forked from cayleygraph/cayley
-
Notifications
You must be signed in to change notification settings - Fork 0
/
fixed_iterator.go
157 lines (136 loc) · 4.22 KB
/
fixed_iterator.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
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
// Copyright 2014 The Cayley Authors. All rights reserved.
//
// 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 graph
// Defines one of the base iterators, the Fixed iterator. A fixed iterator is quite simple; it
// contains an explicit fixed array of values.
//
// A fixed iterator requires an Equality function to be passed to it, by reason that TSVal, the
// opaque Triple store value, may not answer to ==.
import (
"fmt"
"strings"
)
// A Fixed iterator consists of it's values, an index (where it is in the process of Next()ing) and
// an equality function.
type FixedIterator struct {
BaseIterator
values []TSVal
lastIndex int
cmp Equality
}
// Define the signature of an equality function.
type Equality func(a, b TSVal) bool
// Define an equality function of purely ==, which works for native types.
func BasicEquality(a, b TSVal) bool {
if a == b {
return true
}
return false
}
// Creates a new Fixed iterator based around == equality.
func newFixedIterator() *FixedIterator {
return NewFixedIteratorWithCompare(BasicEquality)
}
// Creates a new Fixed iterator with a custom comparitor.
func NewFixedIteratorWithCompare(compareFn Equality) *FixedIterator {
var it FixedIterator
BaseIteratorInit(&it.BaseIterator)
it.values = make([]TSVal, 0, 20)
it.lastIndex = 0
it.cmp = compareFn
return &it
}
func (f *FixedIterator) Reset() {
f.lastIndex = 0
}
func (f *FixedIterator) Close() {
}
func (f *FixedIterator) Clone() Iterator {
out := NewFixedIteratorWithCompare(f.cmp)
for _, val := range f.values {
out.AddValue(val)
}
out.CopyTagsFrom(f)
return out
}
// Add a value to the iterator. The array now contains this value.
// TODO(barakmich): This ought to be a set someday, disallowing repeated values.
func (f *FixedIterator) AddValue(v TSVal) {
f.values = append(f.values, v)
}
// Print some information about the iterator.
func (f *FixedIterator) DebugString(indent int) string {
value := ""
if len(f.values) > 0 {
value = fmt.Sprint(f.values[0])
}
return fmt.Sprintf("%s(%s tags: %s Size: %d id0: %d)",
strings.Repeat(" ", indent),
f.Type(),
f.FixedTags(),
len(f.values),
value,
)
}
// Register this iterator as a Fixed iterator.
func (f *FixedIterator) Type() string {
return "fixed"
}
// Check if the passed value is equal to one of the values stored in the iterator.
func (f *FixedIterator) Check(v TSVal) bool {
// Could be optimized by keeping it sorted or using a better datastructure.
// However, for fixed iterators, which are by definition kind of tiny, this
// isn't a big issue.
CheckLogIn(f, v)
for _, x := range f.values {
if f.cmp(x, v) {
f.Last = x
return CheckLogOut(f, v, true)
}
}
return CheckLogOut(f, v, false)
}
// Return the next stored value from the iterator.
func (f *FixedIterator) Next() (TSVal, bool) {
NextLogIn(f)
if f.lastIndex == len(f.values) {
return NextLogOut(f, nil, false)
}
out := f.values[f.lastIndex]
f.Last = out
f.lastIndex++
return NextLogOut(f, out, true)
}
// Optimize() for a Fixed iterator is simple. Returns a Null iterator if it's empty
// (so that other iterators upstream can treat this as null) or there is no
// optimization.
func (f *FixedIterator) Optimize() (Iterator, bool) {
if len(f.values) == 1 && f.values[0] == nil {
return &NullIterator{}, true
}
return f, false
}
// Size is the number of values stored.
func (f *FixedIterator) Size() (int64, bool) {
return int64(len(f.values)), true
}
// As we right now have to scan the entire list, Next and Check are linear with the
// size. However, a better data structure could remove these limits.
func (a *FixedIterator) GetStats() *IteratorStats {
return &IteratorStats{
CheckCost: int64(len(a.values)),
NextCost: int64(len(a.values)),
Size: int64(len(a.values)),
}
}