[Info-vax] Empty blocks in FILES-11 directory files.

[Arne Vajhøj]

On 9/26/2022 4:42 AM, Johnny Billquist wrote:
> On 2022-09-25 15:00, Mark Daniel wrote:
>> On 25/9/2022 5:01 pm, Volker Halle wrote:
>>> does your utility read until the 'End of file block' or the 'Highest 
>>> block' of the directory file ?
>>
>> It uses a "generic" file read function as "raw" blocks into memory.  
>> It reads the exact number of bytes indicated by the file header.
>>
>>     if (odsptr->XabFhc.xab$l_ebk <= 1)
>>        SizeInBytes = odsptr->XabFhc.xab$w_ffb;
>>     else
>>        SizeInBytes = ((odsptr->XabFhc.xab$l_ebk-1) << 9) +
>>                      odsptr->XabFhc.xab$w_ffb;
> 
> Are directory files in ODS-2 using fixed size records? Because otherwise 
> you have a problem here that you cannot compute how many bytes you have 
> in a file like this.
> 
> The ffb tells where the first free byte is, so that appends to a file 
> can be done. However, the number of bytes you actually have in a file 
> does not include the record lengths of variable sized records, nor the 
> padding for odd length records. But these things only happen on variable 
> record length files, which is why I ask.

Fixed length files are also padded to even number bytes.

But the "standard" FIX 512 is even.

Arne