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| -rw-r--r-- | libjpegtwrp/coderules.doc | 118 |
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diff --git a/libjpegtwrp/coderules.doc b/libjpegtwrp/coderules.doc deleted file mode 100644 index 0ab5d9bd3..000000000 --- a/libjpegtwrp/coderules.doc +++ /dev/null @@ -1,118 +0,0 @@ -IJG JPEG LIBRARY: CODING RULES - -Copyright (C) 1991-1996, Thomas G. Lane. -This file is part of the Independent JPEG Group's software. -For conditions of distribution and use, see the accompanying README file. - - -Since numerous people will be contributing code and bug fixes, it's important -to establish a common coding style. The goal of using similar coding styles -is much more important than the details of just what that style is. - -In general we follow the recommendations of "Recommended C Style and Coding -Standards" revision 6.1 (Cannon et al. as modified by Spencer, Keppel and -Brader). This document is available in the IJG FTP archive (see -jpeg/doc/cstyle.ms.tbl.Z, or cstyle.txt.Z for those without nroff/tbl). - -Block comments should be laid out thusly: - -/* - * Block comments in this style. - */ - -We indent statements in K&R style, e.g., - if (test) { - then-part; - } else { - else-part; - } -with two spaces per indentation level. (This indentation convention is -handled automatically by GNU Emacs and many other text editors.) - -Multi-word names should be written in lower case with underscores, e.g., -multi_word_name (not multiWordName). Preprocessor symbols and enum constants -are similar but upper case (MULTI_WORD_NAME). Names should be unique within -the first fifteen characters. (On some older systems, global names must be -unique within six characters. We accommodate this without cluttering the -source code by using macros to substitute shorter names.) - -We use function prototypes everywhere; we rely on automatic source code -transformation to feed prototype-less C compilers. Transformation is done -by the simple and portable tool 'ansi2knr.c' (courtesy of Ghostscript). -ansi2knr is not very bright, so it imposes a format requirement on function -declarations: the function name MUST BEGIN IN COLUMN 1. Thus all functions -should be written in the following style: - -LOCAL(int *) -function_name (int a, char *b) -{ - code... -} - -Note that each function definition must begin with GLOBAL(type), LOCAL(type), -or METHODDEF(type). These macros expand to "static type" or just "type" as -appropriate. They provide a readable indication of the routine's usage and -can readily be changed for special needs. (For instance, special linkage -keywords can be inserted for use in Windows DLLs.) - -ansi2knr does not transform method declarations (function pointers in -structs). We handle these with a macro JMETHOD, defined as - #ifdef HAVE_PROTOTYPES - #define JMETHOD(type,methodname,arglist) type (*methodname) arglist - #else - #define JMETHOD(type,methodname,arglist) type (*methodname) () - #endif -which is used like this: - struct function_pointers { - JMETHOD(void, init_entropy_encoder, (int somearg, jparms *jp)); - JMETHOD(void, term_entropy_encoder, (void)); - }; -Note the set of parentheses surrounding the parameter list. - -A similar solution is used for forward and external function declarations -(see the EXTERN and JPP macros). - -If the code is to work on non-ANSI compilers, we cannot rely on a prototype -declaration to coerce actual parameters into the right types. Therefore, use -explicit casts on actual parameters whenever the actual parameter type is not -identical to the formal parameter. Beware of implicit conversions to "int". - -It seems there are some non-ANSI compilers in which the sizeof() operator -is defined to return int, yet size_t is defined as long. Needless to say, -this is brain-damaged. Always use the SIZEOF() macro in place of sizeof(), -so that the result is guaranteed to be of type size_t. - - -The JPEG library is intended to be used within larger programs. Furthermore, -we want it to be reentrant so that it can be used by applications that process -multiple images concurrently. The following rules support these requirements: - -1. Avoid direct use of file I/O, "malloc", error report printouts, etc; -pass these through the common routines provided. - -2. Minimize global namespace pollution. Functions should be declared static -wherever possible. (Note that our method-based calling conventions help this -a lot: in many modules only the initialization function will ever need to be -called directly, so only that function need be externally visible.) All -global function names should begin with "jpeg_", and should have an -abbreviated name (unique in the first six characters) substituted by macro -when NEED_SHORT_EXTERNAL_NAMES is set. - -3. Don't use global variables; anything that must be used in another module -should be in the common data structures. - -4. Don't use static variables except for read-only constant tables. Variables -that should be private to a module can be placed into private structures (see -the system architecture document, structure.doc). - -5. Source file names should begin with "j" for files that are part of the -library proper; source files that are not part of the library, such as cjpeg.c -and djpeg.c, do not begin with "j". Keep source file names to eight -characters (plus ".c" or ".h", etc) to make life easy for MS-DOSers. Keep -compression and decompression code in separate source files --- some -applications may want only one half of the library. - -Note: these rules (particularly #4) are not followed religiously in the -modules that are used in cjpeg/djpeg but are not part of the JPEG library -proper. Those modules are not really intended to be used in other -applications. |