aboutsummaryrefslogtreecommitdiffstats
path: root/swarm/shed/index.go
blob: df88b1b62dc36f3503ce5d6397253ad11b665885 (plain) (blame)
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
306
// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package shed

import (
    "bytes"

    "github.com/syndtr/goleveldb/leveldb"
)

// Item holds fields relevant to Swarm Chunk data and metadata.
// All information required for swarm storage and operations
// on that storage must be defined here.
// This structure is logically connected to swarm storage,
// the only part of this package that is not generalized,
// mostly for performance reasons.
//
// Item is a type that is used for retrieving, storing and encoding
// chunk data and metadata. It is passed as an argument to Index encoding
// functions, get function and put function.
// But it is also returned with additional data from get function call
// and as the argument in iterator function definition.
type Item struct {
    Address         []byte
    Data            []byte
    AccessTimestamp int64
    StoreTimestamp  int64
    // UseMockStore is a pointer to identify
    // an unset state of the field in Join function.
    UseMockStore *bool
}

// Merge is a helper method to construct a new
// Item by filling up fields with default values
// of a particular Item with values from another one.
func (i Item) Merge(i2 Item) (new Item) {
    if i.Address == nil {
        i.Address = i2.Address
    }
    if i.Data == nil {
        i.Data = i2.Data
    }
    if i.AccessTimestamp == 0 {
        i.AccessTimestamp = i2.AccessTimestamp
    }
    if i.StoreTimestamp == 0 {
        i.StoreTimestamp = i2.StoreTimestamp
    }
    if i.UseMockStore == nil {
        i.UseMockStore = i2.UseMockStore
    }
    return i
}

// Index represents a set of LevelDB key value pairs that have common
// prefix. It holds functions for encoding and decoding keys and values
// to provide transparent actions on saved data which inclide:
// - getting a particular Item
// - saving a particular Item
// - iterating over a sorted LevelDB keys
// It implements IndexIteratorInterface interface.
type Index struct {
    db              *DB
    prefix          []byte
    encodeKeyFunc   func(fields Item) (key []byte, err error)
    decodeKeyFunc   func(key []byte) (e Item, err error)
    encodeValueFunc func(fields Item) (value []byte, err error)
    decodeValueFunc func(keyFields Item, value []byte) (e Item, err error)
}

// IndexFuncs structure defines functions for encoding and decoding
// LevelDB keys and values for a specific index.
type IndexFuncs struct {
    EncodeKey   func(fields Item) (key []byte, err error)
    DecodeKey   func(key []byte) (e Item, err error)
    EncodeValue func(fields Item) (value []byte, err error)
    DecodeValue func(keyFields Item, value []byte) (e Item, err error)
}

// NewIndex returns a new Index instance with defined name and
// encoding functions. The name must be unique and will be validated
// on database schema for a key prefix byte.
func (db *DB) NewIndex(name string, funcs IndexFuncs) (f Index, err error) {
    id, err := db.schemaIndexPrefix(name)
    if err != nil {
        return f, err
    }
    prefix := []byte{id}
    return Index{
        db:     db,
        prefix: prefix,
        // This function adjusts Index LevelDB key
        // by appending the provided index id byte.
        // This is needed to avoid collisions between keys of different
        // indexes as all index ids are unique.
        encodeKeyFunc: func(e Item) (key []byte, err error) {
            key, err = funcs.EncodeKey(e)
            if err != nil {
                return nil, err
            }
            return append(append(make([]byte, 0, len(key)+1), prefix...), key...), nil
        },
        // This function reverses the encodeKeyFunc constructed key
        // to transparently work with index keys without their index ids.
        // It assumes that index keys are prefixed with only one byte.
        decodeKeyFunc: func(key []byte) (e Item, err error) {
            return funcs.DecodeKey(key[1:])
        },
        encodeValueFunc: funcs.EncodeValue,
        decodeValueFunc: funcs.DecodeValue,
    }, nil
}

// Get accepts key fields represented as Item to retrieve a
// value from the index and return maximum available information
// from the index represented as another Item.
func (f Index) Get(keyFields Item) (out Item, err error) {
    key, err := f.encodeKeyFunc(keyFields)
    if err != nil {
        return out, err
    }
    value, err := f.db.Get(key)
    if err != nil {
        return out, err
    }
    out, err = f.decodeValueFunc(keyFields, value)
    if err != nil {
        return out, err
    }
    return out.Merge(keyFields), nil
}

