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::io::Read;
19use std::sync::Arc;
20
21use tokio::io::AsyncReadExt;
22use tokio::io::ReadBuf;
23
24use super::core::*;
25use crate::raw::*;
26use crate::*;
27
28pub struct FsReader<F> {
29    core: Arc<FsCore>,
30    f: F,
31    read: usize,
32    size: usize,
33    buf_size: usize,
34}
35
36impl<F> FsReader<F> {
37    pub fn new(core: Arc<FsCore>, f: F, size: usize) -> Self {
38        Self {
39            core,
40            f,
41            read: 0,
42            size,
43            // Use 2 MiB as default value.
44            buf_size: 2 * 1024 * 1024,
45        }
46    }
47}
48
49impl oio::Read for FsReader<tokio::fs::File> {
50    async fn read(&mut self) -> Result<Buffer> {
51        if self.read >= self.size {
52            return Ok(Buffer::new());
53        }
54
55        let mut bs = self.core.buf_pool.get();
56        bs.reserve(self.buf_size);
57
58        let size = (self.size - self.read).min(self.buf_size);
59        let buf = &mut bs.spare_capacity_mut()[..size];
60        let mut read_buf: ReadBuf = ReadBuf::uninit(buf);
61
62        // SAFETY: Read at most `limit` bytes into `read_buf`.
63        unsafe {
64            read_buf.assume_init(size);
65        }
66
67        let n = self
68            .f
69            .read_buf(&mut read_buf)
70            .await
71            .map_err(new_std_io_error)?;
72        self.read += n;
73
74        // Safety: We make sure that bs contains `n` more bytes.
75        let filled = read_buf.filled().len();
76        unsafe { bs.set_len(filled) }
77
78        let frozen = bs.split().freeze();
79        // Return the buffer to the pool.
80        self.core.buf_pool.put(bs);
81
82        Ok(Buffer::from(frozen))
83    }
84}
85
86impl oio::BlockingRead for FsReader<std::fs::File> {
87    fn read(&mut self) -> Result<Buffer> {
88        if self.read >= self.size {
89            return Ok(Buffer::new());
90        }
91
92        let mut bs = self.core.buf_pool.get();
93        bs.reserve(self.buf_size);
94
95        let size = (self.size - self.read).min(self.buf_size);
96        let buf = &mut bs.spare_capacity_mut()[..size];
97        let mut read_buf: ReadBuf = ReadBuf::uninit(buf);
98
99        // SAFETY: Read at most `limit` bytes into `read_buf`.
100        unsafe {
101            read_buf.assume_init(size);
102        }
103
104        let n = self
105            .f
106            .read(read_buf.initialize_unfilled())
107            .map_err(new_std_io_error)?;
108        read_buf.advance(n);
109        self.read += n;
110
111        // Safety: We make sure that bs contains `n` more bytes.
112        let filled = read_buf.filled().len();
113        unsafe { bs.set_len(filled) }
114
115        let frozen = bs.split().freeze();
116        // Return the buffer to the pool.
117        self.core.buf_pool.put(bs);
118
119        Ok(Buffer::from(frozen))
120    }
121}
opendal/services/fs/reader.rs

opendal/services/fs/
reader.rs
