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// Copyright 2025 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package loggo
import (
"runtime"
"sync"
)
var (
helperMutex sync.RWMutex
helpers map[uintptr]struct{}
)
// Helper passed 1 marks the caller as a helper function and will skip it when
// capturing the callsite location.
func Helper(skip int) {
helper(skip + 1)
}
func helper(skip int) {
callers := [1]uintptr{}
if runtime.Callers(skip+2, callers[:]) == 0 {
panic("failed to get caller information")
}
pc := callers[0]
helperMutex.RLock()
if _, ok := helpers[pc]; ok {
helperMutex.RUnlock()
return
}
helperMutex.RUnlock()
helperMutex.Lock()
defer helperMutex.Unlock()
if helpers == nil {
helpers = make(map[uintptr]struct{})
}
helpers[pc] = struct{}{}
}
// caller behaves like runtime.Caller but skips functions marked by helper.
func caller(skip int) (uintptr, string, int, bool) {
pc := [8]uintptr{}
n := runtime.Callers(skip+2, pc[:])
if n == 0 {
return 0, "", 0, false
}
helperMutex.RLock()
pcs := pc[:]
for i := n - 1; i >= 0; i-- {
if _, ok := helpers[pc[i]]; ok {
pcs = pc[i:]
break
}
}
helperMutex.RUnlock()
frames := runtime.CallersFrames(pcs)
if frame, ok := frames.Next(); ok {
return frame.PC, frame.File, frame.Line, true
}
return 0, "", 0, false
}
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