mirror of
https://github.com/ceph/ceph-csi.git
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284 lines
11 KiB
Go
284 lines
11 KiB
Go
/*
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Copyright 2022 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 library
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import (
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"math"
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"github.com/google/cel-go/checker"
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"github.com/google/cel-go/common"
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"github.com/google/cel-go/common/types"
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"github.com/google/cel-go/common/types/ref"
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"github.com/google/cel-go/common/types/traits"
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exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
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)
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// CostEstimator implements CEL's interpretable.ActualCostEstimator and checker.CostEstimator.
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type CostEstimator struct {
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// SizeEstimator provides a CostEstimator.EstimateSize that this CostEstimator will delegate size estimation
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// calculations to if the size is not well known (i.e. a constant).
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SizeEstimator checker.CostEstimator
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}
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func (l *CostEstimator) CallCost(function, overloadId string, args []ref.Val, result ref.Val) *uint64 {
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switch function {
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case "check":
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// An authorization check has a fixed cost
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// This cost is set to allow for only two authorization checks per expression
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cost := uint64(350000)
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return &cost
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case "serviceAccount", "path", "group", "resource", "subresource", "namespace", "name", "allowed", "denied", "reason":
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// All authorization builder and accessor functions have a nominal cost
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cost := uint64(1)
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return &cost
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case "isSorted", "sum", "max", "min", "indexOf", "lastIndexOf":
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var cost uint64
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if len(args) > 0 {
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cost += traversalCost(args[0]) // these O(n) operations all cost roughly the cost of a single traversal
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}
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return &cost
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case "url", "lowerAscii", "upperAscii", "substring", "trim":
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if len(args) >= 1 {
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cost := uint64(math.Ceil(float64(actualSize(args[0])) * common.StringTraversalCostFactor))
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return &cost
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}
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case "replace", "split":
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if len(args) >= 1 {
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// cost is the traversal plus the construction of the result
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cost := uint64(math.Ceil(float64(actualSize(args[0])) * 2 * common.StringTraversalCostFactor))
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return &cost
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}
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case "join":
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if len(args) >= 1 {
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cost := uint64(math.Ceil(float64(actualSize(result)) * 2 * common.StringTraversalCostFactor))
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return &cost
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}
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case "find", "findAll":
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if len(args) >= 2 {
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strCost := uint64(math.Ceil((1.0 + float64(actualSize(args[0]))) * common.StringTraversalCostFactor))
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// We don't know how many expressions are in the regex, just the string length (a huge
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// improvement here would be to somehow get a count the number of expressions in the regex or
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// how many states are in the regex state machine and use that to measure regex cost).
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// For now, we're making a guess that each expression in a regex is typically at least 4 chars
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// in length.
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regexCost := uint64(math.Ceil(float64(actualSize(args[1])) * common.RegexStringLengthCostFactor))
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cost := strCost * regexCost
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return &cost
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}
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}
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return nil
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}
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func (l *CostEstimator) EstimateCallCost(function, overloadId string, target *checker.AstNode, args []checker.AstNode) *checker.CallEstimate {
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// WARNING: Any changes to this code impact API compatibility! The estimated cost is used to determine which CEL rules may be written to a
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// CRD and any change (cost increases and cost decreases) are breaking.
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switch function {
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case "check":
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// An authorization check has a fixed cost
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// This cost is set to allow for only two authorization checks per expression
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return &checker.CallEstimate{CostEstimate: checker.CostEstimate{Min: 350000, Max: 350000}}
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case "serviceAccount", "path", "group", "resource", "subresource", "namespace", "name", "allowed", "denied", "reason":
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// All authorization builder and accessor functions have a nominal cost
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return &checker.CallEstimate{CostEstimate: checker.CostEstimate{Min: 1, Max: 1}}
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case "isSorted", "sum", "max", "min", "indexOf", "lastIndexOf":
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if target != nil {
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// Charge 1 cost for comparing each element in the list
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elCost := checker.CostEstimate{Min: 1, Max: 1}
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// If the list contains strings or bytes, add the cost of traversing all the strings/bytes as a way
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// of estimating the additional comparison cost.
