+++ /dev/null
-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.
projects / synfig.git / blobdiff