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
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
#[cfg(not(feature = "std"))]
use alloc::boxed::Box;
#[cfg(not(feature = "std"))]
use alloc::vec::Vec;

use core::fmt::Debug;

use bytes::{Buf, BufMut};

use crate::encoding::{
    decode_key, encode_varint, encoded_len_varint, message, DecodeContext, WireType,
};
use crate::DecodeError;
use crate::EncodeError;

/// A Protocol Buffers message.
pub trait Message: Debug + Send + Sync {
    /// Encodes the message to a buffer.
    ///
    /// This method will panic if the buffer has insufficient capacity.
    ///
    /// Meant to be used only by `Message` implementations.
    #[doc(hidden)]
    fn encode_raw<B>(&self, buf: &mut B)
    where
        B: BufMut,
        Self: Sized;

    /// Decodes a field from a buffer, and merges it into `self`.
    ///
    /// Meant to be used only by `Message` implementations.
    #[doc(hidden)]
    fn merge_field<B>(
        &mut self,
        tag: u32,
        wire_type: WireType,
        buf: &mut B,
        ctx: DecodeContext,
    ) -> Result<(), DecodeError>
    where
        B: Buf,
        Self: Sized;

    /// Returns the encoded length of the message without a length delimiter.
    fn encoded_len(&self) -> usize;

    /// Encodes the message to a buffer.
    ///
    /// An error will be returned if the buffer does not have sufficient capacity.
    fn encode<B>(&self, buf: &mut B) -> Result<(), EncodeError>
    where
        B: BufMut,
        Self: Sized,
    {
        let required = self.encoded_len();
        let remaining = buf.remaining_mut();
        if required > remaining {
            return Err(EncodeError::new(required, remaining));
        }

        self.encode_raw(buf);
        Ok(())
    }

    /// Encodes the message to a newly allocated buffer.
    fn encode_to_vec(&self) -> Vec<u8>
    where
        Self: Sized,
    {
        let mut buf = Vec::with_capacity(self.encoded_len());

        self.encode_raw(&mut buf);
        buf
    }

    /// Encodes the message with a length-delimiter to a buffer.
    ///
    /// An error will be returned if the buffer does not have sufficient capacity.
    fn encode_length_delimited<B>(&self, buf: &mut B) -> Result<(), EncodeError>
    where
        B: BufMut,
        Self: Sized,
    {
        let len = self.encoded_len();
        let required = len + encoded_len_varint(len as u64);
        let remaining = buf.remaining_mut();
        if required > remaining {
            return Err(EncodeError::new(required, remaining));
        }
        encode_varint(len as u64, buf);
        self.encode_raw(buf);
        Ok(())
    }

    /// Encodes the message with a length-delimiter to a newly allocated buffer.
    fn encode_length_delimited_to_vec(&self) -> Vec<u8>
    where
        Self: Sized,
    {
        let len = self.encoded_len();
        let mut buf = Vec::with_capacity(len + encoded_len_varint(len as u64));

        encode_varint(len as u64, &mut buf);
        self.encode_raw(&mut buf);
        buf
    }

    /// Decodes an instance of the message from a buffer.
    ///
    /// The entire buffer will be consumed.
    fn decode<B>(mut buf: B) -> Result<Self, DecodeError>
    where
        B: Buf,
        Self: Default,
    {
        let mut message = Self::default();
        Self::merge(&mut message, &mut buf).map(|_| message)
    }

    /// Decodes a length-delimited instance of the message from the buffer.
    fn decode_length_delimited<B>(buf: B) -> Result<Self, DecodeError>
    where
        B: Buf,
        Self: Default,
    {
        let mut message = Self::default();
        message.merge_length_delimited(buf)?;
        Ok(message)
    }

    /// Decodes an instance of the message from a buffer, and merges it into `self`.
    ///
    /// The entire buffer will be consumed.
    fn merge<B>(&mut self, mut buf: B) -> Result<(), DecodeError>
    where
        B: Buf,
        Self: Sized,
    {
        let ctx = DecodeContext::default();
        while buf.has_remaining() {
            let (tag, wire_type) = decode_key(&mut buf)?;
            self.merge_field(tag, wire_type, &mut buf, ctx.clone())?;
        }
        Ok(())
    }

    /// Decodes a length-delimited instance of the message from buffer, and
    /// merges it into `self`.
    fn merge_length_delimited<B>(&mut self, mut buf: B) -> Result<(), DecodeError>
    where
        B: Buf,
        Self: Sized,
    {
        message::merge(
            WireType::LengthDelimited,
            self,
            &mut buf,
            DecodeContext::default(),
        )
    }

    /// Clears the message, resetting all fields to their default.
    fn clear(&mut self);
}

impl<M> Message for Box<M>
where
    M: Message,
{
    fn encode_raw<B>(&self, buf: &mut B)
    where
        B: BufMut,
    {
        (**self).encode_raw(buf)
    }
    fn merge_field<B>(
        &mut self,
        tag: u32,
        wire_type: WireType,
        buf: &mut B,
        ctx: DecodeContext,
    ) -> Result<(), DecodeError>
    where
        B: Buf,
    {
        (**self).merge_field(tag, wire_type, buf, ctx)
    }
    fn encoded_len(&self) -> usize {
        (**self).encoded_len()
    }
    fn clear(&mut self) {
        (**self).clear()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    const _MESSAGE_IS_OBJECT_SAFE: Option<&dyn Message> = None;
}