102 lines
3.3 KiB
Go
102 lines
3.3 KiB
Go
/*
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*
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* Copyright 2019 gRPC authors.
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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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*/
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// Package attributes defines a generic key/value store used in various gRPC
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// components.
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//
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// Experimental
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//
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// Notice: This package is EXPERIMENTAL and may be changed or removed in a
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// later release.
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package attributes
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// Attributes is an immutable struct for storing and retrieving generic
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// key/value pairs. Keys must be hashable, and users should define their own
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// types for keys. Values should not be modified after they are added to an
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// Attributes or if they were received from one. If values implement 'Equal(o
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// interface{}) bool', it will be called by (*Attributes).Equal to determine
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// whether two values with the same key should be considered equal.
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type Attributes struct {
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m map[interface{}]interface{}
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}
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// New returns a new Attributes containing the key/value pair.
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func New(key, value interface{}) *Attributes {
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return &Attributes{m: map[interface{}]interface{}{key: value}}
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}
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// WithValue returns a new Attributes containing the previous keys and values
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// and the new key/value pair. If the same key appears multiple times, the
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// last value overwrites all previous values for that key. To remove an
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// existing key, use a nil value. value should not be modified later.
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func (a *Attributes) WithValue(key, value interface{}) *Attributes {
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if a == nil {
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return New(key, value)
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}
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n := &Attributes{m: make(map[interface{}]interface{}, len(a.m)+1)}
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for k, v := range a.m {
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n.m[k] = v
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}
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n.m[key] = value
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return n
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}
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// Value returns the value associated with these attributes for key, or nil if
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// no value is associated with key. The returned value should not be modified.
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func (a *Attributes) Value(key interface{}) interface{} {
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if a == nil {
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return nil
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}
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return a.m[key]
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}
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// Equal returns whether a and o are equivalent. If 'Equal(o interface{})
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// bool' is implemented for a value in the attributes, it is called to
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// determine if the value matches the one stored in the other attributes. If
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// Equal is not implemented, standard equality is used to determine if the two
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// values are equal. Note that some types (e.g. maps) aren't comparable by
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// default, so they must be wrapped in a struct, or in an alias type, with Equal
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// defined.
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func (a *Attributes) Equal(o *Attributes) bool {
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if a == nil && o == nil {
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return true
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}
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if a == nil || o == nil {
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return false
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}
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if len(a.m) != len(o.m) {
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return false
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}
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for k, v := range a.m {
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ov, ok := o.m[k]
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if !ok {
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// o missing element of a
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return false
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}
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if eq, ok := v.(interface{ Equal(o interface{}) bool }); ok {
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if !eq.Equal(ov) {
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return false
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}
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} else if v != ov {
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// Fallback to a standard equality check if Value is unimplemented.
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return false
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}
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}
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return true
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}
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