mirror of https://github.com/axmolengine/axmol.git
79 lines
3.4 KiB
Plaintext
79 lines
3.4 KiB
Plaintext
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IJG JPEG LIBRARY: CODING RULES
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This file was part of the Independent JPEG Group's software:
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Copyright (C) 1991-1996, Thomas G. Lane.
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It was modified by The libjpeg-turbo Project to include only information
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relevant to libjpeg-turbo.
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For conditions of distribution and use, see the accompanying README.ijg file.
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Since numerous people will be contributing code and bug fixes, it's important
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to establish a common coding style. The goal of using similar coding styles
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is much more important than the details of just what that style is.
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In general we follow the recommendations of "Recommended C Style and Coding
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Standards" revision 6.1 (Cannon et al. as modified by Spencer, Keppel and
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Brader). This document is available in the IJG FTP archive (see
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jpeg/doc/cstyle.ms.tbl.Z, or cstyle.txt.Z for those without nroff/tbl).
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Block comments should be laid out thusly:
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/*
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* Block comments in this style.
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*/
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We indent statements in K&R style, e.g.,
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if (test) {
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then-part;
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} else {
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else-part;
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}
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with two spaces per indentation level. (This indentation convention is
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handled automatically by GNU Emacs and many other text editors.)
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Multi-word names should be written in lower case with underscores, e.g.,
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multi_word_name (not multiWordName). Preprocessor symbols and enum constants
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are similar but upper case (MULTI_WORD_NAME). Names should be unique within
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the first fifteen characters.
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Note that each function definition must begin with GLOBAL(type), LOCAL(type),
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or METHODDEF(type). These macros expand to "static type" or just "type" as
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appropriate. They provide a readable indication of the routine's usage and
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can readily be changed for special needs. (For instance, special linkage
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keywords can be inserted for use in Windows DLLs.)
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A similar solution is used for external function declarations (see the EXTERN
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macro.)
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The JPEG library is intended to be used within larger programs. Furthermore,
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we want it to be reentrant so that it can be used by applications that process
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multiple images concurrently. The following rules support these requirements:
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1. Avoid direct use of file I/O, "malloc", error report printouts, etc;
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pass these through the common routines provided.
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2. Minimize global namespace pollution. Functions should be declared static
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wherever possible. (Note that our method-based calling conventions help this
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a lot: in many modules only the initialization function will ever need to be
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called directly, so only that function need be externally visible.) All
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global function names should begin with "jpeg_".
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3. Don't use global variables; anything that must be used in another module
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should be in the common data structures.
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4. Don't use static variables except for read-only constant tables. Variables
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that should be private to a module can be placed into private structures (see
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the system architecture document, structure.txt).
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5. Source file names should begin with "j" for files that are part of the
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library proper; source files that are not part of the library, such as cjpeg.c
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and djpeg.c, do not begin with "j". Keep compression and decompression code in
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separate source files --- some applications may want only one half of the
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library.
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Note: these rules (particularly #4) are not followed religiously in the
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modules that are used in cjpeg/djpeg but are not part of the JPEG library
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proper. Those modules are not really intended to be used in other
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applications.
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