133 lines
4.2 KiB
Rust
133 lines
4.2 KiB
Rust
// Copyright 2019-2020 Google LLC
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
use crate::format::Format;
|
|
use crate::{usize_to_nat, StoreError, StoreRatio, StoreResult, StoreUpdate};
|
|
use std::collections::HashMap;
|
|
|
|
/// Models the mutable operations of a store.
|
|
///
|
|
/// The model doesn't model the storage and read-only operations. This is done by the driver.
|
|
#[derive(Clone, Debug)]
|
|
pub struct StoreModel {
|
|
/// Represents the content of the store.
|
|
content: HashMap<usize, Box<[u8]>>,
|
|
|
|
/// The modeled storage configuration.
|
|
format: Format,
|
|
}
|
|
|
|
/// Mutable operations on a store.
|
|
#[derive(Clone, Debug)]
|
|
pub enum StoreOperation {
|
|
/// Applies a transaction.
|
|
Transaction {
|
|
/// The list of updates to be applied.
|
|
updates: Vec<StoreUpdate<Vec<u8>>>,
|
|
},
|
|
|
|
/// Deletes all keys above a threshold.
|
|
Clear {
|
|
/// The minimum key to be deleted.
|
|
min_key: usize,
|
|
},
|
|
|
|
/// Compacts the store until a given capacity is immediately available.
|
|
Prepare {
|
|
/// How much capacity should be immediately available after compaction.
|
|
length: usize,
|
|
},
|
|
}
|
|
|
|
impl StoreModel {
|
|
/// Creates an empty model for a given storage configuration.
|
|
pub fn new(format: Format) -> StoreModel {
|
|
let content = HashMap::new();
|
|
StoreModel { content, format }
|
|
}
|
|
|
|
/// Returns the modeled content.
|
|
pub fn content(&self) -> &HashMap<usize, Box<[u8]>> {
|
|
&self.content
|
|
}
|
|
|
|
/// Returns the storage configuration.
|
|
pub fn format(&self) -> &Format {
|
|
&self.format
|
|
}
|
|
|
|
/// Simulates a store operation.
|
|
pub fn apply(&mut self, operation: StoreOperation) -> StoreResult<()> {
|
|
match operation {
|
|
StoreOperation::Transaction { updates } => self.transaction(updates),
|
|
StoreOperation::Clear { min_key } => self.clear(min_key),
|
|
StoreOperation::Prepare { length } => self.prepare(length),
|
|
}
|
|
}
|
|
|
|
/// Returns the capacity according to the model.
|
|
pub fn capacity(&self) -> StoreRatio {
|
|
let total = self.format.total_capacity();
|
|
let used = usize_to_nat(
|
|
self.content
|
|
.values()
|
|
.map(|x| self.format.entry_size(x) as usize)
|
|
.sum(),
|
|
);
|
|
StoreRatio { used, total }
|
|
}
|
|
|
|
/// Applies a transaction.
|
|
fn transaction(&mut self, updates: Vec<StoreUpdate<Vec<u8>>>) -> StoreResult<()> {
|
|
// Fail if the transaction is invalid.
|
|
if self.format.transaction_valid(&updates).is_none() {
|
|
return Err(StoreError::InvalidArgument);
|
|
}
|
|
// Fail if there is not enough capacity.
|
|
let capacity = self.format.transaction_capacity(&updates) as usize;
|
|
if self.capacity().remaining() < capacity {
|
|
return Err(StoreError::NoCapacity);
|
|
}
|
|
// Apply the updates.
|
|
for update in updates {
|
|
match update {
|
|
StoreUpdate::Insert { key, value } => {
|
|
self.content.insert(key, value.into_boxed_slice());
|
|
}
|
|
StoreUpdate::Remove { key } => {
|
|
self.content.remove(&key);
|
|
}
|
|
}
|
|
}
|
|
Ok(())
|
|
}
|
|
|
|
/// Applies a clear operation.
|
|
fn clear(&mut self, min_key: usize) -> StoreResult<()> {
|
|
if min_key > self.format.max_key() as usize {
|
|
return Err(StoreError::InvalidArgument);
|
|
}
|
|
self.content.retain(|&k, _| k < min_key);
|
|
Ok(())
|
|
}
|
|
|
|
/// Applies a prepare operation.
|
|
fn prepare(&self, length: usize) -> StoreResult<()> {
|
|
if self.capacity().remaining() < length {
|
|
return Err(StoreError::NoCapacity);
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|