have hashdb be generic over DBValue
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@ -6,8 +6,7 @@ description = "trait for hash-keyed databases."
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license = "GPL-3.0"
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[dependencies]
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elastic-array = { version = "0.10", optional = true }
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[features]
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default = ["std"]
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std = ["elastic-array"]
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std = []
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@ -18,13 +18,10 @@
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#![cfg_attr(not(feature = "std"), no_std)]
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#[cfg(feature = "std")]
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extern crate elastic_array;
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#[cfg(feature = "std")]
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extern crate core;
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#[cfg(feature = "std")]
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use elastic_array::ElasticArray128;
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#[cfg(feature = "std")]
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use std::collections::HashMap;
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use core::{fmt::Debug, hash::Hash};
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@ -44,19 +41,15 @@ pub trait Hasher: Sync + Send {
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fn hash(x: &[u8]) -> Self::Out;
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}
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/// `HashDB` value type.
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#[cfg(feature = "std")]
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pub type DBValue = ElasticArray128<u8>;
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/// Trait modelling datastore keyed by a hash defined by the `Hasher`.
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#[cfg(feature = "std")]
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pub trait HashDB<H: Hasher>: Send + Sync + AsHashDB<H> {
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pub trait HashDB<H: Hasher, T>: Send + Sync + AsHashDB<H, T> {
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/// Get the keys in the database together with number of underlying references.
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fn keys(&self) -> HashMap<H::Out, i32>;
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/// Look up a given hash into the bytes that hash to it, returning None if the
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/// hash is not known.
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fn get(&self, key: &H::Out) -> Option<DBValue>;
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fn get(&self, key: &H::Out) -> Option<&T>;
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/// Check for the existance of a hash-key.
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fn contains(&self, key: &H::Out) -> bool;
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@ -67,7 +60,7 @@ pub trait HashDB<H: Hasher>: Send + Sync + AsHashDB<H> {
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fn insert(&mut self, value: &[u8]) -> H::Out;
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/// Like `insert()`, except you provide the key and the data is all moved.
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fn emplace(&mut self, key: H::Out, value: DBValue);
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fn emplace(&mut self, key: H::Out, value: T);
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/// Remove a datum previously inserted. Insertions can be "owed" such that the same number of `insert()`s may
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/// happen without the data being eventually being inserted into the DB. It can be "owed" more than once.
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@ -76,18 +69,18 @@ pub trait HashDB<H: Hasher>: Send + Sync + AsHashDB<H> {
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/// Upcast trait.
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#[cfg(feature = "std")]
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pub trait AsHashDB<H: Hasher> {
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pub trait AsHashDB<H: Hasher, T> {
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/// Perform upcast to HashDB for anything that derives from HashDB.
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fn as_hashdb(&self) -> &HashDB<H>;
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fn as_hashdb(&self) -> &HashDB<H, T>;
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/// Perform mutable upcast to HashDB for anything that derives from HashDB.
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fn as_hashdb_mut(&mut self) -> &mut HashDB<H>;
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fn as_hashdb_mut(&mut self) -> &mut HashDB<H, T>;
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}
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// NOTE: There used to be a `impl<T> AsHashDB for T` but that does not work with generics. See https://stackoverflow.com/questions/48432842/implementing-a-trait-for-reference-and-non-reference-types-causes-conflicting-im
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// This means we need concrete impls of AsHashDB in several places, which somewhat defeats the point of the trait.
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#[cfg(feature = "std")]
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impl<'a, H: Hasher> AsHashDB<H> for &'a mut HashDB<H> {
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fn as_hashdb(&self) -> &HashDB<H> { &**self }
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fn as_hashdb_mut(&mut self) -> &mut HashDB<H> { &mut **self }
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impl<'a, H: Hasher, T> AsHashDB<H, T> for &'a mut HashDB<H, T> {
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fn as_hashdb(&self) -> &HashDB<H, T> { &**self }
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fn as_hashdb_mut(&mut self) -> &mut HashDB<H, T> { &mut **self }
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}
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