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// Package stack provides helpers for querying the callstack.
package stack
import (
"path"
"runtime"
"strings"
)
// Frames returns at most max callstack Frames, starting with its caller and
// skipping skip Frames.
func Frames(skip, max int) []runtime.Frame {
pc := make([]uintptr, max)
n := runtime.Callers(skip+2, pc)
if n == 0 {
return nil
}
pc = pc[:n]
frames := runtime.CallersFrames(pc)
var fs []runtime.Frame
for {
f, more := frames.Next()
fs = append(fs, f)
if !more {
break
}
}
return fs
}
// Match returns the first stack frame for which the predicate function returns
// true. Returns nil if no match is found. Starts matching after skip frames,
// starting with its caller.
func Match(skip int, predicate func(runtime.Frame) bool) *runtime.Frame {
i, n := skip+1, 16
for {
fs := Frames(i, n)
for j, f := range fs {
if predicate(f) {
return &fs[j]
}
}
if len(fs) < n {
break
}
i += n
}
return nil
}
// Main returns the main() function Frame.
func Main() *runtime.Frame {
return Match(1, func(f runtime.Frame) bool {
return f.Function == "main.main"
})
}
// ExternalCaller returns the first frame outside the callers package.
func ExternalCaller() *runtime.Frame {
var first *runtime.Frame
return Match(1, func(f runtime.Frame) bool {
if first == nil {
first = &f
}
return pkg(first.Function) != pkg(f.Function)
})
}
func pkg(ident string) string {
dir, name := path.Split(ident)
parts := strings.Split(name, ".")
return dir + parts[0]
}
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