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package errors
import (
"encoding/binary"
"sync"
"github.com/getlantern/hidden"
)
var (
hiddenErrors = make([]*structured, 100)
nextID = uint64(0)
hiddenMutex sync.RWMutex
)
// This trick saves the error to a ring buffer and embeds a non-printing
// hiddenID in the error's description, so that if the errors is later wrapped
// by a standard error using something like
// fmt.Errorf("An error occurred: %v", thisError), we can subsequently extract
// the error simply using the hiddenID in the string.
func (e *structured) save() {
hiddenMutex.Lock()
b := make([]byte, 8)
binary.BigEndian.PutUint64(b, nextID)
e.id = nextID
e.hiddenID = hidden.ToString(b)
hiddenErrors[idxForID(nextID)] = e
nextID++
hiddenMutex.Unlock()
}
func get(hiddenID []byte) Error {
if len(hiddenID) != 8 {
return nil
}
id := binary.BigEndian.Uint64(hiddenID)
hiddenMutex.RLock()
err := hiddenErrors[idxForID(id)]
hiddenMutex.RUnlock()
if err != nil && err.id == id {
// Found it!
return err
}
// buffer has rolled over
return nil
}
func idxForID(id uint64) int {
return int(id % uint64(len(hiddenErrors)))
}
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