Add stacktrace package for collection of stacktraces

This helps aid our effort of returning useful errors.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

stacktrace/capture.go

@@ -0,0 +1,25 @@
+package stacktrace
+
+import "runtime"
+
+// Caputure captures a stacktrace for the current calling go program
+//
+// skip is the number of frames to skip
+func Capture(userSkip int) Stacktrace {
+	var (
+		skip   = userSkip + 1 // add one for our own function
+		frames []Frame
+	)
+
+	for i := skip; ; i++ {
+		pc, file, line, ok := runtime.Caller(i)
+		if !ok {
+			break
+		}
+		frames = append(frames, NewFrame(pc, file, line))
+	}
+
+	return Stacktrace{
+		Frames: frames,
+	}
+}

stacktrace/capture_test.go

@@ -0,0 +1,27 @@
+package stacktrace
+
+import "testing"
+
+func captureFunc() Stacktrace {
+	return Capture(0)
+}
+
+func TestCaptureTestFunc(t *testing.T) {
+	stack := captureFunc()
+
+	if len(stack.Frames) == 0 {
+		t.Fatal("expected stack frames to be returned")
+	}
+
+	// the first frame is the caller
+	frame := stack.Frames[0]
+	if expected := "captureFunc"; frame.Function != expected {
+		t.Fatalf("expteced function %q but recevied %q", expected, frame.Function)
+	}
+	if expected := "github.com/docker/libcontainer/stacktrace"; frame.Package != expected {
+		t.Fatalf("expected package %q but received %q", expected, frame.Package)
+	}
+	if expected := "capture_test.go"; frame.File != expected {
+		t.Fatalf("expected file %q but received %q", expected, frame.File)
+	}
+}

stacktrace/frame.go

@@ -0,0 +1,35 @@
+package stacktrace
+
+import (
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// NewFrame returns a new stack frame for the provided information
+func NewFrame(pc uintptr, file string, line int) Frame {
+	fn := runtime.FuncForPC(pc)
+	pack, name := parseFunctionName(fn.Name())
+	return Frame{
+		Line:     line,
+		File:     filepath.Base(file),
+		Package:  pack,
+		Function: name,
+	}
+}
+
+func parseFunctionName(name string) (string, string) {
+	i := strings.LastIndex(name, ".")
+	if i == -1 {
+		return "", name
+	}
+	return name[:i], name[i+1:]
+}
+
+// Frame contains all the information for a stack frame within a go program
+type Frame struct {
+	File     string
+	Function string
+	Package  string
+	Line     int
+}

stacktrace/frame_test.go

@@ -0,0 +1,20 @@
+package stacktrace
+
+import "testing"
+
+func TestParsePackageName(t *testing.T) {
+	var (
+		name             = "github.com/docker/libcontainer/stacktrace.captureFunc"
+		expectedPackage  = "github.com/docker/libcontainer/stacktrace"
+		expectedFunction = "captureFunc"
+	)
+
+	pack, funcName := parseFunctionName(name)
+	if pack != expectedPackage {
+		t.Fatalf("expected package %q but received %q", expectedPackage, pack)
+	}
+
+	if funcName != expectedFunction {
+		t.Fatalf("expected function %q but received %q", expectedFunction, funcName)
+	}
+}

stacktrace/stacktrace.go

@@ -0,0 +1,5 @@
+package stacktrace
+
+type Stacktrace struct {
+	Frames []Frame
+}