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64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package continuity
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import (
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"bytes"
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"io"
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"io/ioutil"
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"os"
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"path/filepath"
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)
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// AtomicWriteFile atomically writes data to a file by first writing to a
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// temp file and calling rename.
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func AtomicWriteFile(filename string, data []byte, perm os.FileMode) error {
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buf := bytes.NewBuffer(data)
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return atomicWriteFile(filename, buf, int64(len(data)), perm)
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}
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// atomicWriteFile writes data to a file by first writing to a temp
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// file and calling rename.
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func atomicWriteFile(filename string, r io.Reader, dataSize int64, perm os.FileMode) error {
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f, err := ioutil.TempFile(filepath.Dir(filename), ".tmp-"+filepath.Base(filename))
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if err != nil {
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return err
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}
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err = os.Chmod(f.Name(), perm)
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if err != nil {
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f.Close()
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return err
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}
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n, err := io.Copy(f, r)
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if err == nil && n < dataSize {
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f.Close()
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return io.ErrShortWrite
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}
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if err != nil {
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f.Close()
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return err
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}
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if err := f.Sync(); err != nil {
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f.Close()
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return err
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}
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if err := f.Close(); err != nil {
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return err
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}
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return os.Rename(f.Name(), filename)
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}
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