1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80

// MIT License
//
// Copyright (c) 2023 Robin Doer
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

use std::mem;

/// Error type for the [`PutBytes`] trait.
///
/// [`PutBytes`] can generate one error: Not enough space is available in the
/// target. This kind of error can be created with
/// [`PutBytesError::no_space()`].
pub trait PutBytesError: std::error::Error {
    /// Creates a no space error.
    ///
    /// This error should be raised if the target has not anough space
    /// available.
    fn no_space() -> Self;
}

/// Trait that describes a writer of binary data.
///
/// The [`Writer`](crate::Writer) utility accepts all types that implements
/// this trait.
pub trait PutBytes {
    /// Appends all the given data in `buf` at the end of this writer.
    ///
    /// # Errors
    ///
    /// If not all data could be written, the implementator should
    /// create an no space error with [`PutBytesError::no_space()`].
    fn put_bytes<E: PutBytesError>(&mut self, buf: &[u8]) -> Result<(), E>;
}

/// `PutBytes` is implemented for `&mut [u8]` by copying into the slice,
/// overwriting its data.
///
/// Note that putting bytes updates the slice to point to the yet unwritten part.
/// The slice will be empty when it has been completely overwritten.
///
/// If the number of bytes to be written exceeds the size of the slice, the
/// operation will return an [`PutBytesError::no_space()`] error.
impl PutBytes for &mut [u8] {
    fn put_bytes<E: PutBytesError>(&mut self, buf: &[u8]) -> Result<(), E> {
        if self.len() >= buf.len() {
            let (a, b) = mem::replace(self, &mut []).split_at_mut(buf.len());

            a.copy_from_slice(buf);
            *self = b;

            Ok(())
        } else {
            Err(E::no_space())
        }
    }
}

/// `PutBytes` is implemented for [`Vec<u8>`] by appending bytes to the `Vec`.
impl PutBytes for Vec<u8> {
    fn put_bytes<E: PutBytesError>(&mut self, buf: &[u8]) -> Result<(), E> {
        Ok(self.extend_from_slice(buf))
    }
}