Read File at > 2GB Problem

[Dave]

Hi,

We are talking about a Disk Address not a RAM address. I just want to  
read a small amount of data (say 100 bytes) from *anywhere* in a  
file. For instance:

read from file "myFile" at 2147483647 for 100 works, but

read from file "myFile" at 2147483648 for 100 doesn't!

(I haven't test this but I am assuming that this won't work. I can't  
test it today because I don't have access to the files).

To work stuff like this out, I usually go back to basics:

constant KILO=1024
constant MEGA=KILO * KILO
constant GIGA=MEGA * MEGA

32 Bits is 4 * GIGA which Unsigned allows numbers between 0 and  
4,294,967,295 and signed allows number between -2147483648 and +  
2147483647.


The capacity of 16 Bits is 65536
The capacity of 32 Bits is 4,294,967,296 (65536 * 65536)
The capacity of 64 Bits is 18,446,744,073,709,600,000 (4,294,967,296  
* 4,294,967,296)

So the number of Gigabytes in 64 Bits is  (4,294,967,296 *  
4,294,967,296) / GIGA

All the Best
Dave

On 17 May 2007, at 19:44, J. Landman Gay wrote:

> Dave wrote:
>> Hi,
>> That's what I'm doing, but it's *way* too slow and crashes if you  
>> read too much data. I've got a 60+ GB file and need to read at  
>> "random" positions in the file. Moving from somewhere near the  
>> start to somewhere near the end takes minutes! The ironic thing is  
>> that the data I want to read when I get there is quite small!
>
> There is a limit to the total addressable RAM space that Rev can  
> use. It's 4 gigs on 32-bit systems, and 16P on 64-bit systems. I  
> believe that Rev works with 64-bit systems (for two reasons: they  
> said it would, and it is documented) so it may be that you are  
> reaching one of the limits. However, my brain cannot process how  
> large 16P is so I'm not sure. What's that in gigs?
>
> -- 
> Jacqueline Landman Gay         |     jacque at hyperactivesw.com
> HyperActive Software           |     http://www.hyperactivesw.com
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