95 lines
2.5 KiB
Go
95 lines
2.5 KiB
Go
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package mctx
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import (
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"context"
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"fmt"
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"path/filepath"
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"runtime"
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"strings"
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"text/tabwriter"
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)
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// MaxStackSize indicates the maximum number of stack frames which will be
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// stored when embedding stack traces in errors.
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var MaxStackSize = 50
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type ctxStackKey int
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// Stacktrace represents a stack trace at a particular point in execution.
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type Stacktrace struct {
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frames []uintptr
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}
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// Frame returns the first frame in the stack.
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func (s Stacktrace) Frame() runtime.Frame {
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if len(s.frames) == 0 {
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panic("cannot call Frame on empty stack")
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}
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frame, _ := runtime.CallersFrames([]uintptr(s.frames)).Next()
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return frame
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}
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// Frames returns all runtime.Frame instances for this stack.
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func (s Stacktrace) Frames() []runtime.Frame {
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if len(s.frames) == 0 {
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return nil
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}
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out := make([]runtime.Frame, 0, len(s.frames))
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frames := runtime.CallersFrames([]uintptr(s.frames))
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for {
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frame, more := frames.Next()
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out = append(out, frame)
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if !more {
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break
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}
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}
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return out
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}
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// String returns a string representing the top-most frame of the stack.
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func (s Stacktrace) String() string {
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if len(s.frames) == 0 {
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return ""
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}
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frame := s.Frame()
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file, dir := filepath.Base(frame.File), filepath.Dir(frame.File)
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dir = filepath.Base(dir) // only want the first dirname, ie the pkg name
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return fmt.Sprintf("%s/%s:%d", dir, file, frame.Line)
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}
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// FullString returns the full stack trace.
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func (s Stacktrace) FullString() string {
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sb := new(strings.Builder)
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tw := tabwriter.NewWriter(sb, 0, 4, 4, ' ', 0)
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for _, frame := range s.Frames() {
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file := fmt.Sprintf("%s:%d", frame.File, frame.Line)
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fmt.Fprintf(tw, "%s\t%s\n", file, frame.Function)
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}
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if err := tw.Flush(); err != nil {
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panic(err)
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}
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return sb.String()
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}
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// WithStack returns a Context with the current stacktrace embedded in it (as a
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// Stacktrace type). If skip is non-zero it will skip that many frames from the
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// top of the stack. The frame containing the WithStack call itself is always
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// excluded.
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func WithStack(ctx context.Context, skip int) context.Context {
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stackSlice := make([]uintptr, MaxStackSize)
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// incr skip once for WithStack, and once for runtime.Callers
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l := runtime.Callers(skip+2, stackSlice)
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stack := Stacktrace{frames: stackSlice[:l]}
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return context.WithValue(ctx, ctxStackKey(0), stack)
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}
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// Stack returns the Stacktrace instance which was embedded by WithStack, or false if
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// none ever was.
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func Stack(ctx context.Context) (Stacktrace, bool) {
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stack, ok := ctx.Value(ctxStackKey(0)).(Stacktrace)
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return stack, ok
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}
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