[Bug-ddrescue] direct disk access will not read partial sector

[Scott Dwyer]

I do not know if this would be considered a bug, or just the nature of 
the direct disk access. When using the -d option, ddrescue will not 
attempt to read data that does not start or end on a sector boundary. 
Meaning if you pick a start byte with the -i option that does not line 
up with the beginning of a sector, it will not even try to read that 
partial data and will report a failed read for that chunk. This will 
also happen if you pick a length with the -s option that does not end 
exactly on a sector boundary. It will work fine without the -d option.

This may not be something normally encountered, but then again I am not 
doing normal things. I have a friends failing hard drive that reads much 
faster with direct disk access. And I am trying to write and test 
software to extract individual files using ddrescue, with some actual 
success so far. This means I will be attempting many reads that do not 
end on a sector boundary.