add debug print func! fix #278

+// most reference from github.com/realint/dbgutil
+package toolbox
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"reflect"
+	"runtime"
+)
+
+var (
+	dunno     = []byte("???")
+	centerDot = []byte("·")
+	dot       = []byte(".")
+	lbr       = []byte("{")
+	lbrn      = []byte("{\n")
+	com       = []byte(",")
+	comn      = []byte(",\n")
+	rbr       = []byte("}")
+	comnrbr   = []byte(",\n}")
+)
+
+type pointerInfo struct {
+	prev *pointerInfo
+	n    int
+	addr uintptr
+	pos  int
+	used []int
+}
+
+//
+// print the data in console
+//
+func Display(data ...interface{}) {
+	display(true, data...)
+}
+
+//
+// return string
+//
+func GetDisplayString(data ...interface{}) string {
+	return display(false, data...)
+}
+
+func display(displayed bool, data ...interface{}) string {
+	var pc, file, line, ok = runtime.Caller(2)
+
+	if !ok {
+		return ""
+	}
+
+	var buf = new(bytes.Buffer)
+
+	fmt.Fprintf(buf, "[Debug] at %s() [%s:%d]\n", function(pc), file, line)
+
+	fmt.Fprintf(buf, "\n[Variables]\n")
+
+	for i := 0; i < len(data); i += 2 {
+		var output = fomateinfo(len(data[i].(string))+3, data[i+1])
+		fmt.Fprintf(buf, "%s = %s", data[i], output)
+	}
+
+	if displayed {
+		log.Print(buf)
+	}
+	return buf.String()
+}
+
+//
+// return fomateinfo
+//
+func fomateinfo(headlen int, data ...interface{}) []byte {
+	var buf = new(bytes.Buffer)
+
+	if len(data) > 1 {
+		fmt.Fprint(buf, "    ")
+
+		fmt.Fprint(buf, "[")
+
+		fmt.Fprintln(buf)
+	}
+
+	for k, v := range data {
+		var buf2 = new(bytes.Buffer)
+		var pointers *pointerInfo
+		var interfaces []reflect.Value = make([]reflect.Value, 0, 10)
+
+		printKeyValue(buf2, reflect.ValueOf(v), &pointers, &interfaces, nil, true, "    ", 1)
+
+		if k < len(data)-1 {
+			fmt.Fprint(buf2, ", ")
+		}
+
+		fmt.Fprintln(buf2)
+
+		buf.Write(buf2.Bytes())
+	}
+
+	if len(data) > 1 {
+		fmt.Fprintln(buf)
+
+		fmt.Fprint(buf, "    ")
+
+		fmt.Fprint(buf, "]")
+	}
+
+	return buf.Bytes()
+}
+
+func isSimpleType(val reflect.Value, kind reflect.Kind, pointers **pointerInfo, interfaces *[]reflect.Value) bool {
+	switch kind {
+	case reflect.Bool:
+		return true
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return true
+	case reflect.Uint8, reflect.Uint16, reflect.Uint, reflect.Uint32, reflect.Uint64:
+		return true
+	case reflect.Float32, reflect.Float64:
+		return true
+	case reflect.Complex64, reflect.Complex128:
+		return true
+	case reflect.String:
+		return true
+	case reflect.Chan:
+		return true
+	case reflect.Invalid:
+		return true
+	case reflect.Interface:
+		for _, in := range *interfaces {
+			if reflect.DeepEqual(in, val) {
+				return true
+			}
+		}
+		return false
+	case reflect.UnsafePointer:
+		if val.IsNil() {
+			return true
+		}
+
+		var elem = val.Elem()
+
+		if isSimpleType(elem, elem.Kind(), pointers, interfaces) {
+			return true
+		}
+
+		var addr = val.Elem().UnsafeAddr()
+
+		for p := *pointers; p != nil; p = p.prev {
+			if addr == p.addr {
+				return true
+			}
+		}
+
+		return false
+	}
+
+	return false
+}
+
+func printKeyValue(buf *bytes.Buffer, val reflect.Value, pointers **pointerInfo, interfaces *[]reflect.Value, structFilter func(string, string) bool, formatOutput bool, indent string, level int) {
+	var t = val.Kind()
+
+	switch t {
+	case reflect.Bool:
+		fmt.Fprint(buf, val.Bool())
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		fmt.Fprint(buf, val.Int())
+	case reflect.Uint8, reflect.Uint16, reflect.Uint, reflect.Uint32, reflect.Uint64:
+		fmt.Fprint(buf, val.Uint())
+	case reflect.Float32, reflect.Float64:
