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

// Copyright 2023 Lance Developers.
//
// 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.

use std::ops::Range;

use async_trait::async_trait;
use bytes::Bytes;
use object_store::path::Path;
use prost::Message;
use tokio::io::{AsyncWrite, AsyncWriteExt};

use lance_core::Result;

pub trait ProtoStruct {
    type Proto: Message;
}

/// A trait for writing to a file on local file system or object store.
#[async_trait]
pub trait Writer: AsyncWrite + Unpin + Send {
    /// Tell the current offset.
    async fn tell(&mut self) -> Result<usize>;
}

/// Lance Write Extension.
#[async_trait]
pub trait WriteExt {
    /// Write a Protobuf message to the [Writer], and returns the file position
    /// where the protobuf is written.
    async fn write_protobuf(&mut self, msg: &impl Message) -> Result<usize>;

    async fn write_struct<
        'b,
        M: Message + From<&'b T>,
        T: ProtoStruct<Proto = M> + Send + Sync + 'b,
    >(
        &mut self,
        obj: &'b T,
    ) -> Result<usize> {
        let msg: M = M::from(obj);
        self.write_protobuf(&msg).await
    }
    /// Write magics to the tail of a file before closing the file.
    async fn write_magics(
        &mut self,
        pos: usize,
        major_version: i16,
        minor_version: i16,
        magic: &[u8],
    ) -> Result<()>;
}

#[async_trait]
impl<W: Writer + ?Sized> WriteExt for W {
    async fn write_protobuf(&mut self, msg: &impl Message) -> Result<usize> {
        let offset = self.tell().await?;

        let len = msg.encoded_len();

        self.write_u32_le(len as u32).await?;
        self.write_all(&msg.encode_to_vec()).await?;

        Ok(offset)
    }

    async fn write_magics(
        &mut self,
        pos: usize,
        major_version: i16,
        minor_version: i16,
        magic: &[u8],
    ) -> Result<()> {
        self.write_i64_le(pos as i64).await?;
        self.write_i16_le(major_version).await?;
        self.write_i16_le(minor_version).await?;
        self.write_all(magic).await?;
        Ok(())
    }
}

#[async_trait]
pub trait Reader: Send + Sync {
    fn path(&self) -> &Path;

    /// Suggest optimal I/O size per storage device.
    fn block_size(&self) -> usize;

    /// Object/File Size.
    async fn size(&self) -> Result<usize>;

    /// Read a range of bytes from the object.
    ///
    /// TODO: change to read_at()?
    async fn get_range(&self, range: Range<usize>) -> Result<Bytes>;
}