// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gob

import (
	"fmt"
	"os"
)

// Errors in decoding and encoding are handled using panic and recover.
// Panics caused by user error (that is, everything except run-time panics
// such as "index out of bounds" errors) do not leave the file that caused
// them, but are instead turned into plain os.Error returns.  Encoding and
// decoding functions and methods that do not return an os.Error either use
// panic to report an error or are guaranteed error-free.

// A gobError wraps an os.Error and is used to distinguish errors (panics) generated in this package.
type gobError struct {
	err os.Error
}

// errorf is like error but takes Printf-style arguments to construct an os.Error.
// It always prefixes the message with "gob: ".
func errorf(format string, args ...interface{}) {
	error(fmt.Errorf("gob: "+format, args...))
}

// error wraps the argument error and uses it as the argument to panic.
func error(err os.Error) {
	panic(gobError{err})
}

// catchError is meant to be used as a deferred function to turn a panic(gobError) into a
// plain os.Error.  It overwrites the error return of the function that deferred its call.
func catchError(err *os.Error) {
	if e := recover(); e != nil {
		*err = e.(gobError).err // Will re-panic if not one of our errors, such as a runtime error.
	}
	return
}