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if elNode := l.listElementNode(*target); elNode != nil {
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t := elNode.Type().GetPrimitive()
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if t == exprpb.Type_STRING || t == exprpb.Type_BYTES {
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sz := l.sizeEstimate(elNode)
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elCost = elCost.Add(sz.MultiplyByCostFactor(common.StringTraversalCostFactor))
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}
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return &checker.CallEstimate{CostEstimate: l.sizeEstimate(*target).MultiplyByCost(elCost)}
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} else { // the target is a string, which is supported by indexOf and lastIndexOf
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return &checker.CallEstimate{CostEstimate: l.sizeEstimate(*target).MultiplyByCostFactor(common.StringTraversalCostFactor)}
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}
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}
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case "url":
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if len(args) == 1 {
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sz := l.sizeEstimate(args[0])
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return &checker.CallEstimate{CostEstimate: sz.MultiplyByCostFactor(common.StringTraversalCostFactor)}
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}
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case "lowerAscii", "upperAscii", "substring", "trim":
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if target != nil {
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sz := l.sizeEstimate(*target)
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return &checker.CallEstimate{CostEstimate: sz.MultiplyByCostFactor(common.StringTraversalCostFactor), ResultSize: &sz}
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}
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case "replace":
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if target != nil && len(args) >= 2 {
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sz := l.sizeEstimate(*target)
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toReplaceSz := l.sizeEstimate(args[0])
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replaceWithSz := l.sizeEstimate(args[1])
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// smallest possible result: smallest input size composed of the largest possible substrings being replaced by smallest possible replacement
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minSz := uint64(math.Ceil(float64(sz.Min)/float64(toReplaceSz.Max))) * replaceWithSz.Min
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// largest possible result: largest input size composed of the smallest possible substrings being replaced by largest possible replacement
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maxSz := uint64(math.Ceil(float64(sz.Max)/float64(toReplaceSz.Min))) * replaceWithSz.Max
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// cost is the traversal plus the construction of the result
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return &checker.CallEstimate{CostEstimate: sz.MultiplyByCostFactor(2 * common.StringTraversalCostFactor), ResultSize: &checker.SizeEstimate{Min: minSz, Max: maxSz}}
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}
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case "split":
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if target != nil {
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sz := l.sizeEstimate(*target)
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// Worst case size is where is that a separator of "" is used, and each char is returned as a list element.
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max := sz.Max
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if len(args) > 1 {
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if c := args[1].Expr().GetConstExpr(); c != nil {
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max = uint64(c.GetInt64Value())
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}
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}
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// Cost is the traversal plus the construction of the result.
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return &checker.CallEstimate{CostEstimate: sz.MultiplyByCostFactor(2 * common.StringTraversalCostFactor), ResultSize: &checker.SizeEstimate{Min: 0, Max: max}}
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}
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case "join":
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if target != nil {
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var sz checker.SizeEstimate
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listSize := l.sizeEstimate(*target)
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if elNode := l.listElementNode(*target); elNode != nil {
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elemSize := l.sizeEstimate(elNode)
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sz = listSize.Multiply(elemSize)
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}
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if len(args) > 0 {
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sepSize := l.sizeEstimate(args[0])
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minSeparators := uint64(0)
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maxSeparators := uint64(0)
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if listSize.Min > 0 {
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minSeparators = listSize.Min - 1
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}
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if listSize.Max > 0 {
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maxSeparators = listSize.Max - 1
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}
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sz = sz.Add(sepSize.Multiply(checker.SizeEstimate{Min: minSeparators, Max: maxSeparators}))
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}
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return &checker.CallEstimate{CostEstimate: sz.MultiplyByCostFactor(common.StringTraversalCostFactor), ResultSize: &sz}
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}
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case "find", "findAll":
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if target != nil && len(args) >= 1 {
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sz := l.sizeEstimate(*target)
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// Add one to string length for purposes of cost calculation to prevent product of string and regex to be 0
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// in case where string is empty but regex is still expensive.
