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