401 lines
12 KiB
Go
401 lines
12 KiB
Go
// +build go1.7
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// Package stack implements utilities to capture, manipulate, and format call
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// stacks. It provides a simpler API than package runtime.
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//
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// The implementation takes care of the minutia and special cases of
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// interpreting the program counter (pc) values returned by runtime.Callers.
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//
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// Package stack's types implement fmt.Formatter, which provides a simple and
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// flexible way to declaratively configure formatting when used with logging
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// or error tracking packages.
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package stack
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"runtime"
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"strconv"
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"strings"
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)
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// Call records a single function invocation from a goroutine stack.
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type Call struct {
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frame runtime.Frame
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}
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// Caller returns a Call from the stack of the current goroutine. The argument
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// skip is the number of stack frames to ascend, with 0 identifying the
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// calling function.
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func Caller(skip int) Call {
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// As of Go 1.9 we need room for up to three PC entries.
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//
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// 0. An entry for the stack frame prior to the target to check for
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// special handling needed if that prior entry is runtime.sigpanic.
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// 1. A possible second entry to hold metadata about skipped inlined
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// functions. If inline functions were not skipped the target frame
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// PC will be here.
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// 2. A third entry for the target frame PC when the second entry
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// is used for skipped inline functions.
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var pcs [3]uintptr
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n := runtime.Callers(skip+1, pcs[:])
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frames := runtime.CallersFrames(pcs[:n])
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frame, _ := frames.Next()
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frame, _ = frames.Next()
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return Call{
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frame: frame,
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}
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}
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// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", c).
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func (c Call) String() string {
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return fmt.Sprint(c)
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}
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// MarshalText implements encoding.TextMarshaler. It formats the Call the same
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// as fmt.Sprintf("%v", c).
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func (c Call) MarshalText() ([]byte, error) {
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if c.frame == (runtime.Frame{}) {
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return nil, ErrNoFunc
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}
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buf := bytes.Buffer{}
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fmt.Fprint(&buf, c)
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return buf.Bytes(), nil
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}
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// ErrNoFunc means that the Call has a nil *runtime.Func. The most likely
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// cause is a Call with the zero value.
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var ErrNoFunc = errors.New("no call stack information")
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// Format implements fmt.Formatter with support for the following verbs.
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//
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// %s source file
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// %d line number
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// %n function name
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// %k last segment of the package path
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// %v equivalent to %s:%d
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//
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// It accepts the '+' and '#' flags for most of the verbs as follows.
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//
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// %+s path of source file relative to the compile time GOPATH,
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// or the module path joined to the path of source file relative
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// to module root
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// %#s full path of source file
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// %+n import path qualified function name
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// %+k full package path
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// %+v equivalent to %+s:%d
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// %#v equivalent to %#s:%d
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func (c Call) Format(s fmt.State, verb rune) {
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if c.frame == (runtime.Frame{}) {
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fmt.Fprintf(s, "%%!%c(NOFUNC)", verb)
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return
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}
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switch verb {
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case 's', 'v':
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file := c.frame.File
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switch {
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case s.Flag('#'):
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// done
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case s.Flag('+'):
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file = pkgFilePath(&c.frame)
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default:
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const sep = "/"
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if i := strings.LastIndex(file, sep); i != -1 {
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file = file[i+len(sep):]
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}
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}
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io.WriteString(s, file)
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if verb == 'v' {
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buf := [7]byte{':'}
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s.Write(strconv.AppendInt(buf[:1], int64(c.frame.Line), 10))
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}
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case 'd':
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buf := [6]byte{}
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s.Write(strconv.AppendInt(buf[:0], int64(c.frame.Line), 10))
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case 'k':
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name := c.frame.Function
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const pathSep = "/"
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start, end := 0, len(name)
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if i := strings.LastIndex(name, pathSep); i != -1 {
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start = i + len(pathSep)
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}
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const pkgSep = "."
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if i := strings.Index(name[start:], pkgSep); i != -1 {
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end = start + i
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}
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if s.Flag('+') {
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start = 0
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}
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io.WriteString(s, name[start:end])
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case 'n':
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name := c.frame.Function
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if !s.Flag('+') {
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const pathSep = "/"
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if i := strings.LastIndex(name, pathSep); i != -1 {
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name = name[i+len(pathSep):]
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}
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const pkgSep = "."
