X-Git-Url: http://www.privoxy.org/gitweb/?p=privoxy.git;a=blobdiff_plain;f=doc%2Fwebserver%2Fdeveloper-manual%2Fcoding.html;fp=doc%2Fwebserver%2Fdeveloper-manual%2Fcoding.html;h=d3a94f4fe47cb14e8c6d6d15129a016519265b89;hp=fb4208fe2fd4b7361069d5c91296190966283eff;hb=61a5d3fc15169d9f6b0c21e3a56d893f4d672eb4;hpb=659cbbc13f413ed0c5dacd4d03060f48eb500011 diff --git a/doc/webserver/developer-manual/coding.html b/doc/webserver/developer-manual/coding.html index fb4208fe..d3a94f4f 100644 --- a/doc/webserver/developer-manual/coding.html +++ b/doc/webserver/developer-manual/coding.html @@ -1,161 +1,57 @@ - -Coding Guidelines
Privoxy Developer Manual
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4. Coding Guidelines

4.1. Introduction

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 - Privoxy" consistent and reliable. Thus making - maintenance easier and increasing chances of success of the - project.

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. ;->

4.2. Using Comments

4.2.1. Comment, Comment, Comment

Explanation:

Comment as much as possible without commenting the obvious. - For example do not comment "variable_a is equal to variable_b". - Instead explain why variable_a should be equal to the variable_b. - 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 fellow Privoxy developers out!

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.

Example:

+ +
  /* if page size greater than 1k ... */
+
+
+
+  Coding Guidelines
+  
+  
+  
+  
+  
+  
+
+
+  
+  
+

4. Coding Guidelines

+
+

4.1. Introduction

+

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 Privoxy" consistent and reliable. Thus making + maintenance easier and increasing chances of success of the project.

+

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. ;->

+
+
+

4.2. Using Comments

+
+

4.2.1. Comment, Comment, Comment

+

Explanation:

+

Comment as much as possible without commenting the obvious. For example do not comment "variable_a is equal + to variable_b". Instead explain why variable_a should be equal to the variable_b. 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 fellow Privoxy developers out!

+

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.

+

Example:

+ + +
+
  /* if page size greater than 1k ... */
   if (page_length() > 1024)
   {
       ... "block" the page up ...
@@ -169,50 +65,22 @@ CLASS="PROGRAMLISTING"
 
   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.

4.2.2. Use blocks for comments

Explanation:

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.

Example:

+ +
  /*********************************************************************
+  is actually being done.
+
+
+
+

4.2.2. Use blocks for comments

+

Explanation:

+

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.

+

Example:

+ + +
+
  /*********************************************************************
    * This will stand out clearly in your code!
    *********************************************************************/
   if (this_variable == that_variable)
@@ -231,65 +99,26 @@ CLASS="PROGRAMLISTING"
   if (this_variable == that_variable) /* this may not either */
   {
      do_something_very_important();
-  }

Exception:

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

4.2.3. Keep Comments on their own line

Explanation:

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.

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.

Example:

+ +
  /*********************************************************************
+  }
+
+

Exception:

+

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

+
+
+

4.2.3. Keep Comments on their own line

+

Explanation:

+

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.

+

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.

+

Example:

+ + +
+
  /*********************************************************************
    * This will stand out clearly in your code,
    * But the second example won't.
    *********************************************************************/
@@ -322,116 +151,46 @@ CLASS="PROGRAMLISTING"
   {
      ...code here...
 
-  }   /* -END- do_something_very_important */

4.2.4. Comment each logical step

Explanation:

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

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.

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

4.2.5. Comment All Functions Thoroughly

Explanation:

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.

4.2.6. Comment at the end of braces if the - content is more than one screen length

Explanation:

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.

As a suggestion , use the following flags to make the - comment and its brace more readable:

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

Example:

+ +
  if (1 == X)
+  }   /* -END- do_something_very_important */
+
+
+
+

4.2.4. Comment each logical step

+

Explanation:

+

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

+

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.

+

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

+
+
+

4.2.5. Comment All Functions Thoroughly

+

Explanation:

+

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.

+
+
+

4.2.6. Comment at the end of braces if the content is more than one + screen length

+

Explanation:

+

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.

