lang: funcs: core: Drop unnecessary core prefix from imports

This unbreaks the mcl bindata code. Of course we could change the parser
to allow this prefix, but this is cleaner. The packages still have a
core prefix, which it seems we could also remove, but this isn't
particularly important for anything.

lang/funcs/core/example/vumeter_func.go

@@ -0,0 +1,213 @@
+// 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 coreexample
+
+import (
+	"fmt"
+	"math"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/purpleidea/mgmt/lang/funcs"
+	"github.com/purpleidea/mgmt/lang/interfaces"
+	"github.com/purpleidea/mgmt/lang/types"
+
+	errwrap "github.com/pkg/errors"
+)
+
+func init() {
+	funcs.ModuleRegister(moduleName, "vumeter", func() interfaces.Func { return &VUMeterFunc{} }) // must register the func and name
+}
+
+// VUMeterFunc is a gimmic function to display a vu meter from the microphone.
+type VUMeterFunc struct {
+	init *interfaces.Init
+	last types.Value // last value received to use for diff
+
+	symbol     string
+	multiplier int64
+	peak       float64
+
+	result string // last calculated output
+
+	closeChan chan struct{}
+}
+
+// Validate makes sure we've built our struct properly. It is usually unused for
+// normal functions that users can use directly.
+func (obj *VUMeterFunc) Validate() error {
+	return nil
+}
+
+// Info returns some static info about itself.
+func (obj *VUMeterFunc) Info() *interfaces.Info {
+	return &interfaces.Info{
+		Pure: true,
+		Memo: false,
+		Sig:  types.NewType("func(symbol str, multiplier int, peak float) str"),
+	}
+}
+
+// Init runs some startup code for this function.
+func (obj *VUMeterFunc) Init(init *interfaces.Init) error {
+	obj.init = init
+	obj.closeChan = make(chan struct{})
+	return nil
+}
+
+// Stream returns the changing values that this func has over time.
+func (obj *VUMeterFunc) Stream() error {
+	defer close(obj.init.Output) // the sender closes
+	ticker := newTicker()
+	defer ticker.Stop()
+	// FIXME: this goChan seems to work better than the ticker :)
+	// this is because we have a ~1sec delay in capturing the value in exec
+	goChan := make(chan struct{})
+	close(goChan)
+	for {
+		select {
+		case input, ok := <-obj.init.Input:
+			if !ok {
+				obj.init.Input = nil // don't infinite loop back
+				continue             // no more inputs, but don't return!
+			}
+			//if err := input.Type().Cmp(obj.Info().Sig.Input); err != nil {
+			//	return errwrap.Wrapf(err, "wrong function input")
+			//}
+
+			if obj.last != nil && input.Cmp(obj.last) == nil {
+				continue // value didn't change, skip it
+			}
+			obj.last = input // store for next
+
+			obj.symbol = input.Struct()["symbol"].Str()
+			obj.multiplier = input.Struct()["multiplier"].Int()
+			obj.peak = input.Struct()["peak"].Float()
+
+		//case <-ticker.C: // received the timer event
+		case <-goChan:
+
+			if obj.last == nil {
+				continue // still waiting for input values
+			}
+
+			// arecord -d 1 /dev/shm/mgmt_rec.wav 2>/dev/null
+			args1 := []string{"-d", "1", "/dev/shm/mgmt_rec.wav"}
+			cmd1 := exec.Command("/usr/bin/arecord", args1...)
+			cmd1.SysProcAttr = &syscall.SysProcAttr{
+				Setpgid: true,
+				Pgid:    0,
+			}
+			// start the command
+			if _, err := cmd1.Output(); err != nil {
+				return errwrap.Wrapf(err, "cmd failed to run")
+			}
+
+			// sox -t .wav /dev/shm/mgmt_rec.wav -n stat 2>&1 | grep "Maximum amplitude" | cut -d ':' -f 2
+			args2 := []string{"-t", ".wav", "/dev/shm/mgmt_rec.wav", "-n", "stat"}
+			cmd2 := exec.Command("/usr/bin/sox", args2...)
+			cmd2.SysProcAttr = &syscall.SysProcAttr{
+				Setpgid: true,
+				Pgid:    0,
+			}
+
+			// start the command
+			out, err := cmd2.CombinedOutput() // data comes on stderr
+			if err != nil {
+				return errwrap.Wrapf(err, "cmd failed to run")
+			}
+
+			ratio, err := extract(out)
+			if err != nil {
+				return errwrap.Wrapf(err, "failed to extract")
+			}
+
+			result, err := visual(obj.symbol, int(obj.multiplier), obj.peak, ratio)
+			if err != nil {
+				return errwrap.Wrapf(err, "could not generate visual")
+			}
+
+			if obj.result == result {
+				continue // result didn't change
+			}
+			obj.result = result // store new result
+
+		case <-obj.closeChan:
+			return nil
+		}
+
+		select {
+		case obj.init.Output <- &types.StrValue{
+			V: obj.result,
+		}:
+		case <-obj.closeChan:
+			return nil
+		}
+	}
+}
+
+// Close runs some shutdown code for this function and turns off the stream.
+func (obj *VUMeterFunc) Close() error {
+	close(obj.closeChan)
+	return nil
+}
+
+func newTicker() *time.Ticker {
+	return time.NewTicker(time.Duration(1) * time.Second)
+}
+
+func extract(data []byte) (float64, error) {
+	const prefix = "Maximum amplitude:"
+	str := string(data)
+	lines := strings.Split(str, "\n")
+	for _, line := range lines {
+		if !strings.HasPrefix(line, prefix) {
+			continue
+		}
+		s := strings.TrimSpace(line[len(prefix):])
+		f, err := strconv.ParseFloat(s, 64)
+		if err != nil {
+			return 0, err
+		}
+		return f, nil
+	}
+	return 0, fmt.Errorf("could not extract any data")
+}
+
+func round(f float64) int {
+	return int(f + math.Copysign(0.5, f))
+}
+
+// TODO: make this fancier
+func visual(symbol string, multiplier int, peak, ratio float64) (string, error) {
+	if ratio > 1 || ratio < 0 {
+		return "", fmt.Errorf("invalid ratio of %f", ratio)
+	}
+
+	x := strings.Repeat(symbol, round(ratio*float64(multiplier)))
+	if x == "" {
+		x += symbol // add a minimum
+	}
+	if ratio > peak {
+		x += " PEAK!!!"
+	}
+	return fmt.Sprintf("(%f):\n%s\n%s", ratio, x, x), nil
+}