... instead of the RSA code, the license for which contains an
advertising clause. It is strongly believed that the RSA advertising
clause is innocuous, because:
- A clarification from RSA
(http://www.ietf.org/ietf-ftp/IPR/RSA-MD-all), published in 2000,
stated:
"Implementations of these message-digest algorithms, including
implementations derived from the reference C code in RFC-1319,
RFC-1320, and RFC-1321, may be made, used, and sold without license
from RSA for any purpose."
Referring to the opinion from Fedora's legal team
(https://fedoraproject.org/wiki/Licensing:FAQ?rd=Licensing/FAQ#What_about_the_RSA_license_on_their_MD5_implementation.3F_Isn.27t_that_GPL-incompatible.3F),
this means that md5.c and md5.h, which were derived from the original
RFC 1321 reference code (http://www.faqs.org/rfcs/rfc1321.html), can
be used without the RSA license.
- In the context of libjpeg-turbo, RSA's MD5 code was used only in the
build/test system. It was not part of the libjpeg-turbo binary
distribution, and thus the only "material mentioning or referencing"
the MD5 code was the libjpeg-turbo source code, which-- by virtue of
including RSA's original copyright headers-- properly attributed the
code as required under the RSA license.
However, in light of the open source community's tendency to have
knee-jerk reactions to stuff like this, it would've been necessary to
include the above explanation in our source tree in order to head off
potential FUD, and a simple fix is always better than a complex
explanation.
This commit also assigns the 3-clause BSD license to my modifications of
the MD5 code. This license is the same one used by md5cmp and other
parts of the build system.
With rare exceptions ...
- Always separate line continuation characters by one space from
preceding code.
- Always use two-space indentation. Never use tabs.
- Always use K&R-style conditional blocks.
- Always surround operators with spaces, except in raw assembly code.
- Always put a space after, but not before, a comma.
- Never put a space between type casts and variables/function calls.
- Never put a space between the function name and the argument list in
function declarations and prototypes.
- Always surround braces ('{' and '}') with spaces.
- Always surround statements (if, for, else, catch, while, do, switch)
with spaces.
- Always attach pointer symbols ('*' and '**') to the variable or
function name.
- Always precede pointer symbols ('*' and '**') by a space in type
casts.
- Use the MIN() macro from jpegint.h within the libjpeg and TurboJPEG
API libraries (using min() from tjutil.h is still necessary for
TJBench.)
- Where it makes sense (particularly in the TurboJPEG code), put a blank
line after variable declaration blocks.
- Always separate statements in one-liners by two spaces.
The purpose of this was to ease maintenance on my part and also to make
it easier for contributors to figure out how to format patch
submissions. This was admittedly confusing (even to me sometimes) when
we had 3 or 4 different style conventions in the same source tree. The
new convention is more consistent with the formatting of other OSS code
bases.
This commit corrects deviations from the chosen formatting style in the
libjpeg API code and reformats the TurboJPEG API code such that it
conforms to the same standard.
NOTES:
- Although it is no longer necessary for the function name in function
declarations to begin in Column 1 (this was historically necessary
because of the ansi2knr utility, which allowed libjpeg to be built
with non-ANSI compilers), we retain that formatting for the libjpeg
code because it improves readability when using libjpeg's function
attribute macros (GLOBAL(), etc.)
- This reformatting project was accomplished with the help of AStyle and
Uncrustify, although neither was completely up to the task, and thus
a great deal of manual tweaking was required. Note to developers of
code formatting utilities: the libjpeg-turbo code base is an
excellent test bed, because AFAICT, it breaks every single one of the
utilities that are currently available.
- The legacy (MMX, SSE, 3DNow!) assembly code for i386 has been
formatted to match the SSE2 code (refer to
ff5685d5344273df321eb63a005eaae19d2496e3.) I hadn't intended to
bother with this, but the Loongson MMI implementation demonstrated
that there is still academic value to the MMX implementation, as an
algorithmic model for other 64-bit vector implementations. Thus, it
is desirable to improve its readability in the same manner as that of
the SSE2 implementation.
The main justification for this is to provide new libjpeg-turbo users
with a quick & easy way of developing a complete JPEG
compression/decompression program without requiring them to build
libjpeg-turbo from source (which was necessary in order to use the
project-private bmp API) or to use external libraries. These new
functions build upon significant enhancements to rdbmp.c, wrbmp.c,
rdppm.c, and wrppm.c which allow those engines to convert directly
between the native pixel format of the file and a pixel format
("colorspace" in libjpeg parlance) specified by the calling program.
rdbmp.c and wrbmp.c have also been modified such that the calling
program can choose to read or write image rows in the native (bottom-up)
order of the file format, thus eliminating the need to use an inversion
array. tjLoadImage() and tjSaveImage() leverage these new underlying
features in order to significantly improve upon the performance of the
old bmp API.
Because these new functions cannot work without the libjpeg-turbo
colorspace extensions, the libjpeg-compatible code in turbojpeg.c has
been removed. That code was only there to serve as an example of how
to use the TurboJPEG API on top of libjpeg, but more specific, buildable
examples now exist in the https://github.com/libjpeg-turbo/ijg
repository.