+

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

+

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

+

Example:

+ + +
+
  if (1 == X)
   {
      do_something_very_important();
      ...some long list of commands...
@@ -443,724 +202,272 @@ CLASS="PROGRAMLISTING"
   {
      do_something_very_important();
      ...some long list of commands...
-  } /* -END- if (1 == X) */

4.3. Naming Conventions

4.3.1. Variable Names

Explanation:

Use all lowercase, and separate 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++.

Example:

  int ms_iis5_hack = 0;

Instead of:

  int msiis5hack = 0; int msIis5Hack = 0;

4.3.2. Function Names

Explanation:

Use all lowercase, and separate 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++.

Example:

  int load_some_file(struct client_state *csp)

Instead of:

  int loadsomefile(struct client_state *csp)
-  int loadSomeFile(struct client_state *csp)

4.3.3. Header file prototypes

Explanation:

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.

Example:

  (.h) extern int load_aclfile(struct client_state *csp);
-  (.c) int load_aclfile(struct client_state *csp)

Instead of:

+ +
  (.h) extern int load_aclfile(struct client_state *); or
+  } /* -END- if (1 == X) */
+
+
+
+
+

4.3. Naming Conventions

+
+

4.3.1. Variable Names

+

Explanation:

+

Use all lowercase, and separate 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++.

+

Example:

+ + + + +
+
  int ms_iis5_hack = 0;
+
+

Instead of:

+ + + + +
+
  int msiis5hack = 0; int msIis5Hack = 0;
+
+
+
+

4.3.2. Function Names

+

Explanation:

+

Use all lowercase, and separate 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++.

+

Example:

+ + + + +
+
  int load_some_file(struct client_state *csp)
+
+

Instead of:

+ + + + +
+
  int loadsomefile(struct client_state *csp)
+  int loadSomeFile(struct client_state *csp)
+
+
+
+

4.3.3. Header file prototypes

+

Explanation:

+

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.

+

Example:

+ + + + +
+
  (.h) extern int load_aclfile(struct client_state *csp);
+  (.c) int load_aclfile(struct client_state *csp)
+
+

Instead of:

+ + +
+
  (.h) extern int load_aclfile(struct client_state *); or
   (.h) extern int load_aclfile();
-  (.c) int load_aclfile(struct client_state *csp)

4.3.4. Enumerations, and #defines

Explanation:

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.)

Example:

  (enumeration) : enum Boolean {FALSE, TRUE};
-  (#define) : #define DEFAULT_SIZE 100;

Note: 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.

Example:

+ +
  #define FEATURE_FORCE 1
+  (.c) int load_aclfile(struct client_state *csp)
+
+
+
+

4.3.4. Enumerations, and #defines

+

Explanation:

+

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.)

+

Example:

+ + + + +
+
  (enumeration) : enum Boolean {FALSE, TRUE};
+  (#define) : #define DEFAULT_SIZE 100;
+
+

Note: 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.

+

Example:

+ + +
+
  #define FEATURE_FORCE 1
 
   #ifdef FEATURE_FORCE
   #define FORCE_PREFIX blah
-  #endif /* def FEATURE_FORCE */

4.3.5. Constants

Explanation:

Spell common words out entirely (do not remove vowels).

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

Use underscore (_) to separate adjacent acronyms and - abbreviations. Never terminate a name with an underscore.

Example:

  #define USE_IMAGE_LIST 1

Instead of:

+ +
  #define USE_IMG_LST 1 or
+  #endif /* def FEATURE_FORCE */
+
+
+
+

4.3.5. Constants

+

Explanation:

+

Spell common words out entirely (do not remove vowels).

+

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

+

Use underscore (_) to separate adjacent acronyms and abbreviations. Never terminate a name with an + underscore.

+

Example:

+ + + + +
+
  #define USE_IMAGE_LIST 1
+
+

Instead of:

+ + +
+
  #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

4.4. Using Space

4.4.1. Put braces on a line by themselves.

Explanation:

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.

Example:

+ +
  if (this == that)
+  #define UseImageList 1
+
+
+
+
+

4.4. Using Space

+
+

4.4.1. Put braces on a line by themselves.

+

Explanation:

+

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.

