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

use bytes::buf::UninitSlice;
use bytes::{Buf, BufMut, Bytes, 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(crate) 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;
    }

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

impl<'a> EncodeBuf<'a> {
    pub(crate) 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()
    }

    #[inline]
    fn put<T: Buf>(&mut self, src: T)
    where
        Self: Sized,
    {
        self.buf.put(src)
    }

    #[inline]
    fn put_slice(&mut self, src: &[u8]) {
        self.buf.put_slice(src)
    }

    #[inline]
    fn put_bytes(&mut self, val: u8, cnt: usize) {
        self.buf.put_bytes(val, cnt);
    }
}

#[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);
    }
}