Amiga Old File System: Difference between revisions

Revision as of 10:26, 28 January 2006

Revision as of 21:12, 30 January 2006

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The exact calculation for where it is stored is as follows:

<pre>

<math>numCyls = highCyl - lowCyl + 1</math>

<math>highKey = numCyls * numSurfaces * numBlocksPerTrack - 1</math>

<math>numCyls = highCyl - lowCyl + 1</math>

<math>rootKey = INT (numReserved + highKey) / 2 </math>

<math>highKey = numCyls * numSurfaces * numBlocksPerTrack - 1</math>

</pre>

<math>rootKey = INT (numReserved + highKey) / 2 </math>

The Rootblock contains information about the disk: its name, its formatting date, etc. It also contains information on accessing the files/directories/links located at the uppermost (root) directory.

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It happens that different names can result in the same HashValue. If more than one name has the same HashValue, the other blocks (for files and directory only) are stored in a chained list. This linked list starts at the 'next_hash' field of the File header or Directory block.

For example : '''file_1a''', '''file_24''' and '''file_5u''' have the same hash value.

There was a bug in the old AmigaDOS versions when applying the Hash function to international characters (ASCII codes > 128). Consequently, FFS was then created with the 'international mode' (INTL). Filename characters can be lowercase and uppercase, but are not case sensitive.