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
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143

// Copyright 2020 IOTA Stiftung
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
// an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and limitations under the License.

//! A module that provides a `Packable` trait to serialize and deserialize types.

pub use std::io::{Read, Write};

/// A trait to pack and unpack types to and from bytes.
pub trait Packable {
    /// Associated error type.
    type Error: std::fmt::Debug;

    /// Returns the length of the packed bytes.
    fn packed_len(&self) -> usize;

    /// Packs the instance to bytes and writes them to the passed writer.
    fn pack<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error>;

    /// Packs the instance to bytes and writes them to a newly allocated vector.
    fn pack_new(&self) -> Vec<u8> {
        let mut bytes = Vec::with_capacity(self.packed_len());
        // Packing to bytes can't fail.
        self.pack(&mut bytes).unwrap();

        bytes
    }

    /// Reads bytes from the passed reader and unpacks them into an instance.
    fn unpack<R: Read + ?Sized>(reader: &mut R) -> Result<Self, Self::Error>
    where
        Self: Sized;
}

impl Packable for bool {
    type Error = std::io::Error;

    fn packed_len(&self) -> usize {
        (*self as u8).packed_len()
    }

    fn pack<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error> {
        (*self as u8).pack(writer)
    }

    fn unpack<R: Read + ?Sized>(reader: &mut R) -> Result<Self, Self::Error>
    where
        Self: Sized,
    {
        Ok(!matches!(u8::unpack(reader)?, 0))
    }
}

/// Error that occurs on `Option<P: Packable>` operations.
#[derive(Debug)]
pub enum OptionError<E> {
    /// Error that occurs on boolean `Packable` operations.
    Bool(<bool as Packable>::Error),
    /// Error that occurs on inner `Packable` operations.
    Inner(E),
}

impl<P: Packable> Packable for Option<P> {
    type Error = OptionError<P::Error>;

    fn packed_len(&self) -> usize {
        true.packed_len()
            + match self {
                Some(p) => p.packed_len(),
                None => 0,
            }
    }

    fn pack<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error> {
        match self {
            Some(p) => {
                true.pack(writer).map_err(OptionError::Bool)?;
                p.pack(writer).map_err(OptionError::Inner)?;
            }
            None => {
                false.pack(writer).map_err(OptionError::Bool)?;
            }
        }

        Ok(())
    }

    fn unpack<R: Read + ?Sized>(reader: &mut R) -> Result<Self, Self::Error>
    where
        Self: Sized,
    {
        Ok(match bool::unpack(reader).map_err(OptionError::Bool)? {
            true => Some(P::unpack(reader).map_err(OptionError::Inner)?),
            false => None,
        })
    }
}

macro_rules! impl_packable_for_num {
    ($ty:ident) => {
        impl Packable for $ty {
            type Error = std::io::Error;

            fn packed_len(&self) -> usize {
                std::mem::size_of_val(&self.to_le_bytes())
            }

            fn pack<W: Write>(&self, writer: &mut W) -> Result<(), Self::Error> {
                writer.write_all(&self.to_le_bytes())?;

                Ok(())
            }

            fn unpack<R: Read + ?Sized>(reader: &mut R) -> Result<Self, Self::Error>
            where
                Self: Sized,
            {
                let mut bytes = [0; $ty::MIN.to_le_bytes().len()];
                reader.read_exact(&mut bytes)?;

                Ok($ty::from_le_bytes(bytes))
            }
        }
    };
}

impl_packable_for_num!(i8);
impl_packable_for_num!(u8);
impl_packable_for_num!(i16);
impl_packable_for_num!(u16);
impl_packable_for_num!(i32);
impl_packable_for_num!(u32);
impl_packable_for_num!(i64);
impl_packable_for_num!(u64);
impl_packable_for_num!(i128);
impl_packable_for_num!(u128);