opendal/services/fs/
reader.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use std::sync::Arc;
19
20use tokio::io::AsyncReadExt;
21use tokio::io::ReadBuf;
22
23use super::core::*;
24use crate::raw::*;
25use crate::*;
26
27pub struct FsReader<F> {
28    core: Arc<FsCore>,
29    f: F,
30    read: usize,
31    size: usize,
32    buf_size: usize,
33}
34
35impl<F> FsReader<F> {
36    pub fn new(core: Arc<FsCore>, f: F, size: usize) -> Self {
37        Self {
38            core,
39            f,
40            read: 0,
41            size,
42            // Use 2 MiB as default value.
43            buf_size: 2 * 1024 * 1024,
44        }
45    }
46}
47
48impl oio::Read for FsReader<tokio::fs::File> {
49    async fn read(&mut self) -> Result<Buffer> {
50        if self.read >= self.size {
51            return Ok(Buffer::new());
52        }
53
54        let mut bs = self.core.buf_pool.get();
55        bs.reserve(self.buf_size);
56
57        let size = (self.size - self.read).min(self.buf_size);
58        let buf = &mut bs.spare_capacity_mut()[..size];
59        let mut read_buf: ReadBuf = ReadBuf::uninit(buf);
60
61        // SAFETY: Read at most `limit` bytes into `read_buf`.
62        unsafe {
63            read_buf.assume_init(size);
64        }
65
66        let n = self
67            .f
68            .read_buf(&mut read_buf)
69            .await
70            .map_err(new_std_io_error)?;
71        self.read += n;
72
73        // Safety: We make sure that bs contains `n` more bytes.
74        let filled = read_buf.filled().len();
75        unsafe { bs.set_len(filled) }
76
77        let frozen = bs.split().freeze();
78        // Return the buffer to the pool.
79        self.core.buf_pool.put(bs);
80
81        Ok(Buffer::from(frozen))
82    }
83}
opendal/services/fs/reader.rs

opendal/services/fs/
reader.rs
