a local include */
</programlisting>

    <para><emphasis>Exception:</emphasis></para>

    <para>
<programlisting>
/* This is not a local include, but requires a path element. */ 
#include &lt;sys/fileName.h&gt;
</programlisting>
</para>

    <para><emphasis>Note:</emphasis> Please! do not add "-I." to the Makefile
    without a _very_ good reason. This duplicates the #include
    "file.h" behaviour.</para>

    
  </sect3>
    

    <sect3 id="s32"><title>Provide multiple inclusion
    protection</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Prevents compiler and linker errors resulting from
    redefinition of items.</para>

    <para>Wrap each header file with the following syntax to prevent
    multiple inclusions of the file. Of course, replace PROJECT_H
    with your file name, with "." Changed to "_", and make it
    uppercase.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
#ifndef PROJECT_H_INCLUDED
#define PROJECT_H_INCLUDED
 ...
#endif /* ndef PROJECT_H_INCLUDED */
</programlisting>
  </sect3>
    

    <sect3 id="s33"><title>Use `extern "C"` when appropriate</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>If our headers are included from C++, they must declare our
    functions as `extern "C"`. This has no cost in C, but increases
    the potential re-usability of our code.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
#ifdef __cplusplus
extern "C"
{
#endif /* def __cplusplus */

... function definitions here ...

#ifdef __cplusplus
}
#endif /* def __cplusplus */
</programlisting>
  </sect3>
    

    <sect3 id="s34"><title>Where Possible, Use Forward Struct
    Declaration Instead of Includes</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Useful in headers that include pointers to other struct's.
    Modifications to excess header files may cause needless
    compiles.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
/*********************************************************************
 * We're avoiding an include statement here!
 *********************************************************************/
struct file_list;
extern file_list *xyz;</programlisting>

    <para><emphasis>Note:</emphasis> If you declare "file_list xyz;" (without the
    pointer), then including the proper header file is necessary.
    If you only want to prototype a pointer, however, the header
    file is unneccessary.</para>

    <para><emphasis>Status:</emphasis> Use with discrection.</para>

    
  </sect3>
  </sect2>

    <sect2 id="s35"><title>General Coding Practices</title>

    

    <sect3 id="s36"><title>Turn on warnings</title>

    <para><emphasis>Explanation</emphasis></para>

    <para>Compiler warnings are meant to help you find bugs. You
    should turn on as many as possible. With GCC, the switch is
    "-Wall". Try and fix as many warnings as possible.</para>

    
  </sect3>
    

    <sect3 id="s37"><title>Provide a default case for all switch
    statements</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>What you think is guaranteed is never really guaranteed. The
    value that you don't think you need to check is the one that
    someday will be passed. So, to protect yourself from the
    unknown, always have a default step in a switch statement.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
switch( hash_string( cmd ) )
{
   case hash_actions_file :
      ... code ...
      break;

   case hash_confdir :
      ... code ...
      break;

   default :
      log_error( ... );
      ... anomly code goes here ...
      continue; / break; / exit( 1 ); / etc ...

} /* end switch( hash_string( cmd ) ) */</programlisting>

    <para><emphasis>Note:</emphasis> If you already have a default condition, you
    are obviously exempt from this point. Of note, most of the
    WIN32 code calls `DefWindowProc' after the switch statement.
    This API call *should* be included in a default statement.</para>

    <para><emphasis>Another Note:</emphasis> This is not so much a readability issue
    as a robust programming issue. The "anomly code goes here" may
    be no more than a print to the STDERR stream (as in
    load_config). Or it may really be an ABEND condition.</para>

    <para><emphasis>Status:</emphasis> Programmer discretion is advised.</para>

    
  </sect3>
    

    <sect3 id="s38"><title>Try to avoid falling through cases in a
    switch statement.</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>In general, you will want to have a 'break' statement within
    each 'case' of a switch statement. This allows for the code to
    be more readable and understandable, and furthermore can
    prevent unwanted surprises if someone else later gets creative
    and moves the code around.</para>

    <para>The language allows you to plan the fall through from one
    case statement to another simply by omitting the break
    statement within the case statement. This feature does have
    benefits, but should only be used in rare cases. In general,
    use a break statement for each case statement.</para>

    <para>If you choose to allow fall through, you should comment both
    the fact of the fall through and reason why you felt it was
    necessary.</para>

    
  </sect3>
    

    <sect3 id="s39"><title>Use 'long' or 'short' Instead of
    'int'</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>On 32-bit platforms, int usually has the range of long. On
    16-bit platforms, int has the range of short.</para>

    <para><emphasis>Status:</emphasis> open-to-debate. In the case of most FSF
    projects (including X/GNU-Emacs), there are typedefs to int4,
    int8, int16, (or equivalence ... I forget the exact typedefs
    now). Should we add these to IJB now that we have a "configure"
    script?</para>