+

Example:

+ + +
+
  if (this == that)
   {
      ...
-  }

Instead of:

if (this == that) { ... }

or

if (this == that) { ... }

Note: In the special case that the if-statement is - inside a loop, and it is trivial, i.e. it tests for a - condition 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.

Status: developer-discretion.

Example exception:

+ +
  while (more lines are read)
+  }
+
+

Instead of:

+

if (this == that) { ... }

+

or

+

if (this == that) { ... }

+

Note: In the special case that the if-statement is + inside a loop, and it is trivial, i.e. it tests for a condition 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.

+

Status: developer-discretion.

+

Example exception:

+ + +
+
  while (more lines are read)
   {
      /* Please document what is/is not a comment line here */
      if (it's a comment) continue;
 
      do_something(line);
-  }

4.4.2. ALL control statements should have a - block

Explanation:

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.

Example:

+ +
  if (this == that)
+  }
+
+
+
+

4.4.2. ALL control statements should have a block

+

Explanation:

+

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.

+

Example:

+ + +
+
  if (this == that)
   {
      do_something();
      do_something_else();
-  }

Instead of:

if (this == that) do_something(); do_something_else();

or

if (this == that) do_something();

Note: 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.

4.4.3. Do not belabor/blow-up boolean - expressions

Example:

  structure->flag = (condition);

Instead of:

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

Note: The former is readable and concise. 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-)

4.4.4. Use white space freely because it is - free

Explanation:

Make it readable. The notable exception to using white space - freely is listed in the next guideline.

Example:

+ +
  int first_value   = 0;
+  }
+
+

Instead of:

+

if (this == that) do_something(); do_something_else();

+

or

+

if (this == that) do_something();

+

Note: 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.

+
+
+

4.4.3. Do not belabor/blow-up boolean expressions

+

Example:

+ + + + +
+
  structure->flag = (condition);
+
+

Instead of:

+

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

+

Note: The former is readable and concise. 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-)

+
+
+

4.4.4. Use white space freely because it is free

+

Explanation:

+

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

+

Example:

+ + +
+
  int first_value   = 0;
   int some_value    = 0;
   int another_value = 0;
-  int this_variable = 0;

4.4.5. Don't use white space around structure - operators

Explanation:

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

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.

Example:

+ +
  a_struct->a_member;
+  int this_variable = 0;
+
+
+
+

4.4.5. Don't use white space around structure operators

+

Explanation:

+

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

+

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.

+

Example:

+ + +
+
  a_struct->a_member;
   a_struct.a_member;
-  function_name();

Instead of: a_struct -> a_member; a_struct . a_member; - function_name ();

4.4.6. Make the last brace of a function stand - out

Example:

+ +
  int function1( ... )
+  function_name();
+
+

Instead of: a_struct -> a_member; a_struct . + a_member; function_name ();

+
+
+

4.4.6. Make the last brace of a function stand out

+

Example:

+ + +
+
  int function1( ... )
   {
      ...code...
      return(ret_code);
@@ -1170,83 +477,30 @@ CLASS="PROGRAMLISTING"
 
   int function2( ... )
   {
-  } /* -END- function2 */

Instead of:

int function1( ... ) { ...code... return(ret_code); } int - function2( ... ) { }

Note: Use 1 blank line before the closing brace and 2 - lines afterward. This makes the end of function standout to - the most casual viewer. Although function comments help - separate 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!

Status: developer-discretion on the number of blank - lines. Enforced is the end of function comments.

4.4.7. Use 3 character indentions

Explanation:

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.

Example:

+ +
  static const char * const url_code_map[256] =
+  } /* -END- function2 */
+
+

Instead of:

+

int function1( ... ) { ...code... return(ret_code); } int function2( ... ) { }

+

Note: Use 1 blank line before the closing brace and 2 + lines afterward. This makes the end of function standout to the most casual viewer. Although function comments + help separate 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!

+

Status: developer-discretion on the number of blank + lines. Enforced is the end of function comments.

+
+
+

4.4.7. Use 3 character indentions

+

Explanation:

+

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.

+

Example:

+ + +
+
  static const char * const url_code_map[256] =
   {
      NULL, ...
   };
@@ -1265,475 +519,174 @@ CLASS="PROGRAMLISTING"
 
      return NEVER_GETS_HERE;
 
-  }

4.5. Initializing

4.5.1. Initialize all variables

Explanation:

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.

