use std::cmp;
use std::ptr;
use crate::anyhow::Result;
use crate::runtime::Block;
use crate::runtime::BlockMeta;
use crate::runtime::BlockMetaBuilder;
use crate::runtime::Kernel;
use crate::runtime::MessageIo;
use crate::runtime::MessageIoBuilder;
use crate::runtime::StreamIo;
use crate::runtime::StreamIoBuilder;
use crate::runtime::WorkIo;
pub struct Head<T: Send + 'static> {
n_items: u64,
_type: std::marker::PhantomData<T>,
}
impl<T: Send + 'static> Head<T> {
pub fn new(n_items: u64) -> Block {
Block::new(
BlockMetaBuilder::new("Head").build(),
StreamIoBuilder::new()
.add_input("in", std::mem::size_of::<T>())
.add_output("out", std::mem::size_of::<T>())
.build(),
MessageIoBuilder::new().build(),
Head::<T> {
n_items,
_type: std::marker::PhantomData,
},
)
}
}
#[doc(hidden)]
#[async_trait]
impl<T: Send + 'static> Kernel for Head<T> {
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>();
let item_size = std::mem::size_of::<T>();
let mut m = cmp::min(self.n_items as usize, i.len() / item_size);
m = cmp::min(m, o.len() / item_size);
if m > 0 {
unsafe {
ptr::copy_nonoverlapping(i.as_ptr(), o.as_mut_ptr(), m * 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(())
}
}