mirror of
https://github.com/logos-storage/plonky2.git
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6a7e8d0fb0
Summary of the design: - Tries are stored as immutable, copy-on-write trees - All trie data is stored in the `TrieData` segment. Since it's immutable, data is never modified/deleted, new versions are just appended at the end. - In order to support reverts, each context stores a pointer to the initial state trie version, plus the initial version of each storage trie. One variation which may be worth considering is storing the whole state trie as one big trie (with sub-tries for storage). Reverts would then be simpler - we'd replace a single pointer. I thought that approach might make hashing the trie a bit more complex, as the node associated with an account would be a special type of node, rather than just another leaf. Either approach seems reasonable though.
62 lines
2.5 KiB
Rust
62 lines
2.5 KiB
Rust
/// These metadata fields contain VM state specific to a particular context.
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#[derive(Copy, Clone, Eq, PartialEq, Hash, Ord, PartialOrd, Debug)]
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pub(crate) enum ContextMetadata {
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/// The ID of the context which created this one.
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ParentContext = 0,
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/// The program counter to return to when we return to the parent context.
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ParentProgramCounter = 1,
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CalldataSize = 2,
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ReturndataSize = 3,
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/// The address of the account associated with this context.
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Address = 4,
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/// The size of the code under the account associated with this context.
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/// While this information could be obtained from the state trie, it is best to cache it since
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/// the `CODESIZE` instruction is very cheap.
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CodeSize = 5,
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/// The address of the caller who spawned this context.
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Caller = 6,
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/// The value (in wei) deposited by the caller.
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CallValue = 7,
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/// Whether this context was created by `STATICCALL`, in which case state changes are
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/// prohibited.
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Static = 8,
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/// Pointer to the initial version of the state trie, at the creation of this context. Used when
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/// we need to revert a context. See also `StorageTrieCheckpointPointers`.
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StateTrieCheckpointPointer = 9,
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}
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impl ContextMetadata {
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pub(crate) const COUNT: usize = 10;
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pub(crate) fn all() -> [Self; Self::COUNT] {
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[
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Self::ParentContext,
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Self::ParentProgramCounter,
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Self::CalldataSize,
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Self::ReturndataSize,
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Self::Address,
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Self::CodeSize,
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Self::Caller,
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Self::CallValue,
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Self::Static,
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Self::StateTrieCheckpointPointer,
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]
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}
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/// The variable name that gets passed into kernel assembly code.
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pub(crate) fn var_name(&self) -> &'static str {
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match self {
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ContextMetadata::ParentContext => "CTX_METADATA_PARENT_CONTEXT",
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ContextMetadata::ParentProgramCounter => "CTX_METADATA_PARENT_PC",
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ContextMetadata::CalldataSize => "CTX_METADATA_CALLDATA_SIZE",
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ContextMetadata::ReturndataSize => "CTX_METADATA_RETURNDATA_SIZE",
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ContextMetadata::Address => "CTX_METADATA_ADDRESS",
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ContextMetadata::CodeSize => "CTX_METADATA_CODE_SIZE",
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ContextMetadata::Caller => "CTX_METADATA_CALLER",
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ContextMetadata::CallValue => "CTX_METADATA_CALL_VALUE",
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ContextMetadata::Static => "CTX_METADATA_STATIC",
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ContextMetadata::StateTrieCheckpointPointer => "CTX_METADATA_STATE_TRIE_CHECKPOINT_PTR",
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}
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}
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}
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