Module tezos_smart_rollup::dac

Encoding of DAC payload as a Merkle tree with an arbitrary branching factor greater or equal to 2. The serialization process works as follows:

• A large sequence of bytes, the payload, is split into several pages of fixed size, each of which is prefixed with a small sequence of bytes (also of fixed size), which is referred to as the preamble of the page. Pages obtained directly from the original payload are referred to as Contents pages. Contents pages constitute the leaves of the Merkle tree being built,

• Each contents page (each of which is a sequence of bytes consisting of the preamble followed by the actual contents from the original payload) is then hashed. The size of each hash is fixed. The hashes are concatenated together, and the resulting sequence of bytes is split into pages of the same size of Hashes pages, each of which is prefixed with a preamble whose size is the same as in Contents pages. Hashes pages correspond to nodes of the Merkle tree being built, and the children of a hash page are the (either Payload or Hashes) pages whose hash appear into the former,

• Hashes pages are hashed using the same process described above, leading to a smaller list of hashes pages. To guarantee that the list of hashes pages is actually smaller than the original list of pages being hashed, we require the size of pages to be large enough to contain at least two hashes.

Merkle tree encodings of DAC pages are versioned, to allow for multiple hashing schemes to be used.

Structs

• PreimageHash
  A 32-byte hash corresponding to a preimage.
• V0ContentPage
  Content page consisting of a dynamic number of bytes.
• V0HashPage
  Hash page consisting of a dynamic number of PreimageHash.
• V0SliceContentPage
  Borrowing version of V0ContentPage.
• V0SliceHashPage
  Borrowing version of V0HashPage.

Enums

• Page
  A Dac page: either a leaf node of contents, or node of hashes.
• SlicePage
  A Dac Page that borrows the underlying buffer.
• SlicePageError
  Errors that may occur when dealing with SlicePage.

Constants

• MAX_PAGE_SIZE
  Maximum size of dac pages is 4Kb.

Functions

• fetch_page_raw
  Fetches a page of data from file hash into buffer using Runtime::reveal_preimage. Returns a tuple of the raw page and remaining buffer.
• make_preimage_hash
  Hashes content into a preimage hash.
• prepare_preimages
  Generates the preimages of the given content.
• reveal_loop
  Recursively traverses a Merkle Tree of hashes up to max_dac_levels depth where each hash corresponds to a preimage that can be revealed via Runtime::reveal_preimage. The closure save_content is applied on each content page found.