    
  </sect3>
    

    <sect3 id="s40"><title>Don't mix size_t and other types</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>The type of size_t varies across platforms. Do not make
    assumptions about whether it is signed or unsigned, or about
    how long it is. Do not compare a size_t against another
    variable of a different type (or even against a constant)
    without casting one of the values. Try to avoid using size_t if
    you can.</para>

    
  </sect3>
    

    <sect3 id="s41"><title>Declare each variable and struct on its
    own line.</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>It can be tempting to declare a series of variables all on
    one line. Don't.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
long a = 0;
long b = 0;
long c = 0;</programlisting>

    <para><emphasis>Instead of:</emphasis></para>

    <para>long a, b, c;</para>

    <para><emphasis>Explanation:</emphasis> - there is more room for comments on the
    individual variables - easier to add new variables without
    messing up the original ones - when searching on a variable to
    find its type, there is less clutter to "visually"
    eliminate</para>

    <para><emphasis>Exceptions:</emphasis> when you want to declare a bunch of loop
    variables or other trivial variables; feel free to declare them
    on 1 line. You should, although, provide a good comment on
    their functions.</para>

    <para><emphasis>Status:</emphasis> developer-discrection.</para>

    
  </sect3>
    

    <sect3 id="s42"><title>Use malloc/zalloc sparingly</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>Create a local stuct (on the stack) if the variable will
    live and die within the context of one function call.</para>

    <para>Only "malloc" a struct (on the heap) if the variable's life
    will extend beyond the context of one function call.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
If a function creates a struct and stores a pointer to it in a
list, then it should definately be allocated via `malloc'.
</programlisting>
  </sect3>
    

    <sect3 id="s43"><title>The Programmer Who Uses 'malloc' is
    Responsible for Ensuring 'free'</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>If you have to "malloc" an instance, you are responsible for
    insuring that the instance is `free'd, even if the deallocation
    event falls within some other programmer's code. You are also
    responsible for ensuring that deletion is timely (i.e. not too
    soon, not too late). This is known as "low-coupling" and is a
    "good thing (tm)". You may need to offer a
    free/unload/destuctor type function to accomodate this.</para>

    <para><emphasis>Example:</emphasis></para>
<programlisting>
int load_re_filterfile( struct client_state *csp ) { ... }
static void unload_re_filterfile( void *f ) { ... }</programlisting>

    <para><emphasis>Exceptions:</emphasis></para>

    <para>The developer cannot be expected to provide `free'ing
    functions for C run-time library functions ... such as
    `strdup'.</para>

    <para><emphasis>Status:</emphasis> developer-discrection. The "main" use of this
    standard is for allocating and freeing data structures (complex
    or nested).</para>

    
  </sect3>
    

    <sect3 id="s44"><title>Add loaders to the `file_list' structure
    and in order</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>I have ordered all of the "blocker" file code to be in alpha
    order. It is easier to add/read new blockers when you expect a
    certain order.</para>

    <para><emphasis>Note:</emphasis> It may appear that the alpha order is broken in
    places by POPUP tests coming before PCRS tests. But since
    POPUPs can also be referred to as KILLPOPUPs, it is clear that
    it should come first.</para>

    
  </sect3>
    

    <sect3 id="s45"><title>"Uncertain" new code and/or changes to
    exitinst code, use FIXME</title>

    <para><emphasis>Explanation:</emphasis></para>

    <para>If you have enough confidence in new code or confidence in
    your changes, but are not *quite* sure of the reprocussions,
    add this:</para>

    <para>/* FIXME: this code has a logic error on platform XYZ, *
    attempthing to fix */ #ifdef PLATFORM ...changed code here...
    #endif</para>

    <para>or:</para>

    <para>/* FIXME: I think the original author really meant this...
    */ ...changed code here...</para>

    <para>or:</para>

    <para>/* FIXME: new code that *may* break something else... */
    ...new code here...</para>

    <para><emphasis>Note:</emphasis> If you make it clear that this may or may not
    be a "good thing (tm)", it will be easier to identify and
    include in the project (or conversly exclude from the
    project).</para>

    
  </sect3>

  </sect2>

    <sect2 id="s46"><title>Addendum: Template for files and function
    comment blocks:</title>

