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estimate_size.rs
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estimate_size.rs
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// Copyright 2023 RisingWave Labs
//
// 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 fixedbitset::FixedBitSet;
/// The trait for estimating the actual memory usage of a struct.
///
/// Used for cache eviction now.
pub trait EstimateSize {
/// The estimated heap size of the current struct in bytes.
fn estimated_heap_size(&self) -> usize;
/// The estimated total size of the current struct in bytes, including the `estimated_heap_size`
/// and the size of `Self`.
fn estimated_size(&self) -> usize
where
Self: Sized,
{
self.estimated_heap_size() + std::mem::size_of::<Self>()
}
}
impl EstimateSize for FixedBitSet {
fn estimated_heap_size(&self) -> usize {
self.as_slice().len() * std::mem::size_of::<u32>()
}
}
impl EstimateSize for Vec<u8> {
fn estimated_heap_size(&self) -> usize {
self.capacity()
}
}
impl<T> EstimateSize for Vec<T>
where
T: EstimateSize,
{
fn estimated_heap_size(&self) -> usize {
self.capacity() * std::mem::size_of::<T>()
+ self
.iter()
.map(EstimateSize::estimated_heap_size)
.sum::<usize>()
}
}
impl EstimateSize for String {
fn estimated_heap_size(&self) -> usize {
self.capacity()
}
}