package errors import ( "fmt" "io" "path" "runtime" "strings" ) // Frame represents a program counter inside a stack frame. 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 } // 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 (<funcname>\n\t<path>) // %+v equivalent to %+s:%d func (f Frame) Format(s fmt.State, verb rune) { switch verb { case 's': switch { case s.Flag('+'): pc := f.pc() fn := runtime.FuncForPC(pc) if fn == nil { io.WriteString(s, "unknown") } else { file, _ := fn.FileLine(pc) fmt.Fprintf(s, "%s\n\t%s", fn.Name(), file) } default: io.WriteString(s, path.Base(f.file())) } case 'd': fmt.Fprintf(s, "%d", f.line()) case 'n': name := runtime.FuncForPC(f.pc()).Name() io.WriteString(s, funcname(name)) case 'v': f.Format(s, 's') io.WriteString(s, ":") f.Format(s, 'd') } } // 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 { fmt.Fprintf(s, "\n%+v", f) } case s.Flag('#'): fmt.Fprintf(s, "%#v", []Frame(st)) default: fmt.Fprintf(s, "%v", []Frame(st)) } case 's': fmt.Fprintf(s, "%s", []Frame(st)) } } // 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) } } } } 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 = 32 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:] }