642c6b952f
Some modern features of our function engine and language might require this new API, so port what we can and figure out the rest later.
126 lines
4.0 KiB
Go
126 lines
4.0 KiB
Go
// Mgmt
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// Copyright (C) James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package structs
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import (
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"context"
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"fmt"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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)
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// ChannelBasedSourceFunc is a Func which receives values from a golang channel
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// and emits them to the downstream nodes.
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type ChannelBasedSourceFunc struct {
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Name string
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Source interfaces.Func // for drawing dashed edges in the Graphviz visualization
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Chan chan types.Value
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Type *types.Type
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init *interfaces.Init
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last types.Value // last value received to use for diff
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}
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// String returns a simple name for this function. This is needed so this struct
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// can satisfy the pgraph.Vertex interface.
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func (obj *ChannelBasedSourceFunc) String() string {
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return "ChannelBasedSourceFunc"
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}
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// ArgGen returns the Nth arg name for this function.
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func (obj *ChannelBasedSourceFunc) ArgGen(index int) (string, error) {
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return "", fmt.Errorf("the ChannelBasedSourceFunc doesn't have any arguments")
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}
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// Validate makes sure we've built our struct properly. It is usually unused for
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// normal functions that users can use directly.
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func (obj *ChannelBasedSourceFunc) Validate() error {
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if obj.Chan == nil {
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return fmt.Errorf("the Chan was not set")
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}
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return nil
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}
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// Info returns some static info about itself.
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func (obj *ChannelBasedSourceFunc) Info() *interfaces.Info {
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return &interfaces.Info{
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Pure: false,
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Memo: false,
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Sig: types.NewType(fmt.Sprintf("func() %s", obj.Type)),
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Err: obj.Validate(),
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}
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}
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// Init runs some startup code for this function.
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func (obj *ChannelBasedSourceFunc) Init(init *interfaces.Init) error {
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obj.init = init
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return nil
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}
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// Stream returns the changing values that this func has over time.
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func (obj *ChannelBasedSourceFunc) Stream(ctx context.Context) error {
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defer close(obj.init.Output) // the sender closes
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for {
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select {
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case input, ok := <-obj.Chan:
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if !ok {
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return nil // can't output any more
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}
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//if obj.last != nil && input.Cmp(obj.last) == nil {
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// continue // value didn't change, skip it
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//}
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obj.last = input // store so we can send after this select
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case <-ctx.Done():
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return nil
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}
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select {
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case obj.init.Output <- obj.last: // send
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case <-ctx.Done():
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return nil
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}
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}
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}
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// XXX: Is is correct to implement this here for this particular function?
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// XXX: tricky since this really receives input from a secret channel...
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// XXX: ADD A MUTEX AROUND READING obj.last ???
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//func (obj *ChannelBasedSourceFunc) Call(ctx context.Context, args []types.Value) (types.Value, error) {
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// if obj.last == nil {
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// return nil, fmt.Errorf("programming error")
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// }
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// return obj.last, nil
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//}
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