    <para><emphasis>Example for file comments:</emphasis></para>
<programlisting>
const char FILENAME_rcs[] = "$Id: developer-manual.sgml,v 1.10 2002/03/24 12:33:01 swa Exp $";
/*********************************************************************
 *
 * File        :  $S<!-- Break CVS Substitution -->ource$
 *
 * Purpose     :  (Fill me in with a good description!)
 *
 * Copyright   :  Written by and Copyright (C) 2001 the SourceForge
 *                Privoxy team. http://www.privoxy.org/
 *
 *                Based on the Internet Junkbuster originally written
 *                by and Copyright (C) 1997 Anonymous Coders and
 *                Junkbusters Corporation.  http://www.junkbusters.com
 *
 *                This program is free software; you can redistribute it
 *                and/or modify it under the terms of the GNU General
 *                Public License as published by the Free Software
 *                Foundation; either version 2 of the License, or (at
 *                your option) any later version.
 *
 *                This program is distributed in the hope that it will
 *                be useful, but WITHOUT ANY WARRANTY; without even the
 *                implied warranty of MERCHANTABILITY or FITNESS FOR A
 *                PARTICULAR PURPOSE.  See the GNU General Public
 *                License for more details.
 *
 *                The GNU General Public License should be included with
 *                this file.  If not, you can view it at
 *                http://www.gnu.org/copyleft/gpl.html
 *                or write to the Free Software Foundation, Inc., 59
 *                Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Revisions   :
 *    $L<!-- Break CVS Substitution -->og$
 *
 *********************************************************************/


#include "config.h"

   ...necessary include files for us to do our work...

const char FILENAME_h_rcs[] = FILENAME_H_VERSION;
</programlisting>

    <para><emphasis>Note:</emphasis> This declares the rcs variables that should be
    added to the "show-proxy-args" page. If this is a brand new
    creation by you, you are free to change the "Copyright" section
    to represent the rights you wish to maintain.</para>

    <para><emphasis>Note:</emphasis> The formfeed character that is present right
    after the comment flower box is handy for (X|GNU)Emacs users to
    skip the verbige and get to the heart of the code (via
    `forward-page' and `backward-page'). Please include it if you
    can.</para>

    <para><emphasis>Example for file header comments:</emphasis></para>
<programlisting>
#ifndef _FILENAME_H
#define _FILENAME_H
#define FILENAME_H_VERSION "$Id: developer-manual.sgml,v 1.10 2002/03/24 12:33:01 swa Exp $"
/*********************************************************************
 *
 * File        :  $S<!-- Break CVS Substitution -->ource$
 *
 * Purpose     :  (Fill me in with a good description!)
 *
 * Copyright   :  Written by and Copyright (C) 2001 the SourceForge
 *                Privoxy team. http://www.privoxy.org/
 *
 *                Based on the Internet Junkbuster originally written
 *                by and Copyright (C) 1997 Anonymous Coders and
 *                Junkbusters Corporation.  http://www.junkbusters.com
 *
 *                This program is free software; you can redistribute it
 *                and/or modify it under the terms of the GNU General
 *                Public License as published by the Free Software
 *                Foundation; either version 2 of the License, or (at
 *                your option) any later version.
 *
 *                This program is distributed in the hope that it will
 *                be useful, but WITHOUT ANY WARRANTY; without even the
 *                implied warranty of MERCHANTABILITY or FITNESS FOR A
 *                PARTICULAR PURPOSE.  See the GNU General Public
 *                License for more details.
 *
 *                The GNU General Public License should be included with
 *                this file.  If not, you can view it at
 *                http://www.gnu.org/copyleft/gpl.html
 *                or write to the Free Software Foundation, Inc., 59
 *                Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * Revisions   :
 *    $L<!-- Break CVS Substitution -->og$
 *
 *********************************************************************/


#include "project.h"

#ifdef __cplusplus
extern "C" {
#endif

   ... function headers here ...


/* Revision control strings from this header and associated .c file */
extern const char FILENAME_rcs[];
extern const char FILENAME_h_rcs[];


#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* ndef _FILENAME_H */

/*
  Local Variables:
  tab-width: 3
  end:
*/
</programlisting>

    <para><emphasis>Example for function comments:</emphasis></para>
<programlisting>
/*********************************************************************
 *
 * Function    :  FUNCTION_NAME
 *
 * Description :  (Fill me in with a good description!)
 *
 * parameters  :
 *          1  :  param1 = pointer to an important thing
 *          2  :  x      = pointer to something else
 *
 * Returns     :  0 => Ok, everything else is an error.
 *
 *********************************************************************/
int FUNCTION_NAME( void *param1, const char *x )
{
   ...
   return( 0 );

}
</programlisting>

    <para><emphasis>Note:</emphasis> If we all follow this practice, we should be
    able to parse our code to create a "self-documenting" web
    page.</para>

  </sect2>

  </sect1>

  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="cvs"><title>Version Control Guidelines</title>
    <para>To be filled. note on cvs comments. don't comment what you did, comment
why you did it.
</para>
  </sect1>

  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="testing"><title>Testing Guidelines</title>
    <para>To be filled.
</para>

    <!--   ~~~~~       New section      ~~~~~     -->
    <sect2 id="testing-plan"><title>Testplan for releases</title>
      <para>
Explain release numbers. major, minor. developer releases. etc.