Example:

+ +
  short a_short = 0;
+  }
+
+
+
+
+

4.5. Initializing

+
+

4.5.1. Initialize all variables

+

Explanation:

+

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.

+

Example:

+ + +
+
  short a_short = 0;
   float a_float  = 0;
-  struct *ptr = NULL;

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

Status: developer-discretion if and only if the - variable is assigned a value "shortly after" declaration.

4.6. Functions

4.6.1. Name functions that return a boolean as a - question.

Explanation:

Value should be phrased as a question that would logically - be answered as a true or false statement

Example:

+ +
  should_we_block_this();
+  struct *ptr = NULL;
+
+

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

+

Status: developer-discretion if and only if the + variable is assigned a value "shortly after" declaration.

+
+
+
+

4.6. Functions

+
+

4.6.1. Name functions that return a boolean as a question.

+

Explanation:

+

Value should be phrased as a question that would logically be answered as a true or false statement

+

Example:

+ + +
+
  should_we_block_this();
   contains_an_image();
-  is_web_page_blank();

4.6.2. Always specify a return type for a - function.

Explanation:

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.

4.6.3. Minimize function calls when iterating by - using variables

Explanation:

It is easy to write the following code, and a clear argument - can be made that the code is easy to understand:

Example:

+ +
  for (size_t cnt = 0; cnt < block_list_length(); cnt++)
+  is_web_page_blank();
+
+
+
+

4.6.2. Always specify a return type for a function.

+

Explanation:

+

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.

+
+
+

4.6.3. Minimize function calls when iterating by using + variables

+

Explanation:

+

It is easy to write the following code, and a clear argument can be made that the code is easy to + understand:

+

Example:

+ + +
+
  for (size_t cnt = 0; cnt < block_list_length(); cnt++)
   {
      ....
-  }

Note: 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 block_list_length() 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 block_list_length() is a function - call, with the same overhead.

Instead of using a function call during the iterations, - assign the value to a variable, and evaluate using the - variable.

Example:

+ +
  size_t len = block_list_length();
+  }
+
+

Note: 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 block_list_length() 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 block_list_length() is a function call, + with the same overhead.

+

Instead of using a function call during the iterations, assign the value to a variable, and evaluate using + the variable.

+

Example:

+ + +
+
  size_t len = block_list_length();
 
   for (size_t cnt = 0; cnt < len; cnt++)
   {
      ....
-  }

Exceptions: if the value of block_list_length() - *may* change or could *potentially* change, then you must code the - function call in the for/while loop.

4.6.4. Pass and Return by Const Reference

Explanation:

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);

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

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

4.6.5. Pass and Return by Value

Explanation:

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)

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

4.6.6. Names of include files

Explanation:

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.

Example:

  #include <iostream.h>     /* This is not a local include */
-  #include "config.h"       /* This IS a local include */

Exception:

  /* This is not a local include, but requires a path element. */
-  #include <sys/fileName.h>

Note: Please! do not add "-I." to the Makefile - without a _very_ good reason. This duplicates the #include - "file.h" behavior.

4.6.7. Provide multiple inclusion - protection

Explanation:

Prevents compiler and linker errors resulting from - redefinition of items.

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.

Example:

+ +
  #ifndef PROJECT_H_INCLUDED
+  }
+
+

Exceptions: if the value of block_list_length() *may* + change or could *potentially* change, then you must code the function call in the for/while loop.

+
+
+

4.6.4. Pass and Return by Const Reference

+

Explanation:

+

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);

+

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

+

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

+
+
+

4.6.5. Pass and Return by Value

+

Explanation:

+

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)

+

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

+
+
+

4.6.6. Names of include files

+

Explanation:

+

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.

+

Example:

+ + + + +
+
  #include <iostream.h>     /* This is not a local include */
+  #include "config.h"       /* This IS a local include */
+
+

Exception:

+ + + + +
+
  /* This is not a local include, but requires a path element. */
+  #include <sys/fileName.h>
+
+

Note: Please! do not add "-I." to the Makefile without + a _very_ good reason. This duplicates the #include "file.h" behavior.

+
+
+

4.6.7. Provide multiple inclusion protection

+

Explanation:

+

Prevents compiler and linker errors resulting from redefinition of items.

