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use std::{
marker::PhantomData,
};
use crate::{
header::{Header, ProjectFrom, HasCol},
record::{Record, Col, ExternalRecord}
};
pub struct Projection<I,C> {
inner: I,
cols: PhantomData<C>
}
impl<I,C> Copy for Projection<I,C> where I:Copy {}
impl<I,C> Clone for Projection<I,C> where I:Clone {
fn clone(&self)->Self {
Projection { inner: self.inner.clone(), cols: PhantomData }
}
}
impl<I,C:Header> Projection<I,C> {
pub fn new(inner: I)->Self
where I: Clone + Record, C: ProjectFrom<I::Cols> {
Self { inner, cols: PhantomData }
}
pub fn new_unchecked(inner: I)->Self {
Self { inner, cols: PhantomData }
}
}
impl<I,Cols:Header> Record for Projection<I,Cols>
where I: Record
{
type Cols = Cols;
#[inline(always)]
fn into_cols(self)->Cols {
self.clone_cols()
}
#[inline(always)]
fn clone_cols<'a>(&'a self)->Cols {
Cols::clone_from_rec_unchecked(&self.inner)
}
#[inline(always)]
fn col_ref<C:Col>(&self)->&C where Self::Cols: HasCol<C> {
match self.inner.col_opt() {
Some(c) => c,
None => unreachable!()
}
}
#[inline(always)]
fn col_opt<C:Col>(&self)->Option<&C> {
if Cols::has_col::<C>() {
self.inner.col_opt()
} else {
None
}
}
}
impl<'a, I, Cols:Header> ExternalRecord<'a> for Projection<I,Cols>
where I: ExternalRecord<'a> {
#[inline(always)]
fn ext_col_ref<C:Col>(&self)->&'a C where Self::Cols: HasCol<C> {
match self.inner.ext_col_opt() {
Some(c) => c,
None => unreachable!()
}
}
#[inline(always)]
fn ext_col_opt<C:Col>(&self)->Option<&'a C> {
if Cols::has_col::<C>() {
self.inner.ext_col_opt()
} else {
None
}
}
}