From 7d8e3a434ea1e760190456e8df1359aa8137e16a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastian=20K=C3=B6cher?= <git@kchr.de>
Date: Mon, 13 Jan 2025 13:32:01 +0100
Subject: [PATCH] reference-docs: Start `state` and mention well known keys
(#7037)
Closes: https://github.com/paritytech/polkadot-sdk/issues/7033
---
Cargo.lock | 1 +
docs/sdk/Cargo.toml | 1 +
docs/sdk/src/reference_docs/mod.rs | 3 +++
docs/sdk/src/reference_docs/state.rs | 12 ++++++++++++
substrate/primitives/storage/src/lib.rs | 4 ++++
5 files changed, 21 insertions(+)
create mode 100644 docs/sdk/src/reference_docs/state.rs
diff --git a/Cargo.lock b/Cargo.lock
index 4e2272bdc98..cfb805fbe84 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -19202,6 +19202,7 @@ dependencies = [
"sp-runtime 31.0.1",
"sp-runtime-interface 24.0.0",
"sp-std 14.0.0",
+ "sp-storage 19.0.0",
"sp-tracing 16.0.0",
"sp-version 29.0.0",
"sp-weights 27.0.0",
diff --git a/docs/sdk/Cargo.toml b/docs/sdk/Cargo.toml
index f526c07796e..4d83e2045ab 100644
--- a/docs/sdk/Cargo.toml
+++ b/docs/sdk/Cargo.toml
@@ -110,6 +110,7 @@ sp-offchain = { workspace = true, default-features = true }
sp-runtime = { workspace = true, default-features = true }
sp-runtime-interface = { workspace = true, default-features = true }
sp-std = { workspace = true, default-features = true }
+sp-storage = { workspace = true, default-features = true }
sp-tracing = { workspace = true, default-features = true }
sp-version = { workspace = true, default-features = true }
sp-weights = { workspace = true, default-features = true }
diff --git a/docs/sdk/src/reference_docs/mod.rs b/docs/sdk/src/reference_docs/mod.rs
index e47eece784c..7ad8a37241b 100644
--- a/docs/sdk/src/reference_docs/mod.rs
+++ b/docs/sdk/src/reference_docs/mod.rs
@@ -111,3 +111,6 @@ pub mod custom_runtime_api_rpc;
/// The [`polkadot-omni-node`](https://crates.io/crates/polkadot-omni-node) and its related binaries.
pub mod omni_node;
+
+/// Learn about the state in Substrate.
+pub mod state;
diff --git a/docs/sdk/src/reference_docs/state.rs b/docs/sdk/src/reference_docs/state.rs
new file mode 100644
index 00000000000..a8138caebf1
--- /dev/null
+++ b/docs/sdk/src/reference_docs/state.rs
@@ -0,0 +1,12 @@
+//! # State
+//!
+//! The state is abstracted as a key-value like database. Every item that
+//! needs to be persisted by the [State Transition
+//! Function](crate::reference_docs::blockchain_state_machines) is written to the state.
+//!
+//! ## Special keys
+//!
+//! The key-value pairs in the state are represented as byte sequences. The node
+//! doesn't know how to interpret most the key-value pairs. However, there exist some
+//! special keys and its values that are known to the node, the so-called
+//! [`well-known-keys`](sp_storage::well_known_keys).
diff --git a/substrate/primitives/storage/src/lib.rs b/substrate/primitives/storage/src/lib.rs
index 4b25f85fba6..df7570a1854 100644
--- a/substrate/primitives/storage/src/lib.rs
+++ b/substrate/primitives/storage/src/lib.rs
@@ -191,11 +191,15 @@ pub mod well_known_keys {
/// Wasm code of the runtime.
///
/// Stored as a raw byte vector. Required by substrate.
+ ///
+ /// Encodes to `0x3A636F6465`.
pub const CODE: &[u8] = b":code";
/// Number of wasm linear memory pages required for execution of the runtime.
///
/// The type of this value is encoded `u64`.
+ ///
+ /// Encodes to `0x307833413633364636343635`
pub const HEAP_PAGES: &[u8] = b":heappages";
/// Current extrinsic index (u32) is stored under this key.
--
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