aboutsummaryrefslogtreecommitdiff
path: root/vendor/github.com/spf13/afero/unionFile.go
blob: 1e78f7d1efb6712bb0260df44e11d0b5aec1762b (plain)
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
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
package afero

import (
	"io"
	"os"
	"path/filepath"
	"syscall"
)

// The UnionFile implements the afero.File interface and will be returned
// when reading a directory present at least in the overlay or opening a file
// for writing.
//
// The calls to
// Readdir() and Readdirnames() merge the file os.FileInfo / names from the
// base and the overlay - for files present in both layers, only those
// from the overlay will be used.
//
// When opening files for writing (Create() / OpenFile() with the right flags)
// the operations will be done in both layers, starting with the overlay. A
// successful read in the overlay will move the cursor position in the base layer
// by the number of bytes read.
type UnionFile struct {
	Base   File
	Layer  File
	Merger DirsMerger
	off    int
	files  []os.FileInfo
}

func (f *UnionFile) Close() error {
	// first close base, so we have a newer timestamp in the overlay. If we'd close
	// the overlay first, we'd get a cacheStale the next time we access this file
	// -> cache would be useless ;-)
	if f.Base != nil {
		f.Base.Close()
	}
	if f.Layer != nil {
		return f.Layer.Close()
	}
	return BADFD
}

func (f *UnionFile) Read(s []byte) (int, error) {
	if f.Layer != nil {
		n, err := f.Layer.Read(s)
		if (err == nil || err == io.EOF) && f.Base != nil {
			// advance the file position also in the base file, the next
			// call may be a write at this position (or a seek with SEEK_CUR)
			if _, seekErr := f.Base.Seek(int64(n), os.SEEK_CUR); seekErr != nil {
				// only overwrite err in case the seek fails: we need to
				// report an eventual io.EOF to the caller
				err = seekErr
			}
		}
		return n, err
	}
	if f.Base != nil {
		return f.Base.Read(s)
	}
	return 0, BADFD
}

func (f *UnionFile) ReadAt(s []byte, o int64) (int, error) {
	if f.Layer != nil {
		n, err := f.Layer.ReadAt(s, o)
		if (err == nil || err == io.EOF) && f.Base != nil {
			_, err = f.Base.Seek(o+int64(n), os.SEEK_SET)
		}
		return n, err
	}
	if f.Base != nil {
		return f.Base.ReadAt(s, o)
	}
	return 0, BADFD
}

func (f *UnionFile) Seek(o int64, w int) (pos int64, err error) {
	if f.Layer != nil {
		pos, err = f.Layer.Seek(o, w)
		if (err == nil || err == io.EOF) && f.Base != nil {
			_, err = f.Base.Seek(o, w)
		}
		return pos, err
	}
	if f.Base != nil {
		return f.Base.Seek(o, w)
	}
	return 0, BADFD
}

func (f *UnionFile) Write(s []byte) (n int, err error) {
	if f.Layer != nil {
		n, err = f.Layer.Write(s)
		if err == nil && f.Base != nil { // hmm, do we have fixed size files where a write may hit the EOF mark?
			_, err = f.Base.Write(s)
		}
		return n, err
	}
	if f.Base != nil {
		return f.Base.Write(s)
	}
	return 0, BADFD
}

func (f *UnionFile) WriteAt(s []byte, o int64) (n int, err error) {
	if f.Layer != nil {
		n, err = f.Layer.WriteAt(s, o)
		if err == nil && f.Base != nil {
			_, err = f.Base.WriteAt(s, o)
		}
		return n, err
	}
	if f.Base != nil {
		return f.Base.WriteAt(s, o)
	}
	return 0, BADFD
}

func (f *UnionFile) Name() string {
	if f.Layer != nil {
		return f.Layer.Name()
	}
	return f.Base.Name()
}

