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evaluator.go
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evaluator.go
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// Copyright 2016 Istio Authors
//
// 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 expr
import (
pb "istio.io/api/mixer/v1/config/descriptor"
"istio.io/core/pkg/attribute"
)
type (
// Evaluator evaluates an expression written in the implementation defined
// expression language. It uses attribute.Bag as variable bindings.
Evaluator interface {
// Eval evaluates given expression using the attribute bag
Eval(expr string, attrs attribute.Bag) (interface{}, error)
// Eval evaluates given expression using the attribute bag to a string
EvalString(expr string, attrs attribute.Bag) (string, error)
PredicateEvaluator
TypeChecker
}
// PredicateEvaluator evaluates a predicate to true or false
PredicateEvaluator interface {
// EvalPredicate evaluates given predicate using the attribute bag
EvalPredicate(expr string, attrs attribute.Bag) (bool, error)
}
// TypeChecker validates a given expression for type safety.
TypeChecker interface {
// EvalType produces the type of an expression or an error if the type cannot be evaluated.
// TODO: we probably want to use a golang type rather than pb.ValueType (a proto).
EvalType(expr string, finder AttributeDescriptorFinder) (pb.ValueType, error)
// AssertType evaluates the type of expr using the attribute set; if the evaluated type is equal to
// the expected type we return nil, and return an error otherwise.
AssertType(expr string, finder AttributeDescriptorFinder, expectedType pb.ValueType) error
}
)