lang: Initial implementation of the mgmt language
This is an initial implementation of the mgmt language. It is a declarative (immutable) functional, reactive, domain specific programming language. It is intended to be a language that is: * safe * powerful * easy to reason about With these properties, we hope this language, and the mgmt engine will allow you to model the real-time systems that you'd like to automate. This also includes a number of other associated changes. Sorry for the large size of this patch.
This commit is contained in:
James Shubin
213
lang/funcs/core/vumeterfunc.go
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213
lang/funcs/core/vumeterfunc.go
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// Mgmt
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// Copyright (C) 2013-2018+ 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 <http://www.gnu.org/licenses/>.
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package core // TODO: should this be in its own individual package?
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import (
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"fmt"
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"math"
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"os/exec"
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"strconv"
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"strings"
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"syscall"
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"time"
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"github.com/purpleidea/mgmt/lang/funcs"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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errwrap "github.com/pkg/errors"
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)
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func init() {
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funcs.Register("vumeter", func() interfaces.Func { return &VUMeterFunc{} }) // must register the func and name
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}
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// VUMeter is a gimmic function to display a vu meter from the microphone.
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type VUMeterFunc struct {
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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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symbol string
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multiplier int64
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peak float64
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result string // last calculated output
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closeChan chan struct{}
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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 *VUMeterFunc) Validate() error {
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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 *VUMeterFunc) Info() *interfaces.Info {
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return &interfaces.Info{
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Pure: true,
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Memo: false,
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Sig: types.NewType("func(symbol str, multiplier int, peak float) str"),
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}
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}
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// Init runs some startup code for this fact.
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func (obj *VUMeterFunc) Init(init *interfaces.Init) error {
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obj.init = init
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obj.closeChan = make(chan struct{})
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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 *VUMeterFunc) Stream() error {
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defer close(obj.init.Output) // the sender closes
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ticker := newTicker()
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defer ticker.Stop()
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// FIXME: this goChan seems to work better than the ticker :)
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// this is because we have a ~1sec delay in capturing the value in exec
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goChan := make(chan struct{})
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close(goChan)
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for {
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select {
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case input, ok := <-obj.init.Input:
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if !ok {
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obj.init.Input = nil // don't infinite loop back
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continue // no more inputs, but don't return!
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}
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//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
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// return errwrap.Wrapf(err, "wrong function input")
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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 for next
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obj.symbol = input.Struct()["symbol"].Str()
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obj.multiplier = input.Struct()["multiplier"].Int()
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obj.peak = input.Struct()["peak"].Float()
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//case <-ticker.C: // received the timer event
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case <-goChan:
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if obj.last == nil {
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continue // still waiting for input values
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}
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// arecord -d 1 /dev/shm/mgmt_rec.wav 2>/dev/null
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args1 := []string{"-d", "1", "/dev/shm/mgmt_rec.wav"}
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cmd1 := exec.Command("/usr/bin/arecord", args1...)
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cmd1.SysProcAttr = &syscall.SysProcAttr{
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Setpgid: true,
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Pgid: 0,
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}
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// start the command
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if _, err := cmd1.Output(); err != nil {
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return errwrap.Wrapf(err, "cmd failed to run")
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}
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// sox -t .wav /dev/shm/mgmt_rec.wav -n stat 2>&1 | grep "Maximum amplitude" | cut -d ':' -f 2
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args2 := []string{"-t", ".wav", "/dev/shm/mgmt_rec.wav", "-n", "stat"}
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cmd2 := exec.Command("/usr/bin/sox", args2...)
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cmd2.SysProcAttr = &syscall.SysProcAttr{
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Setpgid: true,
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Pgid: 0,
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}
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// start the command
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out, err := cmd2.CombinedOutput() // data comes on stderr
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if err != nil {
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return errwrap.Wrapf(err, "cmd failed to run")
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}
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ratio, err := extract(out)
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if err != nil {
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return errwrap.Wrapf(err, "failed to extract")
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}
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result, err := visual(obj.symbol, int(obj.multiplier), obj.peak, ratio)
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if err != nil {
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return errwrap.Wrapf(err, "could not generate visual")
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}
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if obj.result == result {
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continue // result didn't change
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}
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obj.result = result // store new result
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case <-obj.closeChan:
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return nil
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}
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select {
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case obj.init.Output <- &types.StrValue{
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V: obj.result,
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}:
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case <-obj.closeChan:
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return nil
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}
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}
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}
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// Close runs some shutdown code for this fact and turns off the stream.
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func (obj *VUMeterFunc) Close() error {
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close(obj.closeChan)
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return nil
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}
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func newTicker() *time.Ticker {
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return time.NewTicker(time.Duration(1) * time.Second)
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}
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func extract(data []byte) (float64, error) {
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const prefix = "Maximum amplitude:"
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str := string(data)
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lines := strings.Split(str, "\n")
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for _, line := range lines {
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if !strings.HasPrefix(line, prefix) {
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continue
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}
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s := strings.TrimSpace(line[len(prefix):])
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f, err := strconv.ParseFloat(s, 64)
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if err != nil {
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return 0, err
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}
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return f, nil
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}
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return 0, fmt.Errorf("could not extract any data")
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}
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func round(f float64) int {
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return int(f + math.Copysign(0.5, f))
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}
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// TODO: make this fancier
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func visual(symbol string, multiplier int, peak, ratio float64) (string, error) {
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if ratio > 1 || ratio < 0 {
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return "", fmt.Errorf("invalid ratio of %f", ratio)
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}
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x := strings.Repeat(symbol, round(ratio*float64(multiplier)))
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if x == "" {
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x += symbol // add a minimum
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}
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if ratio > peak {
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x += " PEAK!!!"
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}
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return fmt.Sprintf("(%f):\n%s\n%s", ratio, x, x), nil
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}
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