Re: [Yaffs] Sequence Number

On Tuesday 21 June 2011 13:46:41 Peter Pilley wrote:
> Hello All on list
>
> I am doing some tests with yaffs at the moment and have a question
> regarding the sequence number.
>
> in the docs howyaffsworks it states
>
> Sequence Number: As each block is allocated, the file system's sequence
> number is incremented and each chunk
> in the block is marked with that sequence number. The sequence number thus
> provides a way of organising the log
> in chronological order
>
> However when I am identifying items in the an image they are all returning
> with the same sequence number
>
> Directory: ./, Size: -1, ParentID 1,ChunkID 0, ObjectID 1, SequenceID 4096.
> Directory: .//test3, Size: -1, ParentID 1,ChunkID 0, ObjectID 257,
> SequenceID 4096.
> Filename: test2.txt, Size: 10, ParentID 257,ChunkID 1, ObjectID 258,
> SequenceID 4096.
> Filename: test, Size: 9, ParentID 1,ChunkID 1, ObjectID 259, SequenceID
> 4096.
> Filename: test4.txt, Size: 11, ParentID 1,ChunkID 1, ObjectID 260,
> SequenceID 4096.
> Directory: .//test5, Size: -1, ParentID 1,ChunkID 0, ObjectID 261,
> SequenceID 4096.
> Filename: test7.txt, Size: 11, ParentID 261,ChunkID 1, ObjectID 262,
> SequenceID 4096.

Where did the image come from?
The sequence Id increments on a block basis.
How many blocks are there in the image you are working with?

>
> I have based my code on wunyaffs which uses unyaffs from googlecode.
>
> I would have thought each chunk received a unique sequence number but it
> looks like it is block?.

No, as you quote above, the sequence number increments on a block basis.

The chunks in a block are written sequentially, therefore we can always figure
out the order of a chunk by using the combination of sequence Id and chunk
offset in block.

-- Charles