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+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 6. Coding Suggestions</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="internals.html" title="Chapter 5. Samba Internals"><link rel="next" href="contributing.html" title="Chapter 7. Contributing code"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 6. Coding Suggestions</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="internals.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="contributing.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="CodingSuggestions"></a>Chapter 6. Coding Suggestions</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Steve</span> <span class="surname">French</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Simo</span> <span class="surname">Sorce</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Andrew</span> <span class="surname">Bartlett</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Tim</span> <span class="surname">Potter</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Martin</span> <span class="surname">Pool</span></h3></div></div></div></div><p>
+So you want to add code to Samba ...
+</p><p>
+One of the daunting tasks facing a programmer attempting to write code for
+Samba is understanding the various coding conventions used by those most
+active in the project. These conventions were mostly unwritten and helped
+improve either the portability, stability or consistency of the code. This
+document will attempt to document a few of the more important coding
+practices used at this time on the Samba project. The coding practices are
+expected to change slightly over time, and even to grow as more is learned
+about obscure portability considerations. Two existing documents
+<code class="filename">samba/source/internals.doc</code> and
+<code class="filename">samba/source/architecture.doc</code> provide
+additional information.
+</p><p>
+The loosely related question of coding style is very personal and this
+document does not attempt to address that subject, except to say that I
+have observed that eight character tabs seem to be preferred in Samba
+source. If you are interested in the topic of coding style, two oft-quoted
+documents are:
+</p><p>
+<a href="http://lxr.linux.no/source/Documentation/CodingStyle" target="_top">http://lxr.linux.no/source/Documentation/CodingStyle</a>
+</p><p>
+<a href="http://www.fsf.org/prep/standards_toc.html" target="_top">http://www.fsf.org/prep/standards_toc.html</a>
+</p><p>
+But note that coding style in Samba varies due to the many different
+programmers who have contributed.
+</p><p>
+Following are some considerations you should use when adding new code to
+Samba. First and foremost remember that:
+</p><p>
+Portability is a primary consideration in adding function, as is network
+compatability with de facto, existing, real world CIFS/SMB implementations.
+There are lots of platforms that Samba builds on so use caution when adding
+a call to a library function that is not invoked in existing Samba code.
+Also note that there are many quite different SMB/CIFS clients that Samba
+tries to support, not all of which follow the SNIA CIFS Technical Reference
+(or the earlier Microsoft reference documents or the X/Open book on the SMB
+Standard) perfectly.
+</p><p>
+Here are some other suggestions:
+</p><div class="orderedlist"><ol type="1"><li><p>
+ use d_printf instead of printf for display text
+ reason: enable auto-substitution of translated language text
+</p></li><li><p>
+ use SAFE_FREE instead of free
+ reason: reduce traps due to null pointers
+</p></li><li><p>
+ don't use bzero use memset, or ZERO_STRUCT and ZERO_STRUCTP macros
+ reason: not POSIX
+</p></li><li><p>
+ don't use strcpy and strlen (use safe_* equivalents)
+ reason: to avoid traps due to buffer overruns
+</p></li><li><p>
+ don't use getopt_long, use popt functions instead
+ reason: portability
+</p></li><li><p>
+ explicitly add const qualifiers on parm passing in functions where parm
+ is input only (somewhat controversial but const can be #defined away)
+</p></li><li><p>
+ when passing a va_list as an arg, or assigning one to another
+ please use the VA_COPY() macro
+ reason: on some platforms, va_list is a struct that must be
+ initialized in each function...can SEGV if you don't.
+</p></li><li><p>
+ discourage use of threads
+ reason: portability (also see architecture.doc)
+</p></li><li><p>
+ don't explicitly include new header files in C files - new h files
+ should be included by adding them once to includes.h
+ reason: consistency
+</p></li><li><p>
+ don't explicitly extern functions (they are autogenerated by
+ "make proto" into proto.h)
+ reason: consistency
+</p></li><li><p>
+ use endian safe macros when unpacking SMBs (see byteorder.h and
+ internals.doc)
+ reason: not everyone uses Intel
+</p></li><li><p>
+ Note Unicode implications of charset handling (see internals.doc). See
+ pull_* and push_* and convert_string functions.
+ reason: Internationalization
+</p></li><li><p>
+ Don't assume English only
+ reason: See above
+</p></li><li><p>
+ Try to avoid using in/out parameters (functions that return data which
+ overwrites input parameters)
+ reason: Can cause stability problems
+</p></li><li><p>
+ Ensure copyright notices are correct, don't append Tridge's name to code
+ that he didn't write. If you did not write the code, make sure that it
+ can coexist with the rest of the Samba GPLed code.
+</p></li><li><p>
+ Consider usage of DATA_BLOBs for length specified byte-data.
+ reason: stability
+</p></li><li><p>
+ Take advantage of tdbs for database like function
+ reason: consistency
+</p></li><li><p>
+ Don't access the SAM_ACCOUNT structure directly, they should be accessed
+ via pdb_get...() and pdb_set...() functions.
+ reason: stability, consistency
+</p></li><li><p>
+ Don't check a password directly against the passdb, always use the
+ check_password() interface.
+ reason: long term pluggability
+</p></li><li><p>
+ Try to use asprintf rather than pstrings and fstrings where possible
+</p></li><li><p>
+ Use normal C comments / * instead of C++ comments // like
+ this. Although the C++ comment format is part of the C99
+ standard, some older vendor C compilers do not accept it.
+</p></li><li><p>
+ Try to write documentation for API functions and structures
+ explaining the point of the code, the way it should be used, and
+ any special conditions or results. Mark these with a double-star
+ comment start / ** so that they can be picked up by Doxygen, as in
+ this file.
+</p></li><li><p>
+ Keep the scope narrow. This means making functions/variables
+ static whenever possible. We don't want our namespace
+ polluted. Each module should have a minimal number of externally
+ visible functions or variables.
+</p></li><li><p>
+ Use function pointers to keep knowledge about particular pieces of
+ code isolated in one place. We don't want a particular piece of
+ functionality to be spread out across lots of places - that makes
+ for fragile, hand to maintain code. Instead, design an interface
+ and use tables containing function pointers to implement specific
+ functionality. This is particularly important for command
+ interpreters.
+</p></li><li><p>
+ Think carefully about what it will be like for someone else to add
+ to and maintain your code. If it would be hard for someone else to
+ maintain then do it another way.
+</p></li></ol></div><p>
+The suggestions above are simply that, suggestions, but the information may
+help in reducing the routine rework done on new code. The preceeding list
+is expected to change routinely as new support routines and macros are
+added.
+</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="internals.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="contributing.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 5. Samba Internals </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 7. Contributing code</td></tr></table></div></body></html>
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