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if i := strings.Index(name, pkgSep); i != -1 {
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name = name[i+len(pkgSep):]
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}
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}
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io.WriteString(s, name)
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}
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}
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// Frame returns the call frame infomation for the Call.
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func (c Call) Frame() runtime.Frame {
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return c.frame
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}
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// PC returns the program counter for this call frame; multiple frames may
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// have the same PC value.
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//
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// Deprecated: Use Call.Frame instead.
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func (c Call) PC() uintptr {
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return c.frame.PC
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}
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// CallStack records a sequence of function invocations from a goroutine
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// stack.
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type CallStack []Call
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// String implements fmt.Stinger. It is equivalent to fmt.Sprintf("%v", cs).
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func (cs CallStack) String() string {
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return fmt.Sprint(cs)
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}
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var (
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openBracketBytes = []byte("[")
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closeBracketBytes = []byte("]")
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spaceBytes = []byte(" ")
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)
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// MarshalText implements encoding.TextMarshaler. It formats the CallStack the
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// same as fmt.Sprintf("%v", cs).
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func (cs CallStack) MarshalText() ([]byte, error) {
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buf := bytes.Buffer{}
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buf.Write(openBracketBytes)
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for i, pc := range cs {
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if i > 0 {
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buf.Write(spaceBytes)
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}
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fmt.Fprint(&buf, pc)
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}
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buf.Write(closeBracketBytes)
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return buf.Bytes(), nil
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}
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// Format implements fmt.Formatter by printing the CallStack as square brackets
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// ([, ]) surrounding a space separated list of Calls each formatted with the
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// supplied verb and options.
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func (cs CallStack) Format(s fmt.State, verb rune) {
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s.Write(openBracketBytes)
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for i, pc := range cs {
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if i > 0 {
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s.Write(spaceBytes)
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}
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pc.Format(s, verb)
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}
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s.Write(closeBracketBytes)
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}
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// Trace returns a CallStack for the current goroutine with element 0
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// identifying the calling function.
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func Trace() CallStack {
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var pcs [512]uintptr
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n := runtime.Callers(1, pcs[:])
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frames := runtime.CallersFrames(pcs[:n])
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cs := make(CallStack, 0, n)
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// Skip extra frame retrieved just to make sure the runtime.sigpanic
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// special case is handled.
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frame, more := frames.Next()
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for more {
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frame, more = frames.Next()
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cs = append(cs, Call{frame: frame})
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}
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return cs
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}
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// TrimBelow returns a slice of the CallStack with all entries below c
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// removed.
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func (cs CallStack) TrimBelow(c Call) CallStack {
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for len(cs) > 0 && cs[0] != c {
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cs = cs[1:]
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}
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return cs
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}
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// TrimAbove returns a slice of the CallStack with all entries above c
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// removed.
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func (cs CallStack) TrimAbove(c Call) CallStack {
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for len(cs) > 0 && cs[len(cs)-1] != c {
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cs = cs[:len(cs)-1]
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}
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return cs
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}
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// pkgIndex returns the index that results in file[index:] being the path of
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// file relative to the compile time GOPATH, and file[:index] being the
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// $GOPATH/src/ portion of file. funcName must be the name of a function in
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// file as returned by runtime.Func.Name.
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func pkgIndex(file, funcName string) int {
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// As of Go 1.6.2 there is no direct way to know the compile time GOPATH
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// at runtime, but we can infer the number of path segments in the GOPATH.
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// We note that runtime.Func.Name() returns the function name qualified by
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// the import path, which does not include the GOPATH. Thus we can trim
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// segments from the beginning of the file path until the number of path
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// separators remaining is one more than the number of path separators in
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// the function name. For example, given:
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//
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// GOPATH /home/user
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// file /home/user/src/pkg/sub/file.go
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// fn.Name() pkg/sub.Type.Method
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//
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// We want to produce:
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//
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// file[:idx] == /home/user/src/
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// file[idx:] == pkg/sub/file.go
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//
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// From this we can easily see that fn.Name() has one less path separator
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// than our desired result for file[idx:]. We count separators from the
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// end of the file path until it finds two more than in the function name
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// and then move one character forward to preserve the initial path
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// segment without a leading separator.