// DirsMerger is how UnionFile weaves two directories together.
// It takes the FileInfo slices from the layer and the base and returns a
// single view.
type DirsMerger func(lofi, bofi []os.FileInfo) ([]os.FileInfo, error)

var defaultUnionMergeDirsFn = func(lofi, bofi []os.FileInfo) ([]os.FileInfo, error) {
	var files = make(map[string]os.FileInfo)

	for _, fi := range lofi {
		files[fi.Name()] = fi
	}

	for _, fi := range bofi {
		if _, exists := files[fi.Name()]; !exists {
			files[fi.Name()] = fi
		}
	}

	rfi := make([]os.FileInfo, len(files))

	i := 0
	for _, fi := range files {
		rfi[i] = fi
		i++
	}

	return rfi, nil

}

// Readdir will weave the two directories together and
// return a single view of the overlayed directories
func (f *UnionFile) Readdir(c int) (ofi []os.FileInfo, err error) {
	var merge DirsMerger = f.Merger
	if merge == nil {
		merge = defaultUnionMergeDirsFn
	}

	if f.off == 0 {
		var lfi []os.FileInfo
		if f.Layer != nil {
			lfi, err = f.Layer.Readdir(-1)
			if err != nil {
				return nil, err
			}
		}

		var bfi []os.FileInfo
		if f.Base != nil {
			bfi, err = f.Base.Readdir(-1)
			if err != nil {
				return nil, err
			}

		}
		merged, err := merge(lfi, bfi)
		if err != nil {
			return nil, err
		}
		f.files = append(f.files, merged...)
	}
	if c == -1 {
		return f.files[f.off:], nil
	}
	defer func() { f.off += c }()
	return f.files[f.off:c], nil
}

func (f *UnionFile) Readdirnames(c int) ([]string, error) {
	rfi, err := f.Readdir(c)
	if err != nil {
		return nil, err
	}
	var names []string
	for _, fi := range rfi {
		names = append(names, fi.Name())
	}
	return names, nil
}

func (f *UnionFile) Stat() (os.FileInfo, error) {
	if f.Layer != nil {
		return f.Layer.Stat()
	}
	if f.Base != nil {
		return f.Base.Stat()
	}
	return nil, BADFD
}

func (f *UnionFile) Sync() (err error) {
	if f.Layer != nil {
		err = f.Layer.Sync()
		if err == nil && f.Base != nil {
			err = f.Base.Sync()
		}
		return err
	}
	if f.Base != nil {
		return f.Base.Sync()
	}
	return BADFD
}

func (f *UnionFile) Truncate(s int64) (err error) {
	if f.Layer != nil {
		err = f.Layer.Truncate(s)
		if err == nil && f.Base != nil {
			err = f.Base.Truncate(s)
		}
		return err
	}
	if f.Base != nil {
		return f.Base.Truncate(s)
	}
	return BADFD
}

func (f *UnionFile) WriteString(s string) (n int, err error) {
	if f.Layer != nil {
		n, err = f.Layer.WriteString(s)
		if err == nil && f.Base != nil {
			_, err = f.Base.WriteString(s)
		}
		return n, err
	}
	if f.Base != nil {
		return f.Base.WriteString(s)
	}
	return 0, BADFD
}

func copyToLayer(base Fs, layer Fs, name string) error {
	bfh, err := base.Open(name)
	if err != nil {
		return err
	}
	defer bfh.Close()

	// First make sure the directory exists
	exists, err := Exists(layer, filepath.Dir(name))
	if err != nil {
		return err
	}
	if !exists {
		err = layer.MkdirAll(filepath.Dir(name), 0777) // FIXME?
		if err != nil {
			return err
		}
	}

	// Create the file on the overlay
	lfh, err := layer.Create(name)
	if err != nil {
		return err
	}
	n, err := io.Copy(lfh, bfh)
	if err != nil {
		// If anything fails, clean up the file
		layer.Remove(name)
		lfh.Close()
		return err
	}

	bfi, err := bfh.Stat()
	if err != nil || bfi.Size() != n {
		layer.Remove(name)
		lfh.Close()
		return syscall.EIO
	}

	err = lfh.Close()
	if err != nil {
		layer.Remove(name)
		lfh.Close()
		return err
	}
	return layer.Chtimes(name, bfi.ModTime(), bfi.ModTime())
}