// Put accepts Item to encode information from it
// and save it to the database.
func (f Index) Put(i Item) (err error) {
    key, err := f.encodeKeyFunc(i)
    if err != nil {
        return err
    }
    value, err := f.encodeValueFunc(i)
    if err != nil {
        return err
    }
    return f.db.Put(key, value)
}

// PutInBatch is the same as Put method, but it just
// saves the key/value pair to the batch instead
// directly to the database.
func (f Index) PutInBatch(batch *leveldb.Batch, i Item) (err error) {
    key, err := f.encodeKeyFunc(i)
    if err != nil {
        return err
    }
    value, err := f.encodeValueFunc(i)
    if err != nil {
        return err
    }
    batch.Put(key, value)
    return nil
}

// Delete accepts Item to remove a key/value pair
// from the database based on its fields.
func (f Index) Delete(keyFields Item) (err error) {
    key, err := f.encodeKeyFunc(keyFields)
    if err != nil {
        return err
    }
    return f.db.Delete(key)
}

// DeleteInBatch is the same as Delete just the operation
// is performed on the batch instead on the database.
func (f Index) DeleteInBatch(batch *leveldb.Batch, keyFields Item) (err error) {
    key, err := f.encodeKeyFunc(keyFields)
    if err != nil {
        return err
    }
    batch.Delete(key)
    return nil
}

// IndexIterFunc is a callback on every Item that is decoded
// by iterating on an Index keys.
// By returning a true for stop variable, iteration will
// stop, and by returning the error, that error will be
// propagated to the called iterator method on Index.
type IndexIterFunc func(item Item) (stop bool, err error)

// IterateOptions defines optional parameters for Iterate function.
type IterateOptions struct {
    // StartFrom is the Item to start the iteration from.
    StartFrom *Item
    // If SkipStartFromItem is true, StartFrom item will not
    // be iterated on.
    SkipStartFromItem bool
    // Iterate over items which keys have a common prefix.
    Prefix []byte
}

// Iterate function iterates over keys of the Index.
// If IterateOptions is nil, the iterations is over all keys.
func (f Index) Iterate(fn IndexIterFunc, options *IterateOptions) (err error) {
    if options == nil {
        options = new(IterateOptions)
    }
    // construct a prefix with Index prefix and optional common key prefix
    prefix := append(f.prefix, options.Prefix...)
    // start from the prefix
    startKey := prefix
    if options.StartFrom != nil {
        // start from the provided StartFrom Item key value
        startKey, err = f.encodeKeyFunc(*options.StartFrom)
        if err != nil {
            return err
        }
    }
    it := f.db.NewIterator()
    defer it.Release()

    // move the cursor to the start key
    ok := it.Seek(startKey)
    if !ok {
        // stop iterator if seek has failed
        return it.Error()
    }
    if options.SkipStartFromItem && bytes.Equal(startKey, it.Key()) {
        // skip the start from Item if it is the first key
        // and it is explicitly configured to skip it
        ok = it.Next()
    }
    for ; ok; ok = it.Next() {
        key := it.Key()
        if !bytes.HasPrefix(key, prefix) {
            break
        }
        // create a copy of key byte slice not to share leveldb underlaying slice array
        keyItem, err := f.decodeKeyFunc(append([]byte(nil), key...))
        if err != nil {
            return err
        }
        // create a copy of value byte slice not to share leveldb underlaying slice array
        valueItem, err := f.decodeValueFunc(keyItem, append([]byte(nil), it.Value()...))
        if err != nil {
            return err
        }
        stop, err := fn(keyItem.Merge(valueItem))
        if err != nil {
            return err
        }
        if stop {
            break
        }
    }
    return it.Error()
}

// Count returns the number of items in index.
func (f Index) Count() (count int, err error) {
    it := f.db.NewIterator()
    defer it.Release()

    for ok := it.Seek(f.prefix); ok; ok = it.Next() {
        key := it.Key()
        if key[0] != f.prefix[0] {
            break
        }
        count++
    }
    return count, it.Error()
}

// CountFrom returns the number of items in index keys
// starting from the key encoded from the provided Item.
func (f Index) CountFrom(start Item) (count int, err error) {
    startKey, err := f.encodeKeyFunc(start)
    if err != nil {
        return 0, err
    }
    it := f.db.NewIterator()
    defer it.Release()

    for ok := it.Seek(startKey); ok; ok = it.Next() {
        key := it.Key()
        if key[0] != f.prefix[0] {
            break
        }
        count++
    }
    return count, it.Error()
}