vendor/github.com/go-stack/stack/stack.go - gddo - Git at Google

 // Package stack implements utilities to capture, manipulate, and format call
 // stacks. It provides a simpler API than package runtime.
 //
 // The implementation takes care of the minutia and special cases of
 // interpreting the program counter (pc) values returned by runtime.Callers.
 //
 // Package stack's types implement fmt.Formatter, which provides a simple and
 // flexible way to declaratively configure formatting when used with logging
 // or error tracking packages.
 package stack

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"runtime"
 	"strconv"
 	"strings"
 )

 // Call records a single function invocation from a goroutine stack.
 type Call struct {
 	fn *runtime.Func
 	pc uintptr
 }

 // Caller returns a Call from the stack of the current goroutine. The argument
 // skip is the number of stack frames to ascend, with 0 identifying the
 // calling function.
 func Caller(skip int) Call {
 	var pcs [2]uintptr
 	n := runtime.Callers(skip+1, pcs[:])

 	var c Call

 	if n < 2 {
 		return c
 	}

 	c.pc = pcs[1]
 	if runtime.FuncForPC(pcs[0]) != sigpanic {
 		c.pc--
 	}
 	c.fn = runtime.FuncForPC(c.pc)
 	return c
 }

 // String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", c).
 func (c Call) String() string {
 	return fmt.Sprint(c)
 }

 // MarshalText implements encoding.TextMarshaler. It formats the Call the same
 // as fmt.Sprintf("%v", c).
 func (c Call) MarshalText() ([]byte, error) {
 	if c.fn == nil {
 		return nil, ErrNoFunc
 	}
 	buf := bytes.Buffer{}
 	fmt.Fprint(&buf, c)
 	return buf.Bytes(), nil
 }

 // ErrNoFunc means that the Call has a nil *runtime.Func. The most likely
 // cause is a Call with the zero value.
 var ErrNoFunc = errors.New("no call stack information")

 // Format implements fmt.Formatter with support for the following verbs.
 //
 //    %s    source file
 //    %d    line number
 //    %n    function name
 //    %v    equivalent to %s:%d
 //
 // It accepts the '+' and '#' flags for most of the verbs as follows.
 //
 //    %+s   path of source file relative to the compile time GOPATH
 //    %#s   full path of source file
 //    %+n   import path qualified function name
 //    %+v   equivalent to %+s:%d
 //    %#v   equivalent to %#s:%d
 func (c Call) Format(s fmt.State, verb rune) {
 	if c.fn == nil {
 		fmt.Fprintf(s, "%%!%c(NOFUNC)", verb)
 		return
 	}

 	switch verb {
 	case 's', 'v':
 		file, line := c.fn.FileLine(c.pc)
 		switch {
 		case s.Flag('#'):
 			// done
 		case s.Flag('+'):
 			file = file[pkgIndex(file, c.fn.Name()):]
 		default:
 			const sep = "/"
 			if i := strings.LastIndex(file, sep); i != -1 {
 				file = file[i+len(sep):]
 			}
 		}
 		io.WriteString(s, file)
 		if verb == 'v' {
 			buf := [7]byte{':'}
 			s.Write(strconv.AppendInt(buf[:1], int64(line), 10))
 		}

 	case 'd':
 		_, line := c.fn.FileLine(c.pc)
 		buf := [6]byte{}
 		s.Write(strconv.AppendInt(buf[:0], int64(line), 10))

 	case 'n':
 		name := c.fn.Name()
 		if !s.Flag('+') {
 			const pathSep = "/"
 			if i := strings.LastIndex(name, pathSep); i != -1 {
 				name = name[i+len(pathSep):]
 			}
 			const pkgSep = "."
 			if i := strings.Index(name, pkgSep); i != -1 {
 				name = name[i+len(pkgSep):]
 			}
 		}
 		io.WriteString(s, name)
 	}
 }

 // PC returns the program counter for this call frame; multiple frames may
 // have the same PC value.
 func (c Call) PC() uintptr {
 	return c.pc
 }

