1package request 2 3import ( 4 "io" 5 "sync" 6 7 "github.com/aws/aws-sdk-go/internal/sdkio" 8) 9 10// offsetReader is a thread-safe io.ReadCloser to prevent racing 11// with retrying requests 12type offsetReader struct { 13 buf io.ReadSeeker 14 lock sync.Mutex 15 closed bool 16} 17 18func newOffsetReader(buf io.ReadSeeker, offset int64) (*offsetReader, error) { 19 reader := &offsetReader{} 20 _, err := buf.Seek(offset, sdkio.SeekStart) 21 if err != nil { 22 return nil, err 23 } 24 25 reader.buf = buf 26 return reader, nil 27} 28 29// Close will close the instance of the offset reader's access to 30// the underlying io.ReadSeeker. 31func (o *offsetReader) Close() error { 32 o.lock.Lock() 33 defer o.lock.Unlock() 34 o.closed = true 35 return nil 36} 37 38// Read is a thread-safe read of the underlying io.ReadSeeker 39func (o *offsetReader) Read(p []byte) (int, error) { 40 o.lock.Lock() 41 defer o.lock.Unlock() 42 43 if o.closed { 44 return 0, io.EOF 45 } 46 47 return o.buf.Read(p) 48} 49 50// Seek is a thread-safe seeking operation. 51func (o *offsetReader) Seek(offset int64, whence int) (int64, error) { 52 o.lock.Lock() 53 defer o.lock.Unlock() 54 55 return o.buf.Seek(offset, whence) 56} 57 58// CloseAndCopy will return a new offsetReader with a copy of the old buffer 59// and close the old buffer. 60func (o *offsetReader) CloseAndCopy(offset int64) (*offsetReader, error) { 61 if err := o.Close(); err != nil { 62 return nil, err 63 } 64 return newOffsetReader(o.buf, offset) 65} 66