Trait concordium_std::HasStateApi

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pub trait HasStateApi: Clone {
    type EntryType: HasStateEntry;
    type IterType: Iterator<Item = Self::EntryType>;

    fn create_entry(&mut self, key: &[u8]) -> Result<Self::EntryType, StateError>;
    fn lookup_entry(&self, key: &[u8]) -> Option<Self::EntryType>;
    fn delete_entry(&mut self, key: Self::EntryType) -> Result<(), StateError>;
    fn delete_prefix(&mut self, prefix: &[u8]) -> Result<bool, StateError>;
    fn iterator(&self, prefix: &[u8]) -> Result<Self::IterType, StateError>;
    fn delete_iterator(&mut self, iter: Self::IterType);

    fn entry<K: AsRef<[u8]> + Into<Key>>(&mut self, key: K) -> EntryRaw<Self> { ... }
}
Expand description

Types which can serve as the contract state.

Required Associated Types

Required Methods

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fn create_entry(&mut self, key: &[u8]) -> Result<Self::EntryType, StateError>

Create a new entry in the state. If an entry with the given key already exists then it is reset to an empty entry. If the part of the tree where the key points to is locked due to an acquired iterator then no entry is created, and an error will be returned.

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fn lookup_entry(&self, key: &[u8]) -> Option<Self::EntryType>

Lookup an entry in the state.

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fn delete_entry(&mut self, key: Self::EntryType) -> Result<(), StateError>

Delete an entry. Returns an error if the entry did not exist, or if it is part of a locked subtree.

Delete the entire subtree. Returns whether any values were deleted, or an error if the given prefix is part of a locked subtree.

Get an iterator over a map in the state.

An iterator locks the subtree with the given prefix. Locking means that the structure of the tree cannot be altered, i.e., that entries cannot be created or deleted. Altering the data inside an entry of a locked subtree is, however, allowed.

Deleting iterators with delete_iterator is necessary to unlock the subtree. To unlock a subtree with prefix p1, all iterators with prefixes p2, where p2 is a prefix of p1, must be deleted.

Returns an error if the number of active iterators for the same prefix exceeds u32::MAX.

Delete an iterator. See the iterator method for why this is necessary.

Provided Methods

Like lookup_entry except that it consumes the key and returns an EntryRaw instead of an optional entry.

For maximal flexibility the function is parametrized by the type of key with the intention that needless allocations are avoided for short keys and existing entries. The most common examples of keys will be Vec<u8> or fixed sized arrays [u8; N].

Implementors