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// Copyright 2018 Google LLC
//
// 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 interpreter
import (
"github.com/google/cel-go/common/overloads"
"github.com/google/cel-go/common/types"
"github.com/google/cel-go/common/types/ref"
"github.com/google/cel-go/common/types/traits"
)
// InterpretableDecorator is a functional interface for decorating or replacing
// Interpretable expression nodes at construction time.
type InterpretableDecorator func(Interpretable) (Interpretable, error)
// decObserveEval records evaluation state into an EvalState object.
func decObserveEval(observer EvalObserver) InterpretableDecorator {
return func(i Interpretable) (Interpretable, error) {
switch inst := i.(type) {
case *evalWatch, *evalWatchAttr, *evalWatchConst, *evalWatchConstructor:
// these instruction are already watching, return straight-away.
return i, nil
case InterpretableAttribute:
return &evalWatchAttr{
InterpretableAttribute: inst,
observer: observer,
}, nil
case InterpretableConst:
return &evalWatchConst{
InterpretableConst: inst,
observer: observer,
}, nil
case InterpretableConstructor:
return &evalWatchConstructor{
constructor: inst,
observer: observer,
}, nil
default:
return &evalWatch{
Interpretable: i,
observer: observer,
}, nil
}
}
}
// decInterruptFolds creates an intepretable decorator which marks comprehensions as interruptable
// where the interrupt state is communicated via a hidden variable on the Activation.
func decInterruptFolds() InterpretableDecorator {
return func(i Interpretable) (Interpretable, error) {
fold, ok := i.(*evalFold)
if !ok {
return i, nil
}
fold.interruptable = true
return fold, nil
}
}
// decDisableShortcircuits ensures that all branches of an expression will be evaluated, no short-circuiting.
func decDisableShortcircuits() InterpretableDecorator {
return func(i Interpretable) (Interpretable, error) {
switch expr := i.(type) {
case *evalOr:
return &evalExhaustiveOr{
id: expr.id,
terms: expr.terms,
}, nil
case *evalAnd:
return &evalExhaustiveAnd{
id: expr.id,
terms: expr.terms,
}, nil
case *evalFold:
expr.exhaustive = true
return expr, nil
case InterpretableAttribute:
cond, isCond := expr.Attr().(*conditionalAttribute)
if isCond {
return &evalExhaustiveConditional{
id: cond.id,
attr: cond,
adapter: expr.Adapter(),
}, nil
}
}
return i, nil
}
}
// decOptimize optimizes the program plan by looking for common evaluation patterns and
// conditionally precomputing the result.
// - build list and map values with constant elements.
// - convert 'in' operations to set membership tests if possible.
func decOptimize() InterpretableDecorator {
return func(i Interpretable) (Interpretable, error) {
switch inst := i.(type) {
case *evalList:
return maybeBuildListLiteral(i, inst)
case *evalMap:
return maybeBuildMapLiteral(i, inst)
case InterpretableCall:
if inst.OverloadID() == overloads.InList {
return maybeOptimizeSetMembership(i, inst)
}
if overloads.IsTypeConversionFunction(inst.Function()) {
return maybeOptimizeConstUnary(i, inst)
}
}
return i, nil
}
}
// decRegexOptimizer compiles regex pattern string constants.
func decRegexOptimizer(regexOptimizations ...*RegexOptimization) InterpretableDecorator {
functionMatchMap := make(map[string]*RegexOptimization)
overloadMatchMap := make(map[string]*RegexOptimization)
for _, m := range regexOptimizations {
functionMatchMap[m.Function] = m
if m.OverloadID != "" {
overloadMatchMap[m.OverloadID] = m
}
}
return func(i Interpretable) (Interpretable, error) {
call, ok := i.(InterpretableCall)
if !ok {
return i, nil
}
var matcher *RegexOptimization
var found bool
if call.OverloadID() != "" {
matcher, found = overloadMatchMap[call.OverloadID()]
}
if !found {
matcher, found = functionMatchMap[call.Function()]
}
if !found || matcher.RegexIndex >= len(call.Args()) {
return i, nil
}
args := call.Args()
regexArg := args[matcher.RegexIndex]
regexStr, isConst := regexArg.(InterpretableConst)
if !isConst {
return i, nil
}
pattern, ok := regexStr.Value().(types.String)
if !ok {
return i, nil
}
return matcher.Factory(call, string(pattern))
}
}
func maybeOptimizeConstUnary(i Interpretable, call InterpretableCall) (Interpretable, error) {
args := call.Args()
if len(args) != 1 {
return i, nil
}
_, isConst := args[0].(InterpretableConst)
if !isConst {
return i, nil
}
val := call.Eval(EmptyActivation())
if types.IsError(val) {
return nil, val.(*types.Err)
}
return NewConstValue(call.ID(), val), nil
}
func maybeBuildListLiteral(i Interpretable, l *evalList) (Interpretable, error) {
for _, elem := range l.elems {
_, isConst := elem.(InterpretableConst)
if !isConst {
return i, nil
}
}
return NewConstValue(l.ID(), l.Eval(EmptyActivation())), nil
}
func maybeBuildMapLiteral(i Interpretable, mp *evalMap) (Interpretable, error) {
for idx, key := range mp.keys {
_, isConst := key.(InterpretableConst)
if !isConst {
return i, nil
}
_, isConst = mp.vals[idx].(InterpretableConst)
if !isConst {
return i, nil
}
}
return NewConstValue(mp.ID(), mp.Eval(EmptyActivation())), nil
}
// maybeOptimizeSetMembership may convert an 'in' operation against a list to map key membership
// test if the following conditions are true:
// - the list is a constant with homogeneous element types.
// - the elements are all of primitive type.
func maybeOptimizeSetMembership(i Interpretable, inlist InterpretableCall) (Interpretable, error) {
args := inlist.Args()
lhs := args[0]
rhs := args[1]
l, isConst := rhs.(InterpretableConst)
if !isConst {
return i, nil
}
// When the incoming binary call is flagged with as the InList overload, the value will
// always be convertible to a `traits.Lister` type.
list := l.Value().(traits.Lister)
if list.Size() == types.IntZero {
return NewConstValue(inlist.ID(), types.False), nil
}
it := list.Iterator()
valueSet := make(map[ref.Val]ref.Val)
for it.HasNext() == types.True {
elem := it.Next()
if !types.IsPrimitiveType(elem) || elem.Type() == types.BytesType {
// Note, non-primitive type are not yet supported, and []byte isn't hashable.
return i, nil
}
valueSet[elem] = types.True
switch ev := elem.(type) {
case types.Double:
iv := ev.ConvertToType(types.IntType)
// Ensure that only lossless conversions are added to the set
if !types.IsError(iv) && iv.Equal(ev) == types.True {
valueSet[iv] = types.True
}
// Ensure that only lossless conversions are added to the set
uv := ev.ConvertToType(types.UintType)
if !types.IsError(uv) && uv.Equal(ev) == types.True {
valueSet[uv] = types.True
}
case types.Int:
dv := ev.ConvertToType(types.DoubleType)
if !types.IsError(dv) {
valueSet[dv] = types.True
}
uv := ev.ConvertToType(types.UintType)
if !types.IsError(uv) {
valueSet[uv] = types.True
}
case types.Uint:
dv := ev.ConvertToType(types.DoubleType)
if !types.IsError(dv) {
valueSet[dv] = types.True
}
iv := ev.ConvertToType(types.IntType)
if !types.IsError(iv) {
valueSet[iv] = types.True
}
}
}
return &evalSetMembership{
inst: inlist,
arg: lhs,
valueSet: valueSet,
}, nil
}
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