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67 lines
1.6 KiB
Go
67 lines
1.6 KiB
Go
package buffer
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import (
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"encoding/hex"
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"fmt"
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"io"
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"math/rand"
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"os"
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"path/filepath"
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)
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// FileBuffer implements Buffer interface using file system.
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type FileBuffer struct {
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Path string
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// LenHint is the size of the stored blob. It can
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// be set to avoid the need to call os.Stat in the
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// Len() method.
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LenHint int
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}
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func (fb FileBuffer) Open() (io.ReadCloser, error) {
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return os.Open(fb.Path)
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}
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func (fb FileBuffer) Len() int {
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if fb.LenHint != 0 {
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return fb.LenHint
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}
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info, err := os.Stat(fb.Path)
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if err != nil {
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// Any access to the file will probably fail too. So we can't return a
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// sensible value.
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return 0
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}
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return int(info.Size())
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}
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func (fb FileBuffer) Remove() error {
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return os.Remove(fb.Path)
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}
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// BufferInFile is a convenience function which creates FileBuffer with underlying
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// file created in the specified directory with the random name.
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func BufferInFile(r io.Reader, dir string) (Buffer, error) {
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// It is assumed that PRNG is initialized somewhere during program startup.
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nameBytes := make([]byte, 32)
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_, err := rand.Read(nameBytes)
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if err != nil {
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return nil, fmt.Errorf("buffer: failed to generate randomness for file name: %v", err)
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}
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path := filepath.Join(dir, hex.EncodeToString(nameBytes))
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f, err := os.Create(path)
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if err != nil {
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return nil, fmt.Errorf("buffer: failed to create file: %v", err)
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}
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if _, err = io.Copy(f, r); err != nil {
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return nil, fmt.Errorf("buffer: failed to write file: %v", err)
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}
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if err := f.Close(); err != nil {
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return nil, fmt.Errorf("buffer: failed to close file: %v", err)
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}
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return FileBuffer{Path: path}, nil
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}
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