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Diffstat (limited to 'coderules.txt')
| -rw-r--r-- | coderules.txt | 53 |
1 files changed, 11 insertions, 42 deletions
diff --git a/coderules.txt b/coderules.txt index 6ee7f5e..f36d5f8 100644 --- a/coderules.txt +++ b/coderules.txt @@ -1,7 +1,11 @@ + + IJG JPEG LIBRARY: CODING RULES Copyright (C) 1991-1996, Thomas G. Lane. -This file is part of the Independent JPEG Group's software. +This file was part of the Independent JPEG Group's software. +It was modified by The libjpeg-turbo Project to include only information +relevant to libjpeg-turbo. For conditions of distribution and use, see the accompanying README file. @@ -32,22 +36,7 @@ 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... -} +the first fifteen characters. 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 @@ -55,27 +44,8 @@ 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". +A similar solution is used for external function declarations (see the EXTERN +macro.) 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, @@ -105,10 +75,9 @@ the system architecture document, structure.txt). 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. +and djpeg.c, do not begin with "j". 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 |