+		fmt.Fprint(buf, val.Float())
+	case reflect.Complex64, reflect.Complex128:
+		fmt.Fprint(buf, val.Complex())
+	case reflect.UnsafePointer:
+		fmt.Fprintf(buf, "unsafe.Pointer(0x%X)", val.Pointer())
+	case reflect.Ptr:
+		if val.IsNil() {
+			fmt.Fprint(buf, "nil")
+			return
+		}
+
+		var addr = val.Elem().UnsafeAddr()
+
+		for p := *pointers; p != nil; p = p.prev {
+			if addr == p.addr {
+				p.used = append(p.used, buf.Len())
+				fmt.Fprintf(buf, "0x%X", addr)
+				return
+			}
+		}
+
+		*pointers = &pointerInfo{
+			prev: *pointers,
+			addr: addr,
+			pos:  buf.Len(),
+			used: make([]int, 0),
+		}
+
+		fmt.Fprint(buf, "&")
+
+		printKeyValue(buf, val.Elem(), pointers, interfaces, structFilter, formatOutput, indent, level)
+	case reflect.String:
+		fmt.Fprint(buf, "\"", val.String(), "\"")
+	case reflect.Interface:
+		var value = val.Elem()
+
+		if !value.IsValid() {
+			fmt.Fprint(buf, "nil")
+		} else {
+			for _, in := range *interfaces {
+				if reflect.DeepEqual(in, val) {
+					fmt.Fprint(buf, "repeat")
+					return
+				}
+			}
+
+			*interfaces = append(*interfaces, val)
+
+			printKeyValue(buf, value, pointers, interfaces, structFilter, formatOutput, indent, level+1)
+		}
+	case reflect.Struct:
+		var t = val.Type()
+
+		fmt.Fprint(buf, t)
+		fmt.Fprint(buf, "{")
+
+		for i := 0; i < val.NumField(); i++ {
+			if formatOutput {
+				fmt.Fprintln(buf)
+			} else {
+				fmt.Fprint(buf, " ")
+			}
+
+			var name = t.Field(i).Name
+
+			if formatOutput {
+				for ind := 0; ind < level; ind++ {
+					fmt.Fprint(buf, indent)
+				}
+			}
+
+			fmt.Fprint(buf, name)
+			fmt.Fprint(buf, ": ")
+
+			if structFilter != nil && structFilter(t.String(), name) {
+				fmt.Fprint(buf, "ignore")
+			} else {
+				printKeyValue(buf, val.Field(i), pointers, interfaces, structFilter, formatOutput, indent, level+1)
+			}
+
+			fmt.Fprint(buf, ",")
+		}
+
+		if formatOutput {
+			fmt.Fprintln(buf)
+
+			for ind := 0; ind < level-1; ind++ {
+				fmt.Fprint(buf, indent)
+			}
+		} else {
+			fmt.Fprint(buf, " ")
+		}
+
+		fmt.Fprint(buf, "}")
+	case reflect.Array, reflect.Slice:
+		fmt.Fprint(buf, val.Type())
+		fmt.Fprint(buf, "{")
+
+		var allSimple = true
+
+		for i := 0; i < val.Len(); i++ {
+			var elem = val.Index(i)
+
+			var isSimple = isSimpleType(elem, elem.Kind(), pointers, interfaces)
+
+			if !isSimple {
+				allSimple = false
+			}
+
+			if formatOutput && !isSimple {
+				fmt.Fprintln(buf)
+			} else {
+				fmt.Fprint(buf, " ")
+			}
+
+			if formatOutput && !isSimple {
+				for ind := 0; ind < level; ind++ {
+					fmt.Fprint(buf, indent)
+				}
+			}
+
+			printKeyValue(buf, elem, pointers, interfaces, structFilter, formatOutput, indent, level+1)
+
+			if i != val.Len()-1 || !allSimple {
+				fmt.Fprint(buf, ",")
+			}
+		}
+
+		if formatOutput && !allSimple {
+			fmt.Fprintln(buf)
+
+			for ind := 0; ind < level-1; ind++ {
+				fmt.Fprint(buf, indent)
+			}
+		} else {
+			fmt.Fprint(buf, " ")
+		}
+
+		fmt.Fprint(buf, "}")
+	case reflect.Map:
+		var t = val.Type()
+		var keys = val.MapKeys()
+
+		fmt.Fprint(buf, t)
+		fmt.Fprint(buf, "{")
+
+		var allSimple = true
+
+		for i := 0; i < len(keys); i++ {
+			var elem = val.MapIndex(keys[i])
+
+			var isSimple = isSimpleType(elem, elem.Kind(), pointers, interfaces)
+
+			if !isSimple {
+				allSimple = false
+			}
+
+			if formatOutput && !isSimple {
+				fmt.Fprintln(buf)
+			} else {
+				fmt.Fprint(buf, " ")
+			}
+
+			if formatOutput && !isSimple {
+				for ind := 0; ind <= level; ind++ {
+					fmt.Fprint(buf, indent)
+				}
