feat: filter can messages via command line "--filter"

filter/filter.go

@@ -0,0 +1,61 @@
+package filter
+
+// ---------------------------------------------------------------------------------------
+//  imports
+// ---------------------------------------------------------------------------------------
+
+import (
+	"github.com/robertkrimen/otto"
+)
+
+// ---------------------------------------------------------------------------------------
+//  constants
+// ---------------------------------------------------------------------------------------
+
+const (
+	InputVariableName = "f"
+)
+
+// ---------------------------------------------------------------------------------------
+//  types
+// ---------------------------------------------------------------------------------------
+
+type Filter struct {
+	Expr string
+}
+
+// ---------------------------------------------------------------------------------------
+//  public functions
+// ---------------------------------------------------------------------------------------
+
+func NewFilter(expr string) *Filter {
+	if expr == "" {
+		expr = "true"
+	}
+
+	return &Filter{Expr: expr}
+}
+
+// ---------------------------------------------------------------------------------------
+//  public members
+// ---------------------------------------------------------------------------------------
+
+func (f *Filter) Eval(v interface{}) (bool, error) {
+	vm := otto.New()
+	v, err := vm.ToValue(v)
+	if err != nil {
+		return false, err
+	}
+
+	err = vm.Set(InputVariableName, v)
+	if err != nil {
+		return false, err
+	}
+
+	ret, err := vm.Run(f.Expr)
+	if err != nil {
+		return false, err
+	}
+
+	return ret.ToBoolean()
+}

go.mod

@@ -3,6 +3,8 @@ module canlisten
 go 1.14
 
 require (
+	github.com/robertkrimen/otto v0.0.0-20191219234010-c382bd3c16ff
 	github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07
 	golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae // indirect
+	gopkg.in/sourcemap.v1 v1.0.5 // indirect
 )

go.sum

@@ -1,4 +1,8 @@
+github.com/robertkrimen/otto v0.0.0-20191219234010-c382bd3c16ff h1:+6NUiITWwE5q1KO6SAfUX918c+Tab0+tGAM/mtdlUyA=
+github.com/robertkrimen/otto v0.0.0-20191219234010-c382bd3c16ff/go.mod h1:xvqspoSXJTIpemEonrMDFq6XzwHYYgToXWj5eRX1OtY=
 github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07 h1:UyzmZLoiDWMRywV4DUYb9Fbt8uiOSooupjTq10vpvnU=
 github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07/go.mod h1:kDXzergiv9cbyO7IOYJZWg1U88JhDg3PB6klq9Hg2pA=
 golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae h1:Ih9Yo4hSPImZOpfGuA4bR/ORKTAbhZo2AbWNRCnevdo=
 golang.org/x/sys v0.0.0-20200625212154-ddb9806d33ae/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+gopkg.in/sourcemap.v1 v1.0.5 h1:inv58fC9f9J3TK2Y2R1NPntXEn3/wjWHkonhIUODNTI=
+gopkg.in/sourcemap.v1 v1.0.5/go.mod h1:2RlvNNSMglmRrcvhfuzp4hQHwOtjxlbjX7UPY/GXb78=

main.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"canlisten/can"
+	"canlisten/filter"
 
 	"github.com/tarm/serial"
 )
@@ -35,8 +36,9 @@ const (
 // ---------------------------------------------------------------------------------------
 
 var (
-	Device  string
-	Running = true
+	Device     string
+	FilterExpr string
+	Running    = true
 )
 
 // ---------------------------------------------------------------------------------------
@@ -85,6 +87,7 @@ func GetPrintableCmd(cmd string) string {
 
 func main() {
 	flag.StringVar(&Device, "dev", "/dev/ttyACM0", "")
+	flag.StringVar(&FilterExpr, "filter", "", "")
 	flag.Parse()
 
 	c := &serial.Config{Name: Device, Baud: 115200, ReadTimeout: 50 * time.Millisecond}
@@ -109,6 +112,9 @@ func main() {
 		log.Println("closing application")
 	}()
 
+	log.Printf("Using filter: \"%s\"", FilterExpr)
+	filterVm := filter.NewFilter(FilterExpr)
+
 	// print all can messages to stdout
 	stdout := log.New(os.Stdout, "", log.LstdFlags|log.Lmicroseconds)
 	canCounter := 0
@@ -132,6 +138,17 @@ func main() {
 		}
 		frame.Timestamp = time.Now()
 
+		// apply the filterVm
+		show, err := filterVm.Eval(frame)
+		if err != nil {
+			log.Println("failed to evaluate filterVm:", err.Error())
+			continue
+		}
+
+		if !show {
+			continue
+		}
+
 		// count message and print to stdout
 		canCounter++
 		stdout.Printf("%s  %s", filepath.Base(Device), frame.String())