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const sep = "/"
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i := len(file)
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for n := strings.Count(funcName, sep) + 2; n > 0; n-- {
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i = strings.LastIndex(file[:i], sep)
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if i == -1 {
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i = -len(sep)
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break
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}
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}
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// get back to 0 or trim the leading separator
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return i + len(sep)
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}
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// pkgFilePath returns the frame's filepath relative to the compile-time GOPATH,
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// or its module path joined to its path relative to the module root.
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//
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// As of Go 1.11 there is no direct way to know the compile time GOPATH or
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// module paths at runtime, but we can piece together the desired information
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// from available information. We note that runtime.Frame.Function contains the
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// function name qualified by the package path, which includes the module path
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// but not the GOPATH. We can extract the package path from that and append the
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// last segments of the file path to arrive at the desired package qualified
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// file path. For example, given:
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//
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// GOPATH /home/user
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// import path pkg/sub
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// frame.File /home/user/src/pkg/sub/file.go
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// frame.Function pkg/sub.Type.Method
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// Desired return pkg/sub/file.go
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//
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// It appears that we simply need to trim ".Type.Method" from frame.Function and
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// append "/" + path.Base(file).
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//
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// But there are other wrinkles. Although it is idiomatic to do so, the internal
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// name of a package is not required to match the last segment of its import
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// path. In addition, the introduction of modules in Go 1.11 allows working
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// without a GOPATH. So we also must make these work right:
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//
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// GOPATH /home/user
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// import path pkg/go-sub
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// package name sub
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// frame.File /home/user/src/pkg/go-sub/file.go
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// frame.Function pkg/sub.Type.Method
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// Desired return pkg/go-sub/file.go
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//
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// Module path pkg/v2
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// import path pkg/v2/go-sub
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// package name sub
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// frame.File /home/user/cloned-pkg/go-sub/file.go
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// frame.Function pkg/v2/sub.Type.Method
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// Desired return pkg/v2/go-sub/file.go
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//
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// We can handle all of these situations by using the package path extracted
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// from frame.Function up to, but not including, the last segment as the prefix
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// and the last two segments of frame.File as the suffix of the returned path.
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// This preserves the existing behavior when working in a GOPATH without modules
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// and a semantically equivalent behavior when used in module aware project.
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func pkgFilePath(frame *runtime.Frame) string {
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pre := pkgPrefix(frame.Function)
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post := pathSuffix(frame.File)
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if pre == "" {
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return post
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}
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return pre + "/" + post
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}
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// pkgPrefix returns the import path of the function's package with the final
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// segment removed.
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func pkgPrefix(funcName string) string {
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const pathSep = "/"
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end := strings.LastIndex(funcName, pathSep)
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if end == -1 {
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return ""
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}
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return funcName[:end]
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}
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// pathSuffix returns the last two segments of path.
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func pathSuffix(path string) string {
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const pathSep = "/"
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lastSep := strings.LastIndex(path, pathSep)
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if lastSep == -1 {
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return path
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}
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return path[strings.LastIndex(path[:lastSep], pathSep)+1:]
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}
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var runtimePath string
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func init() {
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var pcs [3]uintptr
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runtime.Callers(0, pcs[:])
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frames := runtime.CallersFrames(pcs[:])
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frame, _ := frames.Next()
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file := frame.File
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idx := pkgIndex(frame.File, frame.Function)
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runtimePath = file[:idx]
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if runtime.GOOS == "windows" {
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runtimePath = strings.ToLower(runtimePath)
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}
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}
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func inGoroot(c Call) bool {
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file := c.frame.File
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if len(file) == 0 || file[0] == '?' {
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return true
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}
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if runtime.GOOS == "windows" {
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file = strings.ToLower(file)
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}
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return strings.HasPrefix(file, runtimePath) || strings.HasSuffix(file, "/_testmain.go")
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}
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// TrimRuntime returns a slice of the CallStack with the topmost entries from
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// the go runtime removed. It considers any calls originating from unknown
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// files, files under GOROOT, or _testmain.go as part of the runtime.
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func (cs CallStack) TrimRuntime() CallStack {
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for len(cs) > 0 && inGoroot(cs[len(cs)-1]) {
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cs = cs[:len(cs)-1]
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}
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return cs
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}
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