kernel/hil/kv.rs
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// Licensed under the Apache License, Version 2.0 or the MIT License.
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Copyright Tock Contributors 2023.
//! Interface for Key-Value (KV) Stores
//!
//! The KV store implementation in Tock has two levels:
//!
//! 1. **KV Level**: This level provides a standard key-value interface with
//! common get/set/add/update/delete operations.
//!
//! 2. **KV Permissions Level**: This level mirrors the `KV` interface, but each
//! call requires storage permissions. This permits implementing access
//! control permissions with key-value stores in Tock.
//!
//! The expected setup inside Tock will look like this:
//!
//! ```text
//! +-----------------------+
//! | Capsule using K-V |
//! +-----------------------+
//!
//! hil::kv::KVPermissions (this file)
//!
//! +-----------------------+
//! | K-V in Tock |
//! +-----------------------+
//!
//! hil::kv::KV (this file)
//!
//! +-----------------------+
//! | K-V library |
//! +-----------------------+
//!
//! hil::flash
//! ```
use crate::storage_permissions::StoragePermissions;
use crate::utilities::leasable_buffer::SubSliceMut;
use crate::ErrorCode;
/// Callback trait for KV stores.
///
/// Implement this trait and use `set_client()` to receive callbacks.
pub trait KVClient {
/// This callback is called when the get operation completes.
///
/// If there wasn't enough room to store the entire buffer `SIZE` will be
/// returned in `result` and the bytes that did fit will be copied into the
/// buffer.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success
/// - `Err(ErrorCode)` on error. Valid `ErrorCode`s:
/// - `SIZE`: The value is longer than the provided buffer. The amount of
/// the value that fits in the buffer is provided.
/// - `NOSUPPORT`: The key could not be found or the caller does not have
/// permission to read this key. The data in the `value` buffer is
/// meaningless.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
/// - `key`: The key buffer.
/// - `value`: The value buffer.
fn get_complete(
&self,
result: Result<(), ErrorCode>,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
);
/// This callback is called when the set operation completes.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success, `Err(ErrorCode)` on error. Valid
/// `ErrorCode`s:
/// - `NOSUPPORT`: The caller does not have permission to store this key.
/// - `NOMEM`: The key could not be set because the KV store is full.
/// - `SIZE`: The key could not be set because the key or value is too
/// many bytes.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
/// - `key`: The key buffer.
/// - `value`: The value buffer.
fn set_complete(
&self,
result: Result<(), ErrorCode>,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
);
/// This callback is called when the add operation completes.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success, `Err(ErrorCode)` on error. Valid
/// `ErrorCode`s:
/// - `NOSUPPORT`: The key already exists and cannot be added.
/// - `NOMEM`: The key could not be added because the KV store is full.
/// - `SIZE`: The key could not be set because the key or value is too
/// many bytes.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
/// - `key`: The key buffer.
/// - `value`: The value buffer.
fn add_complete(
&self,
result: Result<(), ErrorCode>,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
);
/// This callback is called when the update operation completes.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success, `Err(ErrorCode)` on error. Valid
/// `ErrorCode`s:
/// - `NOSUPPORT`: The key does not already exist and cannot be modified
/// or the caller does not have permission to modify this key.
/// - `NOMEM`: The key could not be updated because the KV store is full.
/// - `SIZE`: The key could not be set because the key or value is too
/// many bytes.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
/// - `key`: The key buffer.
/// - `value`: The value buffer.
fn update_complete(
&self,
result: Result<(), ErrorCode>,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
);
/// This callback is called when the delete operation completes.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success, `Err(ErrorCode)` on error. Valid
/// `ErrorCode`s:
/// - `NOSUPPORT`: The key does not exist or the caller does not have
/// permission to delete this key.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
/// - `key`: The key buffer.
fn delete_complete(&self, result: Result<(), ErrorCode>, key: SubSliceMut<'static, u8>);
/// This callback is called when the garbage collection operation completes.
///
/// ### Return Values
///
/// - `result`: `Ok(())` on success, `Err(ErrorCode)` on error. Valid
/// `ErrorCode`s:
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn garbage_collection_complete(&self, result: Result<(), ErrorCode>);
}
/// Key-Value interface with permissions.
///
/// This interface provides access to key-value storage with access control.
/// Each object is marked with a `write_id` (based on the `StoragePermissions`
/// used to create it), and all further accesses and modifications to that
/// object require suitable permissions.
pub trait KVPermissions<'a> {
/// Configure the client for operation callbacks.
fn set_client(&self, client: &'a dyn KVClient);
/// Retrieve a value based on the given key.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: Where the returned value buffer will be stored.
