flumelog-aligned-offset

flumelog-aligned-offset

a new flumelog format. like flumelog-offset, each record is identified by an integer byte offset, and also, each record is delimited by it's length. But unlike flumelog-offset records within blocks are always aligned to the start of the block, so there is no overlap, and this makes it easy to know wether you have the block for a record or not.

<block
  <record
    <record.length: UInt16LE>
    <record.data>
    <record.length: UInt16LE>
  </record>*
  <footer
    <end sentinel 0xffff>
    <filler: zeros...>
    <pointer.footer: UInt32LE>
  >//end of block.
>

to find the start of the record, take the offset, read 2 bytes (little endian) then record.data from offset + 2, to offset + 2 + length. the first record in a block starts at the first byte in the block.

The last record in the block is followed by padding. The block's last 4 bytes contains a 4 byte (little endian) pointer to the start of the padding, two bytes before that is the length of the record. Records and padding can always be written append only, without overwriting previous records.

Here be dragons

Please note that the default value for adding data is sync = true unless specified. Which is how it works if combined with flumedb.

License

MIT