vendor/github.com/aws/aws-sdk-go/aws/request/offset_reader.go

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