iter_read/
impls.rs

1// Copyright (c) 2015-2023 Georg Brandl.  Licensed under the Apache License,
2// Version 2.0 <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0>
3// or the MIT license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at
4// your option. This file may not be copied, modified, or distributed except
5// according to those terms.
6
7use std::io;
8
9use crate::IterReadItem;
10
11
12macro_rules! impl_byte {
13    ($el_ty:ty, $($deref:tt)*) => {
14        impl<'a> IterReadItem for $el_ty {
15            impl_byte!(@inner [$($deref)*] []);
16        }
17
18        impl<'a, E> IterReadItem for Result<$el_ty, E> where io::Error: From<E> {
19            impl_byte!(@inner [$($deref)*] [?]);
20        }
21    };
22    (@inner [$($deref:tt)*] [$($try:tt)*]) => {
23        type Buffer = ();
24
25        fn read<I: Iterator<Item=Self>>(target: &mut [u8], it: &mut I,
26                                        _: &mut ()) -> io::Result<usize> {
27            let mut len = 0;
28            for (slot, elt) in target.iter_mut().zip(it) {
29                *slot = $($deref)* elt $($try)*;
30                len += 1;
31            }
32            Ok(len)
33        }
34    }
35}
36
37pub struct Buf<T> {
38    bytes: T,
39    consumed: usize,
40}
41
42macro_rules! impl_buf_default {
43    ($ty:ty) => {
44        impl<'a> Default for Buf<$ty> {
45            fn default() -> Self {
46                Buf { bytes: Default::default(), consumed: 0 }
47            }
48        }
49    }
50}
51
52impl_buf_default!(&'a [u8]);
53impl_buf_default!(Vec<u8>);
54
55impl<const N: usize> Default for Buf<[u8; N]> {
56    fn default() -> Self {
57        // The default needs to look like "everything is consumed",
58        // and the array has length N, so consumed needs to be N too.
59        Buf { bytes: [0; N], consumed: N }
60    }
61}
62
63macro_rules! impl_slice_like {
64    ($el_ty:ty [$($const:tt)*], $buf_ty:ty, $conv:ident) => {
65        impl<'a, $($const)*> IterReadItem for $el_ty {
66            impl_slice_like!(@inner $buf_ty, $conv, buf:
67                             Some(v) => {
68                                 *buf = Buf { bytes: v.$conv(), consumed: 0 };
69                             });
70        }
71
72        impl<'a, E, $($const)*> IterReadItem for Result<$el_ty, E> where io::Error: From<E> {
73            impl_slice_like!(@inner $buf_ty, $conv, buf:
74                             Some(Ok(v)) => {
75                                 *buf = Buf { bytes: v.$conv(), consumed: 0 };
76                             }
77                             Some(Err(err)) => {
78                                 *buf = Buf::default();
79                                 return Err(err.into());
80                             });
81        }
82    };
83    (@inner $buf_ty:ty, $conv:ident, $buf:ident : $($match:tt)+) => {
84        type Buffer = Buf<$buf_ty>;
85
86        fn read<I: Iterator<Item=Self>>(target: &mut [u8], it: &mut I,
87                                        $buf: &mut Self::Buffer) -> io::Result<usize> {
88            while $buf.consumed == $buf.bytes.len() {
89                match it.next() {
90                    $($match)+
91                    None => {
92                        *$buf = Buf::default();
93                        return Ok(0);
94                    }
95                }
96            }
97            let mut len = 0;
98            for (slot, elt) in target.iter_mut().zip(&$buf.bytes[$buf.consumed..]) {
99                *slot = *elt;
100                len += 1;
101            }
102            $buf.consumed += len;
103            Ok(len)
104        }
105    }
106}
107
108impl_byte!(u8, );
109impl_byte!(&'a u8, *);
110
111impl_slice_like!(&'a [u8] [], &'a [u8], into);
112impl_slice_like!(&'a Vec<u8> [], &'a [u8], as_slice);
113impl_slice_like!(Vec<u8> [], Vec<u8>, into);
114impl_slice_like!([u8; N] [const N: usize], [u8; N], into);
115impl_slice_like!(&'a [u8; N] [const N: usize], &'a [u8], as_slice);
116
117impl_slice_like!(&'a str [], &'a [u8], as_bytes);
118impl_slice_like!(&'a String [], &'a [u8], as_bytes);
119impl_slice_like!(String [], Vec<u8>, into_bytes);
iter_read/impls.rs

iter_read/
impls.rs
