|0.1.1||Apr 17, 2023|
|0.1.0||Feb 25, 2023|
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Used in 5 crates (4 directly)
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 most important type in the crate is
State, and the closely associated type
SealedState. The yellow paper talks about them further, but in short:
Staterepresents 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 taking
Transactions etc that advance the state, as well as others to produce serializable blocks, headers, etc.
SealedStaterepresents a sealed state. This roughly corresponds to the notion of "the blockchain state at a given height". Blocks represent transitions from one
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
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.
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.