Question about files comparing .....

[opgal]

"Hi !

I have Labview 4.0.1 on Windows-NT:

To compare 2 files i'm ussing 2 "Read characters file.vi" when the
"characters string" output of this 2 functions is connect to one
"Comparison Equal ?" symbol, which it's output is connect to an LED
indicator on the front panel.

"When i Run this application i choose the 2 files for compare ( using
the file browswer ) and as a result i get the Led On/Off ( Equal or Not
Equal ).

My question is if what i did good also for comparing large files for
example if i want to compare the files "Test1.exe" and "Test2.exe" which
are 7 Mbytes ( each one ). i ask this becouse i remember that there is a
limit
for the number of chars in the string i can send to the input of the
"Comparison
Equal ?" symbol, is it true ? is there a limit ? ( Becouse a
7 Mbytes file is a very very long string ..... and i want to be sure
that the comparing is done NOT only on the beginning of this files but
on ALL the file from first till last character )

I hope you understood, please answer as soon, thanks.

Noam.

[shoneill]

Hi Noam,

The way I would do it is as follows...

Read in medium-sized chunks of the file at a time (100 kB) and compare
these. Retain the file position indicator in a FOR loop, read the next
portion and perform an "AND" logic function on the comparison from the last
loop and this loop. This way a TRUE match will remain intact until a FALSE
comparison is recorded which will then propagate throughout the iterations.
At the end the boolean will tell you if there were any mis-matches along the
way.

This won`t work of course if you want to compare EVERY byte of the files and
thus generate millions of TRUE/FALSE answers.

Hope it helps

Shane


opgal schrieb in Nachricht <3B02DB27.ACD87CA0@netvision.net.il>...
>"Hi !
>
>I have Labview 4.0.1 on Windows-NT:
>
>To compare 2 f
iles i'm ussing 2 "Read characters file.vi" when the
>"characters string" output of this 2 functions is connect to one
>"Comparison Equal ?" symbol, which it's output is connect to an LED
>indicator on the front panel.
>
>"When i Run this application i choose the 2 files for compare ( using
>the file browswer ) and as a result i get the Led On/Off ( Equal or Not
>Equal ).
>
>My question is if what i did good also for comparing large files for
>example if i want to compare the files "Test1.exe" and "Test2.exe" which
>are 7 Mbytes ( each one ). i ask this becouse i remember that there is a
>limit
>for the number of chars in the string i can send to the input of the
>"Comparison Equal ?" symbol, is it true ? is there a limit ? ( Becouse a
>7 Mbytes file is a very very long string ..... and i want to be sure
>that the comparing is done NOT only on the beginning of this files but
>on ALL the file from first till last character )
>
>I hope you understood, please answer as soon, thanks.
>
>No
am.
>
>
>