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file.go
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file.go
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// Copyright 2019 RetailNext, Inc.
//
// 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 paranoid
import "os"
func NewFileFromInfo(name string, info os.FileInfo) File {
file := File{
name: name,
}
file.fingerprint.fromInfo(info)
return file
}
func NewFile(name string) (File, error) {
info, err := os.Stat(name)
if err != nil {
return File{}, err
}
return NewFileFromInfo(name, info), nil
}
type File struct {
name string
fingerprint fingerprint
}
func (f File) Name() string {
return f.name
}
func (f File) Len() int64 {
return f.fingerprint.size
}
// Remove a file only if it matches.
// Returns a non-nil error if the file exits and doesn't match, or if os.Remove fails for a non-NotExist reason.
func (f File) Delete() error {
err := f.Check()
if err != nil {
if os.IsNotExist(err) {
return nil
}
return err
}
err = os.Remove(f.name)
if err != nil && !os.IsNotExist(err) {
return err
}
return nil
}
func (f File) Check() error {
info, err := os.Stat(f.name)
if err != nil {
return err
}
return f.check(info)
}
func (f File) CheckFile(file *os.File) error {
info, err := file.Stat()
if err != nil {
return err
}
return f.check(info)
}
func (f File) check(info os.FileInfo) error {
var current fingerprint
current.fromInfo(info)
if f.fingerprint != current {
return FingerprintMismatch{
name: f.name,
expected: f.fingerprint,
actual: current,
}
}
return nil
}
func (f File) Open() (*os.File, error) {
file, err := os.Open(f.name)
if err != nil {
return nil, err
}
err = f.CheckFile(file)
if err != nil {
if closeErr := file.Close(); closeErr != nil {
panic(closeErr)
}
return nil, err
}
return file, nil
}