+

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.

+

Example:

+ + +
+
  #ifndef PROJECT_H_INCLUDED
   #define PROJECT_H_INCLUDED
    ...
-  #endif /* ndef PROJECT_H_INCLUDED */

4.6.8. Use `extern "C"` when appropriate

Explanation:

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.

Example:

+ +
  #ifdef __cplusplus
+  #endif /* ndef PROJECT_H_INCLUDED */
+
+
+
+

4.6.8. Use `extern "C"` when appropriate

+

Explanation:

+

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.

+

Example:

+ + +
+
  #ifdef __cplusplus
   extern "C"
   {
   #endif /* def __cplusplus */
@@ -1742,145 +695,54 @@ CLASS="PROGRAMLISTING"
 
   #ifdef __cplusplus
   }
-  #endif /* def __cplusplus */

4.6.9. Where Possible, Use Forward Struct - Declaration Instead of Includes

Explanation:

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

Example:

+ +
  /*********************************************************************
+  #endif /* def __cplusplus */
+
+
+
+

4.6.9. Where Possible, Use Forward Struct Declaration Instead of + Includes

+

Explanation:

+

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

+

Example:

+ + +
+
  /*********************************************************************
    * We're avoiding an include statement here!
    *********************************************************************/
   struct file_list;
-  extern file_list *xyz;

Note: 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 unnecessary.

Status: Use with discretion.

4.7. General Coding Practices

4.7.1. Turn on warnings

Explanation

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.

4.7.2. Provide a default case for all switch - statements

Explanation:

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.

Example:

+ +
  switch (hash_string(cmd))
+  extern file_list *xyz;
+
+

Note: 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 unnecessary.

+

Status: Use with discretion.

+
+
+
+

4.7. General Coding Practices

+
+

4.7.1. Turn on warnings

+

Explanation

+

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.

+
+
+

4.7.2. Provide a default case for all switch statements

+

Explanation:

+

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.

+

Example:

+ + +
+
  switch (hash_string(cmd))
   {
      case hash_actions_file:
         ... code ...
@@ -1895,402 +757,135 @@ CLASS="PROGRAMLISTING"
         ... anomaly code goes here ...
         continue; / break; / exit( 1 ); / etc ...
 
-  } /* end switch (hash_string(cmd)) */

Note: 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.

Another Note: This is not so much a readability issue - as a robust programming issue. The "anomaly code goes here" may - be no more than a print to the STDERR stream (as in - load_config). Or it may really be an abort condition.

Status: Programmer discretion is advised.

4.7.3. Try to avoid falling through cases in a - switch statement.

Explanation:

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.

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.

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.

4.7.4. Don't mix size_t and other types

Explanation:

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.

4.7.5. Declare each variable and struct on its - own line.

Explanation:

It can be tempting to declare a series of variables all on - one line. Don't.

Example:

+ +
  long a = 0;
+  } /* end switch (hash_string(cmd)) */
+
+

Note: 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.

+

Another Note: This is not so much a readability issue + as a robust programming issue. The "anomaly code goes here" may be no more than a print to the STDERR stream + (as in load_config). Or it may really be an abort condition.

+

Status: Programmer discretion is advised.

+
+
+

4.7.3. Try to avoid falling through cases in a switch + statement.

+

Explanation:

+

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.

+

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.

+

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.

+
+
+

4.7.4. Don't mix size_t and other types

+

Explanation:

+

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.

+
+
+

4.7.5. Declare each variable and struct on its own line.

+

Explanation:

+

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

+

Example:

+ + +
+
  long a = 0;
   long b = 0;
-  long c = 0;

Instead of:

long a, b, c;

Explanation: - 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

Exceptions: when you want to declare a bunch of loop - variables or other trivial variables; feel free to declare them - on one line. You should, although, provide a good comment on - their functions.

Status: developer-discretion.

4.7.6. Use malloc/zalloc sparingly

Explanation:

Create a local struct (on the stack) if the variable will - live and die within the context of one function call.

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

Example:

  If a function creates a struct and stores a pointer to it in a
-  list, then it should definitely be allocated via `malloc'.

4.7.7. The Programmer Who Uses 'malloc' is - Responsible for Ensuring 'free'

Explanation:

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/destructor type function to accommodate this.

