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use anyhow::Result;
use std::cmp;
use std::ptr;
use crate::runtime::AsyncKernel;
use crate::runtime::Block;
use crate::runtime::BlockMeta;
use crate::runtime::BlockMetaBuilder;
use crate::runtime::MessageIo;
use crate::runtime::MessageIoBuilder;
use crate::runtime::StreamIo;
use crate::runtime::StreamIoBuilder;
use crate::runtime::WorkIo;
pub struct Head {
item_size: usize,
n_items: u64,
}
impl Head {
pub fn new(item_size: usize, n_items: u64) -> Block {
Block::new_async(
BlockMetaBuilder::new("Head").build(),
StreamIoBuilder::new()
.add_input("in", item_size)
.add_output("out", item_size)
.build(),
MessageIoBuilder::new().build(),
Head { item_size, n_items },
)
}
}
#[async_trait]
impl AsyncKernel for Head {
async fn work(
&mut self,
io: &mut WorkIo,
sio: &mut StreamIo,
_mio: &mut MessageIo<Self>,
_meta: &mut BlockMeta,
) -> Result<()> {
let i = sio.input(0).slice::<u8>();
let o = sio.output(0).slice::<u8>();
debug_assert_eq!(i.len() % self.item_size, 0);
debug_assert_eq!(o.len() % self.item_size, 0);
let mut m = cmp::min(self.n_items as usize, i.len() / self.item_size);
m = cmp::min(m, o.len() / self.item_size);
if m > 0 {
unsafe {
ptr::copy_nonoverlapping(i.as_ptr(), o.as_mut_ptr(), m * self.item_size);
}
self.n_items -= m as u64;
if self.n_items == 0 {
io.finished = true;
}
sio.input(0).consume(m);
sio.output(0).produce(m);
}
Ok(())
}
}
pub struct HeadBuilder {
n_items: u64,
item_size: usize,
}
impl HeadBuilder {
pub fn new(item_size: usize, n_items: u64) -> HeadBuilder {
HeadBuilder { n_items, item_size }
}
pub fn build(&mut self) -> Block {
Head::new(self.item_size, self.n_items)
}
}