 // name returns the import path qualified name of the function containing the
 // call.
 func (c Call) name() string {
 	if c.fn == nil {
 		return "???"
 	}
 	return c.fn.Name()
 }

 func (c Call) file() string {
 	if c.fn == nil {
 		return "???"
 	}
 	file, _ := c.fn.FileLine(c.pc)
 	return file
 }

 func (c Call) line() int {
 	if c.fn == nil {
 		return 0
 	}
 	_, line := c.fn.FileLine(c.pc)
 	return line
 }

 // CallStack records a sequence of function invocations from a goroutine
 // stack.
 type CallStack []Call

 // String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", cs).
 func (cs CallStack) String() string {
 	return fmt.Sprint(cs)
 }

 var (
 	openBracketBytes  = []byte("[")
 	closeBracketBytes = []byte("]")
 	spaceBytes        = []byte(" ")
 )

 // MarshalText implements encoding.TextMarshaler. It formats the CallStack the
 // same as fmt.Sprintf("%v", cs).
 func (cs CallStack) MarshalText() ([]byte, error) {
 	buf := bytes.Buffer{}
 	buf.Write(openBracketBytes)
 	for i, pc := range cs {
 		if pc.fn == nil {
 			return nil, ErrNoFunc
 		}
 		if i > 0 {
 			buf.Write(spaceBytes)
 		}
 		fmt.Fprint(&buf, pc)
 	}
 	buf.Write(closeBracketBytes)
 	return buf.Bytes(), nil
 }

 // Format implements fmt.Formatter by printing the CallStack as square brackets
 // ([, ]) surrounding a space separated list of Calls each formatted with the
 // supplied verb and options.
 func (cs CallStack) Format(s fmt.State, verb rune) {
 	s.Write(openBracketBytes)
 	for i, pc := range cs {
 		if i > 0 {
 			s.Write(spaceBytes)
 		}
 		pc.Format(s, verb)
 	}
 	s.Write(closeBracketBytes)
 }

 // findSigpanic intentionally executes faulting code to generate a stack trace
 // containing an entry for runtime.sigpanic.
 func findSigpanic() *runtime.Func {
 	var fn *runtime.Func
 	var p *int
 	func() int {
 		defer func() {
 			if p := recover(); p != nil {
 				var pcs [512]uintptr
 				n := runtime.Callers(2, pcs[:])
 				for _, pc := range pcs[:n] {
 					f := runtime.FuncForPC(pc)
 					if f.Name() == "runtime.sigpanic" {
 						fn = f
 						break
 					}
 				}
 			}
 		}()
 		// intentional nil pointer dereference to trigger sigpanic
 		return *p
 	}()
 	return fn
 }

 var sigpanic = findSigpanic()

 // Trace returns a CallStack for the current goroutine with element 0
 // identifying the calling function.
 func Trace() CallStack {
 	var pcs [512]uintptr
 	n := runtime.Callers(2, pcs[:])
 	cs := make([]Call, n)

 	for i, pc := range pcs[:n] {
 		pcFix := pc
 		if i > 0 && cs[i-1].fn != sigpanic {
 			pcFix--
 		}
 		cs[i] = Call{
 			fn: runtime.FuncForPC(pcFix),
 			pc: pcFix,
 		}
 	}

 	return cs
 }

 // TrimBelow returns a slice of the CallStack with all entries below c
 // removed.
 func (cs CallStack) TrimBelow(c Call) CallStack {
 	for len(cs) > 0 && cs[0].pc != c.pc {
 		cs = cs[1:]
 	}
 	return cs
 }

 // TrimAbove returns a slice of the CallStack with all entries above c
 // removed.
 func (cs CallStack) TrimAbove(c Call) CallStack {
 	for len(cs) > 0 && cs[len(cs)-1].pc != c.pc {
 		cs = cs[:len(cs)-1]
 	}
 	return cs
 }