Example:

  int load_re_filterfile(struct client_state *csp) { ... }
-  static void unload_re_filterfile(void *f) { ... }

Exceptions:

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

Status: developer-discretion. The "main" use of this - standard is for allocating and freeing data structures (complex - or nested).

4.7.8. Add loaders to the `file_list' structure - and in order

Explanation:

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.

Note: 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.

4.7.9. "Uncertain" new code and/or changes to - existing code, use XXX

Explanation:

If you have enough confidence in new code or confidence in - your changes, but are not *quite* sure of the repercussions, - add this:

/* XXX: this code has a logic error on platform XYZ, * - attempting to fix */ #ifdef PLATFORM ...changed code here... - #endif

or:

/* XXX: I think the original author really meant this... - */ ...changed code here...

or:

/* XXX: new code that *may* break something else... */ - ...new code here...

Note: 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 conversely exclude from the - project).

4.8. Addendum: Template for files and function - comment blocks:

Example for file comments:

+ +
  /*********************************************************************
+  long c = 0;
+
+

Instead of:

+

long a, b, c;

+

Explanation: - 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

+

Exceptions: when you want to declare a bunch of loop + variables or other trivial variables; feel free to declare them on one line. You should, although, provide a + good comment on their functions.

+

Status: developer-discretion.

+
+
+

4.7.6. Use malloc/zalloc sparingly

+

Explanation:

+

Create a local struct (on the stack) if the variable will live and die within the context of one function + call.

+

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

+

Example:

+ + + + +
+
  If a function creates a struct and stores a pointer to it in a
+  list, then it should definitely be allocated via `malloc'.
+
+
+
+

4.7.7. The Programmer Who Uses 'malloc' is Responsible for Ensuring + 'free'

+

Explanation:

+

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/destructor type function to accommodate this.

+

Example:

+ + + + +
+
  int load_re_filterfile(struct client_state *csp) { ... }
+  static void unload_re_filterfile(void *f) { ... }
+
+

Exceptions:

+

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

+

Status: developer-discretion. The "main" use of this + standard is for allocating and freeing data structures (complex or nested).

+
+
+

4.7.8. Add loaders to the `file_list' structure and in order

+

Explanation:

+

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.

+

Note: 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.

+
+
+

4.7.9. "Uncertain" new code and/or changes to existing code, use + XXX

+

Explanation:

+

If you have enough confidence in new code or confidence in your changes, but are not *quite* sure of the + repercussions, add this:

+

/* XXX: this code has a logic error on platform XYZ, * attempting to fix */ #ifdef PLATFORM ...changed code + here... #endif

+

or:

+

/* XXX: I think the original author really meant this... */ ...changed code here...

+

or:

+

/* XXX: new code that *may* break something else... */ ...new code here...

+

Note: 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 conversely exclude from the + project).

+
+
+
+

4.8. Addendum: Template for files and function comment blocks:

+

Example for file comments:

+ + +
+
  /*********************************************************************
    *
    * File        :  $Source
    *
@@ -2325,50 +920,21 @@ CLASS="PROGRAMLISTING"
 
      ...necessary include files for us to do our work...
 
-  const char FILENAME_h_rcs[] = FILENAME_H_VERSION;

Note: This declares the rcs variables that should be - added to the "show-version" 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.

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

Example for file header comments:

+ +
  #ifndef _FILENAME_H
+  const char FILENAME_h_rcs[] = FILENAME_H_VERSION;
+
+

Note: This declares the rcs variables that should be + added to the "show-version" 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.

+

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

+

Example for file header comments:

+ + +
+
  #ifndef _FILENAME_H
   #define _FILENAME_H
   /*********************************************************************
    *
@@ -2425,27 +991,15 @@ CLASS="PROGRAMLISTING"
     Local Variables:
     tab-width: 3
     end:
-  */

Example for function comments:

+ +
  /*********************************************************************
+  */
+
+

Example for function comments:

+ + +
+
  /*********************************************************************
    *
    * Function    :  FUNCTION_NAME
    *
@@ -2463,80 +1017,28 @@ CLASS="PROGRAMLISTING"
      ...
      return 0;
 
-  }

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


PrevHomeNext
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\ No newline at end of file + }
+
+

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

+
+
+ + +