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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package xerrors
import (
"runtime"
)
// A Frame contains part of a call stack.
type Frame struct {
// Make room for three PCs: the one we were asked for, what it called,
// and possibly a PC for skipPleaseUseCallersFrames. See:
// https://go.googlesource.com/go/+/032678e0fb/src/runtime/extern.go#169
frames [3]uintptr
}
// Caller returns a Frame that describes a frame on the caller's stack.
// The argument skip is the number of frames to skip over.
// Caller(0) returns the frame for the caller of Caller.
func Caller(skip int) Frame {
var s Frame
runtime.Callers(skip+1, s.frames[:])
return s
}
// location reports the file, line, and function of a frame.
//
// The returned function may be "" even if file and line are not.
func (f Frame) location() (function, file string, line int) {
frames := runtime.CallersFrames(f.frames[:])
if _, ok := frames.Next(); !ok {
return "", "", 0
}
fr, ok := frames.Next()
if !ok {
return "", "", 0
}
return fr.Function, fr.File, fr.Line
}
// Format prints the stack as error detail.
// It should be called from an error's Format implementation
// after printing any other error detail.
func (f Frame) Format(p Printer) {
if p.Detail() {
function, file, line := f.location()
if function != "" {
p.Printf("%s\n ", function)
}
if file != "" {
p.Printf("%s:%d\n", file, line)
}
}
}
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