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181//! Specifications for containers
#![forbid(missing_docs)]
#[cfg(feature = "columnation")]
pub mod columnation;
/// A container transferring data through dataflow edges
///
/// A container stores a number of elements and thus is able to describe it length (`len()`) and
/// whether it is empty (`is_empty()`). It supports removing all elements (`clear`).
///
/// A container must implement default. The default implementation is not required to allocate
/// memory for variable-length components.
///
/// We require the container to be cloneable to enable efficient copies when providing references
/// of containers to operators. Care must be taken that the type's `clone_from` implementation
/// is efficient (which is not necessarily the case when deriving `Clone`.)
/// TODO: Don't require `Container: Clone`
pub trait Container: Default + Clone + 'static {
/// The type of elements this container holds.
type Item;
/// The number of elements in this container
///
/// The length of a container must be consistent between sending and receiving it.
/// When exchanging a container and partitioning it into pieces, the sum of the length
/// of all pieces must be equal to the length of the original container.
fn len(&self) -> usize;
/// Determine if the container contains any elements, corresponding to `len() == 0`.
fn is_empty(&self) -> bool {
self.len() == 0
}
/// The capacity of the underlying container
fn capacity(&self) -> usize;
/// Remove all contents from `self` while retaining allocated memory.
/// After calling `clear`, `is_empty` must return `true` and `len` 0.
fn clear(&mut self);
}
impl<T: Clone + 'static> Container for Vec<T> {
type Item = T;
fn len(&self) -> usize {
Vec::len(self)
}
fn is_empty(&self) -> bool {
Vec::is_empty(self)
}
fn capacity(&self) -> usize {
Vec::capacity(self)
}
fn clear(&mut self) { Vec::clear(self) }
}
mod rc {
use std::rc::Rc;
use crate::Container;
impl<T: Container> Container for Rc<T> {
type Item = T::Item;
fn len(&self) -> usize {
std::ops::Deref::deref(self).len()
}
fn is_empty(&self) -> bool {
std::ops::Deref::deref(self).is_empty()
}
fn capacity(&self) -> usize {
std::ops::Deref::deref(self).capacity()
}
fn clear(&mut self) {
// Try to reuse the allocation if possible
if let Some(inner) = Rc::get_mut(self) {
inner.clear();
} else {
*self = Self::default();
}
}
}
}
mod arc {
use std::sync::Arc;
use crate::Container;
impl<T: Container> Container for Arc<T> {
type Item = T::Item;
fn len(&self) -> usize {
std::ops::Deref::deref(self).len()
}
fn is_empty(&self) -> bool {
std::ops::Deref::deref(self).is_empty()
}
fn capacity(&self) -> usize {
std::ops::Deref::deref(self).capacity()
}
fn clear(&mut self) {
// Try to reuse the allocation if possible
if let Some(inner) = Arc::get_mut(self) {
inner.clear();
} else {
*self = Self::default();
}
}
}
}
/// A container that can partition itself into pieces.
pub trait PushPartitioned: Container {
/// Partition and push this container.
///
/// Drain all elements from `self`, and use the function `index` to determine which `buffer` to
/// append an element to. Call `flush` with an index and a buffer to send the data downstream.
fn push_partitioned<I, F>(&mut self, buffers: &mut [Self], index: I, flush: F)
where
I: FnMut(&Self::Item) -> usize,
F: FnMut(usize, &mut Self);
}
impl<T: Clone + 'static> PushPartitioned for Vec<T> {
fn push_partitioned<I, F>(&mut self, buffers: &mut [Self], mut index: I, mut flush: F)
where
I: FnMut(&Self::Item) -> usize,
F: FnMut(usize, &mut Self),
{
fn ensure_capacity<E>(this: &mut Vec<E>) {
let capacity = this.capacity();
let desired_capacity = buffer::default_capacity::<E>();
if capacity < desired_capacity {
this.reserve(desired_capacity - capacity);
}
}
for datum in self.drain(..) {
let index = index(&datum);
ensure_capacity(&mut buffers[index]);
buffers[index].push(datum);
if buffers[index].len() == buffers[index].capacity() {
flush(index, &mut buffers[index]);
}
}
}
}
pub mod buffer {
//! Functionality related to calculating default buffer sizes
/// The upper limit for buffers to allocate, size in bytes. [default_capacity] converts
/// this to size in elements.
pub const BUFFER_SIZE_BYTES: usize = 1 << 13;
/// The maximum buffer capacity in elements. Returns a number between [BUFFER_SIZE_BYTES]
/// and 1, inclusively.
pub const fn default_capacity<T>() -> usize {
let size = ::std::mem::size_of::<T>();
if size == 0 {
BUFFER_SIZE_BYTES
} else if size <= BUFFER_SIZE_BYTES {
BUFFER_SIZE_BYTES / size
} else {
1
}
}
}