🚀 go-pugleaf

In article <c4pK02n=01EQ01@JUTS.ccc.amdahl.com> ked01@JUTS.ccc.amdahl.com (Kim DeVaughn) writes:
>In article <13342@cbmvax.commodore.com> jesup@cbmvax (Randell Jesup) writes:
>> In article <3fco02lsb9LE01@amdahl.uts.amdahl.com> ked01@juts.ccc.amdahl.com (Kim DeVaughn) writes:
>> >Are you saying this is now the documented behavior for the fib_NumBlocks
>> >entry (for the FFS), or is it still better to compute them yourself from
>> >fib_Size, so as not to break in future releases?
>> 
>> 	Computing it yourself is never really safe.  It depends on how the
>> FS works internally.  Take what it gives you, with the understanding that
>> this really is only an internal measure of storage to the filesystem.  On some
>> filesystems I can imagine (easily), the number of blocks a file takes may
>> depend on fragmentation.  Certainly the number of blocks can and will
>> vary from filesystem to filesystem for a given file.
...
>So the bottom line is that there is no supported* way to determine the block
>count of a file.  And hence, there is no supported method of determining if
>a file on one device will "fit" on another device without actually attempting
>the copy operation.
>
>Unfortunate.

	First, it's a multitasking system, and any value you determine
(without writing the file) is no longer valid if anyone else wrote to the disk.
Second, since filesystems are separate from Dos as a very basic level, the
only way you could ever even answer the question would be to have a packet
for specifically asking the filesystem if it has enough space (at the
moment).  Filesystems can store the data any way they want.  Hell, they could
lempel-ziv encode them into data blocks, or allocate storage on the byte
level between files, etc, etc.

	However, there's another solution under 2.0: Open a new file, then
do SetFileSize for the size you want.  That will make a file of the requested
size filled with random data, or fail.  Then just write over it with your
file.

-- 
Randell Jesup, Keeper of AmigaDos, Commodore Engineering.
{uunet|rutgers}!cbmvax!jesup, jesup@cbmvax.cbm.commodore.com  BIX: rjesup  
Common phrase heard at Amiga Devcon '89: "It's in there!"