/
channel_based_source.go
115 lines (99 loc) · 3.65 KB
/
channel_based_source.go
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// Mgmt
// Copyright (C) 2013-2024+ 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 <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.
package structs
import (
"context"
"fmt"
"github.com/purpleidea/mgmt/lang/interfaces"
"github.com/purpleidea/mgmt/lang/types"
)
// ChannelBasedSourceFunc is a Func which receives values from a golang channel
// and emits them to the downstream nodes.
type ChannelBasedSourceFunc struct {
Name string
Source interfaces.Func // for drawing dashed edges in the Graphviz visualization
Chan chan types.Value
Type *types.Type
init *interfaces.Init
last types.Value // last value received to use for diff
}
// String returns a simple name for this function. This is needed so this struct
// can satisfy the pgraph.Vertex interface.
func (obj *ChannelBasedSourceFunc) String() string {
return "ChannelBasedSourceFunc"
}
// ArgGen returns the Nth arg name for this function.
func (obj *ChannelBasedSourceFunc) ArgGen(index int) (string, error) {
return "", fmt.Errorf("the ChannelBasedSourceFunc doesn't have any arguments")
}
// Validate makes sure we've built our struct properly. It is usually unused for
// normal functions that users can use directly.
func (obj *ChannelBasedSourceFunc) Validate() error {
if obj.Chan == nil {
return fmt.Errorf("the Chan was not set")
}
return nil
}
// Info returns some static info about itself.
func (obj *ChannelBasedSourceFunc) Info() *interfaces.Info {
return &interfaces.Info{
Pure: false,
Memo: false,
Sig: types.NewType(fmt.Sprintf("func() %s", obj.Type)),
Err: obj.Validate(),
}
}
// Init runs some startup code for this function.
func (obj *ChannelBasedSourceFunc) Init(init *interfaces.Init) error {
obj.init = init
return nil
}
// Stream returns the changing values that this func has over time.
func (obj *ChannelBasedSourceFunc) Stream(ctx context.Context) error {
defer close(obj.init.Output) // the sender closes
for {
select {
case input, ok := <-obj.Chan:
if !ok {
return nil // can't output any more
}
//if obj.last != nil && input.Cmp(obj.last) == nil {
// continue // value didn't change, skip it
//}
obj.last = input // store so we can send after this select
case <-ctx.Done():
return nil
}
select {
case obj.init.Output <- obj.last: // send
case <-ctx.Done():
return nil
}
}
}