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