156 lines
4.3 KiB
Go
156 lines
4.3 KiB
Go
// 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 (it *FixedIterator) Reset() {
|
|
it.lastIndex = 0
|
|
}
|
|
|
|
func (it *FixedIterator) Close() {}
|
|
|
|
func (it *FixedIterator) Clone() Iterator {
|
|
out := NewFixedIteratorWithCompare(it.cmp)
|
|
for _, val := range it.values {
|
|
out.AddValue(val)
|
|
}
|
|
out.CopyTagsFrom(it)
|
|
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 (it *FixedIterator) AddValue(v TSVal) {
|
|
it.values = append(it.values, v)
|
|
}
|
|
|
|
// Print some information about the iterator.
|
|
func (it *FixedIterator) DebugString(indent int) string {
|
|
value := ""
|
|
if len(it.values) > 0 {
|
|
value = fmt.Sprint(it.values[0])
|
|
}
|
|
return fmt.Sprintf("%s(%s tags: %s Size: %d id0: %d)",
|
|
strings.Repeat(" ", indent),
|
|
it.Type(),
|
|
it.FixedTags(),
|
|
len(it.values),
|
|
value,
|
|
)
|
|
}
|
|
|
|
// Register this iterator as a Fixed iterator.
|
|
func (it *FixedIterator) Type() string {
|
|
return "fixed"
|
|
}
|
|
|
|
// Check if the passed value is equal to one of the values stored in the iterator.
|
|
func (it *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(it, v)
|
|
for _, x := range it.values {
|
|
if it.cmp(x, v) {
|
|
it.Last = x
|
|
return CheckLogOut(it, v, true)
|
|
}
|
|
}
|
|
return CheckLogOut(it, v, false)
|
|
}
|
|
|
|
// Return the next stored value from the iterator.
|
|
func (it *FixedIterator) Next() (TSVal, bool) {
|
|
NextLogIn(it)
|
|
if it.lastIndex == len(it.values) {
|
|
return NextLogOut(it, nil, false)
|
|
}
|
|
out := it.values[it.lastIndex]
|
|
it.Last = out
|
|
it.lastIndex++
|
|
return NextLogOut(it, 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 (it *FixedIterator) Optimize() (Iterator, bool) {
|
|
|
|
if len(it.values) == 1 && it.values[0] == nil {
|
|
return &NullIterator{}, true
|
|
}
|
|
|
|
return it, false
|
|
}
|
|
|
|
// Size is the number of values stored.
|
|
func (it *FixedIterator) Size() (int64, bool) {
|
|
return int64(len(it.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 (it *FixedIterator) GetStats() *IteratorStats {
|
|
return &IteratorStats{
|
|
CheckCost: int64(len(it.values)),
|
|
NextCost: int64(len(it.values)),
|
|
Size: int64(len(it.values)),
|
|
}
|
|
}
|