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

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

use bytes::{buf::UninitSlice, Buf, BufMut, BytesMut};

/// A specialized buffer to decode gRPC messages from.
#[derive(Debug)]
pub struct DecodeBuf<'a> {
    buf: &'a mut BytesMut,
    len: usize,
}

/// A specialized buffer to encode gRPC messages into.
#[derive(Debug)]
pub struct EncodeBuf<'a> {
    buf: &'a mut BytesMut,
}

impl<'a> DecodeBuf<'a> {
    pub fn new(buf: &'a mut BytesMut, len: usize) -> Self {
        DecodeBuf { buf, len }
    }
}

impl Buf for DecodeBuf<'_> {
    #[inline]
    fn remaining(&self) -> usize {
        self.len
    }

    #[inline]
    fn chunk(&self) -> &[u8] {
        let ret = self.buf.chunk();

        if ret.len() > self.len {
            &ret[..self.len]
        } else {
            ret
        }
    }

    #[inline]
    fn advance(&mut self, cnt: usize) {
        assert!(cnt <= self.len);
        self.buf.advance(cnt);
        self.len -= cnt;
    }
}

impl<'a> EncodeBuf<'a> {
    pub fn new(buf: &'a mut BytesMut) -> Self {
        EncodeBuf { buf }
    }
}

impl EncodeBuf<'_> {
    /// Reserves capacity for at least `additional` more bytes to be inserted
    /// into the buffer.
    ///
    /// More than `additional` bytes may be reserved in order to avoid frequent
    /// reallocations. A call to `reserve` may result in an allocation.
    #[inline]
    pub fn reserve(&mut self, additional: usize) {
        self.buf.reserve(additional);
    }
}

unsafe impl BufMut for EncodeBuf<'_> {
    #[inline]
    fn remaining_mut(&self) -> usize {
        self.buf.remaining_mut()
    }

    #[inline]
    unsafe fn advance_mut(&mut self, cnt: usize) {
        self.buf.advance_mut(cnt)
    }

    #[inline]
    fn chunk_mut(&mut self) -> &mut UninitSlice {
        self.buf.chunk_mut()
    }
}

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

    #[test]
    fn decode_buf() {
        let mut payload = BytesMut::with_capacity(100);
        payload.put(&vec![0u8; 50][..]);
        let mut buf = DecodeBuf::new(&mut payload, 20);

        assert_eq!(buf.len, 20);
        assert_eq!(buf.remaining(), 20);
        assert_eq!(buf.chunk().len(), 20);

        buf.advance(10);
        assert_eq!(buf.remaining(), 10);

        let mut out = [0; 5];
        buf.copy_to_slice(&mut out);
        assert_eq!(buf.remaining(), 5);
        assert_eq!(buf.chunk().len(), 5);

        assert_eq!(buf.copy_to_bytes(5).len(), 5);
        assert!(!buf.has_remaining());
    }

    #[test]
    fn encode_buf() {
        let mut bytes = BytesMut::with_capacity(100);
        let mut buf = EncodeBuf::new(&mut bytes);

        let initial = buf.remaining_mut();
        unsafe { buf.advance_mut(20) };
        assert_eq!(buf.remaining_mut(), initial - 20);

        buf.put_u8(b'a');
        assert_eq!(buf.remaining_mut(), initial - 20 - 1);
    }
}