140 lines
4.6 KiB
Go
140 lines
4.6 KiB
Go
/*
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Copyright 2019 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package value
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// List represents a list object.
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type List interface {
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// Length returns how many items can be found in the map.
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Length() int
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// At returns the item at the given position in the map. It will
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// panic if the index is out of range.
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At(int) Value
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// AtUsing uses the provided allocator and returns the item at the given
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// position in the map. It will panic if the index is out of range.
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// The returned Value should be given back to the Allocator when no longer needed
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// by calling Allocator.Free(Value).
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AtUsing(Allocator, int) Value
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// Range returns a ListRange for iterating over the items in the list.
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Range() ListRange
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// RangeUsing uses the provided allocator and returns a ListRange for
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// iterating over the items in the list.
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// The returned Range should be given back to the Allocator when no longer needed
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// by calling Allocator.Free(Value).
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RangeUsing(Allocator) ListRange
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// Equals compares the two lists, and return true if they are the same, false otherwise.
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// Implementations can use ListEquals as a general implementation for this methods.
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Equals(List) bool
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// EqualsUsing uses the provided allocator and compares the two lists, and return true if
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// they are the same, false otherwise. Implementations can use ListEqualsUsing as a general
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// implementation for this methods.
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EqualsUsing(Allocator, List) bool
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}
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// ListRange represents a single iteration across the items of a list.
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type ListRange interface {
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// Next increments to the next item in the range, if there is one, and returns true, or returns false if there are no more items.
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Next() bool
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// Item returns the index and value of the current item in the range. or panics if there is no current item.
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// For efficiency, Item may reuse the values returned by previous Item calls. Callers should be careful avoid holding
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// pointers to the value returned by Item() that escape the iteration loop since they become invalid once either
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// Item() or Allocator.Free() is called.
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Item() (index int, value Value)
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}
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var EmptyRange = &emptyRange{}
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type emptyRange struct{}
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func (_ *emptyRange) Next() bool {
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return false
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}
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func (_ *emptyRange) Item() (index int, value Value) {
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panic("Item called on empty ListRange")
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}
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// ListEquals compares two lists lexically.
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// WARN: This is a naive implementation, calling lhs.Equals(rhs) is typically the most efficient.
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func ListEquals(lhs, rhs List) bool {
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return ListEqualsUsing(HeapAllocator, lhs, rhs)
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}
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// ListEqualsUsing uses the provided allocator and compares two lists lexically.
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// WARN: This is a naive implementation, calling lhs.EqualsUsing(allocator, rhs) is typically the most efficient.
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func ListEqualsUsing(a Allocator, lhs, rhs List) bool {
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if lhs.Length() != rhs.Length() {
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return false
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}
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lhsRange := lhs.RangeUsing(a)
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defer a.Free(lhsRange)
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rhsRange := rhs.RangeUsing(a)
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defer a.Free(rhsRange)
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for lhsRange.Next() && rhsRange.Next() {
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_, lv := lhsRange.Item()
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_, rv := rhsRange.Item()
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if !EqualsUsing(a, lv, rv) {
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return false
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}
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}
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return true
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}
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// ListLess compares two lists lexically.
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func ListLess(lhs, rhs List) bool {
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return ListCompare(lhs, rhs) == -1
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}
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// ListCompare compares two lists lexically. The result will be 0 if l==rhs, -1
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// if l < rhs, and +1 if l > rhs.
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func ListCompare(lhs, rhs List) int {
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return ListCompareUsing(HeapAllocator, lhs, rhs)
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}
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// ListCompareUsing uses the provided allocator and compares two lists lexically. The result will be 0 if l==rhs, -1
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// if l < rhs, and +1 if l > rhs.
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func ListCompareUsing(a Allocator, lhs, rhs List) int {
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lhsRange := lhs.RangeUsing(a)
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defer a.Free(lhsRange)
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rhsRange := rhs.RangeUsing(a)
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defer a.Free(rhsRange)
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for {
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lhsOk := lhsRange.Next()
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rhsOk := rhsRange.Next()
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if !lhsOk && !rhsOk {
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// Lists are the same length and all items are equal.
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return 0
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}
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if !lhsOk {
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// LHS is shorter.
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return -1
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}
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if !rhsOk {
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// RHS is shorter.
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return 1
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}
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_, lv := lhsRange.Item()
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_, rv := rhsRange.Item()
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if c := CompareUsing(a, lv, rv); c != 0 {
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return c
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}
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// The items are equal; continue.
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}
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}
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