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decl_storage document hasher choice (#2387)

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* doc

* fix

* grammar and line wrapping

* small changes to end

* Update lib.rs

* update after demi's review
This commit is contained in:
thiolliere
2019-04-27 16:33:21 +02:00
committed by Gavin Wood
parent 3c988ea7e9
commit 2b10d8e080
1 changed files with 41 additions and 17 deletions
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substrate/srml/support/procedural/src/lib.rs
+41 -17
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@@ -40,23 +40,47 @@ use proc_macro::TokenStream;
/// }
/// ```
///
/// Declaration is set with this header `(pub) trait Store for Module<T: Trait> as Example`
/// with `Store` a (pub) trait generated associating each storage to the `Module` and
/// `as Example` setting the prefix used for storages of this module. `Example` must be unique:
/// another module with same name and same inner storage item name will conflict.
/// Declaration is set with the header `(pub) trait Store for Module<T: Trait> as Example`,
/// with `Store` a (pub) trait generated associating each storage item to the `Module` and
/// `as Example` setting the prefix used for storage items of this module. `Example` must be unique:
/// another module with the same name and the same inner storage item name will conflict.
///
/// Basic storage consists of a name and a type; supported types are:
///
/// * Value: `Foo: type`: Implements [StorageValue](../srml_support/storage/trait.StorageValue.html).
/// * Map: `Foo: map type => type`: implements [StorageMap](../srml_support/storage/trait.StorageMap.html)
/// * Linked map: `Foo: linked_map type => type`: Implements [StorageMap](../srml_support/storage/trait.StorageMap.html)
/// and [EnumarableStorageMap](../srml_support/storage/trait.EnumerableStorageMap.html).
/// * Double map: `Foo: double_map u32, $hash(u32) => u32;`: Implements `StorageDoubleMap` with `$hash` representing a
/// choice of hashing algorithms available in [`Hashable` trait](../srml_support/trait.Hashable.html).
/// * Map: `Foo: map hasher($hash) type => type`: Implements [StorageMap](../srml_support/storage/trait.StorageMap.html)
/// with `$hash` representing a choice of hashing algorithms available in the
/// [`Hashable` trait](../srml_support/trait.Hashable.html).
///
/// /!\ Be careful when choosing the hash function, malicious actors could craft second keys to lower the trie.
/// `hasher($hash)` is optional and its default is `blake2_256`.
///
/// And it can be extended as such:
/// /!\ Be careful with each key in the map that is inserted in the trie `$hash(module_name ++ storage_name ++ key)`.
/// If the keys are not trusted (e.g. can be set by a user), a cryptographic `hasher` such as
/// `blake2_256` must be used. Otherwise, other values in storage can be compromised.
///
/// * Linked map: `Foo: linked_map hasher($hash) type => type`: Same as `Map` but also implements
/// [EnumarableStorageMap](../srml_support/storage/trait.EnumerableStorageMap.html).
///
/// * Double map: `Foo: double_map hasher($hash) u32, $hash2(u32) => u32`: Implements `StorageDoubleMap` with
/// `$hash` and `$hash2` representing choices of hashing algorithms available in the
/// [`Hashable` trait](../srml_support/trait.Hashable.html).
///
/// `hasher($hash)` is optional and its default is `blake2_256`.
///
/// /!\ Be careful with each key pair in the double map that is inserted in the trie.
/// The final key is calculated as follows:
///
/// ```nocompile
/// $hash(module_name ++ storage_name ++ first_key) ++ $hash2(second_key)
/// ```
///
/// If the first key is untrusted, a cryptographic `hasher` such as `blake2_256` must be used.
/// Otherwise, other values of all storage items can be compromised.
///
/// If the second key is untrusted, a cryptographic `hasher` such as `blake2_256` must be used.
/// Otherwise, other items in storage with the same first key can be compromised.
///
/// Basic storage can be extended as such:
///
/// `#vis #name get(#getter) config(#field_name) build(#closure): #type = #default;`
///
@@ -100,18 +124,18 @@ use proc_macro::TokenStream;
///
/// This struct can be exposed as `Config` by the `decl_runtime!` macro.
///
/// ### Module with instances
/// ### Module with Instances
///
/// The `decl_storage!` macro supports building modules with instances with the following syntax:
/// (`DefaultInstance` type is optional)
/// The `decl_storage!` macro supports building modules with instances with the following syntax
/// (`DefaultInstance` type is optional):
///
/// ```nocompile
/// trait Store for Module<T: Trait<I>, I: Instance=DefaultInstance> as Example {}
/// ```
///
/// Then the genesis config is generated with two generic parameter `GenesisConfig<T, I>`
/// and storage items are now accessible using two generic parameters, e.g.:
/// `<Dummy<T, I>>::get()` or `Dummy::<T, I>::get()`
/// Then the genesis config is generated with two generic parameters (i.e. `GenesisConfig<T, I>`)
/// and storage items are accessible using two generic parameters, e.g.:
/// `<Dummy<T, I>>::get()` or `Dummy::<T, I>::get()`.
#[proc_macro]
pub fn decl_storage(input: TokenStream) -> TokenStream {
storage::transformation::decl_storage_impl(input)