-
Notifications
You must be signed in to change notification settings - Fork 0
/
mmap.go
130 lines (116 loc) · 2.72 KB
/
mmap.go
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
// Copyright 2019 shimingyah.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.
package ioengine
import (
"errors"
"io"
"os"
"runtime"
"sync"
)
// MemoryMap disk IO mode
// page faults and dirty page writes can degrade mmap performance
// we impl ReadAt by mmap, other API impled by standardIO.
type MemoryMap struct {
path string
opt Options
data []byte
once sync.Once
*os.File
*FileLock
}
func newMemoryMap(name string, opt Options) (*MemoryMap, error) {
fd, err := os.OpenFile(name, opt.Flag, opt.Perm)
if err != nil {
return nil, err
}
data, err := Mmap(fd, 0, opt.MmapSize, opt.MmapWritable)
if err != nil {
return nil, err
}
if err := Madvise(data); err != nil {
return nil, err
}
mmap := &MemoryMap{
path: name,
opt: opt,
data: data,
File: fd,
}
// runtime.SetFinalizer(mmap, (*mmap).Close())
return mmap, nil
}
// ReadAt like any io.ReaderAt, clients can execute parallel ReadAt calls.
func (mmap *MemoryMap) ReadAt(b []byte, off int64) (int, error) {
// If the caller wanted a zero byte read, return immediately.
if len(b) == 0 {
return 0, nil
}
if mmap.data == nil {
return 0, errors.New("mmap: closed")
}
if off < 0 {
return 0, errors.New("negative offset")
}
if int64(len(mmap.data)) < off {
return 0, io.EOF
}
n := copy(b, mmap.data[off:])
if n < len(b) {
return n, io.EOF
}
return n, nil
}
// FLock a file lock is a recommended lock.
// if file lock not init, we will init once
func (mmap *MemoryMap) FLock() (err error) {
if mmap.FileLock == nil {
mmap.once.Do(func() {
if mmap.FileLock == nil {
mmap.FileLock, err = NewFileLock(mmap.path, true)
}
})
}
if err != nil {
return err
}
if mmap.FileLock == nil {
return errors.New("Uninitialized file lock")
}
return mmap.FileLock.FLock()
}
// FUnlock file unlock
func (mmap *MemoryMap) FUnlock() error {
if mmap.FileLock == nil {
return nil
}
return mmap.FileLock.FUnlock()
}
// Close closes the File
func (mmap *MemoryMap) Close() error {
if mmap.File != nil {
mmap.File.Close()
}
if mmap.data == nil {
return nil
}
data := mmap.data
mmap.data = nil
runtime.SetFinalizer(mmap, nil)
return Munmap(data)
}
// Option return file options
func (mmap *MemoryMap) Option() Options {
return mmap.opt
}