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

use bird_protocol::packet::{CustomError, InputPacketBytes, InputPacketBytesError, InputPacketBytesResult, PacketReadable, PacketReadableResult};
use tokio::io::AsyncReadExt;
use tokio::net::tcp::OwnedReadHalf;
use bird_protocol::types::VarInt;

#[derive(Clone, Copy)]
struct SlicePointer {
    ptr: *mut u8,
}

unsafe impl Send for SlicePointer {}

unsafe impl Sync for SlicePointer {}

pub struct ReadStreamQueue<const BUFFER_SIZE: usize> {
    read_half: OwnedReadHalf,
    packet_length: usize,
    packet_offset: usize,
    buffer: [u8; BUFFER_SIZE],
    buffer_size: usize,
    buffer_offset: usize,
}

impl<const BUFFER_SIZE: usize> From<OwnedReadHalf> for ReadStreamQueue<BUFFER_SIZE> {
    fn from(read_half: OwnedReadHalf) -> Self {
        ReadStreamQueue::new(read_half)
    }
}

impl<const BUFFER_SIZE: usize> From<ReadStreamQueue<BUFFER_SIZE>> for OwnedReadHalf {
    fn from(queue: ReadStreamQueue<BUFFER_SIZE>) -> Self {
        queue.read_half
    }
}

impl<const BUFFER_SIZE: usize> ReadStreamQueue<BUFFER_SIZE> {
    pub fn new(read_half: OwnedReadHalf) -> Self {
        Self {
            read_half,
            packet_length: 0,
            packet_offset: 0,
            buffer: [0; BUFFER_SIZE],
            buffer_size: 0,
            buffer_offset: 0,
        }
    }

    pub fn close(self) -> (OwnedReadHalf, Box<[u8]>) {
        (
            self.read_half,
            self.buffer[self.buffer_offset..self.buffer_size].into(),
        )
    }

    async fn read_next_bytes(&mut self) -> InputPacketBytesResult<()> {
        match self.read_half.read(&mut self.buffer).await {
            Ok(0) | Err(_) => Err(
                CustomError::StaticStr("Connection was closed during reading").into()
            ),
            Ok(len) => {
                self.buffer_size = len;
                self.buffer_offset = 0;
                log::debug!("Received bytes: {:?}", &self.buffer[0..self.buffer_size]);
                Ok(())
            }
        }
    }

    async fn read_next_bytes_if_need(&mut self) -> InputPacketBytesResult<()> {
        match self.buffer_offset == self.buffer_size {
            true => self.read_next_bytes().await,
            false => Ok(())
        }
    }

    pub async fn next_packet(&mut self) -> PacketReadableResult<()> {
        self.packet_length = 5; // maximum VarInt length
        self.packet_offset = 0;
        self.packet_length = <VarInt as PacketReadable>::read(self).await?.0 as usize;
        self.packet_offset = 0;
        Ok(())
    }

    async unsafe fn copy_into(&mut self, mut dst: SlicePointer, count: usize) -> InputPacketBytesResult<()> {
        let mut offset: usize = 0;
        loop {
            let can_copy = self.buffer_size - self.buffer_offset;
            let need_copy = count - offset;
            match need_copy > can_copy {
                true => {
                    std::ptr::copy_nonoverlapping(
                        self.buffer.as_ptr().add(self.buffer_offset), dst.ptr, can_copy,
                    );
                    dst.ptr = dst.ptr.add(can_copy);
                    offset += can_copy;
                    self.read_next_bytes().await?
                }
                false => {
                    std::ptr::copy_nonoverlapping(
                        self.buffer.as_ptr().add(self.buffer_offset), dst.ptr, need_copy,
                    );
                    self.buffer_offset += need_copy;
                    break Ok(());
                }
            }
        }
    }
}

#[async_trait::async_trait]
impl<const BUFFER_SIZE: usize> InputPacketBytes for ReadStreamQueue<BUFFER_SIZE> {
    async fn take_byte(&mut self) -> InputPacketBytesResult<u8> {
        match self.packet_offset == self.packet_length {
            true => Err(InputPacketBytesError::NoBytes(self.packet_length)),
            false => {
                self.read_next_bytes_if_need().await?;
                let byte = self.buffer[self.buffer_offset];
                self.buffer_offset += 1;
                self.packet_offset += 1;
                Ok(byte)
            }
        }
    }

    async fn take_slice(&mut self, slice: &mut [u8]) -> InputPacketBytesResult<()> {
        match self.has_bytes(slice.len()) {
            true => unsafe {
                let slice_pointer = SlicePointer { ptr: slice.as_mut_ptr() };
                self.copy_into(slice_pointer, slice.len()).await
            },
            false => Err(InputPacketBytesError::NoBytes(self.packet_length)),
        }
    }

    async fn take_vec(&mut self, vec: &mut Vec<u8>, count: usize) -> InputPacketBytesResult<()> {
        match self.has_bytes(count) {
            true => unsafe {
                vec.resize(count, 0);
                let slice_pointer = SlicePointer { ptr: vec.as_mut_ptr() };
                self.copy_into(slice_pointer, count).await
            },
            false => Err(InputPacketBytesError::NoBytes(self.packet_length))
        }
    }

    fn has_bytes(&self, count: usize) -> bool {
        self.remaining_bytes() >= count
    }

    fn remaining_bytes(&self) -> usize {
        match self.packet_length > self.packet_offset {
            true => self.packet_length - self.packet_offset,
            false => 0
        }
    }
}