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strCost := sz.Add(checker.SizeEstimate{Min: 1, Max: 1}).MultiplyByCostFactor(common.StringTraversalCostFactor)
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// We don't know how many expressions are in the regex, just the string length (a huge
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// improvement here would be to somehow get a count the number of expressions in the regex or
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// how many states are in the regex state machine and use that to measure regex cost).
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// For now, we're making a guess that each expression in a regex is typically at least 4 chars
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// in length.
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regexCost := l.sizeEstimate(args[0]).MultiplyByCostFactor(common.RegexStringLengthCostFactor)
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// worst case size of result is that every char is returned as separate find result.
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return &checker.CallEstimate{CostEstimate: strCost.Multiply(regexCost), ResultSize: &checker.SizeEstimate{Min: 0, Max: sz.Max}}
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}
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}
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return nil
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}
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func actualSize(value ref.Val) uint64 {
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if sz, ok := value.(traits.Sizer); ok {
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return uint64(sz.Size().(types.Int))
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}
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return 1
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}
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func (l *CostEstimator) sizeEstimate(t checker.AstNode) checker.SizeEstimate {
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if sz := t.ComputedSize(); sz != nil {
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return *sz
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}
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if sz := l.EstimateSize(t); sz != nil {
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return *sz
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}
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return checker.SizeEstimate{Min: 0, Max: math.MaxUint64}
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}
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func (l *CostEstimator) listElementNode(list checker.AstNode) checker.AstNode {
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if lt := list.Type().GetListType(); lt != nil {
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nodePath := list.Path()
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if nodePath != nil {
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// Provide path if we have it so that a OpenAPIv3 maxLength validation can be looked up, if it exists
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// for this node.
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path := make([]string, len(nodePath)+1)
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copy(path, nodePath)
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path[len(nodePath)] = "@items"
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return &itemsNode{path: path, t: lt.GetElemType(), expr: nil}
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} else {
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// Provide just the type if no path is available so that worst case size can be looked up based on type.
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return &itemsNode{t: lt.GetElemType(), expr: nil}
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}
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}
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return nil
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}
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func (l *CostEstimator) EstimateSize(element checker.AstNode) *checker.SizeEstimate {
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if l.SizeEstimator != nil {
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return l.SizeEstimator.EstimateSize(element)
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}
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return nil
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}
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type itemsNode struct {
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path []string
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t *exprpb.Type
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expr *exprpb.Expr
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}
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func (i *itemsNode) Path() []string {
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return i.path
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}
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func (i *itemsNode) Type() *exprpb.Type {
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return i.t
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}
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func (i *itemsNode) Expr() *exprpb.Expr {
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return i.expr
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}
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func (i *itemsNode) ComputedSize() *checker.SizeEstimate {
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return nil
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}
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// traversalCost computes the cost of traversing a ref.Val as a data tree.
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func traversalCost(v ref.Val) uint64 {
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// TODO: This could potentially be optimized by sampling maps and lists instead of traversing.
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switch vt := v.(type) {
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case types.String:
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return uint64(float64(len(string(vt))) * common.StringTraversalCostFactor)
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case types.Bytes:
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return uint64(float64(len([]byte(vt))) * common.StringTraversalCostFactor)
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case traits.Lister:
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cost := uint64(0)
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for it := vt.Iterator(); it.HasNext() == types.True; {
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i := it.Next()
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cost += traversalCost(i)
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}
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return cost
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case traits.Mapper: // maps and objects
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cost := uint64(0)
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for it := vt.Iterator(); it.HasNext() == types.True; {
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k := it.Next()
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cost += traversalCost(k) + traversalCost(vt.Get(k))
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}
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return cost
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default:
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return 1
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}
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}
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