libjpeg-turbo has never supported non-ANSI C compilers. Per the spec,
ANSI C compilers must have locale.h, stddef.h, stdlib.h, memset(),
memcpy(), unsigned char, and unsigned short. They must also handle
undefined structures.
- Use JERR_NOTIMPL ("Not implemented yet") rather than JERR_NOT_COMPILED
("Requested feature was omitted at compile time") to indicate that
arithmetic coding is incompatible with Huffman table optimization.
This is more consistent with other parts of the libjpeg API code.
JERR_NOT_COMPILED is typically used to indicate that a major feature
was not compiled in, whereas JERR_NOTIMPL is typically used to
indicate that two features were compiled in but are incompatible with
each other (such as, for instance, two-pass color quantization and
partial image decompression.)
- Change the text of JERR_NOTIMPL to "Requested features are
incompatible". This is a more accurate description of the situation.
"Not implemented yet" implies that it may be possible to support the
requested combination of features in the future, but that is not true
in most of the cases where JERR_NOTIMPL is used.
Fixes#567
- When referring to specific clauses, annexes, tables, and figures, a
"timed reference" (a reference that includes the year) must be used in
order to avoid confusion.
- "CCITT" = "ITU-T"
- Replace ambiguous "JPEG spec" with the specific document number.
Within the libjpeg API code, it seems to be more the convention than not
to separate the macro name and value by two or more spaces, which
improves general readability. Making this consistent across all of
libjpeg-turbo is less about my individual preferences and more about
making it easy to automatically detect variations from our chosen
formatting convention. I intend to release the script I'm using to
validate this stuff, once it matures and stabilizes a bit.
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.
* libjpeg-turbo/master: (140 commits)
Increase severity of tjDecompressToYUV2() bug desc
Catch libjpeg errors in tjDecompressToYUV2()
BUILDING.md: Fix "... OR ..." indentation again
BUILDING.md: Fix confusing Windows build reqs
ChangeLog.md: Improve readability of plain text
change.log: Refer users to ChangeLog.md
Markdown version of ChangeLog.txt
Rename ChangeLog.txt
README.md: Link to BUILDING.md
BUILDING.md and README.md: Cosmetic tweaks
ChangeLog: "1.5 beta1" --> "1.4.90 (1.5 beta1)"
Java: Fix parallel make with autotools
Win/x64: Fix improper callee save of xmm8-xmm11
Bump TurboJPEG C API revision to 1.5
ChangeLog: Mention jpeg_crop_scanline() function
1.5 beta1
Fix v7/v8-compatible build
libjpeg API: Partial scanline decompression
Build: Make the NASM autoconf variable persistent
Use consistent/modern code formatting for dbl ptrs
...
The convention used by libjpeg:
type * variable;
is not very common anymore, because it looks too much like
multiplication. Some (particularly C++ programmers) prefer to tuck the
pointer symbol against the type:
type* variable;
to emphasize that a pointer to a type is effectively a new type.
However, this can also be confusing, since defining multiple variables
on the same line would not work properly:
type* variable1, variable2; /* Only variable1 is actually a
pointer. */
This commit reformats the entirety of the libjpeg-turbo code base so
that it uses the same code formatting convention for pointers that the
TurboJPEG API code uses:
type *variable1, *variable2;
This seems to be the most common convention among C programmers, and
it is the convention used by other codec libraries, such as libpng and
libtiff.
These days, INT32 is a commonly-defined datatype in system headers. We
cannot eliminate the definition of that datatype from jmorecfg.h, since
the INT32 typedef has technically been part of the libjpeg API since
version 5 (1994.) However, using INT32 internally is risky, because the
inclusion of a particular header (Xmd.h, for instance) could change the
definition of INT32 from long to int on 64-bit platforms and thus change
the internal behavior of libjpeg-turbo in unexpected ways (for instance,
failing to correctly set __INT32_IS_ACTUALLY_LONG to match the INT32
typedef-- perhaps as a result of including the wrong version of
jpeglib.h-- could cause libjpeg-turbo to produce incorrect results.)
The library has always been built in environments in which INT32 is
effectively long (on Windows, long is always 32-bit, so effectively it's
the same as int), so it makes sense to turn INT32 into an explicitly
long datatype. This ensures that libjpeg-turbo will always behave
consistently, regardless of the headers included at compile time.
Addresses a concern expressed in #26.
The IJG README file has been renamed to README.ijg, in order to avoid
confusion (many people were assuming that that was our project's README
file and weren't reading README-turbo.txt) and to lay the groundwork for
markdown versions of the libjpeg-turbo README and build instructions.
Initial implementation of trellis quantization for arithmetic coding.
The rate computation does not yet implement all rules of the entropy
coder and may thus be suboptimal.
