Alejandro Tejada wrote:
Hi all,
i've been porting this md4digest function
from Macromedia Director to Runtime Revolution:
<http://www.isometrik.org/md5/lingo_md4_fastest.txt>
Some differences i had noticed while handling
numbers are:
Numeric Arrays in Director starts from 0 (zero)
Numeric Arrays in Runrev starts from 1 (one)
In Director:
put (24 + 64) / 512 * 16 + 16
results in 16
In RunRev
put (24 + 64) / 512 * 16 + 16
results in 18.75
To get the same result in RunRev
i had to rewrite the operation like this:
put round((24 + 64)/( 512 * 16)) + 16
Right.
Director is using all integer arithmetic, so 88/512 gives 0, multiply by
16 is still 0, and add 16 is 16.
Rev uses dynamic typing, so 88/512 gives some small fraction, multiply
by 16 gives 2.75m and add 16 gives you the 18.75
More problematic is that bitwise operations
do not return the same results in
Director and Runrev... for example
in Director
put bitAnd(-271733879,-1732584194)
returns -2004318072
in RunRev
put -271733879 bitand -1732584194
returns 0 (zero)
How could i get the same the result in RunRev as
this bitAnd operation made in Director?
The problem here is that Rev's bitand operator is defined to work for
positive numbers only. From the docs:
Parameters:
The number1 and number2 are numbers, or expressions that evaluate to
numbers, between zero and 4,294,967,295 (2^32 - 1).
Because your values are "less than 0", it gives wrong answer - they
appear to be < 0 because the top bit is set - the original code probably
had them defined as unsigned integers (which Director probably doesn't
support). You can get the right result with
function mybitand p1, p2
if p1 < 0 then add 2^32 to p1
if p2 < 0 then add 2^32 to p2
return p1 bitand p2
end mybitand
but you may be able to avoid the need for this depending on how the
input values here are built-up. If they are the results of other bit
operators, then in Rev it ought to be possible to keep everything as
positive values, and then just use the standard bitand operator.
If the code isn't too long, I'd be happy to take a look ....
--
Alex Tweedly http://www.tweedly.net
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