 // pkgIndex returns the index that results in file[index:] being the path of
 // file relative to the compile time GOPATH, and file[:index] being the
 // $GOPATH/src/ portion of file. funcName must be the name of a function in
 // file as returned by runtime.Func.Name.
 func pkgIndex(file, funcName string) int {
 	// As of Go 1.6.2 there is no direct way to know the compile time GOPATH
 	// at runtime, but we can infer the number of path segments in the GOPATH.
 	// We note that runtime.Func.Name() returns the function name qualified by
 	// the import path, which does not include the GOPATH. Thus we can trim
 	// segments from the beginning of the file path until the number of path
 	// separators remaining is one more than the number of path separators in
 	// the function name. For example, given:
 	//
 	//    GOPATH     /home/user
 	//    file       /home/user/src/pkg/sub/file.go
 	//    fn.Name()  pkg/sub.Type.Method
 	//
 	// We want to produce:
 	//
 	//    file[:idx] == /home/user/src/
 	//    file[idx:] == pkg/sub/file.go
 	//
 	// From this we can easily see that fn.Name() has one less path separator
 	// than our desired result for file[idx:]. We count separators from the
 	// end of the file path until it finds two more than in the function name
 	// and then move one character forward to preserve the initial path
 	// segment without a leading separator.
 	const sep = "/"
 	i := len(file)
 	for n := strings.Count(funcName, sep) + 2; n > 0; n-- {
 		i = strings.LastIndex(file[:i], sep)
 		if i == -1 {
 			i = -len(sep)
 			break
 		}
 	}
 	// get back to 0 or trim the leading separator
 	return i + len(sep)
 }

 var runtimePath string

 func init() {
 	var pcs [1]uintptr
 	runtime.Callers(0, pcs[:])
 	fn := runtime.FuncForPC(pcs[0])
 	file, _ := fn.FileLine(pcs[0])

 	idx := pkgIndex(file, fn.Name())

 	runtimePath = file[:idx]
 	if runtime.GOOS == "windows" {
 		runtimePath = strings.ToLower(runtimePath)
 	}
 }

 func inGoroot(c Call) bool {
 	file := c.file()
 	if len(file) == 0 || file[0] == '?' {
 		return true
 	}
 	if runtime.GOOS == "windows" {
 		file = strings.ToLower(file)
 	}
 	return strings.HasPrefix(file, runtimePath) || strings.HasSuffix(file, "/_testmain.go")
 }

 // TrimRuntime returns a slice of the CallStack with the topmost entries from
 // the go runtime removed. It considers any calls originating from unknown
 // files, files under GOROOT, or _testmain.go as part of the runtime.
 func (cs CallStack) TrimRuntime() CallStack {
 	for len(cs) > 0 && inGoroot(cs[len(cs)-1]) {
 		cs = cs[:len(cs)-1]
 	}
 	return cs
 }
	// Package stack implements utilities to capture, manipulate, and format call
	// stacks. It provides a simpler API than package runtime.
	//
	// The implementation takes care of the minutia and special cases of
	// interpreting the program counter (pc) values returned by runtime.Callers.
	//
	// Package stack's types implement fmt.Formatter, which provides a simple and
	// flexible way to declaratively configure formatting when used with logging
	// or error tracking packages.
	package stack

	import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"runtime"
	"strconv"
	"strings"
	)

	// Call records a single function invocation from a goroutine stack.
	type Call struct {
	fn *runtime.Func
	pc uintptr
	}

	// Caller returns a Call from the stack of the current goroutine. The argument
	// skip is the number of stack frames to ascend, with 0 identifying the
	// calling function.
	func Caller(skip int) Call {
	var pcs [2]uintptr
	n := runtime.Callers(skip+1, pcs[:])

	var c Call

	if n < 2 {
	return c
	}

	c.pc = pcs[1]
	if runtime.FuncForPC(pcs[0]) != sigpanic {
	c.pc--
	}
	c.fn = runtime.FuncForPC(c.pc)
	return c
	}

	// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", c).
	func (c Call) String() string {
	return fmt.Sprint(c)
	}

	// MarshalText implements encoding.TextMarshaler. It formats the Call the same
	// as fmt.Sprintf("%v", c).
	func (c Call) MarshalText() ([]byte, error) {
	if c.fn == nil {
	return nil, ErrNoFunc
	}
	buf := bytes.Buffer{}
	fmt.Fprint(&buf, c)
	return buf.Bytes(), nil
	}

	// ErrNoFunc means that the Call has a nil *runtime.Func. The most likely
	// cause is a Call with the zero value.
	var ErrNoFunc = errors.New("no call stack information")

