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lazy_copy.go
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lazy_copy.go
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// Copyright (c) 2018 Ashley Jeffs
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package metadata
import (
"github.com/Jeffail/benthos/lib/types"
)
//------------------------------------------------------------------------------
// lazyCopy is a types.Metadata implementation that takes an existing metadata
// object and lazily returns its values. If a call is made to edit the contents
// of the metadata then a copy is made of the original before doing so.
type lazyCopy struct {
copied bool
m types.Metadata
}
func (l *lazyCopy) ensureCopied() {
if l.copied {
return
}
var newMap map[string]string
if t, ok := l.m.(*Type); ok {
newMap = make(map[string]string, len(t.m))
} else {
newMap = map[string]string{}
}
l.m.Iter(func(k, v string) error {
newMap[k] = v
return nil
})
l.m = New(newMap)
l.copied = true
}
// Get returns a metadata value if a key exists, otherwise an empty string.
func (l *lazyCopy) Get(key string) string {
return l.m.Get(key)
}
// Set sets the value of a metadata key.
func (l *lazyCopy) Set(key, value string) types.Metadata {
l.ensureCopied()
l.m.Set(key, value)
return l
}
// Delete removes the value of a metadata key.
func (l *lazyCopy) Delete(key string) types.Metadata {
l.ensureCopied()
l.m.Delete(key)
return l
}
// Iter iterates each metadata key/value pair.
func (l *lazyCopy) Iter(f func(k, v string) error) error {
return l.m.Iter(f)
}
// Copy returns a copy of the metadata object that can be edited without
// changing the contents of the original.
func (l *lazyCopy) Copy() types.Metadata {
return l.m.Copy()
}
//------------------------------------------------------------------------------
// LazyCopy takes an existing metadata object and returns a new implementation
// that lazily returns its values. If a call is made to edit the contents of the
// metadata then a copy is made of the original before doing so.
func LazyCopy(m types.Metadata) types.Metadata {
return &lazyCopy{
m: m,
}
}
//------------------------------------------------------------------------------