+			}
+
+			printKeyValue(buf, keys[i], pointers, interfaces, structFilter, formatOutput, indent, level+1)
+			fmt.Fprint(buf, ": ")
+			printKeyValue(buf, elem, pointers, interfaces, structFilter, formatOutput, indent, level+1)
+
+			if i != val.Len()-1 || !allSimple {
+				fmt.Fprint(buf, ",")
+			}
+		}
+
+		if formatOutput && !allSimple {
+			fmt.Fprintln(buf)
+
+			for ind := 0; ind < level-1; ind++ {
+				fmt.Fprint(buf, indent)
+			}
+		} else {
+			fmt.Fprint(buf, " ")
+		}
+
+		fmt.Fprint(buf, "}")
+	case reflect.Chan:
+		fmt.Fprint(buf, val.Type())
+	case reflect.Invalid:
+		fmt.Fprint(buf, "invalid")
+	default:
+		fmt.Fprint(buf, "unknow")
+	}
+}
+
+func printPointerInfo(buf *bytes.Buffer, headlen int, pointers *pointerInfo) {
+	var anyused = false
+	var pointerNum = 0
+
+	for p := pointers; p != nil; p = p.prev {
+		if len(p.used) > 0 {
+			anyused = true
+		}
+		pointerNum += 1
+		p.n = pointerNum
+	}
+
+	if anyused {
+		var pointerBufs = make([][]rune, pointerNum+1)
+
+		for i := 0; i < len(pointerBufs); i++ {
+			var pointerBuf = make([]rune, buf.Len()+headlen)
+
+			for j := 0; j < len(pointerBuf); j++ {
+				pointerBuf[j] = ' '
+			}
+
+			pointerBufs[i] = pointerBuf
+		}
+
+		for pn := 0; pn <= pointerNum; pn++ {
+			for p := pointers; p != nil; p = p.prev {
+				if len(p.used) > 0 && p.n >= pn {
+					if pn == p.n {
+						pointerBufs[pn][p.pos+headlen] = '└'
+
+						var maxpos = 0
+
+						for i, pos := range p.used {
+							if i < len(p.used)-1 {
+								pointerBufs[pn][pos+headlen] = '┴'
+							} else {
+								pointerBufs[pn][pos+headlen] = '┘'
+							}
+
+							maxpos = pos
+						}
+
+						for i := 0; i < maxpos-p.pos-1; i++ {
+							if pointerBufs[pn][i+p.pos+headlen+1] == ' ' {
+								pointerBufs[pn][i+p.pos+headlen+1] = '─'
+							}
+						}
+					} else {
+						pointerBufs[pn][p.pos+headlen] = '│'
+
+						for _, pos := range p.used {
+							if pointerBufs[pn][pos+headlen] == ' ' {
+								pointerBufs[pn][pos+headlen] = '│'
+							} else {
+								pointerBufs[pn][pos+headlen] = '┼'
+							}
+						}
+					}
+				}
+			}
+
+			buf.WriteString(string(pointerBufs[pn]) + "\n")
+		}
+	}
+}
+
+//
+// get stack info
+//
+func stack(skip int, indent string) []byte {
+	var buf = new(bytes.Buffer)
+
+	for i := skip; ; i++ {
+		var pc, file, line, ok = runtime.Caller(i)
+
+		if !ok {
+			break
+		}
+
+		buf.WriteString(indent)
+
+		fmt.Fprintf(buf, "at %s() [%s:%d]\n", function(pc), file, line)
+	}
+
+	return buf.Bytes()
+}
+
+// function returns, if possible, the name of the function containing the PC.
+func function(pc uintptr) []byte {
+	fn := runtime.FuncForPC(pc)
+	if fn == nil {
+		return dunno
+	}
+	name := []byte(fn.Name())
+	// The name includes the path name to the package, which is unnecessary
+	// since the file name is already included.  Plus, it has center dots.
+	// That is, we see
+	//	runtime/debug.*T·ptrmethod
+	// and want
+	//	*T.ptrmethod
+	if period := bytes.Index(name, dot); period >= 0 {
+		name = name[period+1:]
+	}
+	name = bytes.Replace(name, centerDot, dot, -1)
+	return name
+}

+package toolbox
+
+import (
+	"testing"
+)
+
+type mytype struct {
+	next *mytype
+	prev *mytype
+}
+
+func TestPrint(t *testing.T) {
+	Display("v1", 1, "v2", 2, "v3", 3)
+}
+
+func TestPrintPoint(t *testing.T) {
+	var v1 = new(mytype)
+	var v2 = new(mytype)
+
+	v1.prev = nil
+	v1.next = v2
+
+	v2.prev = v1
+	v2.next = nil
+
+	Display("v1", v1, "v2", v2)
+}
+
+func TestPrintString(t *testing.T) {
+	str := GetDisplayString("v1", 1, "v2", 2)
+	println(str)
+}