	// Format implements fmt.Formatter with support for the following verbs.
	//
	// %s source file
	// %d line number
	// %n function name
	// %v equivalent to %s:%d
	//
	// It accepts the '+' and '#' flags for most of the verbs as follows.
	//
	// %+s path of source file relative to the compile time GOPATH
	// %#s full path of source file
	// %+n import path qualified function name
	// %+v equivalent to %+s:%d
	// %#v equivalent to %#s:%d
	func (c Call) Format(s fmt.State, verb rune) {
	if c.fn == nil {
	fmt.Fprintf(s, "%%!%c(NOFUNC)", verb)
	return
	}

	switch verb {
	case 's', 'v':
	file, line := c.fn.FileLine(c.pc)
	switch {
	case s.Flag('#'):
	// done
	case s.Flag('+'):
	file = file[pkgIndex(file, c.fn.Name()):]
	default:
	const sep = "/"
	if i := strings.LastIndex(file, sep); i != -1 {
	file = file[i+len(sep):]
	}
	}
	io.WriteString(s, file)
	if verb == 'v' {
	buf := [7]byte{':'}
	s.Write(strconv.AppendInt(buf[:1], int64(line), 10))
	}

	case 'd':
	_, line := c.fn.FileLine(c.pc)
	buf := [6]byte{}
	s.Write(strconv.AppendInt(buf[:0], int64(line), 10))

	case 'n':
	name := c.fn.Name()
	if !s.Flag('+') {
	const pathSep = "/"
	if i := strings.LastIndex(name, pathSep); i != -1 {
	name = name[i+len(pathSep):]
	}
	const pkgSep = "."
	if i := strings.Index(name, pkgSep); i != -1 {
	name = name[i+len(pkgSep):]
	}
	}
	io.WriteString(s, name)
	}
	}

	// PC returns the program counter for this call frame; multiple frames may
	// have the same PC value.
	func (c Call) PC() uintptr {
	return c.pc
	}

	// name returns the import path qualified name of the function containing the
	// call.
	func (c Call) name() string {
	if c.fn == nil {
	return "???"
	}
	return c.fn.Name()
	}

	func (c Call) file() string {
	if c.fn == nil {
	return "???"
	}
	file, _ := c.fn.FileLine(c.pc)
	return file
	}

	func (c Call) line() int {
	if c.fn == nil {
	return 0
	}
	_, line := c.fn.FileLine(c.pc)
	return line
	}

	// CallStack records a sequence of function invocations from a goroutine
	// stack.
	type CallStack []Call

	// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", cs).
	func (cs CallStack) String() string {
	return fmt.Sprint(cs)
	}

	var (
	openBracketBytes = []byte("[")
	closeBracketBytes = []byte("]")
	spaceBytes = []byte(" ")
	)

	// MarshalText implements encoding.TextMarshaler. It formats the CallStack the
	// same as fmt.Sprintf("%v", cs).
	func (cs CallStack) MarshalText() ([]byte, error) {
	buf := bytes.Buffer{}
	buf.Write(openBracketBytes)
	for i, pc := range cs {
	if pc.fn == nil {
	return nil, ErrNoFunc
	}
	if i > 0 {
	buf.Write(spaceBytes)
	}
	fmt.Fprint(&buf, pc)
	}
	buf.Write(closeBracketBytes)
	return buf.Bytes(), nil
	}

	// Format implements fmt.Formatter by printing the CallStack as square brackets
	// ([, ]) surrounding a space separated list of Calls each formatted with the
	// supplied verb and options.
	func (cs CallStack) Format(s fmt.State, verb rune) {
	s.Write(openBracketBytes)
	for i, pc := range cs {
	if i > 0 {
	s.Write(spaceBytes)
	}
	pc.Format(s, verb)
	}
	s.Write(closeBracketBytes)
	}

