github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/api/meta/help.go (about)

     1  /*
     2  Copyright 2015 The Kubernetes Authors All rights reserved.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package meta
    18  
    19  import (
    20  	"fmt"
    21  	"reflect"
    22  
    23  	"k8s.io/kubernetes/pkg/conversion"
    24  	"k8s.io/kubernetes/pkg/runtime"
    25  )
    26  
    27  // IsListType returns true if the provided Object has a slice called Items
    28  func IsListType(obj runtime.Object) bool {
    29  	_, err := GetItemsPtr(obj)
    30  	return err == nil
    31  }
    32  
    33  // GetItemsPtr returns a pointer to the list object's Items member.
    34  // If 'list' doesn't have an Items member, it's not really a list type
    35  // and an error will be returned.
    36  // This function will either return a pointer to a slice, or an error, but not both.
    37  func GetItemsPtr(list runtime.Object) (interface{}, error) {
    38  	v, err := conversion.EnforcePtr(list)
    39  	if err != nil {
    40  		return nil, err
    41  	}
    42  	items := v.FieldByName("Items")
    43  	if !items.IsValid() {
    44  		return nil, fmt.Errorf("no Items field in %#v", list)
    45  	}
    46  	switch items.Kind() {
    47  	case reflect.Interface, reflect.Ptr:
    48  		target := reflect.TypeOf(items.Interface()).Elem()
    49  		if target.Kind() != reflect.Slice {
    50  			return nil, fmt.Errorf("items: Expected slice, got %s", target.Kind())
    51  		}
    52  		return items.Interface(), nil
    53  	case reflect.Slice:
    54  		return items.Addr().Interface(), nil
    55  	default:
    56  		return nil, fmt.Errorf("items: Expected slice, got %s", items.Kind())
    57  	}
    58  }
    59  
    60  // ExtractList returns obj's Items element as an array of runtime.Objects.
    61  // Returns an error if obj is not a List type (does not have an Items member).
    62  func ExtractList(obj runtime.Object) ([]runtime.Object, error) {
    63  	itemsPtr, err := GetItemsPtr(obj)
    64  	if err != nil {
    65  		return nil, err
    66  	}
    67  	items, err := conversion.EnforcePtr(itemsPtr)
    68  	if err != nil {
    69  		return nil, err
    70  	}
    71  	list := make([]runtime.Object, items.Len())
    72  	for i := range list {
    73  		raw := items.Index(i)
    74  		switch item := raw.Interface().(type) {
    75  		case runtime.Object:
    76  			list[i] = item
    77  		case runtime.RawExtension:
    78  			list[i] = &runtime.Unknown{
    79  				RawJSON: item.RawJSON,
    80  			}
    81  		default:
    82  			var found bool
    83  			if list[i], found = raw.Addr().Interface().(runtime.Object); !found {
    84  				return nil, fmt.Errorf("%v: item[%v]: Expected object, got %#v(%s)", obj, i, raw.Interface(), raw.Kind())
    85  			}
    86  		}
    87  	}
    88  	return list, nil
    89  }
    90  
    91  // objectSliceType is the type of a slice of Objects
    92  var objectSliceType = reflect.TypeOf([]runtime.Object{})
    93  
    94  // SetList sets the given list object's Items member have the elements given in
    95  // objects.
    96  // Returns an error if list is not a List type (does not have an Items member),
    97  // or if any of the objects are not of the right type.
    98  func SetList(list runtime.Object, objects []runtime.Object) error {
    99  	itemsPtr, err := GetItemsPtr(list)
   100  	if err != nil {
   101  		return err
   102  	}
   103  	items, err := conversion.EnforcePtr(itemsPtr)
   104  	if err != nil {
   105  		return err
   106  	}
   107  	if items.Type() == objectSliceType {
   108  		items.Set(reflect.ValueOf(objects))
   109  		return nil
   110  	}
   111  	slice := reflect.MakeSlice(items.Type(), len(objects), len(objects))
   112  	for i := range objects {
   113  		dest := slice.Index(i)
   114  		src, err := conversion.EnforcePtr(objects[i])
   115  		if err != nil {
   116  			return err
   117  		}
   118  		if src.Type().AssignableTo(dest.Type()) {
   119  			dest.Set(src)
   120  		} else if src.Type().ConvertibleTo(dest.Type()) {
   121  			dest.Set(src.Convert(dest.Type()))
   122  		} else {
   123  			return fmt.Errorf("item[%d]: Type mismatch: Expected %v, got %v", i, dest.Type(), src.Type())
   124  		}
   125  	}
   126  	items.Set(slice)
   127  	return nil
   128  }