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/*
* errors.go - Custom errors and error functions used by fscrypt
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package util
import (
"fmt"
"io"
"log"
"os"
)
// ErrReader wraps an io.Reader, passing along calls to Read() until a read
// fails. Then, the error is stored, and all subsequent calls to Read() do
// nothing. This allows you to write code which has many subsequent reads and
// do all of the error checking at the end. For example:
//
// r := NewErrReader(reader)
// r.Read(foo)
// r.Read(bar)
// r.Read(baz)
// if r.Err() != nil {
// // Handle error
// }
//
// Taken from https://blog.golang.org/errors-are-values by Rob Pike.
type ErrReader struct {
r io.Reader
err error
}
// NewErrReader creates an ErrReader which wraps the provided reader.
func NewErrReader(reader io.Reader) *ErrReader {
return &ErrReader{r: reader, err: nil}
}
// Read runs ReadFull on the wrapped reader if no errors have occurred.
// Otherwise, the previous error is just returned and no reads are attempted.
func (e *ErrReader) Read(p []byte) (n int, err error) {
if e.err == nil {
n, e.err = io.ReadFull(e.r, p)
}
return n, e.err
}
// Err returns the first encountered err (or nil if no errors occurred).
func (e *ErrReader) Err() error {
return e.err
}
// ErrWriter works exactly like ErrReader, except with io.Writer.
type ErrWriter struct {
w io.Writer
err error
}
// NewErrWriter creates an ErrWriter which wraps the provided reader.
func NewErrWriter(writer io.Writer) *ErrWriter {
return &ErrWriter{w: writer, err: nil}
}
// Write runs the wrapped writer's Write if no errors have occurred. Otherwise,
// the previous error is just returned and no writes are attempted.
func (e *ErrWriter) Write(p []byte) (n int, err error) {
if e.err == nil {
n, e.err = e.w.Write(p)
}
return n, e.err
}
// Err returns the first encountered err (or nil if no errors occurred).
func (e *ErrWriter) Err() error {
return e.err
}
// CheckValidLength returns an invalid length error if expected != actual
func CheckValidLength(expected, actual int) error {
if expected == actual {
return nil
}
return fmt.Errorf("expected length of %d, got %d", expected, actual)
}
// SystemError is an error that should indicate something has gone wrong in the
// underlying system (syscall failure, bad ioctl, etc...).
type SystemError string
func (s SystemError) Error() string {
return "system error: " + string(s)
}
// NeverError panics if a non-nil error is passed in. It should be used to check
// for logic errors, not to handle recoverable errors.
func NeverError(err error) {
if err != nil {
log.Panicf("NeverError() check failed: %v", err)
}
}
// TestEnvVarName is the name on an environment variable that should be set to
// an empty mountpoint. This is only used for integration tests.
var TestEnvVarName = "TEST_FILESYSTEM_ROOT"
// TestPath returns a the path specified by TestEnvVarName. The function
// panics if the environment variable is not set. This function is only used for
// integration tests.
func TestPath() (string, error) {
path := os.Getenv(TestEnvVarName)
if path == "" {
return "", fmt.Errorf("%s: environment variable not set", TestEnvVarName)
}
return path, nil
}
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