#![allow(clippy::len_without_is_empty)]
use core::convert::TryInto;
use core::ops::Range;
use core::{mem, result};
use crate::pod::{from_bytes, slice_from_bytes, Pod};
type Result<T> = result::Result<T, ()>;
pub trait ReadRef<'a>: Clone + Copy {
fn len(self) -> Result<u64>;
fn read_bytes_at(self, offset: u64, size: u64) -> Result<&'a [u8]>;
fn read_bytes_at_until(self, range: Range<u64>, delimiter: u8) -> Result<&'a [u8]>;
fn read_bytes(self, offset: &mut u64, size: u64) -> Result<&'a [u8]> {
let bytes = self.read_bytes_at(*offset, size)?;
*offset = offset.wrapping_add(size);
Ok(bytes)
}
fn read<T: Pod>(self, offset: &mut u64) -> Result<&'a T> {
let size = mem::size_of::<T>().try_into().map_err(|_| ())?;
let bytes = self.read_bytes(offset, size)?;
let (t, _) = from_bytes(bytes)?;
Ok(t)
}
fn read_at<T: Pod>(self, mut offset: u64) -> Result<&'a T> {
self.read(&mut offset)
}
fn read_slice<T: Pod>(self, offset: &mut u64, count: usize) -> Result<&'a [T]> {
let size = count
.checked_mul(mem::size_of::<T>())
.ok_or(())?
.try_into()
.map_err(|_| ())?;
let bytes = self.read_bytes(offset, size)?;
let (t, _) = slice_from_bytes(bytes, count)?;
Ok(t)
}
fn read_slice_at<T: Pod>(self, mut offset: u64, count: usize) -> Result<&'a [T]> {
self.read_slice(&mut offset, count)
}
}
impl<'a> ReadRef<'a> for &'a [u8] {
fn len(self) -> Result<u64> {
self.len().try_into().map_err(|_| ())
}
fn read_bytes_at(self, offset: u64, size: u64) -> Result<&'a [u8]> {
let offset: usize = offset.try_into().map_err(|_| ())?;
let size: usize = size.try_into().map_err(|_| ())?;
self.get(offset..).ok_or(())?.get(..size).ok_or(())
}
fn read_bytes_at_until(self, range: Range<u64>, delimiter: u8) -> Result<&'a [u8]> {
let start: usize = range.start.try_into().map_err(|_| ())?;
let end: usize = range.end.try_into().map_err(|_| ())?;
let bytes = self.get(start..end).ok_or(())?;
match memchr::memchr(delimiter, bytes) {
Some(len) => {
bytes.get(..len).ok_or(())
}
None => Err(()),
}
}
}