350 lines
8.6 KiB
Go
350 lines
8.6 KiB
Go
// 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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fn *runtime.Func
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pc uintptr
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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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var pcs [2]uintptr
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n := runtime.Callers(skip+1, pcs[:])
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var c Call
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if n < 2 {
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return c
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}
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c.pc = pcs[1]
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if runtime.FuncForPC(pcs[0]) != sigpanic {
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c.pc--
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}
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c.fn = runtime.FuncForPC(c.pc)
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return c
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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.fn == nil {
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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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// %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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// %#s full path of source file
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// %+n import path qualified function name
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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.fn == nil {
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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, line := c.fn.FileLine(c.pc)
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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 = file[pkgIndex(file, c.fn.Name()):]
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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(line), 10))
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}
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case 'd':
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_, line := c.fn.FileLine(c.pc)
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buf := [6]byte{}
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s.Write(strconv.AppendInt(buf[:0], int64(line), 10))
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case 'n':
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name := c.fn.Name()
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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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// 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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func (c Call) PC() uintptr {
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return c.pc
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}
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// name returns the import path qualified name of the function containing the
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// call.
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func (c Call) name() string {
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if c.fn == nil {
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return "???"
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}
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return c.fn.Name()
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}
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func (c Call) file() string {
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if c.fn == nil {
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return "???"
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}
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file, _ := c.fn.FileLine(c.pc)
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return file
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}
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func (c Call) line() int {
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if c.fn == nil {
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return 0
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}
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_, line := c.fn.FileLine(c.pc)
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return line
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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 pc.fn == nil {
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return nil, ErrNoFunc
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}
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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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// findSigpanic intentionally executes faulting code to generate a stack trace
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// containing an entry for runtime.sigpanic.
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func findSigpanic() *runtime.Func {
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var fn *runtime.Func
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var p *int
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func() int {
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defer func() {
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if p := recover(); p != nil {
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var pcs [512]uintptr
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n := runtime.Callers(2, pcs[:])
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for _, pc := range pcs[:n] {
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f := runtime.FuncForPC(pc)
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if f.Name() == "runtime.sigpanic" {
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fn = f
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break
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}
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}
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}
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}()
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// intentional nil pointer dereference to trigger sigpanic
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return *p
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}()
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return fn
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}
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var sigpanic = findSigpanic()
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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(2, pcs[:])
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cs := make([]Call, n)
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for i, pc := range pcs[:n] {
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pcFix := pc
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if i > 0 && cs[i-1].fn != sigpanic {
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pcFix--
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}
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cs[i] = Call{
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fn: runtime.FuncForPC(pcFix),
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pc: pcFix,
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}
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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].pc != c.pc {
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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].pc != c.pc {
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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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var runtimePath string
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func init() {
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var pcs [1]uintptr
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runtime.Callers(0, pcs[:])
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fn := runtime.FuncForPC(pcs[0])
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file, _ := fn.FileLine(pcs[0])
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idx := pkgIndex(file, fn.Name())
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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.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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