File: file.go

package info (click to toggle)
golang-github-couchbase-moss 0.0~git20170914.0.07c86e8-4
  • links: PTS, VCS
  • area: main
  • in suites: bullseye, buster, sid
  • size: 664 kB
  • sloc: python: 230; makefile: 37
file content (288 lines) | stat: -rw-r--r-- 6,549 bytes parent folder | download
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
//  Copyright (c) 2016 Couchbase, Inc.
//  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.

package moss

import (
	"io"
	"os"
	"sync"
)

// An InitCloser holds onto an io.Closer, and is used for chaining
// io.Closer's.  That is, we often want the closing of one resource to
// close related resources.
type InitCloser interface {
	InitCloser(io.Closer) error
}

// The File interface is implemented by os.File.  App specific
// implementations may add concurrency, caching, stats, fuzzing, etc.
type File interface {
	io.ReaderAt
	io.WriterAt
	io.Closer
	Stat() (os.FileInfo, error)
	Sync() error
	Truncate(size int64) error
}

// The OpenFile func signature is similar to os.OpenFile().
type OpenFile func(name string, flag int, perm os.FileMode) (File, error)

// FileRef provides a ref-counting wrapper around a File.
type FileRef struct {
	file File
	m    sync.Mutex // Protects the fields that follow.
	refs int

	beforeCloseCallbacks []func() // Optional callbacks invoked before final close.
	afterCloseCallbacks  []func() // Optional callbacks invoked after final close.
}

type ioResult struct {
	kind string // Kind of io attempted.
	want int    // Num bytes expected to be written or read.
	got  int    // Num bytes actually written or read.
	err  error
}

// --------------------------------------------------------

// OnBeforeClose registers event callback func's that are invoked before the
// file is closed.
func (r *FileRef) OnBeforeClose(cb func()) {
	r.m.Lock()
	r.beforeCloseCallbacks = append(r.beforeCloseCallbacks, cb)
	r.m.Unlock()
}

// OnAfterClose registers event callback func's that are invoked after the
// file is closed.
func (r *FileRef) OnAfterClose(cb func()) {
	r.m.Lock()
	r.afterCloseCallbacks = append(r.afterCloseCallbacks, cb)
	r.m.Unlock()
}

// AddRef increases the ref-count on the file ref.
func (r *FileRef) AddRef() File {
	if r == nil {
		return nil
	}

	r.m.Lock()
	r.refs++
	file := r.file
	r.m.Unlock()

	return file
}

// DecRef decreases the ref-count on the file ref, and closing the
// underlying file when the ref-count reaches zero.
func (r *FileRef) DecRef() (err error) {
	if r == nil {
		return nil
	}

	r.m.Lock()

	r.refs--
	if r.refs <= 0 {
		for _, cb := range r.beforeCloseCallbacks {
			cb()
		}
		r.beforeCloseCallbacks = nil

		err = r.file.Close()

		for _, cb := range r.afterCloseCallbacks {
			cb()
		}
		r.afterCloseCallbacks = nil

		r.file = nil
	}

	r.m.Unlock()

	return err
}

// Close allows the FileRef to implement the io.Closer interface.  It actually
// just performs what should be the final DecRef() call which takes the
// reference count to 0.  Once 0, it allows the file to actually be closed.
func (r *FileRef) Close() error {
	return r.DecRef()
}

// FetchRefCount fetches the ref-count on the file ref.
func (r *FileRef) FetchRefCount() int {
	if r == nil {
		return 0
	}

	r.m.Lock()
	ref := r.refs
	r.m.Unlock()

	return ref
}

// --------------------------------------------------------

// OsFile interface allows conversion from a File to an os.File.
type OsFile interface {
	OsFile() *os.File
}

// ToOsFile provides the underlying os.File for a File, if available.
func ToOsFile(f File) *os.File {
	if osFile, ok := f.(*os.File); ok {
		return osFile
	}
	if osFile2, ok := f.(OsFile); ok {
		return osFile2.OsFile()
	}
	return nil
}

// --------------------------------------------------------

type bufferedSectionWriter struct {
	err error
	w   io.WriterAt
	beg int64 // Start position where we started writing in file.
	cur int64 // Current write-at position in file.
	max int64 // When > 0, max number of bytes we can write.
	buf []byte
	n   int

	stopCh chan struct{}
	doneCh chan struct{}
	reqCh  chan ioBuf
	resCh  chan ioBuf
}

type ioBuf struct {
	buf []byte
	pos int64
	err error
}

// newBufferedSectionWriter converts incoming Write() requests into
// buffered, asynchronous WriteAt()'s in a section of a file.
func newBufferedSectionWriter(w io.WriterAt, begPos, maxBytes int64,
	bufSize int, s statsReporter) *bufferedSectionWriter {
	stopCh := make(chan struct{})
	doneCh := make(chan struct{})
	reqCh := make(chan ioBuf)
	resCh := make(chan ioBuf)

	go func() {
		defer close(doneCh)
		defer close(resCh)

		buf := make([]byte, bufSize)
		var pos int64
		var err error

		for {
			select {
			case <-stopCh:
				return
			case resCh <- ioBuf{buf: buf, pos: pos, err: err}:
			}

			req, ok := <-reqCh
			if ok {
				buf, pos = req.buf, req.pos
				if len(buf) > 0 {
					nBytes, err := w.WriteAt(buf, pos)
					if err == nil && s != nil {
						s.reportBytesWritten(uint64(nBytes))
					}
				}
			}
		}
	}()

	return &bufferedSectionWriter{
		w:   w,
		beg: begPos,
		cur: begPos,
		max: maxBytes,
		buf: make([]byte, bufSize),

		stopCh: stopCh,
		doneCh: doneCh,
		reqCh:  reqCh,
		resCh:  resCh,
	}
}

// Offset returns the byte offset into the file where the
// bufferedSectionWriter is currently logically positioned.
func (b *bufferedSectionWriter) Offset() int64 { return b.cur + int64(b.n) }

// Written returns the logical number of bytes written to this
// bufferedSectionWriter; or, the sum of bytes to Write() calls.
func (b *bufferedSectionWriter) Written() int64 { return b.Offset() - b.beg }

func (b *bufferedSectionWriter) Write(p []byte) (nn int, err error) {
	if b.max > 0 && b.Written()+int64(len(p)) > b.max {
		return 0, io.ErrShortBuffer // Would go over b.max.
	}
	for len(p) > 0 && b.err == nil {
		n := copy(b.buf[b.n:], p)
		b.n += n
		nn += n
		if n < len(p) {
			b.err = b.Flush()
		}
		p = p[n:]
	}
	return nn, b.err
}

func (b *bufferedSectionWriter) Flush() error {
	if b.err != nil {
		return b.err
	}
	if b.n <= 0 {
		return nil
	}

	prevWrite := <-b.resCh
	b.err = prevWrite.err
	if b.err != nil {
		return b.err
	}

	b.reqCh <- ioBuf{buf: b.buf[0:b.n], pos: b.cur}

	b.cur += int64(b.n)
	b.buf = prevWrite.buf[:]
	b.n = 0

	return nil
}

func (b *bufferedSectionWriter) Stop() error {
	if b.stopCh != nil {
		close(b.stopCh)
		close(b.reqCh)
		<-b.doneCh
		b.stopCh = nil
	}
	return b.err
}