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utils.go
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utils.go
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/*
* Copyright (c) 2016, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package server
import (
"fmt"
"io"
"sync/atomic"
)
// IntentionalPanicError is an error type that is used
// when calling panic() in a situation where recovers
// should propagate the panic.
type IntentionalPanicError struct {
message string
}
// NewIntentionalPanicError creates a new IntentionalPanicError.
func NewIntentionalPanicError(errorMessage string) error {
return IntentionalPanicError{
message: fmt.Sprintf("intentional panic error: %s", errorMessage)}
}
// Error implements the error interface.
func (err IntentionalPanicError) Error() string {
return err.message
}
// PanickingLogWriter wraps an io.Writer and intentionally
// panics when a Write() fails.
type PanickingLogWriter struct {
name string
writer io.Writer
}
// NewPanickingLogWriter creates a new PanickingLogWriter.
func NewPanickingLogWriter(
name string, writer io.Writer) *PanickingLogWriter {
return &PanickingLogWriter{
name: name,
writer: writer,
}
}
// Write implements the io.Writer interface.
func (w *PanickingLogWriter) Write(p []byte) (n int, err error) {
n, err = w.writer.Write(p)
if err != nil {
panic(
NewIntentionalPanicError(
fmt.Sprintf("fatal write to %s failed: %s", w.name, err)))
}
return
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
func greaterThanSwapInt64(addr *int64, new int64) bool {
old := atomic.LoadInt64(addr)
if new > old {
return atomic.CompareAndSwapInt64(addr, old, new)
}
return false
}