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.
delta = cur0 * 2;
cur0 += delta; /* form error * 3 */
errorptr[0] = (FSERROR) (bpreverr0 + cur0);
cur0 += delta; /* form error * 5 */
bpreverr0 = belowerr0 + cur0;
cur0 += delta; /* form error * 7 */
Each time cur0 is incremented by delta, the compiled code doubles the value of delta (WTF?!) Thus, by the time the end of the block is reached, cur0 is equal to 15 times its former self, not 7 times its former self as it should be. At any rate, it was a lot simpler to just refactor the code so that it uses multiplication.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1253 632fc199-4ca6-4c93-a231-07263d6284db
delta = cur0 * 2;
cur0 += delta; /* form error * 3 */
errorptr[0] = (FSERROR) (bpreverr0 + cur0);
cur0 += delta; /* form error * 5 */
bpreverr0 = belowerr0 + cur0;
cur0 += delta; /* form error * 7 */
Each time cur0 is incremented by delta, the compiled code doubles the value of delta (WTF?!) Thus, by the time the end of the block is reached, cur0 is equal to 15 times its former self, not 7 times its former self as it should be. At any rate, it was a lot simpler to just refactor the code so that it uses multiplication.
git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.2.x@1255 632fc199-4ca6-4c93-a231-07263d6284db