	// findSigpanic intentionally executes faulting code to generate a stack trace
	// containing an entry for runtime.sigpanic.
	func findSigpanic() *runtime.Func {
	var fn *runtime.Func
	var p *int
	func() int {
	defer func() {
	if p := recover(); p != nil {
	var pcs [512]uintptr
	n := runtime.Callers(2, pcs[:])
	for _, pc := range pcs[:n] {
	f := runtime.FuncForPC(pc)
	if f.Name() == "runtime.sigpanic" {
	fn = f
	break
	}
	}
	}
	}()
	// intentional nil pointer dereference to trigger sigpanic
	return *p
	}()
	return fn
	}

	var sigpanic = findSigpanic()

	// Trace returns a CallStack for the current goroutine with element 0
	// identifying the calling function.
	func Trace() CallStack {
	var pcs [512]uintptr
	n := runtime.Callers(2, pcs[:])
	cs := make([]Call, n)

	for i, pc := range pcs[:n] {
	pcFix := pc
	if i > 0 && cs[i-1].fn != sigpanic {
	pcFix--
	}
	cs[i] = Call{
	fn: runtime.FuncForPC(pcFix),
	pc: pcFix,
	}
	}

	return cs
	}

	// TrimBelow returns a slice of the CallStack with all entries below c
	// removed.
	func (cs CallStack) TrimBelow(c Call) CallStack {
	for len(cs) > 0 && cs[0].pc != c.pc {
	cs = cs[1:]
	}
	return cs
	}

	// TrimAbove returns a slice of the CallStack with all entries above c
	// removed.
	func (cs CallStack) TrimAbove(c Call) CallStack {
	for len(cs) > 0 && cs[len(cs)-1].pc != c.pc {
	cs = cs[:len(cs)-1]
	}
	return cs
	}

	// pkgIndex returns the index that results in file[index:] being the path of
	// file relative to the compile time GOPATH, and file[:index] being the
	// $GOPATH/src/ portion of file. funcName must be the name of a function in
	// file as returned by runtime.Func.Name.
	func pkgIndex(file, funcName string) int {
	// As of Go 1.6.2 there is no direct way to know the compile time GOPATH
	// at runtime, but we can infer the number of path segments in the GOPATH.
	// We note that runtime.Func.Name() returns the function name qualified by
	// the import path, which does not include the GOPATH. Thus we can trim
	// segments from the beginning of the file path until the number of path
	// separators remaining is one more than the number of path separators in
	// the function name. For example, given:
	//
	// GOPATH /home/user
	// file /home/user/src/pkg/sub/file.go
	// fn.Name() pkg/sub.Type.Method
	//
	// We want to produce:
	//
	// file[:idx] == /home/user/src/
	// file[idx:] == pkg/sub/file.go
	//
	// From this we can easily see that fn.Name() has one less path separator
	// than our desired result for file[idx:]. We count separators from the
	// end of the file path until it finds two more than in the function name
	// and then move one character forward to preserve the initial path
	// segment without a leading separator.
	const sep = "/"
	i := len(file)
	for n := strings.Count(funcName, sep) + 2; n > 0; n-- {
	i = strings.LastIndex(file[:i], sep)
	if i == -1 {
	i = -len(sep)
	break
	}
	}
	// get back to 0 or trim the leading separator
	return i + len(sep)
	}

	var runtimePath string

	func init() {
	var pcs [1]uintptr
	runtime.Callers(0, pcs[:])
	fn := runtime.FuncForPC(pcs[0])
	file, _ := fn.FileLine(pcs[0])

	idx := pkgIndex(file, fn.Name())

	runtimePath = file[:idx]
	if runtime.GOOS == "windows" {
	runtimePath = strings.ToLower(runtimePath)
	}
	}

	func inGoroot(c Call) bool {
	file := c.file()
	if len(file) == 0 \|\| file[0] == '?' {
	return true
	}
	if runtime.GOOS == "windows" {
	file = strings.ToLower(file)
	}
	return strings.HasPrefix(file, runtimePath) \|\| strings.HasSuffix(file, "/_testmain.go")
	}

	// TrimRuntime returns a slice of the CallStack with the topmost entries from
	// the go runtime removed. It considers any calls originating from unknown
	// files, files under GOROOT, or _testmain.go as part of the runtime.
	func (cs CallStack) TrimRuntime() CallStack {
	for len(cs) > 0 && inGoroot(cs[len(cs)-1]) {
	cs = cs[:len(cs)-1]
	}
	return cs
	}