/// - `permissions`: The read/write/modify permissions for this access.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn get(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
permissions: StoragePermissions,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Store a value based on the given key. If the key does not exist it will
/// be added. If the key already exists the value will be updated.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store. The provided buffer MUST start
/// `KVPermissions.header_size()` bytes after the beginning of the buffer
/// to enable the implementation to insert a header.
/// - `permissions`: The read/write/modify permissions for this access.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: There is insufficient room to include the permission header
/// in the `value` buffer or the key/value is too large to store.
/// - `INVAL`: The caller does not have write permissions.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn set(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
permissions: StoragePermissions,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Store a new value based on the given key. If the key does not exist it
/// will be added. If the key already exists an error callback will be
/// provided.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store. The provided buffer MUST start
/// `KVPermissions.header_size()` bytes after the beginning of the buffer
/// to enable the implementation to insert a header.
/// - `permissions`: The read/write/modify permissions for this access.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: There is insufficient room to include the permission header
/// in the `value` buffer or the key/value is too large to store.
/// - `INVAL`: The caller does not have write permissions.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn add(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
permissions: StoragePermissions,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Modify a value based on the given key. If the key does not exist it an
/// error callback will be provided.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store. The provided buffer MUST start
/// `KVPermissions.header_size()` bytes after the beginning of the buffer
/// to enable the implementation to insert a header.
/// - `permissions`: The read/write/modify permissions for this access.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: There is insufficient room to include the permission header
/// in the `value` buffer or the key/value is too large to store.
/// - `INVAL`: The caller does not have write permissions.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn update(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
permissions: StoragePermissions,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Delete a key-value object based on the given key.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `permissions`: The read/write/modify permissions for this access.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `INVAL`: The caller does not have modify permissions.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn delete(
&self,
key: SubSliceMut<'static, u8>,
permissions: StoragePermissions,
) -> Result<(), (SubSliceMut<'static, u8>, ErrorCode)>;
/// Run garbage collection on the underlying Key/Value store.
///
/// This is generally used to reclaim keys that have been removed with
/// the `delete()` call.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn garbage_collect(&self) -> Result<(), ErrorCode>;
/// Returns the length of the key-value store's header in bytes.
///
/// Room for this header must be accommodated in a `set`, `add`, or `update`
/// operation.
fn header_size(&self) -> usize;
}
/// Key-Value interface.
///
/// This interface provides access to key-value storage.
///
/// `KV` includes five typical commands:
/// - `get(key) -> value`
/// - `set(key, value)`
/// - `add(key, value)`
/// - `update(key, value)`
/// - `delete(key)`
pub trait KV<'a> {
/// Configure the client for operation callbacks.
fn set_client(&self, client: &'a dyn KVClient);
/// Retrieve a value based on the given key.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: Where the returned value buffer will be stored.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn get(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Store a value based on the given key. If the key does not exist it will
/// be added. If the key already exists the value will be updated.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: The key/value is too large to store.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn set(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Store a new value based on the given key. If the key does not exist it
/// will be added. If the key already exists an error callback will be
/// provided.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: The key/value is too large to store.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn add(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Modify a value based on the given key. If the key does not exist it an
/// error callback will be provided.
///
/// The `value` buffer must have room for a header.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
/// - `value`: The value to store.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `SIZE`: The key/value is too large to store.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn update(
&self,
key: SubSliceMut<'static, u8>,
value: SubSliceMut<'static, u8>,
) -> Result<
(),
(
SubSliceMut<'static, u8>,
SubSliceMut<'static, u8>,
ErrorCode,
),
>;
/// Delete a key-value object based on the given key.
///
/// ### Arguments
///
/// - `key`: The key to identify the k-v pair.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn delete(
&self,
key: SubSliceMut<'static, u8>,
) -> Result<(), (SubSliceMut<'static, u8>, ErrorCode)>;
/// Run garbage collection on the underlying Key/Value store.
///
/// This is generally used to reclaim keys that have been removed with
/// the `delete()` call.
///
/// ### Return
///
/// - On success returns `Ok(())`. A callback will be issued.
/// - On error, returns the buffers and:
/// - `BUSY`: An operation is already in progress.
/// - `FAIL`: An internal error occurred and the operation cannot be
/// completed.
fn garbage_collect(&self) -> Result<(), ErrorCode>;
}