package errors import ( "fmt" "io" "path" "runtime" "strconv" "strings" ) // Frame represents a program counter inside a stack frame. // For historical reasons if Frame is interpreted as a uintptr // its value represents the program counter + 1. type Frame uintptr // pc returns the program counter for this frame; // multiple frames may have the same PC value. func (f Frame) pc() uintptr { return uintptr(f) - 1 } // file returns the full path to the file that contains the // function for this Frame's pc. func (f Frame) file() string { fn := runtime.FuncForPC(f.pc()) if fn == nil { return "unknown" } file, _ := fn.FileLine(f.pc()) return file } // line returns the line number of source code of the // function for this Frame's pc. func (f Frame) line() int { fn := runtime.FuncForPC(f.pc()) if fn == nil { return 0 } _, line := fn.FileLine(f.pc()) return line } // name returns the name of this function, if known. func (f Frame) name() string { fn := runtime.FuncForPC(f.pc()) if fn == nil { return "unknown" } return fn.Name() } // Format formats the frame according to the fmt.Formatter interface. // // %s source file // %d source line // %n function name // %v equivalent to %s:%d // // Format accepts flags that alter the printing of some verbs, as follows: // // %+s function name and path of source file relative to the compile time // GOPATH separated by \n\t (\n\t) // %+v equivalent to %+s:%d func (f Frame) Format(s fmt.State, verb rune) { switch verb { case 's': switch { case s.Flag('-'): io.WriteString(s, path.Ext(f.name())) io.WriteString(s, " ") dir, file := path.Split(f.file()) io.WriteString(s, path.Join(path.Base(path.Dir(dir)), path.Base(dir), file)) case s.Flag('+'): io.WriteString(s, f.name()) io.WriteString(s, "\n\t") io.WriteString(s, f.file()) default: io.WriteString(s, path.Base(f.file())) } case 'd': io.WriteString(s, strconv.Itoa(f.line())) case 'n': io.WriteString(s, funcname(f.name())) case 'v': if s.Flag('-') { io.WriteString(s, "[") } f.Format(s, 's') io.WriteString(s, ":") f.Format(s, 'd') if s.Flag('-') { io.WriteString(s, "]") } } } // MarshalText formats a stacktrace Frame as a text string. The output is the // same as that of fmt.Sprintf("%+v", f), but without newlines or tabs. func (f Frame) MarshalText() ([]byte, error) { name := f.name() if name == "unknown" { return []byte(name), nil } return []byte(fmt.Sprintf("%s %s:%d", name, f.file(), f.line())), nil } // StackTrace is stack of Frames from innermost (newest) to outermost (oldest). type StackTrace []Frame // Format formats the stack of Frames according to the fmt.Formatter interface. // // %s lists source files for each Frame in the stack // %v lists the source file and line number for each Frame in the stack // // Format accepts flags that alter the printing of some verbs, as follows: // // %+v Prints filename, function, and line number for each Frame in the stack. func (st StackTrace) Format(s fmt.State, verb rune) { switch verb { case 'v': switch { case s.Flag('+'): for _, f := range st { io.WriteString(s, "\n") f.Format(s, verb) } case s.Flag('-'): for _, f := range st { io.WriteString(s, " ") f.Format(s, verb) } case s.Flag('#'): fmt.Fprintf(s, "%#v", []Frame(st)) default: st.formatSlice(s, verb) } case 's': st.formatSlice(s, verb) } } // formatSlice will format this StackTrace into the given buffer as a slice of // Frame, only valid when called with '%s' or '%v'. func (st StackTrace) formatSlice(s fmt.State, verb rune) { io.WriteString(s, "[") for i, f := range st { if i > 0 { io.WriteString(s, " ") } f.Format(s, verb) } io.WriteString(s, "]") } // stack represents a stack of program counters. type stack []uintptr func (s *stack) Format(st fmt.State, verb rune) { switch verb { case 'v': switch { case st.Flag('+'): for _, pc := range *s { f := Frame(pc) fmt.Fprintf(st, "\n%+v", f) } case st.Flag('-'): for _, pc := range *s { f := Frame(pc) fmt.Fprintf(st, " < %-v", f) } } } } func (s *stack) StackTrace() StackTrace { f := make([]Frame, len(*s)) for i := 0; i < len(f); i++ { f[i] = Frame((*s)[i]) } return f } func callers() *stack { const depth = 7 var pcs [depth]uintptr n := runtime.Callers(3, pcs[:]) var st stack = pcs[0:n] return &st } // funcname removes the path prefix component of a function's name reported by func.Name(). func funcname(name string) string { i := strings.LastIndex(name, "/") name = name[i+1:] i = strings.Index(name, ".") return name[i+1:] }