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minio/pkg/s3select/sql/jsonpath.go

101 lines
2.4 KiB

/*
* Minio Cloud Storage, (C) 2019 Minio, Inc.
*
* 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 sql
import (
"errors"
"github.com/bcicen/jstream"
)
var (
errKeyLookup = errors.New("Cannot look up key in non-object value")
errIndexLookup = errors.New("Cannot look up array index in non-array value")
errWildcardObjectLookup = errors.New("Object wildcard used on non-object value")
errWildcardArrayLookup = errors.New("Array wildcard used on non-array value")
errWilcardObjectUsageInvalid = errors.New("Invalid usage of object wildcard")
)
func jsonpathEval(p []*JSONPathElement, v interface{}) (r interface{}, err error) {
// fmt.Printf("JPATHexpr: %v jsonobj: %v\n\n", p, v)
if len(p) == 0 || v == nil {
return v, nil
}
switch {
case p[0].Key != nil:
key := p[0].Key.keyString()
kvs, ok := v.(jstream.KVS)
if !ok {
return nil, errKeyLookup
}
for _, kv := range kvs {
if kv.Key == key {
return jsonpathEval(p[1:], kv.Value)
}
}
// Key not found - return nil result
return nil, nil
case p[0].Index != nil:
idx := *p[0].Index
arr, ok := v.([]interface{})
if !ok {
return nil, errIndexLookup
}
if idx >= len(arr) {
return nil, nil
}
return jsonpathEval(p[1:], arr[idx])
case p[0].ObjectWildcard:
kvs, ok := v.(jstream.KVS)
if !ok {
return nil, errWildcardObjectLookup
}
if len(p[1:]) > 0 {
return nil, errWilcardObjectUsageInvalid
}
return kvs, nil
case p[0].ArrayWildcard:
arr, ok := v.([]interface{})
if !ok {
return nil, errWildcardArrayLookup
}
// Lookup remainder of path in each array element and
// make result array.
var result []interface{}
for _, a := range arr {
rval, err := jsonpathEval(p[1:], a)
if err != nil {
return nil, err
}
result = append(result, rval)
}
return result, nil
}
panic("cannot reach here")
}