4 releases
0.12.3 | Feb 27, 2023 |
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0.12.2 | Feb 26, 2023 |
0.12.1 | Feb 26, 2023 |
0.12.0 | Feb 25, 2023 |
#18 in #mel
Used in 2 crates
120KB
2.5K
SLoC
melstructs: Mel's core state transition function
This crate contains the data structures and core algorithms that comprise Mel's core state transition function. Any piece of software needing to validate Mel transactions or answer questions like "what happens to the Mel state if transactions A, B, and C happen" can use this minimal-dependency crate.
The State
type
The most important type in the crate is State
, and the closely associated type SealedState
. The yellow paper talks about them further, but in short:
State
represents an mutable Mel world-state and it's not directly serializable. It includes all the information needed to validate new transactions and blocks, such as a SMT of all outstanding coins, Melmint parameters, etc. It has methods takingTransaction
s etc that advance the state, as well as others to produce serializable blocks, headers, etc.SealedState
represents a sealed state. This roughly corresponds to the notion of "the blockchain state at a given height". Blocks represent transitions from oneSealedState
to another.
Note
This crate is the most consensus-critical part of Mel, and essentially defines the entire on-chain logic of the Mel blockchain.
Versions incompatible with the latest Mel state are thus all yanked.
Example Usage in themelio-node
To illustrate STF's usage, let's look at themelio-node
as an example.
When a node is run for the first time, it will instantiate storage to keep track of the State
. It does this by reading it from persisted history data, or create a new genesis state.
During it's lifetime, the node will need to update it's current knowledge of the State
by doing things like handling incoming apply_tx
RPCs, or syncing up its blocks (apply_block
) with other nodes.
For example, an incoming apply_tx
RPC call to the node will take the current provisional State
and call State::apply_tx
. If the node is a staker, this provisional state is later used to participate in the consensus algorithm (e.g. streamlette
).
When a slower node syncs its state with a peer at a higher height, it will continuously call apply_block
on its current highest state.
Dependencies
~14–32MB
~675K SLoC