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// +build debug
package errors
import (
"bytes"
"fmt"
"runtime"
"strings"
)
type stack struct {
callers []uintptr
// TODO(adg): add time of creation
}
func (e *Error) populateStack() {
e.callers = callers()
e2, ok := e.Err.(*Error)
if !ok {
return
}
i := 0
ok = false
for ; i < len(e.callers) && i < len(e2.callers); i++ {
// check for similar
if e.callers[len(e.callers)-1-i] != e2.callers[len(e2.callers)-1-i] {
break
}
ok = true
}
if ok { //we have common PCs
e2Head := e2.callers[:len(e2.callers)-i]
eTail := e.callers
e.callers = make([]uintptr, len(e2Head)+len(eTail))
copy(e.callers, e2Head)
copy(e.callers[len(e2Head):], eTail)
e2.callers = nil
}
}
// frame returns the nth frame, with the frame at top of stack being 0.
func frame(callers []uintptr, n int) runtime.Frame {
frames := runtime.CallersFrames(callers)
var f runtime.Frame
for i := len(callers) - 1; i >= n; i-- {
var ok bool
f, ok = frames.Next()
if !ok {
break
}
}
return f
}
func (e *Error) printStack(b *bytes.Buffer) {
c := callers()
var prev string
var diff bool
for i := 0; i < len(e.callers); i++ {
pc := e.callers[len(e.callers)-i-1] // get current PC
fn := runtime.FuncForPC(pc) // get function by pc
name := fn.Name()
if !diff && i < len(c) {
ppc := c[len(c)-i-1]
pname := runtime.FuncForPC(ppc).Name()
if name == pname {
continue
}
diff = true
}
if name == prev {
continue
}
trim := 0
for {
j := strings.IndexAny(name[trim:], "./")
if j < 0 {
break
}
if !strings.HasPrefix(prev, name[:j+trim]) {
break
}
trim += j + 1 // skip over the separator
}
// Do the printing.
appendStrToBuf(b, Separator)
file, line := fn.FileLine(pc)
fmt.Fprintf(b, "%v:%d: ", file, line)
if trim > 0 {
b.WriteString("...")
}
b.WriteString(name[trim:])
prev = name
}
}
func callers() []uintptr {
var stk [64]uintptr
const skip = 4
n := runtime.Callers(skip, stk[:])
return stk[:n]
}
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