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
|
/*
* Copyright (C) 2024 The Android Open Source Project
*
* 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 anyhow::anyhow;
use memmap2::MmapMut;
use std::fs::{self, OpenOptions};
use aconfig_storage_file::AconfigStorageError::{self, FileReadFail, MapFileFail};
/// Get the mutable memory mapping of a storage file
///
/// # Safety
///
/// The memory mapped file may have undefined behavior if there are writes to this
/// file not thru this memory mapped file or there are concurrent writes to this
/// memory mapped file. Ensure all writes to the underlying file are thru this memory
/// mapped file and there are no concurrent writes.
pub(crate) unsafe fn map_file(file_path: &str) -> Result<MmapMut, AconfigStorageError> {
// make sure file has read write permission
let perms = fs::metadata(file_path).unwrap().permissions();
if perms.readonly() {
return Err(MapFileFail(anyhow!("fail to map non read write storage file {}", file_path)));
}
let file =
OpenOptions::new().read(true).write(true).open(file_path).map_err(|errmsg| {
FileReadFail(anyhow!("Failed to open file {}: {}", file_path, errmsg))
})?;
unsafe {
let mapped_file = MmapMut::map_mut(&file).map_err(|errmsg| {
MapFileFail(anyhow!("fail to map storage file {}: {}", file_path, errmsg))
})?;
Ok(mapped_file)
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::test_utils::copy_to_temp_file;
use std::io::Read;
#[test]
fn test_mapped_file_contents() {
let mut rw_val_file = copy_to_temp_file("./tests/flag.val", false).unwrap();
let mut rw_info_file = copy_to_temp_file("./tests/flag.info", false).unwrap();
let flag_val = rw_val_file.path().display().to_string();
let flag_info = rw_info_file.path().display().to_string();
let mut content = Vec::new();
rw_val_file.read_to_end(&mut content).unwrap();
// SAFETY:
// The safety here is guaranteed here as no writes happens to this temp file
unsafe {
let mmaped_file = map_file(&flag_val).unwrap();
assert_eq!(mmaped_file[..], content[..]);
}
let mut content = Vec::new();
rw_info_file.read_to_end(&mut content).unwrap();
// SAFETY:
// The safety here is guaranteed here as no writes happens to this temp file
unsafe {
let mmaped_file = map_file(&flag_info).unwrap();
assert_eq!(mmaped_file[..], content[..]);
}
}
#[test]
fn test_mapped_read_only_file() {
let ro_val_file = copy_to_temp_file("./tests/flag.val", true).unwrap();
let flag_val = ro_val_file.path().display().to_string();
// SAFETY:
// The safety here is guaranteed here as no writes happens to this temp file
unsafe {
let error = map_file(&flag_val).unwrap_err();
assert_eq!(
format!("{:?}", error),
format!("MapFileFail(fail to map non read write storage file {})", flag_val)
);
}
}
}
|