<orderedlist numeration="arabic">
          <listitem><para>
Remove any existing rpm with rpm -e
</para></listitem>
          <listitem><para>
Remove any file that was left over. This includes (but is not limited to)
      <itemizedlist>
                <listitem><para>/var/log/privoxy</para></listitem>
                <listitem><para>/etc/privoxy</para></listitem>
                <listitem><para>/usr/sbin/privoxy</para></listitem>
                <listitem><para>/etc/init.d/privoxy</para></listitem>
                <listitem><para>/usr/doc/privoxy*</para></listitem>
              </itemizedlist>
</para></listitem>
          <listitem><para>
Install the rpm. Any error messages?
</para></listitem>
          <listitem><para>start,stop,status <application>Privoxy</application> with the specific script
      (e.g. /etc/rc.d/init/privoxy stop). Reboot your machine. Does
      autostart work?</para></listitem>
          <listitem><para>Start browsing. Does <application>Privoxy</application> work? Logfile written?</para></listitem>
          <listitem><para>Remove the rpm. Any error messages? All files removed?</para></listitem>
        </orderedlist>
</para>
    </sect2>

    <!--   ~~~~~       New section      ~~~~~     -->
    <sect2 id="testing-report"><title>Test reports</title>
      <para>
Please submit test reports only with the <ulink url="http://sourceforge.net/tracker/?func=add&amp;group_id=11118&amp;atid=395005">test form</ulink>
at sourceforge. Three simple steps:
        <itemizedlist>
          
          <listitem><para>Select category: the distribution you test on.</para></listitem>
          <listitem><para>Select group: the version of <application>Privoxy</application> that we are about to release.</para></listitem>
          <listitem><para>Fill the Summary and Detailed Description with something
              intelligent (keep it short and precise).</para>
          </listitem>
        </itemizedlist>
        Do not mail to the mailinglist (we cannot keep track on issues there).
      </para>
    </sect2>
    
  </sect1>
  
  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="contact"><title>Contact the developers</title>
    <para>Please see the user manual for information on how to contact the developers.
    </para>
  </sect1>
  
  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="copyright"><title>Copyright and History</title>
    <para>Please see the user manual for information on Copyright and History.
    </para>
  </sect1>
  
  <!--   ~~~~~       New section      ~~~~~     -->
  <sect1 id="seealso"><title>See also</title>
    <para>Please see the user manual for information on references.
    </para>
  </sect1>

  <!--

  This program is free software; you can redistribute it 
  and/or modify it under the terms of the GNU General
  Public License as published by the Free Software
  Foundation; either version 2 of the License, or (at
  your option) any later version.

  This program is distributed in the hope that it will
  be useful, but WITHOUT ANY WARRANTY; without even the
  implied warranty of MERCHANTABILITY or FITNESS FOR A
  PARTICULAR PURPOSE.  See the GNU General Public
  License for more details.

  The GNU General Public License should be included with
  this file.  If not, you can view it at
  http://www.gnu.org/copyleft/gpl.html
  or write to the Free Software Foundation, Inc., 59
  Temple Place - Suite 330, Boston, MA  02111-1307, USA.

  $Log: developer-manual.sgml,v $
  Revision 1.10  2002/03/24 12:33:01  swa
  more additions.

  Revision 1.9  2002/03/24 11:01:05  swa
  name change

  Revision 1.8  2002/03/23 15:13:11  swa
  renamed every reference to the old name with foobar.
  fixed "application foobar application" tag, fixed
  "the foobar" with "foobar". left junkbustser in cvs
  comments and remarks to history untouched.

  Revision 1.7  2002/03/11 13:13:27  swa
  correct feedback channels

  Revision 1.6  2002/02/24 14:25:06  jongfoster
  Formatting changes.  Now changing the doctype to DocBook XML 4.1
  will work - no other changes are needed.

  Revision 1.5  2001/10/31 18:16:51  swa
  documentation added: howto generate docs in text and html
  format, howto move stuff to the webserver.

  Revision 1.4  2001/09/23 10:13:48  swa
  upload process established. run make webserver and
  the documentation is moved to the webserver. documents
  are now linked correctly.

  Revision 1.3  2001/09/13 15:27:40  swa
  cosmetics

  Revision 1.2  2001/09/13 15:20:17  swa
  merged standards into developer manual

  Revision 1.1  2001/09/12 15:36:41  swa
  source files for junkbuster documentation

  Revision 1.3  2001/09/10 17:43:59  swa
  first proposal of a structure.

  Revision 1.2  2001/06/13 14:28:31  swa
  docs should have an author.

  Revision 1.1  2001/06/13 14:20:37  swa
  first import of project's documentation for the webserver.

  -->

</article>