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const.go
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const.go
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// Mgmt
// Copyright (C) 2013-2018+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package structs
import (
"fmt"
"github.com/purpleidea/mgmt/lang/interfaces"
"github.com/purpleidea/mgmt/lang/types"
)
// ConstFunc is a function that returns the constant value passed to Value.
type ConstFunc struct {
Value types.Value
init *interfaces.Init
closeChan chan struct{}
}
// Validate makes sure we've built our struct properly.
func (obj *ConstFunc) Validate() error {
if obj.Value == nil {
return fmt.Errorf("must specify `Value` input")
}
return nil
}
// Info returns some static info about itself.
func (obj *ConstFunc) Info() *interfaces.Info {
return &interfaces.Info{
Pure: true,
Memo: false, // TODO: ???
Sig: types.NewType(fmt.Sprintf("func() %s", obj.Value.Type().String())),
Err: obj.Validate(), // XXX: implement this and check .Err in engine!
}
}
// Init runs some startup code for this const.
func (obj *ConstFunc) Init(init *interfaces.Init) error {
obj.init = init
obj.closeChan = make(chan struct{})
return nil
}
// Stream returns the single value that this const has, and then closes.
func (obj *ConstFunc) Stream() error {
select {
case obj.init.Output <- obj.Value:
// pass
case <-obj.closeChan:
return nil
}
close(obj.init.Output) // signal that we're done sending
return nil
}
// Close runs some shutdown code for this const and turns off the stream.
func (obj *ConstFunc) Close() error {
close(obj.closeChan)
return nil
}