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

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